KR102206695B1 - Nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery - Google Patents

Abstract

In particular, it is an object to provide a non-aqueous electrolyte secondary battery having excellent low-generated gas amount and high-temperature cycle durability characteristics in a battery having a high upper limit operating potential of a positive electrode. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a lithium salt and a non-aqueous solvent that dissolves the same, a negative electrode capable of storing and releasing lithium ions, and a positive electrode, wherein the non-aqueous electrolyte is represented by the general formula (1). A carbonate, a fluorinated cyclic carbonate represented by the general formula (2), and a fluorinated chain carbonate represented by the general formula (3) are contained, and the cyclic carbonate represented by the general formula (1) in a non-aqueous solvent is more than 15% by volume. A non-aqueous electrolyte secondary battery characterized by containing a large amount of the non-aqueous electrolyte secondary battery excellent in low gas amount and high temperature cycle durability even when the upper limit operating potential of the positive electrode is 4.5 V or more based on Li/Li ⁺ do.

Description

Nonaqueous electrolyte and nonaqueous electrolyte secondary battery {NONAQUEOUS ELECTROLYTE SOLUTION AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY}

The present invention relates to a non-aqueous electrolytic solution and a secondary battery comprising the non-aqueous electrolytic solution, specifically containing a specific cyclic carbonate, a fluorinated cyclic carbonate, and a fluorinated chain carbonate, and the ring in a non-aqueous solvent It relates to a non-aqueous electrolyte solution containing more than 20% by volume of type carbonate.

In addition, a non-aqueous electrolyte solution containing a specific cyclic carbonate, a fluorinated cyclic carbonate, and a fluorinated chain carbonate, and containing more than 15% by volume of the cyclic carbonate in a non-aqueous solvent is provided, and a positive electrode It relates to a non-aqueous electrolyte secondary battery having an upper limit operating potential of 4.5 V or more based on Li/Li ⁺ .

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries have been put into practical use as a wide range of power sources ranging from power sources for portable electronic devices such as mobile phones and notebook PCs to vehicle-mounted power sources for driving such as automobiles and large power supplies for stationary use. However, with the recent high performance of electronic devices or application to a vehicle-mounted power supply for driving or a large-sized power supply for stationary use, the demand for a secondary battery to be applied is gradually increasing, and high performance of the battery characteristics of the secondary battery, for example, high capacity, high temperature. It is required to achieve high levels of improvement in storage characteristics and cycle characteristics.

In particular, high functionality or multi-functionalization of portable devices, etc., is gradually progressing, and further improvement in energy density of a lithium secondary battery, which is a power source, is strongly desired. In addition, there is a demand for a battery having a good balance of performance in terms of safety, cost competitiveness, life (especially under high temperature), and the like, and the development of lithium secondary batteries that can meet these demands is being actively made.

In such a situation, various proposals have been made in order to improve the energy density of a lithium secondary battery. There are several ways to improve the energy density of the battery, but one of them is raising the operating voltage of the battery. In particular, for devices operating at high voltages, the use of high voltage batteries with high operating voltages is a particularly effective means, and it is believed that the demand for such batteries will increase in the future.

Non-aqueous electrolyte solution The non-aqueous electrolyte solution used in a secondary battery is usually mainly composed of an electrolyte and a non-aqueous solvent. As a main component of the non-aqueous solvent, cyclic carbonates such as ethylene carbonate and propylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; Cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone are used.

Further, in order to improve battery characteristics such as load characteristics, cycle characteristics, storage characteristics, and low-temperature characteristics of batteries using these non-aqueous electrolyte solutions, various non-aqueous solvents, electrolytes, auxiliary agents, and the like have also been proposed. For example, by using vinylene carbonate and its derivatives or vinyl ethylene carbonate derivatives, a cyclic carbonate having a double bond preferentially reacts with the negative electrode to form a high-quality film on the surface of the negative electrode. It is disclosed in Patent Documents 1 and 2 that the storage characteristics and cycle characteristics are improved.

However, in response to the increasing demand for a high-capacity, high-voltage battery, in a battery using a conventional non-aqueous electrolyte, the required battery performance could not be satisfactorily obtained. Therefore, in recent years, as a policy of developing a non-aqueous electrolyte solution capable of stably operating in a high voltage battery system, a method of improving oxidation resistance by fluorinating a conventional non-aqueous solvent has been studied.

For example, in Patent Document 3, there is a description of a graphite negative electrode 5.0 V class battery using a non-aqueous electrolyte solution in which 4,5-difluoroethylene carbonate obtained by fluorinating cyclic carbonate and ethylene carbonate are mixed, Examples The inhibitory effect of gas generation has been confirmed. However, with regard to battery characteristics, only improvements in initial capacity and initial load characteristics have been confirmed, and durability battery characteristics are still unclear.

In addition, the electrolytic solution composed of only such a highly viscous solvent is not only significantly deteriorated in battery characteristics at low temperatures in a non-aqueous electrolytic solution, but also difficult to handle during injection, and the wettability of the separator is very low. Lose.

In Patent Documents 4 and 5, as a method for improving battery characteristics such as cycle characteristics in a 4.2 to 4.3 V battery based on a graphite negative electrode, that is, a battery having a positive electrode potential of approximately 4.35 V, ethylene carbonate and 4-fluoroethylene A technology related to a mixed non-aqueous electrolyte solution of carbonate and fluorinated chain carbonate is described. However, in the present technology, it is essential to contain a carboxylic acid ester or a non-fluorinated chain carbonate for the purpose of improving the rate characteristics of the battery or reducing the viscosity of the electrolyte solution, and the positive electrode potential is 4.35 V. In the above region, there is a concern about their oxidative decomposition. The patent document does not disclose a means for solving these problems.

In addition, Patent Document 6 describes a non-aqueous electrolyte solution in which ethylene carbonate, 4-fluoroethylene carbonate, and fluorinated chain carbonate are mixed for the purpose of reducing cycle deterioration and suppressing the generation of gas. In the literature as well as in the above known literature, only a technique relating to a battery using a low-potential region of a specific LiCoO ₂ positive electrode is disclosed in Examples. The patent document does not disclose a technique for solving high-temperature storage under a high voltage in which the upper limit operating potential of the positive electrode exceeds 4.35 V and deterioration in durability during cycling.

Patent Document 7 discloses a technology for suppressing capacity deterioration using a mixed solvent of cyclic carbonate, fluorinated cyclic carbonate, and fluorinated chain carbonate for a 4.3 V-based battery using a silicon negative electrode. However, in the graphite negative electrode exemplified as a negative electrode other than silicon, only remarkable deterioration in capacity due to reductive decomposition of the fluorinated cyclic carbonate appears, and the patent document discloses only the characteristics of the technology for suppressing deterioration of the silicon negative electrode. . In addition, there is no mention or suggestion of a high-voltage battery exceeding 4.3 V in the patent document.

Patent Document 8 discloses a technique for reducing swelling due to high temperature charge/discharge cycle characteristics and high temperature storage gas by using a mixed solvent of cyclic carbonate, fluorinated cyclic carbonate, and fluorinated chain carbonate with a battery of 4.35 V or more. Has been. However, what is actually confirmed is the result at 4.4 V, and the characteristic in the higher voltage region is not known.

Japanese Laid-Open Patent Publication No. Hei 8-45545 Japanese Laid-Open Patent Publication No. Hei 4-87156 Japanese Unexamined Patent Publication No. 2003-168480 International Publication No. 2010/004952 International Publication No. 2010/013739 International Publication No. 2007/043526 Japanese Unexamined Patent Publication No. 2007-294433 Japanese Unexamined Patent Publication No. 2007-250415

The present invention solves the above-described various problems that arise when trying to achieve the performance required for recent secondary batteries, and in particular, in a battery having a high upper limit operating potential of a positive electrode, a low amount of gas generated and high temperature cycle durability characteristics It is an object to provide this excellent nonaqueous electrolyte secondary battery.

In order to solve the above problems, the inventors repeated intensive studies to solve the above problems. As a result of using a specific solvent as a nonaqueous electrolyte used in a nonaqueous electrolyte secondary battery, the upper limit potential of the positive electrode was 4.5 V or higher based on Li/Li ⁺ In this regard, it was found that a non-aqueous electrolyte secondary battery having excellent durability characteristics such as a low amount of gas generated and a high-temperature cycle can be realized, and the present invention was completed.

That is, the gist of the present invention is as follows.

a) A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a lithium salt and a non-aqueous solvent that dissolves the same, a negative electrode capable of storing and releasing lithium ions, and a positive electrode, wherein the upper limit operating potential of the positive electrode is Li/Li ⁺ 4.5 V or more as a reference, the non-aqueous electrolyte is a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain carbonate represented by the following general formula (3) A non-aqueous electrolyte secondary battery containing more than 15 vol% of a cyclic carbonate represented by the general formula (1) in the non-aqueous solvent.

[Formula 1]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 2]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 3]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do)

b) The non-aqueous electrolyte secondary battery according to a), wherein in the non-aqueous electrolyte solution, the total amount of carbonates represented by the general formulas (1) to (3) is 50 vol% or more of the non-aqueous solvent.

c) The non-aqueous electrolyte secondary battery according to a) or b), wherein in the non-aqueous electrolyte, the fluorinated chain carbonate represented by the general formula (3) is contained in a non-aqueous solvent in an amount of 5% by volume or more.

d) In the non-aqueous electrolyte solution, the total amount of carbonates represented by the general formulas (1) and (2) is 25 vol% or more of the non-aqueous solvent, wherein the non-aqueous electrolyte secondary solution according to any one of a) to c) battery.

e) The non-aqueous electrolyte secondary battery according to any one of a) to d), wherein in the non-aqueous electrolyte, the cyclic carbonate represented by the general formula (1) is contained in a non-aqueous solvent at 20% by volume or more. .

f) The non-aqueous electrolyte secondary battery according to any one of a) to e), wherein the cyclic carbonate represented by the general formula (1) is at least one selected from ethylene carbonate and propylene carbonate.

g) In any one of a) to f), characterized in that the fluorinated cyclic carbonate represented by the general formula (2) is at least one selected from 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate. Non-aqueous electrolyte secondary battery described.

h) The nonaqueous electrolyte secondary battery according to any one of a) to g), wherein the fluorinated chain carbonate represented by the general formula (3) contains trifluoroethylmethylcarbonate.

i) Any one of a) to h) characterized in that the positive electrode contains a positive electrode active material containing at least one selected from the group consisting of lithium transition metal compounds represented by the following general formulas (4) to (6). The nonaqueous electrolyte secondary battery described in.

Li[Li _a M _x Mn _{2 -xa} ]O _4+δ … (4)

(In formula (4), 0 ≤ a ≤ 0.3, 0.4 <x <1.1, -0.5 <δ <0.5 is satisfied, and M is at least one of transition metals selected from Ni, Cr, Fe, Co, and Cu. Indicate)

Li _x M1 _y M2 _z O _{2 -δ} ... (5)

(In formula (5), 1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 0.3, -0.1 ≤ δ ≤ 0.1 is satisfied, M1 represents Ni, Co and/or Mn, and M2 represents Fe , Cr, V, Ti, Cu, Ga, Bi, Sn, B, P, Zn, Mg, Ge, Nb, W, Ta, Be, Al, Ca, Sc, and at least one of the elements selected from Zr )

αLi₂MO₃·(1-α) LiM'O₂ … (6)

(In formula (6), 0<α<1 is satisfied, M represents at least one metal element with an average oxidation number of +4, and M'represents at least one metal element with an average oxidation number of +3)

j) The non-aqueous electrolyte secondary battery according to any one of a) to i), wherein the negative electrode contains a negative electrode active material made of graphite particles.

k) A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a lithium salt and a non-aqueous solvent that dissolves the same, a negative electrode capable of storing and releasing lithium ions, and a positive electrode, wherein the non-aqueous electrolyte is represented by the following general formula (1) A cyclic carbonate represented by, a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain carbonate represented by the following general formula (3), and a cyclic type represented by the general formula (1) in a non-aqueous solvent It is characterized in that it contains more than 15% by volume of carbonate, and the positive electrode contains a positive electrode active material containing at least one selected from the group consisting of lithium transition metal compounds represented by the following general formulas (4) to (6). Non-aqueous electrolyte secondary battery.

[Formula 4]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 5]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 6]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do)

Li[Li _a M _x Mn _{2 -xa} ]O _4+δ … (4)

(In formula (4), 0 ≤ a ≤ 0.3, 0.4 <x <1.1, -0.5 <δ <0.5 is satisfied, and M is at least one of transition metals selected from Ni, Cr, Fe, Co, and Cu. Indicate)

Li _x M1 _y M2 _z O _{2 -δ} ... (5)

(In formula (5), 1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 0.3, -0.1 ≤ δ ≤ 0.1 is satisfied, M1 represents Ni, Co and/or Mn, and M2 represents Fe , Cr, V, Ti, Cu, Ga, Bi, Sn, B, P, Zn, Mg, Ge, Nb, W, Ta, Be, Al, Ca, Sc, and at least one of the elements selected from Zr )

αLi₂MO₃·(1-α)LiM'O₂ … (6)

(In formula (6), 0<α<1 is satisfied, M represents at least one metal element with an average oxidation number of +4, and M'represents at least one metal element with an average oxidation number of +3)

l) a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous solvent dissolving it, wherein the non-aqueous electrolyte is a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), And a fluorinated chain carbonate represented by the following general formula (3), and a cyclic carbonate represented by the general formula (1) is contained in a proportion of more than 20% by volume in the nonaqueous solvent.

[Formula 7]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 8]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 9]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do)

m) Use of a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous solvent dissolving it for a non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte secondary battery has an upper limit operating potential of the positive electrode of 4.5 based on Li/Li ⁺ A secondary battery used at V or higher, wherein the non-aqueous electrolyte is a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain represented by the following general formula (3) Use of a nonaqueous electrolytic solution for a nonaqueous electrolytic secondary battery, characterized in that it contains a type carbonate and contains more than 15% by volume of a cyclic carbonate represented by the general formula (1) in the nonaqueous solvent.

[Formula 10]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 11]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

[Formula 12]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do.)

In designing a battery having a high operating voltage, a method of improving battery durability such as storage characteristics and cycle characteristics by using a fluorinated-modified non-aqueous electrolyte solution, which is conventionally considered to have high oxidation resistance, has been generally proposed.

On the other hand, it has been considered that the cyclic carbonate solvent represented by the general formula (1) is not suitable for high-voltage systems because of its low resistance to the positive electrode oxidation reaction, but in the present invention, the cyclic carbonate solvent represented by the general formula (1) One of the features is that cyclic carbonate is introduced into a non-aqueous electrolyte. That is, the inventors of the present invention use a cyclic carbonate represented by the general formula (1), which has been considered to be disadvantageous for high voltage systems, as an essential solvent, and a mixture of a fluorinated cyclic carbonate and a fluorinated chain carbonate is surprisingly completely fluorinated. Compared to the non-aqueous electrolyte solution composed of a solvent, battery durability has been dramatically improved, and findings capable of solving the above problems have been found to complete the present invention.

According to the present invention, in particular, in a lithium secondary battery designed with a high voltage specification, not only excellent durability characteristics such as cycle and storage of the battery at high temperatures, but also excellent battery characteristics at low temperatures are also excellent. An aqueous electrolyte secondary battery can be provided.

Hereinafter, an embodiment of the present invention will be described in detail, but the present invention is not limited to these, and can be carried out with arbitrary modifications.

As the nonaqueous electrolyte secondary battery of the present invention, particularly, a lithium secondary battery is mentioned as a preferred example. The nonaqueous electrolyte secondary battery of the present invention can take a known structure, and typically includes a negative electrode and a positive electrode capable of storing and releasing ions (for example, lithium ions), a nonaqueous electrolyte, and a separator.

1. Non-aqueous electrolyte

1-1. Non-aqueous solvent

1-1-1. menstruum

The non-aqueous electrolyte solution according to the present invention contains a cyclic carbonate represented by the following general formula (1), and a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain type represented by the following general formula (3) It is characterized by containing carbonate. In addition, as the non-aqueous solvent, it is possible to use a non-fluorinated chain carbonate, a cyclic and chain carboxylic acid ester, an ether compound, a sulfone compound, and the like.

<cyclic carbonate represented by general formula (1)>

[Formula 13]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

R ₁ is hydrogen or a hydrocarbon group which may have a substituent, but examples of the hydrocarbon group which may have a substituent include an alkyl group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, etc. are mentioned.

Examples of the cyclic carbonate represented by the general formula (1) (hereinafter, also referred to as a non-fluorinated cyclic carbonate) include those having an alkylene group having 2 to 4 carbon atoms.

Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, etc. are mentioned as a cyclic carbonate which has a C2-C4 alkylene group. Among them, ethylene carbonate and propylene carbonate are particularly preferable in terms of improving battery characteristics resulting from an improvement in lithium ion dissociation degree and improving durability of the battery.

The cyclic carbonate represented by the general formula (1) may be used alone or in combination of two or more in any combination and ratio.

The amount of the cyclic carbonate represented by the general formula (1) is not particularly limited as long as it is more than 15% by volume in 100% by volume of the non-aqueous solvent, and is arbitrary as long as the effect of the present invention is not significantly impaired, but the lower limit of the amount Silver is preferably 20% by volume or more, more preferably 25% by volume or more, and most preferably 30% by volume or more in 100% by volume of the non-aqueous solvent. By setting it as this range, the decrease in electrical conductivity resulting from the decrease in the dielectric constant of the nonaqueous electrolyte solution is avoided, and the high current discharge characteristics, stability to the negative electrode, and cycle characteristics of the nonaqueous electrolyte secondary battery are easily set within a favorable range. Moreover, the upper limit is preferably 70% by volume or less, more preferably 65% by volume or less, and most preferably 60% by volume or less. By setting it as this range, the viscosity of a nonaqueous electrolyte solution is made into an appropriate range, a fall of ionic conductivity is suppressed, and it becomes easy to make the load characteristic and durability of a nonaqueous electrolyte secondary battery into a favorable range further.

<Fluorinated cyclic carbonate represented by general formula (2)>

[Formula 14]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group which may have a substituent, and may be the same or different from each other.)

R ₂ is hydrogen, fluorine, or a hydrocarbon group which may have a substituent, but examples of the hydrocarbon group which may have a substituent include an alkyl group having 1 to 4 carbon atoms, a monofluoroalkyl group having 1 to 4 carbon atoms, and a difluoro having 1 to 4 carbon atoms. A roalkyl group and a C1-C4 trifluoroalkyl group, preferably a C1-C2 alkyl group, a C1-C2 monofluoroalkyl group, a C1-C2 difluoroalkyl group, and a C1-C2 alkyl group The trifluoroalkyl group of is mentioned. Specifically, a methyl group, a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, an ethyl group, a monofluoroethyl group, a difluoroethyl group, a trifluoroethyl group, and the like are mentioned.

Examples of the fluorinated cyclic carbonate represented by the general formula (2) include derivatives of cyclic carbonates having an alkylene group having 2 to 6 carbon atoms.

Specific examples of the fluorinated cyclic carbonate include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (eg, an alkyl group having 1 to 4 carbon atoms).

The number of fluorine atoms in the fluorinated cyclic carbonate is not particularly limited as long as it is 1 or more, but preferably 1 to 8 fluorine atoms.

Specifically, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4 -Methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4-(difluoromethyl)-ethylene carbonate, 4-(fluoromethyl)- 4-fluoroethylene carbonate, 4-(fluoromethyl)-5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate And 4,4-difluoro-5,5-dimethylethylene carbonate.

Among them, selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate At least one species imparts high ionic conductivity and is more preferable in terms of forming an interfacial protective film preferably, and furthermore, at least one species selected from monofluoroethylene carbonate and 4,5-difluoroethylene carbonate is preferable. In particular, fluoroethylene carbonate is preferable because it makes it easy to make the storage characteristics and cycle characteristics of the nonaqueous electrolyte secondary battery within a good range.

The fluorinated cyclic carbonate represented by the general formula (2) may be used alone or in combination of two or more in any combination and ratio.

The blending amount of the fluorinated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention, but in 100% by volume of the non-aqueous solvent, preferably at least 1% by volume, more preferably at least 2% by volume , Most preferably 4% by volume or more, preferably 40% by volume or less, more preferably 30% by volume or less, and most preferably 15% by volume or less. Within this range, the nonaqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and it is easy to avoid a decrease in the discharge capacity retention rate due to a decrease in high temperature storage characteristics or an increase in the amount of gas generated.

In addition, the total amount (compounding amount) of the cyclic carbonate represented by the general formula (1) and the fluorinated cyclic carbonate represented by the general formula (2) is in 100% by volume of the non-aqueous solvent, preferably more than 15% by volume, and more preferably It is preferably 20% by volume or more, most preferably 25% by volume or more, and preferably 98% by volume or less, more preferably 95% by volume or less, and still more preferably 90% by volume or less. Within this range, the nonaqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid a decrease in high temperature storage characteristics and a decrease in discharge capacity retention due to an increase in the amount of gas generated. In addition, in 100% by volume of a cyclic carbonate solvent composed of a cyclic carbonate represented by the general formula (1) and a fluorinated cyclic carbonate represented by the general formula (2), the amount of the cyclic carbonate represented by the general formula (1) is preferably Preferably it is 50% or more, more preferably 55% or more, and still more preferably 60% or more. By specifying the amount of the non-fluorinated cyclic carbonate in this way, there is a tendency that the amount of gas generated is suppressed and the effect of improving the cycle characteristics is also easily expressed.

In addition, the fluorinated cyclic carbonate represented by the general formula (2) exhibits an effective function not only as a solvent but also as an auxiliary agent described in the following 1-3. When the fluorinated cyclic carbonate represented by the general formula (2) is used as both a solvent and an auxiliary agent, there is no clear boundary in the blending amount, and the blending amount described in the shear lock can be followed as it is.

<Fluorinated chain carbonate represented by general formula (3)>

[Formula 15]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do)

R ₃ may have a substituent and is a hydrocarbon group containing at least one fluorine, but examples of such a hydrocarbon group include a C 1 to C 4 monofluoroalkyl group, a C 1 to C 4 difluoroalkyl group, and a C 1 to C 4 carbon atom. The trifluoroalkyl group of, Preferably, a C1-C2 monofluoroalkyl group, a C1-C2 difluoroalkyl group, and a C1-C2 trifluoroalkyl group are mentioned. Specifically, a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a monofluoroethyl group, a difluoroethyl group, and a trifluoroethyl group are mentioned.

R ₄ is a hydrocarbon group which may have a substituent, but examples of the hydrocarbon group which may have a substituent include an alkyl group having 1 to 4 carbon atoms, a monofluoroalkyl group having 1 to 4 carbon atoms, a difluoroalkyl group having 1 to 4 carbon atoms, and A trifluoroalkyl group having 1 to 4, preferably an alkyl group having 1 to 2 carbon atoms, a monofluoroalkyl group having 1 to 2 carbon atoms, a difluoroalkyl group having 1 to 2 carbon atoms, and a trifluoroalkyl group having 1 to 2 carbon atoms Can be mentioned. Specifically, a methyl group, a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, an ethyl group, a monofluoroethyl group, a difluoroethyl group, a trifluoroethyl group, and the like are mentioned.

As the fluorinated chain carbonate represented by the general formula (3), those having 3 to 7 carbon atoms are preferable. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, and preferably 4 or less. When a fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or to different carbons. Examples of fluorinated chain carbonates include fluorinated dimethyl carbonate derivatives, fluorinated ethylmethyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

Examples of fluorinated dimethyl carbonate derivatives include fluoromethylmethylcarbonate, difluoromethylmethylcarbonate, trifluoromethylmethylcarbonate, bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, and bis(trifluoromethyl). ) Carbonate, etc. are mentioned.

Examples of fluorinated ethyl methyl carbonate derivatives include (2-fluoroethyl) methyl carbonate, ethyl fluoromethyl carbonate, (2,2-difluoroethyl) methyl carbonate, (2-fluoroethyl) fluoromethyl carbonate, and ethyl Difluoromethylcarbonate, (2,2,2-trifluoroethyl)methylcarbonate, (2,2-difluoroethyl)fluoromethylcarbonate, (2-fluoroethyl)difluoromethylcarbonate, ethyl Trifluoromethyl carbonate, etc. are mentioned.

Examples of fluorinated diethyl carbonate derivatives include ethyl-(2-fluoroethyl) carbonate, ethyl-(2,2-difluoroethyl) carbonate, bis(2-fluoroethyl) carbonate, ethyl-(2,2, 2-trifluoroethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl- 2'-fluoroethyl carbonate, 2,2,2-trifluoroethyl-2',2'-difluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, etc. are mentioned. .

The fluorinated chain carbonate represented by the general formula (3) may be used singly, or two or more may be used in any combination and ratio.

The blending amount of the fluorinated chain carbonate represented by the general formula (3) is preferably 1% by volume or more, more preferably 5% by volume or more, still more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent, Most preferably, it is 15 vol% or more. By containing the fluorinated chain carbonate in such a lower limit range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, making it easy to handle when injecting, and suppressing a decrease in ionic conductivity, and furthermore, a non-aqueous electrolyte secondary battery It becomes easy to make the high-current discharge characteristics and battery characteristics at low temperature in a favorable range. In addition, the fluorinated chain carbonate represented by the general formula (3) is preferably 90% by volume or less, more preferably 80% by volume or less, and most preferably 75% by volume or less in 100% by volume of the non-aqueous solvent. Do. By setting the upper limit in this way, a decrease in electrical conductivity resulting from a decrease in the dielectric constant of the nonaqueous electrolyte solution is avoided, and the high current discharge characteristics of the nonaqueous electrolyte secondary battery and the battery characteristics at low temperatures are easily set within a favorable range.

In addition, the total amount (compounding amount) of the cyclic carbonate represented by the general formula (1) and the fluorinated chain carbonate represented by the general formula (3) is in 100% by volume of the non-aqueous solvent, preferably more than 15% by volume, and more preferably Preferably, it is 30% by volume or more, most preferably 50% by volume or more, and preferably 97% by volume or less, and more preferably 95% by volume or less. Within this range, the nonaqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid a decrease in high temperature storage characteristics and a decrease in discharge capacity retention due to an increase in the amount of gas generated.

In addition, the total amount (compound amount) of the cyclic carbonate represented by the general formula (1), the fluorinated cyclic carbonate represented by the general formula (2), and the fluorinated chain carbonate represented by the general formula (3) is 100% by volume of the non-aqueous solvent. Among them, it is 50% by volume or more, preferably 70% by volume or more, more preferably 75% by volume or more, and most preferably 85% by volume or more. Within this range, not only the durability of the battery is excellent, but also the viscosity of the non-aqueous electrolyte is set in an appropriate range to suppress a decrease in ionic conductivity, and furthermore, the high current discharge characteristics of the non-aqueous electrolyte secondary battery or the battery characteristics at low temperatures are improved. It becomes easy to make it into a favorable range. In addition, the upper limit is not particularly set and may be 100% by volume.

1-1-2. Other solvents

In addition to the cyclic carbonate represented by the general formula (1), the fluorinated cyclic carbonate represented by the general formula (2), and the fluorinated chain carbonate represented by the general formula (3), in the range not impairing the effect of the present invention, various You may mix and use a solvent. Examples of these solvents include non-fluorinated chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, ether compounds, sulfone compounds, and the like.

<Non-fluorinated chain carbonate>

As the non-fluorinated chain carbonate, those having 3 to 7 carbon atoms are preferable. Specifically, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, di-i-propyl carbonate, n-propyl-i-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate , i-butyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, i-butyl ethyl carbonate, t-butyl ethyl carbonate, and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, di-i-propyl carbonate, n-propyl-i-propyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferable, and particularly preferably Is dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

The blending amount of the non-fluorinated chain carbonate is usually 0.1% by volume or more, more preferably 0.3% by volume or more, and still more preferably 0.5% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, it becomes easy to improve the electric conductivity of the nonaqueous electrolyte solution and to improve the high current discharge characteristics of the nonaqueous electrolyte secondary battery. Moreover, the compounding amount of the non-fluorinated chain carbonate is preferably 40% by volume or less, and more preferably 35% by volume or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and the high-current discharge characteristics of the non-aqueous electrolyte secondary battery are easily in a good range. .

<cyclic carboxylic acid ester>

Examples of the cyclic carboxylic acid ester include those having 3 to 12 carbon atoms in the total number of carbon atoms in the structural formula.

Specifically, gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, etc. are mentioned. Among them, gamma butyrolactone is particularly preferred from the viewpoint of improving battery characteristics resulting from an improvement in lithium ion dissociation degree.

The blending amount of the cyclic carboxylic acid ester is usually 0.3% by volume or more, more preferably 0.5% by volume or more, and still more preferably 1% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, it becomes easy to improve the electric conductivity of the nonaqueous electrolyte solution and to improve the high current discharge characteristics of the nonaqueous electrolyte secondary battery. Moreover, the blending amount of the cyclic carboxylic acid ester is preferably 15% by volume or less, more preferably 10% by volume or less, and still more preferably 5% by volume or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and the high-current discharge characteristics of the non-aqueous electrolyte secondary battery are easily in a good range. .

<Chain type carboxylic acid ester>

Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in total in the structural formula.

Specifically, methyl acetate, ethyl acetate, acetate-n-propyl, isopropyl acetate, acetate-n-butyl, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propionate-n-propyl, isopropionate Propyl, propionate-n-butyl, propionate isobutyl, propionate-t-butyl, methyl butyrate, ethyl butyrate, butyric acid-n-propyl, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyrate-n-propyl, iso Isopropyl butyrate, and the like.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl, acetate-n-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improvement of.

The blending amount of the chain carboxylic acid ester is usually in 100% by volume of the non-aqueous solvent, preferably at least 0.3% by volume, more preferably at least 0.5% by volume, and still more preferably at least 1% by volume. By setting the lower limit in this way, it becomes easy to improve the electric conductivity of the nonaqueous electrolyte solution and to improve the high current discharge characteristics of the nonaqueous electrolyte secondary battery. Further, the blending amount of the chain carboxylic acid ester is preferably 15% by volume or less, more preferably 10% by volume or less, and still more preferably 5% by volume or less in 100% by volume of the non-aqueous solvent. By setting the upper limit in this way, an increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery are easily set within a favorable range.

<Ether compound>

As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms in which some hydrogens may be substituted with fluorine are preferable.

Examples of chain ethers having 3 to 10 carbon atoms include diethyl ether, bis(2-fluoroethyl) ether, bis(2,2-difluoroethyl) ether, and bis(2,2,2-trifluoroethyl). ) Ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoro Ethyl) (2,2,2-trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (1,1,2,2-tetrafluoro Roethyl) (2,2,2-trifluoroethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n -Propyl) ether, ethyl (2,2,3,3-tetrafluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoro Roethyl-n-propyl ether, (2-fluoroethyl) (3-fluoro-n-propyl) ether, (2-fluoroethyl) (3,3,3-trifluoro-n-propyl) ether , (2-fluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3,3-pentafluoro-n -Propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (3-fluoro-n-propyl) (2,2,2-trifluoroethyl) ether, (2,2, 2-trifluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,2-trifluoro Roethyl) ether, (2,2,3,3,3-pentafluoro-n-propyl) (2,2,2-trifluoroethyl) ether, n-propyl (1,1,2,2- Tetrafluoroethyl) ether, (3-fluoro-n-propyl) (1,1,2,2-tetrafluoroethyl) ether, (1,1,2,2-tetrafluoroethyl) (3, 3,3-trifluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2, 2,3,3,3-pentafluoro-n-propyl) (1,1,2,2-tetrafluoroethyl) ether, di-n-propyl ether, (3-fluoro-n-propyl) ( n-propyl) ether, (n-propyl) (3,3,3-trifluoro- n-propyl) ether, (n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3,3-pentafluoro-n-propyl) ( n-propyl) ether, bis(3-fluoro-n-propyl) ether, (3-fluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, (3-fluoro Rho-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3,3-pentafluoro- n-propyl) ether, bis(3,3,3-trifluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (3,3,3-trifluoro Rho-n-propyl) ether, (2,2,3,3,3-pentafluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, bis (2,2, 3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) Ether, bis(2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, ethoxymethoxymethane, (2-fluoroethoxy)methoxy Methoxymethane, methoxy(2,2,2-trifluoroethoxy)methane, methoxy(1,1,2,2-tetrafluoroethoxy)methane, diethoxymethane, ethoxy(2-fluoro) Ethoxy) methane, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, bis (2-fluoroethoxy) Methane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)methane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane, Bis(2,2,2-trifluoroethoxy)methane, (1,1,2,2-tetrafluoroethoxy)(2,2,2-trifluoroethoxy)methane, bis(1, 1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, ethoxymethoxyethane, (2-fluoroethoxy) methoxyethane, methoxy (2,2,2-trifluoroethoxy) )Ethane, methoxy (1,1,2,2-tetrafluoroethoxy) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoro Ethoxy)ethane, ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, bis(2-fluoroethoxy)ethane, (2-flu Oroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, bis (2,2, 2-trifluoroethoxy)ethane, (1,1,2,2-tetrafluoroethoxy)(2,2,2-trifluoroethoxy)ethane, bis(1,1,2,2- Tetrafluoroethoxy)ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

As a C3-C6 cyclic ether, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl -1,3-dioxane, 1,4-dioxane, and the like, and fluorinated compounds thereof.

Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability for lithium ions. , From the viewpoint of improving ionic dissociation property, and particularly preferably, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane from the viewpoint of providing low viscosity and high ionic conductivity.

The blending amount of the ether-based compound is usually in 100% by volume of the non-aqueous solvent, preferably at least 0.3% by volume, more preferably at least 0.5% by volume, still more preferably at least 1% by volume, and preferably 40% by volume. % Or less, more preferably 35 volume% or less, still more preferably 30 volume% or less. Within this range, it is easy to ensure the effect of improving the degree of dissociation of lithium ions of the chain ether and the improvement of the ionic conductivity resulting from the decrease in viscosity. When the negative electrode active material is a carbonaceous material, the chain ether is co-valent with lithium ions. It is easy to avoid the situation that the capacity is reduced due to insertion.

<Sulfone compound>

As the sulfone-based compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. It is preferable that the number of sulfonyl groups in one molecule is 1 or 2.

Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones which are monosulfone compounds; Trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones, which are disulfone compounds, may be mentioned. Among them, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

As the sulfolane, a sulfolane and/or a sulfolane derivative (hereinafter, sulfolane may also be abbreviated as "sulfolane" in some cases) is preferable. As the sulfolane derivative, it is preferable that at least one of the hydrogen atoms bonded on the carbon atom constituting the sulfolane ring is substituted with a fluorine atom or an alkyl group. Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2 ,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane , 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro- 3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoromethylsulfolane , 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3-(trifluoromethyl)sulfolane, 3-fluoro-3-(trifluoromethyl)sulfolane , 4-fluoro-3-(trifluoromethyl)sulfolane, 5-fluoro-3-(trifluoromethyl)sulfolane, and the like are preferable in terms of high ionic conductivity and high input/output.

In addition, as a chain sulfone, dimethylsulfone, ethylmethylsulfone, diethylsulfone, methyl-n-propylsulfone, ethyl-n-propylsulfone, di-n-propylsulfone, i-propylmethylsulfone, isopropylethylsulfone , Diisopropylsulfone, n-butylmethylsulfone, n-butylethylsulfone, t-butylmethylsulfone, t-butylethylsulfone, fluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, (2-fluoro)ethylmethylsulfone, (2,2-difluoroethyl)methylsulfone, trifluoroethylmethylsulfone, pentafluoroethylmethylsulfone, ethylfluoromethylsulfone, ethyldifluoromethylsulfone, Ethyltrifluoromethylsulfone, perfluoroethylmethylsulfone, ethyl(2,2,2-trifluoroethyl)sulfone, ethylpentafluoroethylsulfone, bis(trifluoroethyl)sulfone, bis(perfluoro Ethyl)sulfone, fluoromethyl-n-propylsulfone, difluoromethyl-n-propylsulfone, trifluoromethyl-n-propylsulfone, fluoromethyl-i-propylsulfone, difluoromethyl-i-propyl Sulfone, trifluoromethyl-i-propylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethyl-i-propylsulfone, pentafluoroethyl-n-propylsulfone, pentafluoroethyl-i-propyl Sulfone, n-butyl (2,2,2-trifluoroethyl) sulfone, t-butyl (2,2,2-trifluoroethyl) sulfone, n-butylpentafluoroethylsulfone, t-butylpentafluoro Roethyl sulfone, etc. are mentioned.

Among them, dimethylsulfone, ethylmethylsulfone, diethylsulfone, methyl-n-propylsulfone, methyl-i-propylsulfone, methyl-n-butylsulfone, t-butylmethylsulfone, fluoromethylmethylsulfone, difluoro Methylmethylsulfone, trifluoromethylmethylsulfone, (2-fluoroethyl)methylsulfone, (2,2-difluoroethyl)methylsulfone, methyltrifluoroethylsulfone, methylpentafluoroethylsulfone, ethylfluoro Romethylsulfone, difluoromethylethylsulfone, ethyltrifluoromethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoroethylsulfone, n-propyltrifluoromethylsulfone, i-propyltrifluoromethylsulfone, n-butyltrifluoroethylsulfone, t-butyltrifluoroethylsulfone, n-butyltrifluoromethylsulfone, t-butyltrifluoromethylsulfone, etc. are preferable in terms of high ionic conductivity and high input/output.

The blending amount of the sulfone compound is usually in 100% by volume of the non-aqueous solvent, preferably at least 0.3% by volume, more preferably at least 0.5% by volume, still more preferably at least 1% by volume, and more preferably 40 It is volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 30 volume% or less. Within this range, it is easy to obtain an effect of improving durability such as cycle characteristics and storage characteristics, and by setting the viscosity of the non-aqueous electrolyte to an appropriate range, a decrease in electrical conductivity can be avoided, and charging and discharging of the non-aqueous electrolyte secondary battery In the case of performing at a high current density, it is easy to avoid the situation that the charge/discharge capacity retention rate is lowered.

1-2. Electrolyte

<Lithium salt>

As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any one can be used. Specifically, the following ones are mentioned.

For example, inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiNbF ₆ , LiTaF ₆ and LiWF ₇ ;

Lithium fluorophosphates such as LiPO ₃ F and LiPO ₂ F ₂ ;

Lithium tungstate, such as LiWOF ₅ ;

HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Lithium carboxylate salts such as CO ₂ Li and CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;

FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ Lithium sulfonic acid salts such as CF ₂ CF ₂ SO ₃ Li;

LiN(FCO) ₂ , LiN(FCO)(FSO ₂ ), LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) Lithium imide salts; Lithium methide salts such as LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , and LiC(C ₂ F ₅ SO ₂ ) ₃ ;

Lithium oxalato borate salts such as lithium difluorooxalatoborate and lithium bis(oxalato)borate;

Lithium oxalato phosphate salts such as lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, and lithium tris (oxalato) phosphate;

In addition, LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF ₃ C ₃ F ₇ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) Fluorinated organic lithium salts such as ₂ ; And the like.

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , LiPO ₂ F ₂ , FSO ₃ Li, CF ₃ SO ₃ Li, LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide , LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxala Tophosphate, lithium difluorobisoxalatophosphate, lithium tris (oxalato) phosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ and the like are particularly preferred in that they have an effect of improving output characteristics, high-rate charge/discharge characteristics, high temperature storage characteristics, cycle characteristics, and the like.

These lithium salts may be used alone or in combination of two or more. A preferred example in the case of using two or more types together is LiPF ₆ and LiBF ₄ , LiPF ₆ and FSO ₃ Li, and LiPF ₆ and LiPO ₂ F ₂ in combination, and there is an effect of improving load characteristics and cycle characteristics. Among these, the combination of LiPF ₆ and FSO ₃ Li, and LiPF ₆ and LiPO ₂ F ₂ is preferable because the effect is remarkable.

When LiPF ₆ and LiBF ₄ and LiPF ₆ and FSO ₃ Li are used in combination, the concentration of LiBF ₄ or FSO ₃ Li relative to the total 100% by mass of the non-aqueous electrolyte is not limited in the amount of mixing, and the effect of the present invention is not significantly inhibited. Unless it is arbitrary, with respect to the non-aqueous electrolytic solution, it is usually 0.01 mass% or more, preferably 0.1 mass% or more, while its upper limit is usually 30 mass% or less, preferably 20 mass% or less, more preferably By setting it as 10 mass% or less, more preferably 5 mass% or less, effects, such as output characteristic, load characteristic, low temperature characteristic, cycle characteristic, high temperature characteristic, may improve. On the other hand, even in the case of the combination of LiPF ₆ and LiPO ₂ F ₂ , the concentration of LiPO ₂ F ₂ relative to the total 100 mass% of the non-aqueous electrolyte is not limited in the amount of the mixture, and is arbitrary as long as the effect of the present invention is not significantly impaired. , With respect to the non-aqueous electrolytic solution, it is usually 0.001 mass% or more, preferably 0.01 mass% or more, and the upper limit thereof is usually 10 mass% or less, preferably 5 mass% or less. In this range, effects such as output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, and high-temperature characteristics are improved. On the other hand, if too much, it may precipitate at a low temperature to lower the battery characteristics, and if too small, the effect of improving such as low temperature characteristics, cycle characteristics, and high temperature storage characteristics may decrease.

Here, in the case of containing LiPO ₂ F ₂ in the electrolytic solution, the preparation of the electrolytic solution is a method of adding LiPO ₂ F ₂ synthesized by a separately known method to an electrolytic solution containing LiPF ₆ , or a battery configuration such as an active material or an electrode plate described later. A method of generating LiPO ₂ F ₂ in a system when water is allowed to coexist in the urea and the battery is assembled using an electrolytic solution containing LiPF ₆ , and any method may be used in the present invention.

The method for measuring the content of LiPO ₂ F ₂ in the non-aqueous electrolyte and the non-aqueous electrolyte secondary battery is not particularly limited, and any known method may be used, but specifically, ion chromatography or F Nuclear magnetic resonance spectroscopy (hereinafter, it may be omitted in NMR), and the like.

Another example is the combination of an inorganic lithium salt and an organic lithium salt, and the combination of both has an effect of suppressing deterioration due to high temperature storage. As organic lithium salt, CF ₃ SO ₃ Li, LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , Lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , It is preferably LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _{3 or the} like. In this case, the ratio of the organolithium salt to the total 100 mass% of the non-aqueous electrolyte solution is preferably 0.1 mass% or more, particularly preferably 0.5 mass% or more, preferably 30 mass% or less, particularly preferably 20 mass% % Or less.

The concentration of these lithium salts in the non-aqueous electrolytic solution is not particularly limited as long as the effect of the present invention is not impaired. However, since the electric conductivity of the electrolytic solution is in a good range and good battery performance is ensured, The total molar concentration of lithium is preferably 0.3 mol/L or more, more preferably 0.4 mol/L or more, still more preferably 0.5 mol/L or more, and preferably 3 mol/L or less, more preferably Is 2.5 mol/L or less, more preferably 2.0 mol/L or less. In this range, effects such as low-temperature characteristics, cycle characteristics, and high-temperature characteristics are improved. On the other hand, when the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte solution may be insufficient. On the other hand, when the concentration is too high, the electrical conductivity may decrease in order to increase the viscosity, and battery performance may decrease. .

1-3. Supplements

In the nonaqueous electrolyte secondary battery of the present invention, an auxiliary agent may be appropriately used depending on the purpose. As auxiliary agents, compounds having a carbon-carbon triple bond shown below, a cyclic carbonate having an unsaturated bond excluding the carbon-carbon triple bond, an unsaturated cyclic carbonate having a fluorine atom, a cyclic sulfonic acid ester, and a cyano group Compounds, compounds having an isocyanato group, and other auxiliary agents.

<Compound having a carbon-carbon triple bond>

In the non-aqueous electrolyte secondary battery of the present invention, a compound having a carbon-carbon triple bond may be contained in order to form a film on the surface of the negative electrode and achieve a longer battery life. The compound having a carbon-carbon triple bond is not particularly limited as long as it is a compound having a carbon-carbon triple bond, but is classified into a chain compound having a carbon-carbon triple bond and a cyclic compound having a carbon-carbon triple bond. .

As the chain compound having a carbon-carbon triple bond, at least one alkyne derivative represented by the following general formula (11) or formula (12) is preferably used.

[Formula 16]

In General Formulas (11) to (12), R ₁₁ to R ₁₉ each independently represent hydrogen, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ₁₂ and R ₁₃ , R ₁₅ and R ₁₆ , R ₁₇ and R ₁₈ may be bonded to each other to form a C 3 to C 6 cycloalkyl group. x and y represent the integer of 1 or 2. Y ₁ and Y ₂ are each represented by any of the following formulas (13), and may be the same or different.

[Formula 17]

Z ₁ represents hydrogen, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms.

Among the compounds represented by the general formula (11), 2-propynylmethylcarbonate, 1-methyl-2-propynylmethylcarbonate, 1,1-dimethyl-2-propynylmethylcarbonate, 2-propynylethylcarbonate, 1- Methyl-2-propynylethylcarbonate, 1,1-dimethyl-2-propynylethylcarbonate, 2-butynylmethylcarbonate, 1-methyl-2-butynylmethylcarbonate, 1,1-dimethyl-2-butynyl Methyl carbonate, formic acid-2-propynyl, formic acid-1-methyl-2-propynyl, formic acid-1,1-dimethyl-2-propynyl, formic acid-2-butynyl, formic acid-1-methyl-2-buty Nyl, formic acid-1,1-dimethyl-2-butynyl, acetic acid-2-propynyl, acetic acid-1-methyl-2-propynyl, acetic acid-1,1-dimethyl-2-propynyl, acetic acid-2- Butynyl, acetic acid-1-methyl-2-butynyl, acetic acid-1,1-dimethyl-2-butynyl, 2-propynylmethyloxalate, 1-methyl-2-propynylmethyloxalate, 1,1 -Dimethyl-2-propynylmethyloxalate, 2-butynylmethyloxalate, 1-methyl-2-butynylmethyloxalate, 1,1-dimethyl-2-butynylmethyloxalate, 2-propynylethyl Oxalate, 1-methyl-2-propynylethyloxalate, 1,1-dimethyl-2-propynylethyloxalate, 2-butynylethyloxalate, 1-methyl-2-butynylethyloxalate, 1 ,1-dimethyl-2-butynylethyloxalate, methanesulfonic acid-2-propynyl, methanesulfonic acid-1-methyl-2-propynyl, methanesulfonic acid-1,1-dimethyl-2-propynyl, methanesulfonic acid- 2-butynyl, methanesulfonic acid-1-methyl-2-butynyl, methanesulfonic acid-1,1-dimethyl-2-butynyl, trifluoromethanesulfonic acid-2-propynyl, trifluoromethanesulfonic acid-1- Methyl-2-propynyl, trifluoromethanesulfonic acid-1,1-dimethyl-2-propynyl, trifluoromethanesulfonic acid-2-butynyl, trifluoromethanesulfonic acid-1-methyl-2-butynyl, Trifluoromethanesulfonic acid-1,1-dimethyl-2-butynyl, trifluoroethanesulfonic acid-2-propynyl, trifluoroethanesulfonic acid-1-methyl-2-propynyl, trifluoroethanesulfonic acid-1 ,1-dimethyl-2-propynyl, trifluoroethanesulfonic acid-2-butynyl, trifluoroethanesulfonic acid-1-methyl-2-butynyl, trifluoroethanesulfonic acid-1,1 -Dimethyl-2-butynyl, benzenesulfonic acid-2-propynyl, benzenesulfonic acid-1-methyl-2-propynyl, benzenesulfonic acid-1,1-dimethyl-2-propynyl, benzenesulfonic acid-2-butynyl, Benzenesulfonic acid-1-methyl-2-butynyl, benzenesulfonic acid-1,1-dimethyl-2-butynyl, p-toluenesulfonic acid-2-propynyl, p-toluenesulfonic acid-1-methyl-2-propynyl, p-toluenesulfonic acid-1,1-dimethyl-2-propynyl, p-toluenesulfonic acid-2-butynyl, p-toluenesulfonic acid-1-methyl-2-butynyl, p-toluenesulfonic acid-1,1-dimethyl -2-butynyl, methyl sulfate-2-propynyl, methyl sulfate-1-methyl-2-propynyl, methyl sulfate-1,1-dimethyl-2-propynyl, methyl sulfate-2-butynyl, methyl sulfate -1-methyl-2-butynyl, methyl sulfate-1,1-dimethyl-2-propynyl, ethyl sulfate-2-propynyl, ethyl sulfate-1-methyl-2-propynyl, ethyl sulfate-1,1 -At least one selected from dimethyl-2-propynyl, ethyl sulfate-2-butynyl, ethyl sulfate-1-methyl-2-butynyl, and ethyl sulfate-1,1-dimethyl-2-butynyl is preferred .

2-propynylmethylcarbonate, 1-methyl-2-propynylmethylcarbonate, 1,1-dimethyl-2-propynylmethylcarbonate, 2-propynylethylcarbonate, 2-butynylmethylcarbonate, formic acid-2-propy Nyl, formic acid-1-methyl-2-propynyl, formic acid-1,1-dimethyl-2-propynyl, formic acid-2-butynyl, acetate-2-propynyl, acetate-1-methyl-2-propynyl , Acetic acid-1,1-dimethyl-2-propynyl, acetic acid-2-butynyl, 2-propynylmethyloxalate, 1-methyl-2-propynylmethyloxalate, 1,1-dimethyl-2-propy Nylmethyloxalate, 2-butynylmethyloxalate, methanesulfonic acid-2-propynyl, methanesulfonic acid-1-methyl-2-propynyl, methanesulfonic acid-1,1-dimethyl-2-propynyl, methanesulfonic acid- 2-butynyl, methanesulfonic acid-1-methyl-2-butynyl, methyl sulfate-2-propynyl, methyl sulfate-1-methyl-2-propynyl, methyl sulfate-1,1-dimethyl-2-propynyl It is particularly preferable to contain at least one selected from methylsulfate-2-butynyl.

Among the compounds represented by the general formula (2), di(2-propynyl)carbonate, di(2-butynyl)carbonate, di(1-methyl-2-propynyl)carbonate, and di(1-methyl-2-buty) Nyl) carbonate, di(1,1-dimethyl-2-propynyl) carbonate, di(1,1-dimethyl-2-butynyl) carbonate, di(2-propynyl) oxalate, di(2-butynyl) ) Oxalate, di(1-methyl-2-propynyl)oxalate, di(1-methyl-2-butynyl)oxalate, di(1,1-dimethyl-2-propynyl)oxalate, di( 1,1-dimethyl-2-butynyl)oxalate, di(2-propynyl)sulfite, di(2-butynyl)sulfite, di(1-methyl-2-propynyl)sulfite, di( 1-methyl-2-butynyl)sulfite, di(1,1-dimethyl-2-propynyl)sulfite, di(1,1-dimethyl-2-butynyl)sulfite, di(2-propynyl )Sulfuric acid, di(2-butynyl)sulfuric acid, di(1-methyl-2-propynyl)sulfuric acid, di(1-methyl-2-butynyl)sulfuric acid, di(1,1-dimethyl-2-propynyl) ) At least one selected from sulfuric acid and di(1,1-dimethyl-2-butynyl)sulfuric acid is preferable, and in particular, di(2-propynyl)carbonate, di(2-butynyl)carbonate, di(2 It is preferable to contain at least one selected from -propynyl)oxalate, di(2-butynyl)oxalate, di(2-propynyl)sulfuric acid, and di(2-butynyl)sulfuric acid.

Among the alkyne derivatives, the most preferred compounds are 2-propynylmethylcarbonate, 2-propynylethylcarbonate, 2-butynylmethylcarbonate, formic acid-2-propynyl, formic acid-2-butynyl, and acetic acid-2-propy Nyl, acetic acid-2-butynyl, 2-propynylmethyloxalate, 2-butynylmethyloxalate, methanesulfonic acid-2-propynyl, methanesulfonic acid-2-butynyl, methanesulfonic acid-1-methyl-2- Butynyl, methyl sulfate-2-propynyl, methyl sulfate-2-butynyl, di(2-propynyl) carbonate, di(2-butynyl) carbonate, di(2-propynyl) oxalate, di(2 -Butynyl)oxalate, di(2-propynyl)sulfuric acid, di(2-butynyl)sulfuric acid.

The compounds represented by the general formulas (11) to (12) may be used alone or in combination of two or more in any combination and ratio. In addition, the compounding amount of the compound represented by the general formulas (11) to (12) is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. The compounding amount of the compound represented by the general formulas (11) to (12) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more in 100% by mass of the non-aqueous electrolytic solution. And, more preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and the high temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity retention rate is easily avoided. On the other hand, if it is too small, the effect in the present invention may be difficult to be sufficiently exhibited, and if it is too large, the resistance increases and the output and load characteristics may decrease.

Moreover, as a cyclic compound which has a carbon-carbon triple bond, it is preferable that it is a compound represented by the following general formula (14).

[Formula 18]

(In general formula (14), X and Z represent CR ¹ ₂ , C=O, C=NR ¹ , C=PR ¹ , O, S, NR ¹ , PR ¹ , and may be the same or different. Y Represents CR ¹ ₂ , C=O, S=O, S(=O) ₂ , P(=O)-R ² , P(=O)-OR ^{3. In the} formula, R and R ¹ are hydrogen, Halogen or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and may be the same or different from each other, R ² is a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent R ³ is Li, NR ⁴ ₄ Or a C1-C20 hydrocarbon group which may have a substituent R ⁴ is a C1-C20 hydrocarbon group which may have a substituent, and may be the same as or different from each other, and n and m represent an integer of 0 or more. W has the same meaning as R, and may be the same as or different from R.)

In the general formula (14), X and Z are not particularly limited as long as they are within the ranges described in the general formula (4), but CR ¹ ₂ , O, S, and NR ¹ are more preferable. In addition, Y is also not particularly limited as long as it is a range described in the general formula (14), but preferably C=O, S=O, S(=O) ₂ , P(=O)-R ² , P(=O) -OR ³ is more preferable. R and R ¹ are not particularly limited as long as they are in the range described in the general formula (14), but preferably hydrogen, fluorine, a saturated aliphatic hydrocarbon group which may have a substituent, an unsaturated aliphatic hydrocarbon group that may have a substituent, or a substituent. And aromatic hydrocarbon groups to be used.

R ² and R ⁴ are not particularly limited as long as they are in the range described in the general formula (14), but preferably a saturated aliphatic hydrocarbon group which may have a substituent, an unsaturated aliphatic hydrocarbon group which may have a substituent, and an aromatic hydrocarbon that may have a substituent Aromatic hetero rings.

R ³ is not particularly limited as long as it is the range described in the general formula (14), but preferably Li, a saturated aliphatic hydrocarbon which may have a substituent, an unsaturated aliphatic hydrocarbon that may have a substituent, and an aromatic hydrocarbon/aromatic hetero which may have a substituent. Rings.

Although it does not specifically limit as a substituent of a saturated aliphatic hydrocarbon which may have a substituent, an unsaturated aliphatic hydrocarbon which may have a substituent, and an aromatic hydrocarbon/aromatic heterocycle which may have a substituent, preferably halogen, carboxylic acid, carbonic acid, A saturated aliphatic hydrocarbon group that may have a substituent such as sulfonic acid, phosphoric acid, or phosphorous acid, an unsaturated aliphatic hydrocarbon group that may have a substituent, and an ester of an aromatic hydrocarbon group that may have a substituent. More preferably, halogen Preferably fluorine is preferred.

As a preferable saturated aliphatic hydrocarbon, specifically, methyl group, ethyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 1-fluoroethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group, 1, 2-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group phenyl group, A cyclopentyl group and a cyclohexyl group are preferable.

Preferred unsaturated aliphatic hydrocarbons include, specifically, ethenyl group, 1-fluoroethenyl group, 2-fluoroethenyl group, 1-methylethenyl group, 2-propenyl group, and 2-fluoro-2-pro Phenyl group, 3-fluoro-2-propenyl group, ethynyl group, 2-fluoroethynyl group, 2-propynyl group, and 3-fluoro-2propynyl group are preferable.

Preferred aromatic hydrocarbons include phenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 2,4-difluorophenyl group, 2,6-difluorophenyl group, 3,5-difluorophenyl group, 2,4 ,6-trifluorophenyl group is preferred.

As a preferable aromatic hetero ring, 2-furanyl group, 3-furanyl group, 2-thiophenyl group, 3-thiophenyl group, 1-methyl-2-pyrrolyl group, and 1-methyl-3-pyrrolyl group are preferable.

Among these, a methyl group, an ethyl group, a fluoromethyl group, a trifluoromethyl group, a 2-fluoroethyl group, a 2,2,2-trifluoroethyl group, an ethenyl group, an ethynyl group, and a phenyl group are preferable.

More preferably, a methyl group, an ethyl group, and an ethynyl group are preferable.

Although n and m are not particularly limited as long as they are in the range described in the general formula (14), preferably 0 or 1, more preferably n=m=1 or n=1, m=0. Moreover, the molecular weight is preferably 50 or more. Moreover, it is preferably 500 or less. Within this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution, and the effects of the present invention are easily exhibited.

Moreover, it is preferable that R is hydrogen, fluorine, or an ethynyl group from both sides of the reactivity and stability of the compound represented by general formula (14). In the case of other substituents, the reactivity may decrease, and there is a fear that the expected characteristics may decrease. Moreover, in the case of halogen other than fluorine, the reactivity is too high and there is a fear that side reactions may increase.

Moreover, it is preferable that the number of fluorine or ethynyl groups in R is 2 or less in total. When these numbers are too large, the compatibility with the electrolyte solution may deteriorate, and the reactivity may be too high, and side reactions may increase.

Moreover, among these, n=1 and m=0 are preferable. When both are 0, stability deteriorates from deformation of the ring, reactivity becomes too high, and side reactions may increase. Moreover, even if n=2 or more or n=1, when m=1 or more, there exists a possibility that a chain shape rather than a cyclic type becomes stable, and there exists a possibility that an initial characteristic may not be shown.

In addition, in the formula, X and Z are more preferably CR ¹ ₂ or O. In the case of other than these, the reactivity is too high and there is a fear that side reactions may increase.

Moreover, the molecular weight is more preferably 100 or more, and more preferably 200 or less. Within this range, the solubility of the general formula (14) in the non-aqueous electrolytic solution is more easily secured, and the effects of the present invention are sufficiently more easily expressed.

More preferably, all of R are hydrogen. In this case, the side reaction is most likely to be suppressed while maintaining the expected characteristics. In addition, when Y is C=O or S=O, if any one of X and Z is O, then Y is S(=O) ₂ , P(=O)-R ² , P(=O)-OR ^In the case of ³ , it is preferable that X and Z are both O or CH _2, or one of X and Z is O, and the other is CH ₂ . When Y is C=O or S=O, when X and Z are both CH ₂ , the reactivity is too high, and side reactions may increase.

Specific examples of these compounds are shown below.

[Formula 19]

Among the compounds represented by the general formula (14), the compound represented by the general formula (15) is preferred from the viewpoint of industrial ease of production.

[Formula 20]

In the above formula (15), Y represents C=O, S=O, S(=O) ₂ , P(=O)-R ² , and P(=O)-OR ³ . As a compound having these preferable conditions, it is specifically shown below.

[Formula 21]

The compounds having a carbon-carbon triple bond may be used alone or in combination of two or more in any combination and ratio. In addition, the compounding amount of the compound having a carbon-carbon triple bond is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. The blending amount of the compound having a carbon-carbon triple bond is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, and more preferably in 100% by mass of the non-aqueous electrolyte solution. It is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and the high temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity retention rate is easily avoided. On the other hand, if it is too small, the effect in the present invention may be difficult to be sufficiently exhibited, and if it is too large, the resistance increases and the output and load characteristics may decrease.

<Cyclic carbonate having an unsaturated bond excluding the carbon-carbon triple bond>

In the nonaqueous electrolyte secondary battery of the present invention, in order to form a film on the surface of the negative electrode and achieve a longer battery life, a cyclic carbonate having an unsaturated bond excluding the compound having a carbon-carbon triple bond (hereinafter, `` Unsaturated cyclic carbonate" may be abbreviated in some cases).

The unsaturated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond, and any unsaturated carbonate can be used. In addition, a cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond, phenyl carbonates, vinyl carbonates, allyl carbonates, catechol carbonates, etc. have.

As vinylene carbonates, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl Vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, etc. are mentioned.

Specific examples of ethylene carbonates substituted with an aromatic ring or a substituent having a carbon-carbon double bond include vinylethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, and 4-allyl- 5-vinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene Carbonate and 4-methyl-5-allylethylene carbonate.

Among them, particularly preferred unsaturated cyclic carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4 ,5-diallylvinylene carbonate, vinylethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5 -Allylethylene carbonate and 4-allyl-5-vinylethylene carbonate form a stable interfacial protective film, so they are more preferably used.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention. The molecular weight is preferably 50 or more and 250 or less. Within this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution, and the effects of the present invention are easily exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less. The method for producing an unsaturated cyclic carbonate is not particularly limited, and a known method may be arbitrarily selected and prepared.

Unsaturated cyclic carbonates may be used alone or in combination of two or more in any combination and ratio.

In addition, the blending amount of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. The blending amount of the unsaturated cyclic carbonate is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and preferably 5% by mass in 100% by mass of the non-aqueous electrolyte. % Or less, more preferably 4 mass% or less, still more preferably 3 mass% or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and the high temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity retention rate is easily avoided. On the other hand, when it is too small, the effect in the present invention may not be sufficiently exhibited, and when it is too large, the resistance increases and the output or load characteristics may decrease.

<Unsaturated cyclic carbonate having a fluorine atom>

In the nonaqueous electrolyte secondary battery of the present invention, it is also preferable to use an unsaturated cyclic carbonate having a fluorine atom (hereinafter, abbreviated as "fluorinated unsaturated cyclic carbonate" in some cases). The number of fluorine atoms in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as there is 1 or more. Among these, the fluorine atom is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 fluorine atoms.

Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond.

Examples of fluorinated vinylene carbonate derivatives include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, and 4-allyl-5-fluorovinylene Carbonate, 4-fluoro-5-vinylvinylene carbonate, and the like.

Examples of fluorinated ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, and 4-fluoro-5- Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro -4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4 ,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5 -Phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, etc. are mentioned.

Among them, particularly preferred fluorinated unsaturated cyclic carbonates include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, and 4-allyl-5 -Fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate , 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro -4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene Carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, is more preferably used because it forms a stable interfacial protective film.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention. The molecular weight is preferably 50 or more and 250 or less. Within this range, it is easy to ensure the solubility of the fluorinated cyclic carbonate in the non-aqueous electrolytic solution, and the effects of the present invention are easily exhibited. The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method may be arbitrarily selected for production. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

The fluorinated unsaturated cyclic carbonate may be used singly or in combination of two or more in any combination and ratio.

In addition, the blending amount of the fluorinated unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. The blending amount of the fluorinated unsaturated cyclic carbonate is usually in 100% by mass of the non-aqueous electrolyte, preferably at least 0.01% by mass, more preferably at least 0.1% by mass, still more preferably at least 0.2% by mass, and more preferably Is 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and the high temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity retention rate is easily avoided. On the other hand, when it is too small, the effect in the present invention may not be sufficiently exhibited, and when it is too large, the resistance increases and the output or load characteristics may decrease.

<cyclic sulfonic acid ester>

In the nonaqueous electrolyte secondary battery of the present invention, it is also preferable to use a cyclic sulfonic acid ester. The molecular weight of the cyclic sulfonic acid ester compound is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention. The molecular weight is preferably 100 or more and 250 or less. Within this range, it is easy to ensure the solubility of the cyclic sulfonic acid ester compound in the non-aqueous electrolytic solution, and the effect of the present invention is easily exhibited. The method for producing the cyclic sulfonic acid ester compound is not particularly limited, and a known method can be arbitrarily selected and produced.

In the nonaqueous electrolyte secondary battery of the present invention, examples of the cyclic sulfonic acid ester compound that can be used include 1,3-propane sultone, 1-fluoro-1,3-propane sultone, and 2-fluoro- 1,3-propanesultone, 3-fluoro-1,3-propanesultone, 1-methyl-1,3-propanesultone, 2-methyl-1,3-propanesultone, 3-methyl-1,3-propane Sultone, 1,4-butanesultone, 1-fluoro-1,4-butanesultone, 2-fluoro-1,4-butanesultone, 3-fluoro-1,4-butanesultone, 4-fluoro- 1,4-butanesultone, 1-methyl-1,4-butanesultone, 2-methyl-1,4-butanesultone, 3-methyl-1,4-butanesultone, 4-methyl-1,4-butanesultone , 1,5-pentanesultone, 1-fluoro-1,5-pentanesultone, 2-fluoro-1,5-pentanesultone, 3-fluoro-1,5-pentanesultone, 4-fluoro-1 ,5-pentanesultone, 5-fluoro-1,5-pentanesultone, 1-methyl-1,5-pentanesultone, 2-methyl-1,5-pentanesultone, 3-methyl-1,5-pentanesultone , Monosulfonic acid ester compounds such as 4-methyl-1,5-pentanesultone and 5-methyl-1,5-pentanesultone;

Disulfonic acid ester compounds such as methylene methane disulfonate, ethylene methane disulfonate, and ethylene ethane disulfonate;

And the like.

Among these, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1,4- Butane sultone, methylene methane disulfonate, and ethylene methane disulfonate are preferable from the viewpoint of improving storage properties, and 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1, 3-propanesultone and 3-fluoro-1,3-propanesultone are more preferable.

Moreover, it is also preferable to use a cyclic sulfonic acid ester having a carbon-carbon double bond. As a cyclic sulfonic acid ester having a carbon-carbon double bond, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3- Sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2 -Methyl-1-propene-1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-butene-1,4-sultone, 2-butene-1,4-sultone, 3 -Butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone, 3-fluoro-1-butene-1, 4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-methyl-1-butene-1,4-sultone, 2-methyl-1-butene-1,4-sultone, 3-methyl 1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone, and the like.

Among these, 1-propene-1,3-sultone, 1-butene-1,4-sultone, 2-butene-1,4-sultone, and 3-butene-1,4-sultone are more preferable.

The cyclic sulfonic acid ester compounds may be used alone or in combination of two or more in any combination and ratio.

There is no limitation on the amount of the cyclic sulfonic acid ester compound to be blended with respect to the non-aqueous electrolyte solution, and it is arbitrary as long as the effect of the present invention is not significantly impaired, but with respect to the non-aqueous electrolyte, usually 0.001 mass% or more, preferably 0.1 mass%. % Or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. When the above range is satisfied, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

<Compound having a cyano group>

In the non-aqueous electrolyte secondary battery of the present invention, it is also preferable to use a compound having a cyano group. Here, as the compound having a cyano group, the kind is not particularly limited as long as it is a compound having a cyano group in the molecule, but a compound represented by the general formula (9) is more preferable.

[Formula 22]

In the general formula (9), T represents an organic group consisting of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom, and U is 1 carbon number which may have a substituent It is a V-valent organic group of -10. V is an integer of 1 or more, and when V is 2 or more, T may be the same or different from each other.

The molecular weight of the compound having a cyano group is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention. The molecular weight is preferably 50 or more, more preferably 80 or more, still more preferably 100 or more, and 200 or less. Within this range, it is easy to ensure the solubility of the compound having a cyano group in the non-aqueous electrolytic solution, and the effect of the present invention is easily exhibited. The method for producing the compound having a cyano group is not particularly limited, and a known method can be arbitrarily selected and produced.

As a specific example of the compound represented by general formula (9), for example,

Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, 2,2-dimethylbutyronitrile, hexanenitrile, cyclopentane Carbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile , 3-methyl-2-pentenenitrile, 2-hexenitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2, 2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3- Trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile And compounds having one cyano group such as pentafluoropropionitrile;

Malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecandinitrile, dodecanedinitrile, methylmalononitrile, ethylmalononitrile, i -Propylmalononitrile, t-butylmalononitrile, methyl succinonitrile, 2,2-dimethyl succinonitrile, 2,3-dimethyl succinonitrile, trimethyl succinonitrile, tetramethyl succinonitrile, 3,3 Compounds having two cyano groups such as'-(ethylenedioxy)dipropionitrile and 3,3'-(ethylenedithio)dipropionitrile;

Compounds having three cyano groups such as 1,2,3-tris(2-cyanoethoxy)propane and tris(2-cyanoethyl)amine;

Cyanate compounds such as methyl cyanate, ethyl cyanate, propyl cyanate, butyl cyanate, pentyl cyanate, hexyl cyanate, and heptyl cyanate;

Methylthiocyanate, ethylthiocyanate, propylthiocyanate, butylthiocyanate, pentylthiocyanate, hexylthiocyanate, heptylthiocyanate, methanesulfonylcyanide, ethanesulfonylcyanide, propanesulfonyl Cyanide, butanesulfonyl cyanide, pentanesulfonyl cyanide, hexanesulfonyl cyanide, heptanesulfonyl cyanide, methylsulfurocyanidate, ethylsulfurocyanidate, propylsulfurocyanidate, butylsulfur Sulfur-containing compounds such as furocyanidate, pentylsulfurocyanidate, hexylsulfurocyanidate, and heptylsulfurocyanidate;

Cyanodimethylphosphine, cyanodimethylphosphine oxide, cyanomethylphosphinate methyl, cyanomethylaphosphinate methyl, dimethylphosphinate cyanide, dimethyl aphosphinate cyanide, cyanophosphonate dimethyl, cyanoaphosphonic acid Phosphorus compounds such as dimethyl, cyanomethyl methylphosphonate, cyanomethyl methylaphosphonate, cyanodimethyl phosphate, and cyanodimethyl phosphonate;

And the like.

among them,

Acetonitrile, propionitrile, butyronitrile, i-butyronitrile, valeronitrile, i-valeronitrile, lauronitrile, crotononitrile, 3-methylcrotononitrile, malononitrile, succinonitrile, Glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecandinitrile, and dodecanedinitrile are preferred from the viewpoint of improving the storage properties, and malononitrile, succinonitrile, glutaro Compounds having two cyano groups such as nitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanidinitrile, and dodecanedinitrile are more preferable.

Compounds having a cyano group may be used alone or in combination of two or more in any combination and ratio.

There is no restriction on the amount of the compound having a cyano group with respect to the entire nonaqueous electrolyte solution, and it is arbitrary as long as the effect of the present invention is not significantly impaired, but with respect to the nonaqueous electrolyte solution, usually 0.001 mass% or more, preferably 0.1 mass% % Or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. When the above range is satisfied, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

<Compound having an isocyanato group>

In the nonaqueous electrolyte secondary battery of the present invention, it is also preferable to use an isocyanate compound. Here, the type of the compound having an isocyanato group is not particularly limited as long as it is a compound having an isocyanato group in the molecule, but as a specific example,

Isocyanatomethane, 1-isocyanatoethane, 1-isocyanato-2-methoxyethane, 3-isocyanato-1-propene, isocyanatocyclopropane, 2-isocyanatopropane, 1- Isocyanatopropane, 1-isocyanato-3-methoxypropane, 1-isocyanato-3-ethoxypropane, 2-isocyanato-2-methylpropane, 1-isocyanatobutane, 2-iso Cyanatobutane, 1-isocyanato-4-methoxybutane, 1-isocyanato-4-ethoxybutane, methylisocyanatoformate, isocyanatocyclopentane, 1-isocyanatopentane, 1- Isocyanato-5-methoxypentane, 1-isocyanato-5-ethoxypentane, 2-(isocyanatomethyl)furan, isocyanatocyclohexane, 1-isocyanatohexane, 1-isocyanato -6-methoxyhexane, 1-isocyanato-6-ethoxyhexane, ethyl isocyanatoacetate, isocyanatocyclopentane, isocyanatomethyl (cyclohexane), monomethylene diisocyanate, dimethylene diisocyanate, Trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,3-diisocyanate, 1 ,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato- 2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3 -Fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1, 3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4- Diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclo Hexylmethane-4,4'-diisocyanate, isophorone diisocyanate, and biuret, isocyanurate, adduct and bifunctional type modified by the basic structures of formulas (10-1) to (10-4) respectively Polyisocyanates and the like are mentioned (in the formula, R ⁵ and R ⁶ are each an arbitrary hydrocarbon group).

[Formula 23]

[Formula 24]

[Formula 25]

[Formula 26]

Among the compounds having an isocyanato group, in order to form a good protective film, a compound represented by the general formula (10-5) is preferable.

[Formula 27]

(In the formula, A represents an organic group having 1 to 20 carbon atoms composed of an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom, and n'is an integer of 2 or more. )

An organic group having 1 to 20 carbon atoms consisting of an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom means, in addition to the organic group consisting of carbon atoms and hydrogen atoms, a nitrogen atom, It means an organic group which may contain an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom. An organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom means an organic group in which some of the carbon atoms in the skeleton are substituted with these atoms, or an organic group having a substituent composed of these atoms. it means.

The molecular weight of the compound represented by the general formula (10-5) is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. The molecular weight is preferably 80 or more, more preferably 115 or more, still more preferably 180 or more, and 400 or less, and more preferably 270 or less. In this range, it is easy to ensure the solubility of the compound represented by the general formula (10-5) in the non-aqueous electrolytic solution, and the effects of the present invention are easily expressed. The method for producing the compound represented by the general formula (10-5) is not particularly limited, and a known method can be arbitrarily selected and produced.

As a specific example of A in General Formula (10-5), for example,

Alkylene group or its derivative, alkenylene group or its derivative, cycloalkylene group or its derivative, alkynylene group or its derivative, cycloalkenylene group or its derivative, arylene group or its derivative, carbonyl group or its derivative, sulfonyl group or its A derivative, a sulfinyl group or a derivative thereof, a phosphonyl group or a derivative thereof, a phosphinyl group or a derivative thereof, an amide group or a derivative thereof, an imide group or a derivative thereof, an ether group or a derivative thereof, a thioether group or a derivative thereof, a boric acid group, or And derivatives thereof, borane groups, or derivatives thereof.

Among these, from the viewpoint of improving battery characteristics, an alkylene group or a derivative thereof, an alkenylene group or a derivative thereof, a cycloalkylene group or a derivative thereof, an alkynylene group or a derivative thereof, an arylene group or a derivative thereof are preferable. Moreover, it is more preferable that B is a C2-C14 organic group which may have a substituent.

As a specific example of the compound represented by general formula (10-5), for example, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, Heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,3-diisocyanatopropane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2 -Fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6 -Diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluoro Hexane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanate) Natomethyl)cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dish Chlohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, and the formula (10- Biuret, isocyanurate, adduct, and bifunctional-type modified polyisocyanates represented by the basic structures of 1) to (10-4), and the like (in the formula, R ⁵ and R ⁶ are each arbitrary hydrocarbon It is).

[Formula 28]

[Chemical Formula 29]

[Formula 30]

[Formula 31]

Among these, trimethylene diisocyanate, hexamethylene diisocyanate (HMDI), 1,3-bis(isocyanatomethyl)cyclohexane (BIMCH), dicyclohexylmethane-4,4'-diisocyanate, formula (10- Biuret, isocyanurate, adduct, and bifunctional type modified polyisocyanate represented by the basic structures of 1) to (10-4) are preferable from the viewpoint of forming a more stable film.

Moreover, the isocyanate compound mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The compounding amount of the compound represented by the general formula (10-5) with respect to the whole non-aqueous electrolyte is not limited, and it is arbitrary as long as the effect of the present invention is not significantly impaired, but with respect to the non-aqueous electrolyte, usually 0.001 mass% or more, Preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and usually 5% by mass or less, preferably 4.0% by mass or less, more preferably 3.0% by mass Hereinafter, it is more preferably 2% by mass or less. When the content is within the above range, durability such as cycle and storage can be improved, and the effects of the present invention can be sufficiently exhibited.

<Other supplements>

In the nonaqueous electrolyte secondary battery of the present invention, other known auxiliary agents can be used. Examples of other auxiliary agents include carbonate compounds such as erytritan carbonate, spiro-bis-dimethylene carbonate, and methoxyethyl-methyl carbonate; Succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic acid Carboxylic anhydrides such as anhydrides; Spiro compounds such as 2,4,8,10-tetraoxaspiro[5.5]undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane; Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonic acid, busulfan, sulforene, diphenylsulfone, N,N-dimethylmethanesulfonamide, N And sulfur-containing compounds such as N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide, etc. Nitrogen-containing compounds; Hydrocarbon compounds such as heptane, octane, nonane, decane, and cycloheptane, and fluorinated aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, and benzotrifluoride; Methyl dimethyl phosphinate, ethyl dimethyl phosphinate, ethyl diethyl phosphinate, trimethylphosphonoformate, triethylphosphonoformate, trimethylphosphonoacetate, triethylphosphonoacetate, trimethyl-3-phosphonopro Phosphorus compounds, such as cypionate and triethyl-3-phosphonopropionate, etc. are mentioned. These may be used individually by 1 type, and may use 2 or more types together. By adding these auxiliary agents, the capacity retention characteristics and cycle characteristics after high temperature storage can be improved.

Among these, sulfur-containing, such as ethylene sulfite, methyl fluorosulfonate, methyl methanesulfonate, methyl ethanesulfonate, ethyl methanesulfonate, busulfan, and 1,4-butanediolbis (2,2,2-trifluoroethanesulfonate) The compound is particularly preferable because it has a large effect of improving capacity retention characteristics and cycle characteristics after high temperature storage.

The blending amount of the other auxiliary agents is not particularly limited, and is arbitrary as long as the effect of the present invention is not significantly impaired. Other auxiliary agents are, in 100% by mass of the non-aqueous electrolytic solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and 5% by mass or less, more preferably Is 3% by mass or less, more preferably 1% by mass or less. Within this range, it is easy to sufficiently express the effects of other auxiliary agents, and it is easy to avoid the situation that the battery characteristics such as high-load discharge characteristics are deteriorated.

The nonaqueous electrolyte solution described above includes those present inside the nonaqueous electrolyte secondary battery of the present invention. Specifically, constituents of a non-aqueous electrolyte such as lithium salt, solvent, and auxiliary are separately synthesized, and a non-aqueous electrolyte is prepared from the substantially isolated one, and obtained by injecting into a separately assembled battery by the method described below. In the case of a non-aqueous electrolyte solution in a non-aqueous electrolyte secondary battery, or a case of obtaining the same composition as the non-aqueous electrolyte solution according to the present invention by individually placing the constituents of the non-aqueous electrolyte solution according to the present invention into the battery and mixing in the battery, Furthermore, it is assumed that a case where the compound constituting the non-aqueous electrolyte according to the present invention is generated in the non-aqueous electrolyte secondary battery to obtain the same composition as the non-aqueous electrolyte according to the present invention is also included.

The non-aqueous electrolyte according to the present invention is preferably used as an electrolyte for a secondary battery used in which the upper limit operating potential of the positive electrode is at least 4.5 V, preferably at least 4.55 V, more preferably at least 4.60 V based on Li/Li ⁺ do. On the other hand, the upper limit operating potential of the positive electrode is usually 5.05 V or less based on Li/Li ⁺ . In addition, as described in the embodiments of the present invention, if a battery with a lower upper limit operating potential is used, the durability of the battery is improved, and therefore, depending on the intended use of the battery, it may be preferable.

2. Positive electrode

<positive electrode active material>

The positive electrode active material used for the positive electrode is described below.

(Furtherance)

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but a transition metal compound containing at least one or more metal elements other than Li and Mn, and at least Li, Ni, Co and/or Mn. It is preferable to contain at least one selected from the group consisting of a transition metal compound and a mixed-valent transition metal compound each containing at least one transition metal element having an average oxidation number of +4 and +3.

As a specific example of a transition metal type compound, the lithium transition metal type compound represented by following General formulas (4)-(6) is mentioned.

Li[Li _a M _x Mn _{2 -xa} ]O _4+δ … (4)

(In formula (4), 0 ≤ a ≤ 0.3, 0.4 <x <1.1, -0.5 <δ <0.5 is satisfied, and M is at least one of transition metals selected from Ni, Cr, Fe, Co, and Cu. Indicate)

Li _x M1 _y M2 _z O _{2 -δ} ... (5)

(In formula (5), 1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 0.3, -0.1 ≤ δ ≤ 0.1 is satisfied, M1 represents Ni, Co and/or Mn, and M2 represents Fe , Cr, V, Ti, Cu, Ga, Bi, Sn, B, P, Zn, Mg, Ge, Nb, W, Ta, Be, Al, Ca, Sc, and at least one of the elements selected from Zr )

αLi₂MO₃·(1-α)LiM'O₂ … (6)

(In formula (6), 0 <α <1 is satisfied, M represents at least one of the metal elements with an average oxidation number of +4, and M'represents at least one of the metal elements with an average oxidation number of +3. )

As the transition metal of the lithium transition metal compound represented by the general formula (4), Ni, Cr, Mn, Fe, Co and Cu are preferable, and as specific examples, LiMn ₂ O ₄ , Li ₂ MnO ₄ , Li _{1 + a Mn 2 O 4 (a; 0} <a ≤ 3.0) lithium manganese compound oxide such _{as, LiMn x Ni 2 - x O} 4, Li 1 + a Mn 1 .5 Ni 0 .5 O 4 (a; 0 <a ≦3.0) and other lithium-nickel-manganese composite oxides.

As the transition metal of the lithium transition metal compound represented by the general formula (5), V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable, and as a specific example, lithium-cobalt composites such as LiCoO ₂ Oxides, lithium-manganese composite oxides such as LiMnO ₂ , lithium-nickel composite oxides such as LiNiO _2, and the like. In addition, in Formula (5), 0 ≤ y ≤ 1 and 0 ≤ z ≤ 0.3 are satisfied, but when y and z are 0 together, that is, that does not contain a transition metal, it is represented by General Formula (5). It shall not be contained in the lithium transition metal compound.

In addition, some of the transition metal atoms that are the main bodies of these lithium transition metal composite oxides are other than Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, etc. And those substituted with metals, and specific examples include lithium-nickel-cobalt-aluminum composite oxide, lithium-cobalt-nickel composite oxide, lithium-cobalt-manganese composite oxide, lithium-nickel-manganese composite oxide, Lithium-nickel-cobalt-manganese composite oxides, and the like. Among these, since battery characteristics are good, a lithium-nickel-manganese composite oxide and a lithium-nickel-cobalt-manganese composite oxide are preferable. For example, LiNi _x Mn _{1 - x} O ₂ , LiNi _x Co _y Al _1-xy O ₂ , LiNi _x Co _y Mn _z O ₂ (x + y + z = 1), LiMn _x Al _{2 - x} O ₄ , αLi ₂ MO ₃ ·(1-α)LiM'O ₂ (0 <α <1), Li ₂ MPO ₄ F, Li ₂ MSiO ₄ , LiMPO ₄ (M=Fe, Ni, Mn, Co), etc. I can.

Specific examples of what is substituted, for example, Li _{1 + a} Mn Ni _{0 .5 0 .5} O _2, Li _{1 + a} Ni _{0 .8 .2 0} Co O _2, Li _{1 + a} Ni _0.85 Co _{0.10 Al 0.05 O 2, Li 1 +} a Ni 0 .33 Co 0 .33 Mn 0 .33 O 2, Li 1 + a Ni 0 .45 Mn 0 .45 Co 0 .1 O 2, Li 1 + a Ni 0.475 Mn _{0.475 Co 0.05 O 2, Li 1} + a Mn 1 .8 Al 0 .2 O 4, xLi and _{2 MnO 3 · (1-x} ) Li 1 + a MO 2 (M = transition metal, for example, Li, A metal selected from the group consisting of Ni, Mn, and Co) and the like (a: 0 <a ≤ 3.0). The ratio in the composition formula of these substituted metal elements is appropriately adjusted depending on the relationship such as the battery characteristics of the battery using the same and the cost of materials.

Further, as the lithium transition metal compound, αLi ₂ MO ₃ ·(1-α)LiM'O ₂ can be mentioned as represented by the general formula (6). Here, 0 <α <1 is a number that satisfies, M is at least one metal element with an average oxidation number of +4, preferably at least 1 selected from the group consisting of Mn, Zr, Ti, Ru, Re, and Pt. It is a species, more preferably at least one species selected from the group consisting of Mn, Zr and Ti. M'is at least one metal element having an average oxidation number of +3, preferably at least one metal element selected from the group consisting of V, Mn, Fe, Co, and Ni, and more preferably Mn, Co And at least one metal element selected from the group consisting of Ni.

Among these positive electrode active materials, as a positive electrode for a battery having a high open voltage between battery terminals, it is preferable to use the general formula (4) and the general formula (6), more preferably the general formula (4) It is preferable from the viewpoint of stability of the active material. Specifically, among the lithium transition metal compounds represented by the general formula (4), lithium such as LiMn _x Ni _{2 - x} O ₄ and Li _1+a Mn _1.5 Ni _0.5 O ₄ (a; 0 <a ≤ 3.0) A nickel-manganese composite oxide is preferable from the viewpoint of stability and charging capacity of the positive electrode active material.

In the present invention, although it is not particularly limited, a lithium-containing transition metal phosphate compound is also preferably used as a positive electrode active material, and as the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and lithium transition metal phosphoric acid. Some of the transition metal atoms that are the main body of the compound are substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc. And the like.

Further, when lithium phosphate is contained in the positive electrode active material, since the continuous charging characteristic is improved, it is preferable. Although there is no restriction on the use of lithium phosphate, it is preferable to use a mixture of the positive electrode active material and lithium phosphate. The amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, and the upper limit is preferably with respect to the total of the positive electrode active material and lithium phosphate. Is 10% by mass or less, more preferably 8% by mass or less, and still more preferably 5% by mass or less.

(Surface coating)

Further, a substance having a composition different from this may be used on the surface of the positive electrode active material. As the surface adhesion substance, oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

These surface-attached substances are, for example, dissolved or suspended in a solvent and impregnated to the positive electrode active material, followed by drying, dissolving or suspending the surface-attached substance precursor in a solvent and impregnating the positive electrode active material, followed by heating, etc. It can adhere to the surface of the positive electrode active material by a method of making, adding to the positive electrode active material precursor and simultaneously firing. Further, in the case of attaching carbon, a method of mechanically attaching the carbonaceous material later in the form of, for example, activated carbon may also be used.

The amount of the substance attached to the surface is by mass relative to the positive electrode active material, preferably 0.1 ppm or more as a lower limit, more preferably 1 ppm or more, still more preferably 10 ppm or more, and preferably 20% or less as an upper limit, More preferably, it is used at 10% or less, still more preferably 5% or less. The surface-attached substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material and improve the battery life. However, if the amount of adhesion is too small, the effect is not sufficiently expressed, and if the amount is too large, lithium ion The resistance may increase because it impedes the entry and exit.

In the present invention, also included in the "positive electrode active material" that a substance having a composition different from this adheres to the surface of the positive electrode active material.

(shape)

As for the shape of the particle|grains of a positive electrode active material, a block shape, a polyhedron shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a column shape, etc. as conventionally used are mentioned. Moreover, primary particles may aggregate to form secondary particles.

(Tap density)

The tap density of the positive electrode active material is preferably 0.5 g/cm 3 or more, more preferably 0.8 g/cm 3 or more, and still more preferably 1.0 g/cm 3 or more. If the tap density of the positive electrode active material is less than the above lower limit, the amount of dispersion medium required for forming the positive electrode active material layer increases, and the required amount of a conductive material or a binder increases, thereby limiting the filling rate of the positive electrode active material to the positive electrode active material layer, There are cases where battery capacity is limited. By using a composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. The larger the tap density is, the more preferable, and there is no upper limit in particular, but when the tap density is too large, the diffusion of lithium ions using the electrolyte solution as a medium in the positive electrode active material layer becomes a rate control, and the load characteristics may be liable to decrease. Therefore, the upper limit is preferably 3.0 g/cm 3 or less, more preferably 2.7 g/cm 3 or less, and still more preferably 2.5 g/cm 3 or less.

Further, in the present invention, the tap density is determined as the powder packing density (tap density) g/cc when 5 to 10 g of the positive electrode active material powder is placed in a 10 ml glass female cylinder and tapped 200 times with a stroke of about 20 mm.

(Median diameter d ₅₀ )

The median diameter d ₅₀ of the lithium-nickel-cobalt-manganese composite oxide particles that may be contained in the positive electrode active material (secondary particle diameter when the primary particles are aggregated to form secondary particles) is preferably 0.3 µm or more, more preferably Preferably 0.5 µm or more, more preferably 0.8 µm or more, most preferably 1.0 µm or more, and the upper limit is preferably 30 µm or less, more preferably 27 µm or less, still more preferably 25 µm or less, most preferably It is less than 22 μm. If it is less than the above lower limit, it may not be possible to obtain a high tap density product, and if it exceeds the upper limit, it takes time for the diffusion of lithium in the particles, resulting in a decrease in battery performance, or in the production of a positive electrode of a battery, i.e. When ash or a binder is slurried with a solvent and applied in a thin film, a problem such as streaks may occur. Here, by mixing two or more types of the positive electrode active materials having different median diameters d ₅₀ , it is possible to further improve the filling properties at the time of manufacturing the positive electrode.

Further, in the present invention, the median diameter d ₅₀ is measured by a known laser diffraction/scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as the particle size distribution meter, it is measured by setting the measurement refractive index of 1.24 after ultrasonic dispersion for 5 minutes using a 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium used at the time of measurement.

(Median diameter d ₉₀ )

The median diameter of the lithium-nickel-manganese composite oxide that may be contained in the positive electrode active material is usually 2 µm or more, preferably 2.5 µm or more, more preferably 3 µm or more, even more preferably 3.5 µm or more, most preferably Is 4 μm or more, usually 60 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and most preferably 20 μm or less. If the median diameter is less than this lower limit, there is a possibility that a problem may occur in the coatability at the time of forming the positive electrode active material layer, and if it exceeds the upper limit, there is a possibility that the battery performance may be deteriorated.

Further, the 90% cumulative diameter (D ₉₀ ) of the secondary particles of the lithium-nickel-manganese composite oxide that may be contained in the positive electrode active material is usually 30 μm or less, preferably 25 μm or less, more preferably 22 μm or less, It is most preferably 20 µm or less, usually 3 µm or more, preferably 4 µm or more, more preferably 5 µm or more, and most preferably 6 µm or more. If the 90% cumulative diameter (D ₉₀ ) exceeds the above upper limit, there is a possibility of causing a decrease in battery performance, and if it is less than the lower limit, there is a possibility of causing a problem in the coatability at the time of forming the positive electrode active material layer.

In addition, in the present invention, the median diameter as the average particle diameter and the 90% integrated diameter (D ₉₀ ) are measured using a known laser diffraction/scattering particle size distribution measuring device with a refractive index of 1.60, and the particle diameter standard as a volume standard. It was done. In the present invention, measurement was carried out using 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium used at the time of measurement.

(Average primary particle diameter)

In the lithium-nickel-cobalt-manganese composite oxide that may be contained in the positive electrode active material, when the primary particles aggregate to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, More preferably 0.1 μm or more, still more preferably 0.2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, most preferably 2 μm or less . If the above upper limit is exceeded, it is difficult to form spherical secondary particles, and since the powder filling property is adversely affected or the specific surface area is greatly reduced, the possibility of deteriorating battery performance such as output characteristics may increase. Conversely, if it is less than the above lower limit, there may be a problem such as poor reversibility of charging and discharging because the crystal is usually not developed.

The average diameter (average primary particle diameter) of the lithium-nickel-manganese composite oxide that may be contained in the positive electrode active material is not particularly limited, but the lower limit is preferably 0.1 µm or more, more preferably 0.2 µm or more, most preferably Preferably, it is 0.3 µm or more, and the upper limit is preferably 3 µm or less, more preferably 2 µm or less, still more preferably 1.5 µm or less, and most preferably 1.2 µm or less. If the average primary particle diameter exceeds the above upper limit, the powder filling property is adversely affected or the specific surface area is lowered, so there is a possibility that the battery performance such as rate characteristics and output characteristics may be increased. If it is less than the above lower limit, there is a possibility of causing problems such as poor reversibility of charging and discharging because the crystal is not developed.

Further, in the present invention, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to a horizontal straight line is obtained for any 50 primary particles, and the average value is obtained.

(BET specific surface area)

The BET specific surface area of the lithium-nickel-cobalt-manganese composite oxide that may be contained in the positive electrode active material is preferably 0.1 m2/g or more, more preferably 0.2 m2/g or more, even more preferably 0.3 m2/g or more. And the upper limit is 50 m 2 /g or less, preferably 40 m 2 /g or less, and more preferably 30 m 2 /g or less. If the BET specific surface area is smaller than this range, the battery performance is liable to deteriorate, and if the BET specific surface area is large, the tap density is not easily increased, and a problem in the coating properties at the time of forming the positive electrode active material layer is likely to occur.

In addition, the lithium-nickel-manganese composite oxide that may be contained in the positive electrode active material also has a BET specific surface area of usually 0.2 m 2 /g or more, preferably 0.3 m 2 /g or more, more preferably 0.35 m 2 /g or more, most preferably It is preferably 0.4 m2/g or more, usually 3 m2/g or less, preferably 2.5 m2/g or less, more preferably 2 m2/g or less, and most preferably 1.5 m2/g or less. If the BET specific surface area is smaller than this range, the battery performance is liable to deteriorate, and if the BET specific surface area is large, the bulk density is not easily increased, and there is a possibility that the energy density as a positive electrode active material material is not improved.

In addition, the BET specific surface area can be measured by a known BET type powder specific surface area measuring device. In the present invention, the Okura Riken: AMS8000 type fully automatic powder specific surface area measuring apparatus was used, nitrogen as an adsorption gas and helium as a carrier gas were used, and BET one-point method measurement by a continuous flow method was performed. Specifically, the powder sample was heated and degassed with a mixed gas at a temperature of 150°C, and then cooled to a liquid nitrogen temperature to adsorb the mixed gas, and then heated to room temperature with water to desorb the adsorbed nitrogen gas. The amount was detected by a heat conduction detector, and the specific surface area of the sample was calculated from this.

(Manufacturing method of positive electrode active material)

As a manufacturing method of a positive electrode active material, a general method is used as a manufacturing method of an inorganic compound. In particular, in order to prepare a spherical or elliptical spherical active material, various methods are considered, but for example, a raw material of a transition metal is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to prepare a spherical precursor. After recovering and drying this as necessary, a method of obtaining an active material by adding a Li source such as LiOH, Li ₂ CO ₃ , and LiNO ₃ and firing at high temperature to obtain an active material may be mentioned. In addition, a lithium compound, at least one transition metal compound selected from Mn, Ni, Cr, Fe, Co, and Cu, and the additive of the present invention are pulverized in a liquid medium to prepare a slurry to obtain a slurry uniformly dispersed therein. It is preferably produced by a method for producing a lithium transition metal-based compound for a lithium secondary battery positive electrode material of the present invention including a step, a spray drying step of spray drying the obtained slurry, and a firing step of firing the obtained spray dried body.

In order to manufacture a positive electrode, the above positive electrode active material may be used alone, or one or more types of different compositions may be used in combination or ratio in any combination. As a preferable combination of the case, LiCoO ₂ and _{LiNi 0 .33 Co 0 .33 Mn 0} .33 O 2 such as LiMn ₂ O ₄ or a combination of those is substituted with a transition metal such as Mn other portions of, or LiCoO ₂ or a combination of a part of this Co substituted with another transition metal or the like.

<Composition and manufacturing method of positive electrode>

Below, the configuration of the positive electrode is described. In the present invention, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Production of a positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener, etc., are dry-mixed to form a sheet and compressed into a positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry. By coating and drying the current collector, the positive electrode active material layer is formed on the current collector, whereby a positive electrode can be obtained.

The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, the upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. When the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may become insufficient. Conversely, when the content is too large, the strength of the positive electrode may be insufficient.

In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably compacted by hand press or roller press. The density of the positive electrode active material layer is preferably 1.5 g/cm 3 or more, more preferably 2 g/cm 3, further preferably 2.2 g/cm 3 or more, and the upper limit is preferably 5 g/cm 3 or less. , More preferably 4.5 g/cm 3 or less, further preferably 4 g/cm 3 or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector/active material interface decreases, and in particular, charge/discharge characteristics at a high current density decrease, and high output may not be obtained. Further, if less, the conductivity between the active materials decreases, the battery resistance increases, and high output may not be obtained.

(Conductor)

As the conductive material, a known conductive material can be arbitrarily used. As a specific example, metal materials, such as copper and nickel; Graphite (graphite), such as natural graphite and artificial graphite; Carbon black such as acetylene black; Carbon materials, such as amorphous carbon, such as needle coke, etc. are mentioned. In addition, these may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and the upper limit is usually 50% by mass or less, preferably 30% by mass or less in the positive electrode active material layer. , More preferably, it is used so as to contain 15% by mass or less. If the content is lower than this range, the conductivity may become insufficient. Conversely, when the content is higher than this range, the battery capacity may decrease.

(Binder)

The binder used for the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that is dissolved or dispersed in the liquid medium used during electrode production may be used. Specific examples include polyethylene, polypropylene, Resin polymers such as polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; Rubber polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; Styrene/butadiene/styrene block copolymer or hydrogenated products thereof, EPDM (ethylene/propylene/diene ternary copolymer), styrene/ethylene/butadiene/ethylene copolymer, styrene/isoprene/styrene block copolymer or hydrogenated products thereof, etc. Thermoplastic elastomer polymer; Soft dendritic polymers, such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymer, and propylene/α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene/ethylene copolymer; And polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions). In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60% by mass. % Or less, more preferably 40 mass% or less, most preferably 10 mass% or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently maintained, the mechanical strength of the positive electrode is insufficient, and battery performance such as cycle characteristics may be deteriorated in some cases. On the other hand, if it is too high, it may lead to a decrease in battery capacity or conductivity.

(Slurry formation solvent)

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing a positive electrode active material, a conductive material, a binder, and a thickener used as necessary, and any of an aqueous solvent and an organic solvent You can also use indigo. As an aqueous medium, water, a mixed medium of alcohol and water, etc. are mentioned, for example. Examples of the organic medium include aliphatic hydrocarbons such as hexane; Aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; Heterocyclic compounds such as quinoline and pyridine; Ketones such as acetone, methyl ethyl ketone, and cyclohexanone; Esters such as methyl acetate and methyl acrylate; Amines such as diethylenetriamine and N,N-dimethylaminopropylamine; Ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); Amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; And aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide.

In particular, when using an aqueous medium, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to form a slurry. The thickener is usually used to adjust the viscosity of the slurry. Although there is no restriction|limiting in particular as a thickener, Specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof etc. are mentioned. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. In the case of adding a thickener, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and the upper limit is 5% by mass or less, preferably It is preferably 3% by mass or less, more preferably 2% by mass or less. If it is less than this range, there may be a case where the coatability is markedly lowered. If it exceeds, the ratio of the active material occupied in the positive electrode active material layer decreases, resulting in a problem in that the capacity of the battery decreases or the resistance between the positive electrode active materials increases in some cases.

(The current collector)

The material of the positive electrode current collector is not particularly limited, and a known material may be arbitrarily used. As a specific example, metal materials, such as aluminum, stainless steel, nickel plating, titanium, and tantalum; Carbon materials, such as carbon cloth and carbon paper, are mentioned. Among them, metal materials, particularly aluminum are preferred.

As the shape of the current collector, in the case of a metal material, a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc. can be mentioned. In the case of a carbon material, a carbon plate, a carbon thin film, And a carbon column. Among these, a metal thin film is preferable. Further, the thin film may be appropriately formed in a mesh shape. The thickness of the thin film is arbitrary, but is usually 1 µm or more, preferably 3 µm or more, more preferably 5 µm or more, and the upper limit is usually 1 mm or less, preferably 100 µm or less, more preferably 50 It is not more than µm. If the thin film is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the thin film is thicker than this range, handling properties may be impaired.

Moreover, it is also preferable that a conductive auxiliary agent is applied to the surface of the current collector from the viewpoint of lowering the electromagnetic contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive auxiliary agent include carbon and precious metals such as gold, platinum, and silver.

The ratio of the thickness of the current collector and the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection)/(thickness of the current collector) is preferably 20 or less, more preferably 15 Below, it is most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during charging and discharging at a high current density. If it is less than this range, the volume ratio of the current collector to the positive electrode active material increases, and the capacity of the battery may decrease.

(Electrode area)

In the nonaqueous electrolyte secondary battery of the present invention, from the viewpoint of enhancing stability at high output and high temperature, the area of the positive electrode active material layer is preferably made larger than the outer surface area of the battery case. Specifically, the total area of the positive electrode with respect to the external surface area of the secondary battery is preferably 15 times or more, and more preferably 40 times or more in terms of the area ratio. The outer surface area of the outer case is the total area calculated from the dimensions of the length, width, and thickness of the case portion in which the power generating element excluding the protruding portion of the terminal, excluding the protruding portion of the terminal, in the case of a user square shape. In the case of a user cylindrical shape, it is a geometric surface area approximating the case portion filled with the power generating element excluding the protruding portion of the terminal as a cylinder. The sum of the electrode areas of the positive electrode is the geometric surface of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure formed by forming the positive electrode mixture layer on both sides through the current collector foil, each surface is calculated separately. It is the sum of the area to be done.

(Thickness of positive plate)

The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture layer minus the thickness of the metal foil of the core material is a lower limit with respect to one side of the current collector, preferably 10 µm or more, more preferably 20 µm. Or more, and the upper limit is preferably 500 µm or less, and more preferably 450 µm or less.

(Surface coating of positive plate)

Further, a substance having a composition different from this may be used on the surface of the positive electrode plate. As the surface adhesion substance, oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

3. negative pole

The negative electrode active material used for the negative electrode is described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, etc., but carbonaceous materials are used. In the case of doing so, it is preferable to contain at least one or more types of negative electrode active materials composed of graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less. These may be used alone or in combination of two or more.

<Negative electrode active material>

Examples of the negative electrode active material include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and mixtures thereof.

As a carbonaceous material used as a negative electrode active material,

(1) natural graphite,

(2) artificial carbonaceous material and carbonaceous material obtained by heat treatment of artificial graphite material at least once in the range of 400 to 3200 ℃,

(3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystalline properties, and/or has an interface in which the carbonaceous materials of different crystalline properties contact,

(4) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different orientations and/or has an interface in which carbonaceous materials of different orientations are in contact,

What is selected from is preferable because the balance between initial irreversible capacity and high current density charge/discharge characteristics is good. In addition, the carbonaceous materials of (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

As the artificial carbonaceous material and artificial graphite material of the above (2), natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch and those obtained by oxidation treatment of these pitches, needle coke, pitch coke, and some of these Thermal decomposition products of organic substances such as graphitized carbon materials, furnace black, acetylene black, pitch-based carbon fiber, carbonizable organic substances and their carbides, or carbonizable organic substances such as benzene, toluene, xylene, quinoline, n-hexane, etc. And a solution dissolved in a low-molecular organic solvent, and carbides thereof.

As the alloy-based material used as the negative electrode active material, if lithium can be occluded and released, any one of lithium alone, a single metal and alloy forming a lithium alloy, or compounds such as oxides, carbides, nitrides, silicides, sulfides or phosphides thereof. It may be, and is not particularly limited. As the single metal and alloy forming the lithium alloy, it is preferable to use a material containing a metal/semimetal element of groups 13 and 14 (ie, excluding carbon), more preferably aluminum, silicon and tin (hereinafter , In some cases abbreviated as "specific metal element") and an alloy or compound containing these atoms.

Examples of the negative electrode active material having at least one atom selected from specific metal elements include a single metal element of any one specific metal element, an alloy consisting of two or more specific metal elements, one or two or more specific metal elements and the same. Other alloys comprising one or two or more metal elements, and compounds containing one or two or more specific metal elements, and complex compounds such as oxides, carbides, nitrides, silicides, sulfides or phosphides of the compounds. have. By using these metals, alloys, or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

Further, compounds in which these composite compounds are complexly bonded with various types of elements such as a single metal, an alloy, or a non-metal element are also mentioned. Specifically, in silicon or tin, for example, an alloy of these elements and a metal that does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 elements in combination of a metal that acts as a negative electrode other than tin and silicon, a metal that does not act as a negative electrode, and a non-metal element can also be used.

Among these negative electrode active materials, since the capacity per unit mass is large when used as a battery, a single metal element of one specific metal element, an alloy of two or more specific metal elements, oxides, carbides, nitrides, etc. of a specific metal element are preferable. In particular, silicon and/or tin metals, alloys, oxides, carbides, nitrides, etc. are preferable from the viewpoint of capacity per unit mass and environmental load.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge/discharge characteristics, and more preferably titanium. A lithium-containing composite metal oxide material containing is preferable, and is a composite oxide of lithium and titanium (hereinafter, abbreviated as "lithium-titanium composite oxide" in some cases). That is, when a lithium titanium composite oxide having a spinel structure is contained in a negative electrode active material for a non-aqueous electrolyte secondary battery and used, the output resistance is greatly reduced, so it is particularly preferable.

In addition, lithium or titanium of the lithium titanium composite oxide is at least 1 selected from the group consisting of other metal elements, for example, Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. It is also preferable to be substituted with a species element.

The metal oxide is a lithium-titanium composite oxide represented by the general formula (A), and in the general formula (A), 0.7≦x≦1.5, 1.5≦y≦2.3, and 0≦z≦1.6 are lithium ions doping and dedoping. It is preferable because the structure of the city is stable.

Li _x Ti _y M _z O ₄ … (A)

[In general formula (A), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb]

Among the compositions represented by the above general formula (A),

(a) 1.2 ≤ x ≤ 1.4, 1.5 ≤ y ≤ 1.7, z = 0

(b) 0.9 ≤ x ≤ 1.1, 1.9 ≤ y ≤ 2.1, z = 0

(c) 0.7 ≤ x ≤ 0.9, 2.1 ≤ y ≤ 2.3, z = 0

The structure of is particularly preferable because the balance of battery performance is good.

A particularly preferred representative composition of the compound is Li _{4 /3} Ti _{5 /3} O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _{4 /5} Ti _{11 /5} O ₄ in (c). . Moreover, about the structure of Z≠0, Li _{4 /3} Ti _{4 /3} Al _{1 /3} O ₄ is mentioned as a preferable thing, for example.

[Rhombohedral consolidation rate]

The rhombohedral crystal ratio defined in the present invention is from the ratio of the rhombohedral crystal structure graphite layer (ABC stacking layer) and the hexagonal crystal structure graphite layer (AB stacking layer) by X-ray wide-angle diffraction method (XRD), using the following equation: You can get it.

Rhombohedral crystallinity (%) = Integral intensity of ABC (101) peak in XRD ÷ Integral intensity of AB (101) peak in XRD × 100

Here, the rhombohedral crystallinity of the graphite particles of the present invention is usually 0% or more, preferably more than 0%, more preferably 3% or more, still more preferably 5% or more, particularly preferably 12% or more. And, it is usually 35% or less, preferably 27% or less, more preferably 24% or less, and particularly preferably 20% or less of the range. Here, the rhombohedral crystallinity of 0% indicates that no XRD peak originating from the ABC stacking layer is detected. In addition, when it is larger than 0%, it indicates that even a slight XRD peak originating from the ABC stacking layer is detected.

If the rhombohedral crystallinity is too large, since a large number of defects are contained in the crystal structure of the graphite particles, there is a tendency that the amount of Li inserted decreases, making it difficult to obtain a high capacity. Further, since the electrolytic solution is decomposed during the cycle due to the above defect, the cycle characteristics tend to decrease. On the other hand, if the rhombohedral crystallinity is within the range of the present invention, for example, there are few defects in the crystal structure of graphite particles, so that the reactivity with the electrolyte solution is small, and the consumption of the electrolyte solution during the cycle is small, so that the cycle characteristics are excellent.

The measurement method of XRD for determining the rhombohedral crystallization is as follows.

A sample plate of 0.2 mm is filled so that the graphite powder is not oriented, and is measured with an X-ray diffraction apparatus (for example, an output of 45 kV and 40 mA by a CuKα ray with an X'Pert Pro MPD manufactured by PANalytical). Using the obtained diffraction pattern, using analysis software JADE5.0, the peak integral intensities were each calculated by profile fitting using an asymmetric Pearson VII function, and the rhombohedral crystallinity was calculated from the equation.

X-ray diffraction measurement conditions are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα line) graphite monochromator

・Slit:

Solar slit 0.04 degrees

Divergence slit 0.5 degree

Lateral divergence mask 15 mm

1 degree anti-scatter slit

Measurement range and step angle/measurement time:

(101) plane: 41 degrees ≤ 2θ ≤ 47.5 degrees 0.3 degrees/60 seconds

·Background correction: Connect between 42.7 and 45.5 degrees in a straight line and subtract it as the background.

-Peak of the rhombohedral structured graphite particle layer: indicates the peak near 43.4 degrees.

-Peak of hexagonal crystal structure graphite particle layer: indicates a peak near 44.5 degrees.

The method of obtaining graphite particles having a rhombohedral crystallinity in the above range may employ a method of manufacturing using a conventional technique, and is not particularly limited, but is preferably manufactured by heat treating the graphite particles at a temperature of 500° C. or higher. Do. In addition, it is also desirable to impart mechanical actions such as compression, friction, and shearing force to the graphite particles, including the interaction of the particles based on impact force. In addition, it is possible to adjust the rhombohedral crystallinity by changing the strength of the mechanical action, the treatment time, the presence or absence of repetition, and the like. As a specific device for adjusting the rhombohedral stability, it has a rotor with a number of blades installed inside the casing, and the rotor rotates at high speed, thereby mechanical actions such as impact compression, friction, and shear force on the carbon material introduced inside. Apparatus for performing a surface treatment by imparting to is preferable. In addition, it is preferable to have a mechanism for repeatedly imparting a mechanical action by circulating the carbon material, or a mechanism that does not have a circulation mechanism but connects a plurality of devices for processing. As an example of a preferable device, a hybridization system manufactured by Nara Machinery Co., Ltd. can be mentioned.

Further, it is more preferable to apply heat treatment after imparting the mechanical action.

Further, it is particularly preferable to perform heat treatment at a temperature of 700° C. or higher by complexing with a carbon precursor after imparting the mechanical action.

[Specific aspect of negative electrode active material]

Specific embodiments of the negative electrode active material include, for example, (a) graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less consisting of a composite and/or mixture of nuclear graphite and carbon, and (b) a composite of nuclear graphite and graphite. And/or a mixture of graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less, (c) graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less, and a mixture of (a) to (c). have.

Here, as the nuclear graphite, the aforementioned natural graphite or artificial graphite may be mentioned. In addition, the natural graphite as nuclear graphite is preferably spheroidal natural graphite (in this specification, spheroidal natural graphite is also referred to as spheroidized graphite).

For example, in the case of a mixture combining (a) and (b), with respect to the complex and/or mixture of (a), the ratio of the complex and/or mixture of (b) is usually 5 wt% or more, It is preferably 10 wt% or more, more preferably 15 wt% or more. Moreover, it is usually 95 wt% or less, preferably 90 wt% or less, and more preferably 85 wt% or less. If the mixing ratio of (b) is too small, the irreversible capacity increases and the battery capacity tends to decrease. If the mixing ratio is too large, the Li water solubility at low temperature tends to decrease.

In the case of a mixture in which (a) and (c) are combined, the ratio of the graphite particles in (c) to the composite and/or mixture of (a) is usually 5 wt% or more, preferably 10 wt% or more , More preferably 15 wt% or more. Moreover, it is usually 70 wt% or less, preferably 60 wt% or less, and more preferably 50 wt% or less. If the mixing ratio of (c) is too small, when the electrode is pressed at high density in order to increase the battery capacity, there is a fear that the press load becomes high and it is difficult to increase the density. If it is too large, the irreversible capacity increases and the battery capacity may decrease. .

In the case of a mixture combining (b) and (c), the ratio of the graphite particles of (c) to the composite and/or mixture of (b) is usually 5 wt% or more, preferably 10 wt% or more , More preferably 20 wt% or more. Moreover, it is usually 70 wt% or less, preferably 60 wt% or less, and more preferably 50 wt% or less. If the mixing ratio of (c) is too small, when pressing the electrode at high density in order to increase the battery capacity, the press load tends to be high and it is difficult to increase the density, and if it is too large, the irreversible capacity increases and the battery capacity tends to decrease. .

As these combinations, the combination of the composite of (a) and the composite of (b), the combination of the composite of (a) and the graphite particles of (c), and the combination of the composite of (b) and the graphite particles of (c) are preferred, The combination of the composite of (a) and the composite of (b), and the combination of the composite of (a) and the graphite particles of (c) are more preferable because it is easy to produce a high-density electrode, easy to secure a conductive path, and excellent cycle characteristics. .

Moreover, the negative electrode according to the present invention may contain graphite particles whose rhombohedral crystallinity does not satisfy the above range. When the graphite particles are mixed with other graphite whose rhombohedral crystallinity is outside the range of 0% or more and 35% or less, the other graphite is usually 2 wt% or more, preferably 5 to the graphite particle mass of the present invention. It is wt% or more, more preferably 10 wt% or more. Moreover, it is usually 50 wt% or less, preferably 45 wt% or less, and more preferably 40 wt% or less. When there is too little other graphite, there is a tendency that it is difficult to obtain the effect of mixing other graphite, and when it is too much, the effect of the present invention tends to be small.

In addition, when the negative electrode active material contains (a) and/or (b), the rhombohedral crystallinity of the nuclear graphite constituting these composites is usually 0% or more, preferably 3% or more, similar to the graphite particles, It is more preferably 5% or more, and usually 35% or less, preferably 27% or less, still more preferably 24% or less, and particularly preferably 20% or less. The rhombohedral crystallinity of nuclear graphite constituting these composites can be determined by the same method as the graphite particles described above.

(a) Graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less consisting of a composite and/or mixture of nuclear graphite and carbon.

Graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less composed of a composite and/or mixture of nuclear graphite and carbon are, for example, coated or bonded with a carbon precursor to nuclear graphite, and then at 600°C to 2200°C. Firing or vapor deposition by CVD (Chemical Vapor Deposition) method

It can be obtained by, etc.

The composite refers to graphite particles in which carbon is coated or bonded to nuclear graphite and the rhombohedral crystallinity is within the above range. Further, the carbon coverage is usually 1% by mass or more, preferably 2% by mass or more, and is usually 15% by mass or less, and preferably 10% by mass or less.

The coverage of the present invention can be calculated from the mass of nuclear graphite and the mass of carbon derived from the carbon precursor after firing, using the following equation.

Coverage ratio (mass%) = carbon mass ÷ (nuclear graphite mass + carbon mass) × 100

In addition, the said mixture means that graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less and carbon are mixed in an arbitrary ratio without coating or bonding.

(b) Graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less consisting of a composite and/or mixture of nuclear graphite and graphite.

Graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less composed of a composite and/or mixture of nuclear graphite and graphite are, for example, coated or bonded with a carbon precursor to nuclear graphite, and then 2300° C. or more to 3200° C. It can be obtained by graphitizing at the following temperature.

The composite refers to graphite particles in which graphite and/or non-graphite are coated or bonded to nuclear graphite and have a rhombohedral crystallinity of 0% or more and 35% or less.

Further, the coverage of graphite is usually 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less.

The coverage used in the present invention can be calculated from the mass of nuclear graphite and the mass of graphite derived from the carbon precursor after graphitization using the following equation.

Coverage (% by mass) = mass of graphite derived from precursor ÷ (mass of nuclear graphite + mass of graphite derived from precursor) × 100

In addition, the said mixture means that graphite particles and graphite having a rhombohedral crystallinity of 0% or more and 35% or less are mixed in an arbitrary ratio without coating or bonding.

(c) Graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less

The graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less refer to those made of only graphite particles having a rhombohedral crystallization of 0% or more and 35% or less that do not contain the structures (a) and (b). Specifically, it is nuclear graphite subjected to mechanical energy treatment, and refers to graphite particles in which carbon and/or graphite are not compounded or mixed. Further, graphite particles obtained by firing graphite particles having a rhombohedral crystallinity of 0% or more and 35% or less at 400°C to 3200°C can also be used.

The graphite particles may be composed of one type, or may be composed of a plurality of graphite particles having different shapes and particle diameters.

<Physical properties of carbonaceous materials>

When using a carbonaceous material as the negative electrode active material, it is preferable to have the following physical properties.

(X-ray parameter)

The d value (interlayer distance) of the grating plane (002 plane) determined by X-ray diffraction of the carbonaceous material by the Hakjin method is preferably 0.335 nm or more, and usually 0.360 nm or less, preferably 0.350 nm or less, 0.345 nm or less is more preferable. In addition, the crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Hakjin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Average particle diameter based on volume)

The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) determined by laser diffraction/scattering method, and is usually 1 µm or more, preferably 3 µm or more, and more preferably 5 µm or more. , 7 µm or more is particularly preferable, and usually 100 µm or less, 50 µm or less is preferable, 40 µm or less is more preferable, 30 µm or less is still more preferable, and 25 µm or less is particularly preferable.

If the volume-based average particle diameter is less than the above range, the irreversible capacity increases, resulting in loss of initial battery capacity in some cases. Moreover, when it exceeds the said range, when manufacturing an electrode by application|coating, it is easy to become non-uniform drawing, and it may not be preferable in the battery manufacturing process.

The measurement of the volume-based average particle diameter was carried out by dispersing carbon powder in a 0.2% by mass aqueous solution (about 10 ml) of polyoxyethylene (20-mer) sorbitan monolaurate as a surfactant, and a laser diffraction/scattering type particle size distribution meter (Horiba It is carried out using LA-700 manufactured by the manufacturing company. The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.

(Raman R value, Raman half width)

The Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1.5 or less, and 1.2 The following are preferable, 1 or less are more preferable, and 0.5 or less are especially preferable.

When the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where there are fewer sites where Li enters between the layers along with charging and discharging. In other words, there is a case where the charging acceptability decreases. In addition, when the negative electrode is increased in density by applying it to the current collector and then pressing, the crystals are liable to be oriented in a direction parallel to the electrode plate, resulting in a decrease in load characteristics in some cases. Particularly, when the Raman R value is 0.1 or more, a preferable film is formed on the surface of the negative electrode, thereby improving storage characteristics, cycle characteristics, and load characteristics.

On the other hand, if it exceeds the above range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolytic solution increases, and thus the efficiency may decrease or gas generation may increase.

In addition, the Raman half width of the carbonaceous material in the vicinity of 1580 cm ^-1 is not particularly limited, but is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and usually 100 cm ^-1 or less, and 80 ㎝ ^-1 or less is preferable, and more preferably 60 ㎝ ^-1 or less, and is 40 ㎝ ^-1 or less are especially preferred.

When the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where there are few sites where Li enters between the layers along with charging and discharging. In other words, there is a case where the charging acceptability decreases. In addition, when the negative electrode is increased in density by pressing after applying it to the current collector, the crystals are liable to be oriented in a direction parallel to the electrode plate, resulting in a decrease in load characteristics in some cases. On the other hand, if it exceeds the above range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolytic solution increases, and thus the efficiency may decrease or gas generation may increase.

For the measurement of the Raman spectrum, a Raman spectrometer (Raman spectrometer manufactured by Nippon Spectroscope) was used, the sample was naturally dropped into the measurement cell and charged, and the cell was perpendicular to the laser light while irradiating the surface of the sample in the cell with argon ion laser light. It is carried out by rotating within the seal surface. For the obtained Raman spectrum, the intensity I _A of the peak P _{A in} the vicinity of 1580 cm ^-1 and the intensity I _B of the peak P _{B in} the vicinity of 1360 cm ^-1 were measured, and the intensity ratio R (R = I _B /I _A ) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention. Moreover, the half value width of the peak P _{A in} the vicinity of 1580 cm ^-1 of the obtained Raman spectrum is measured, and this is defined as the Raman half value width of the carbonaceous material.

In addition, the Raman measurement conditions are as follows.

Argon ion laser wavelength: 514.5 nm

·Laser power on the sample: 15 ∼ 25 mW

·Resolution: 10 ∼ 20 ㎝ ^-1

·Measurement range: 1100 ㎝ ^-1 ∼ 1730 ㎝ ^-1

Raman R value, Raman half width analysis: background processing

Smoothing process: simple average, convolution 5 points

(BET specific surface area)

The BET specific surface area of the carbonaceous material is a value of the specific surface area measured using the BET method, and is usually 0.1 m2·g ^-1 or more, preferably 0.7 m2·g ^-1 or more, and 1.0 m2·g ^-1 or more more preferably, 1.5 ㎡ · g ^-1 or more is particularly preferable, and further, and typically less than ^{100 ㎡ · g -1, 25 ㎡} · g -1 or less is preferable, and 15 ㎡ · g ^-1 or less, more It is preferable, and 10 m 2 ·g ^-1 or less is particularly preferable.

If the value of the BET specific surface area is less than this range, the water solubility of lithium tends to deteriorate during charging when used as a negative electrode material, lithium tends to precipitate on the electrode surface, and stability may decrease. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte solution increases, gas generation tends to increase, and it may be difficult to obtain a preferable battery.

The measurement of the specific surface area by the BET method was performed using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken), pre-drying the sample at 350°C for 15 minutes under nitrogen flow, and then the relative pressure of nitrogen to atmospheric pressure. Using a nitrogen helium mixed gas accurately adjusted so that the value of is 0.3, it is carried out by the nitrogen adsorption BET one point method by the gas flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material.

(Circular diagram)

When circularity is measured as the degree of sphericity of a carbonaceous material, it is preferable to fall into the following range. In addition, circularity is defined as ``circularity = (circumferential length of an equivalent circle having the same area as the projected particle shape)/(actual circumferential length of the projected particle shape)'', and when the circularity is 1, the theoretical true sphere is do.

The circularity of the particles having a particle diameter of 3 to 40 µm of the carbonaceous material is preferably closer to 1, more preferably 0.1 or more, especially 0.5 or more, more preferably 0.8 or more, and 0.85 The above is more preferable, and 0.9 or more is particularly preferable. The high current density charging and discharging characteristics are improved as the circularity increases. Therefore, if the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge/discharge characteristics for a short time may be lowered.

The measurement of the circularity is performed using a flow-type particle image analysis device (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2 mass% aqueous solution (about 50 ml) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and after irradiating an ultrasonic wave of 28 kHz with an output of 60 W for 1 minute, the detection range was determined. It is specified as 0.6 to 400 µm, and it is measured for particles having a particle diameter in the range of 3 to 40 µm. The circularity obtained by the measurement is defined as the circularity of the carbonaceous material.

The method of improving the circularity is not particularly limited, but it is preferable that the shape of the voids between particles when the electrode body is formed by performing a spheroidization treatment to be spherical is obtained. Examples of spheronization treatment include a method of mechanically approximating a spherical shape by applying a shearing force and a compressive force, and a mechanical/physical treatment method in which a plurality of fine particles are granulated by a binder or the adhesive force of the particles themselves. have.

(Tap density)

The tap density of the carbonaceous material is usually 0.1 g·cm ^-3 or more, preferably 0.5 g·cm ^-3 or more, more preferably 0.7 g·cm ^-3 or more, and 1 g·cm ^-3 or more is particularly It is preferable, and 2 g·cm ^-3 or less is preferable, 1.8 g·cm ^-3 or less is more preferable, and 1.6 g·cm ^-3 or less is particularly preferable. If the tap density is less than the above range, when used as a negative electrode, the packing density does not increase well, and a high-capacity battery may not be obtained. In addition, if it exceeds the above range, the voids between particles in the electrode become too small, the conductivity between particles is difficult to be secured, and desirable battery characteristics may be difficult to obtain.

To measure the tap density, after passing through a sieve having a graduation spacing of 300 μm, dropping the sample into a 20 cm 3 tapping cell, filling the sample up to the top surface of the cell, a powder density meter (for example, a tap made by Seishin Denser), tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material.

(Orientation ratio)

The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. If the orientation ratio is less than the above range, the high-density charge/discharge characteristics may decrease. In addition, the upper limit of the said range is the theoretical upper limit of the orientation ratio of a carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressing the sample. 0.47 g of a sample was charged into a molding machine with a diameter of 17 mm, and the molded article obtained by compressing it to 58.8 MN·m ^{- 2} was set so as to be the same surface as the surface of the sample holder for measurement using clay, and X-ray diffraction was measured. From the peak intensities of (110) diffraction and (004) diffraction of the obtained carbon, a ratio represented by (110) diffraction peak intensity/(004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material.

X-ray diffraction measurement conditions are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα line) graphite monochromator

・Slit:

Divergence slit = 0.5 degree

Light receiving slit = 0.15 mm

Scattering slit = 0.5 degree

Measurement range and step angle/measurement time:

(110) plane: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree/60 seconds

(004) plane: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree/60 seconds

(Aspect ratio (powder))

The aspect ratio of the carbonaceous material is usually 1 or more, and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaks are formed during electrode plate formation, and a uniform coated surface may not be obtained, and high current density charge/discharge characteristics may be deteriorated. In addition, the lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing particles of a carbonaceous material with a scanning electron microscope. Carbonaceous material particles when an arbitrary 50 graphite particles fixed to a cross section of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and inclined to observe three-dimensionally The longest diameter A of and the shortest diameter B orthogonal thereto are measured, and the average value of A/B is calculated. The aspect ratio (A/B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material.

<Configuration and manufacturing method of negative electrode>

Any known method can be used for the manufacture of the electrode as long as the effect of the present invention is not significantly impaired. For example, a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, and the like are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed.

(The current collector)

As the current collector holding the negative electrode active material, a known one can be arbitrarily used. Examples of the current collector of the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred from the viewpoints of ease of processing and cost.

In addition, as for the shape of the current collector, when the current collector is a metal material, for example, a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, and the like may be mentioned. Among them, preferably a metal thin film, more preferably a copper foil, more preferably a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolysis method, and either can be used as a current collector.

The thickness of the current collector is usually 1 µm or more, preferably 5 µm or more, and usually 100 µm or less, preferably 50 µm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, whereas if it is too thin, handling may become difficult.

(Ratio of thickness of current collector and negative electrode active material layer)

The ratio of the thickness of the current collector and the negative electrode active material layer is not particularly limited, but the value of ``(the thickness of the negative electrode active material layer on one side immediately before injecting the nonaqueous electrolyte solution)/(thickness of the current collector)'' is preferably 150 or less, and 20 The following are more preferable, 10 or less are especially preferable, 0.1 or more are preferable, 0.4 or more are more preferable, and 1 or more are especially preferable. When the ratio of the thickness of the current collector and the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charging and discharging. Further, if it is less than the above range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease.

(Binder)

The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to a non-aqueous electrolyte solution or a solvent used in manufacturing an electrode.

Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; Rubber-like polymers such as SBR (styrene/butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR (acrylonitrile/butadiene rubber), and ethylene/propylene rubber; Styrene/butadiene/styrene block copolymer or a hydrogenated product thereof; Thermoplastic elastomer polymers such as EPDM (ethylene/propylene/diene ternary copolymer), styrene/ethylene/butadiene/styrene copolymer, styrene/isoprene/styrene block copolymer or a hydrogenated product thereof; Soft dendritic polymers, such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymer, and propylene/α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene/ethylene copolymer; And polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions). These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, further preferably 20% by mass or less, and 15% by mass or less. It is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder that does not contribute to the battery capacity increases, resulting in a decrease in battery capacity. In addition, if it is less than the above range, a decrease in the strength of the negative electrode may be caused.

In particular, when a rubber-like polymer represented by SBR is contained in the main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. Moreover, it is usually 5 mass% or less, 3 mass% or less is preferable, and 2 mass% or less is more preferable. In addition, when containing a fluorine-based polymer typified by polyvinylidene fluoride as a main component, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. And, it is usually 15 mass% or less, 10 mass% or less is preferable, and 8 mass% or less is more preferable.

(Slurry formation solvent)

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing a negative electrode active material, a binder, and a thickener and a conductive material used if necessary, and either an aqueous solvent or an organic solvent is used. You can use it.

Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, Diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, Pyridine, methylnaphthalene, hexane, etc. are mentioned.

In particular, when an aqueous solvent is used, it is preferable to contain a dispersant or the like in addition to the thickener, and to form a slurry using latex such as SBR. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

(Thickener)

Thickeners are usually used to adjust the viscosity of the slurry. Although it does not specifically limit as a thickener, Specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof, etc. are mentioned. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

In the case of using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less. And 3 mass% or less is preferable, and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is less than the above range, the coatability may be markedly lowered. In addition, if it exceeds the above range, the proportion of the negative electrode active material occupied in the negative electrode active material layer decreases, resulting in a problem in that the capacity of the battery decreases, or the resistance between the negative electrode active materials may increase.

(Electrode density)

The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g·cm ^-3 or more, more preferably 1.2 g·cm ^-3 or more. , 1.3 g·cm ^-3 or more is particularly preferable, and 2.2 g·cm ^-3 or less is preferable, 2.1 g·cm ^-3 or less is more preferable, and 2.0 g·cm ^-3 or less is still more preferable, 1.9 g·cm ^-3 or less is particularly preferred. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, resulting in an increase in initial irreversible capacity or a high current due to a decrease in the permeability of the non-aqueous electrolyte solution to the current collector/negative electrode active material interface. Density charge/discharge characteristics may be deteriorated. Further, if less than the above range, the conductivity between negative electrode active materials decreases, battery resistance increases, and the capacity per unit volume may decrease.

(Thickness of negative electrode plate)

The thickness of the negative electrode plate is designed according to the positive electrode plate used, and is not particularly limited, but the thickness of the mixture layer minus the thickness of the metal foil of the core material is usually 15 µm or more, preferably 20 µm or more, and more preferably 30 µm. It is more preferably 300 µm or less, preferably 280 µm or less, and more preferably 250 µm or less.

(Surface coating of negative electrode plate)

Further, a substance having a composition different from this may be used on the surface of the negative electrode plate. As the surface adhesion substance, oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, Sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

4. Separator

In the nonaqueous electrolyte secondary battery of the present invention, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the non-aqueous electrolytic solution of the present invention is usually used by impregnating this separator.

The material and shape of the separator are not particularly limited, and any known material may be arbitrarily employed as long as the effect of the present invention is not significantly impaired. Among them, in the present invention, a polyolefin resin formed of a material stable to the non-aqueous electrolyte solution of the present invention, other resins, glass fibers, inorganic substances, and the like can be used as constituent components. As the shape, it is preferable to use a porous sheet or nonwoven fabric-like shape having excellent liquid retention properties.

It is preferable that the separator used in the present invention has a polyolefin resin as a part of its constituent components. Here, examples of the polyolefin resin include polyethylene resin, polypropylene resin, 1-polymethylpentene, polyphenylene sulfide, and the like.

Examples of polyethylene-based resins include low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, and copolymers mainly composed of ethylene, ie, ethylene and propylene, butene-1, pentene-1, hexene- 1, C3-C10 alpha-olefins, such as heptene-1 and octene-1; Vinyl esters such as vinyl acetate and vinyl propionate; Unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and other unsaturated compounds such as conjugated diene or non-conjugated diene. Copolymer or polyvalent of one or more comonomers A copolymer or a mixed composition thereof is mentioned. The content of the ethylene unit in the ethylene polymer is usually more than 50% by mass.

Among these polyethylene resins, at least one type of polyethylene resin selected from low density polyethylene, linear low density polyethylene, and high density polyethylene is preferred, and high density polyethylene is most preferred.

In addition, the polymerization catalyst of the polyethylene resin is not particularly limited, and any of a Ziegler type catalyst, a Phillips type catalyst, a Kaminsky type catalyst, and the like may be used. As a polymerization method of the polyethylene-based resin, there are single-stage polymerization, two-stage polymerization, or more multi-stage polymerization, and any method of polyethylene-based resin can also be used.

The melt flow rate (MFR) of the polyethylene-based resin is not particularly limited, but usually, the MFR is preferably 0.03 to 15 g/10 minutes, and preferably 0.3 to 10 g/10 minutes. When the MFR is within the above range, the back pressure of the extruder does not become too high during molding, and productivity is excellent. In addition, MFR in the present invention refers to a measured value under conditions of a temperature of 190°C and a load of 2.16 kg in accordance with JIS K7210.

The production method of the polyethylene-based resin is not particularly limited, and a known polymerization method using a known catalyst for olefin polymerization, for example, a multi-site catalyst represented by a Ziegler-Natta type catalyst or a metallocene catalyst. A polymerization method using a single site catalyst is mentioned.

Next, an example of a polypropylene resin will be described. As the polypropylene resin in the present invention, homopolypropylene (propylene homopolymer), or propylene and ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, or Random copolymers or block copolymers with α-olefins such as 1-decene. Among these, when used for a battery separator, homopolypropylene is more preferably used from the viewpoint of mechanical strength.

In addition, as the polypropylene resin, the isotactic pentad fraction showing stereoregularity is preferably 80 to 99%, more preferably 83 to 98%, still more preferably 85 to 97%. do. If the isotactic pentad fraction is too low, there is a fear that the mechanical strength of the battery separator may decrease. On the other hand, the upper limit of the fraction of the isotactic pentad is currently defined as the upper limit obtained industrially, but is not limited thereto when a resin having higher regularity at the industrial level is developed in the future.

The isotactic pentad fraction refers to a three-dimensional structure or a ratio thereof in which all five methyl groups, which are side chains, are located in the same direction with respect to the main chain formed by a carbon-carbon bond consisting of five consecutive propylene units. . The attribution of the signal in the methyl group region is A. Zambellietatal. (Macromol. 8, 687 (1975)).

Moreover, it is preferable that Mw/Mn which is a parameter showing a molecular weight distribution of a polypropylene resin is 1.5-10.0. More preferably, 2.0 to 8.0, still more preferably 2.0 to 6.0 are used. The smaller Mw/Mn means that the molecular weight distribution is narrower, but when Mw/Mn is less than 1.5, problems such as lowering of extrusion moldability arise and industrial production is often difficult. On the other hand, when Mw/Mn exceeds 10.0, the low molecular weight component increases, and the mechanical strength of the battery separator obtained is liable to decrease. Mw/Mn is obtained by GPC (gel permeation chromatography) method.

In addition, the melt flow rate (MFR) of the polypropylene resin is not particularly limited, but usually, the MFR is preferably 0.1 to 15 g/10 minutes, and more preferably 0.5 to 10 g/10 minutes. When the MFR is less than 0.1 g/10 minutes, the melt viscosity of the resin during molding processing is high, and the productivity decreases. On the other hand, when it exceeds 15 g/10 min, practical problems such as insufficient strength of the battery separator obtained are likely to occur. In addition, MFR is measured under conditions of a temperature of 230°C and a load of 2.16 kg in accordance with JIS K7210.

As materials for other resins and glass fiber separators, for example, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, glass filter, etc. can be used in combination with the polyolefin resin. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, and further 30 μm or less. desirable. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. Further, if it is too thick than the above range, not only the battery performance such as rate characteristics may be lowered, but also the energy density of the non-aqueous electrolyte secondary battery as a whole may decrease.

In the case of using a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but it is usually 20% or more, preferably 35% or more, and more preferably 45% or more. Moreover, it is 90% or less normally, 85% or less is preferable, and 75% or less is more preferable. If the porosity is too small than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. In addition, when it is too large than the above range, the mechanical strength of the separator decreases and the insulation property tends to decrease.

Moreover, although the average pore diameter of the separator is also arbitrary, it is usually 0.5 µm or less, preferably 0.2 µm or less, and usually 0.05 µm or more. When the average pore diameter exceeds the above range, short circuit is likely to occur. Further, if it is less than the above range, the film resistance may increase and the rate characteristics may decrease.

On the other hand, as the material of the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate or calcium sulfate are used, and those in the form of particles or fibers are used.

As a form, a nonwoven fabric, a woven fabric, a thin film such as a microporous film is used. In a thin film shape, those having a pore diameter of 0.01 to 1 µm and a thickness of 5 to 50 µm are preferably used. In addition to the above independent thin film shape, a separator formed by forming a composite porous layer containing particles of the inorganic substance on the surface layer of the positive electrode and/or the negative electrode using a resin binder can be used. For example, forming a porous layer using a fluororesin as a binder is exemplified by forming alumina particles having a 90% particle diameter of less than 1 µm on both surfaces of the positive electrode.

5. Battery design

<electrode group>

The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral wound shape through the separator. Any of the following may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy) is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80 % Or less is preferable.

If the electrode group occupancy is less than the above range, the battery capacity decreases. In addition, if it exceeds the above range, the void space is small, the member expands due to the high temperature of the battery, or the vapor pressure of the liquid component of the electrolyte increases, thereby increasing the internal pressure, and various characteristics such as charge/discharge repeatability and high temperature storage as a battery. There are cases in which a gas discharge valve that lowers the pressure or, further, discharges the internal pressure to the outside is operated.

<Collection structure>

Although the current collecting structure is not particularly limited, in order to more effectively realize the improvement of the charging/discharging characteristics at a high current density by the non-aqueous electrolyte solution of the present invention, it is preferable to have a structure in which the resistance of the wiring portion or the junction portion is reduced. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolyte solution of the present invention is exhibited particularly favorably.

When the electrode group has the above-described stacked structure, a structure formed by bundling metal core portions of each electrode layer and welding to a terminal is preferably used. When the area of one electrode is increased, the internal resistance is increased, and therefore, it is also preferably used to form a plurality of terminals in the electrode to reduce the resistance. In the case where the electrode group has the above wound structure, the internal resistance can be lowered by forming a plurality of lead structures on the positive electrode and the negative electrode, respectively, and binding them to the terminals.

<Exterior case>

The material of the outer case is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte used. Specifically, a metal such as a nickel plated steel sheet, stainless steel, aluminum or aluminum alloy, or magnesium alloy, or a laminated film (laminate film) of resin and aluminum foil is used. From the viewpoint of weight reduction, a metal of aluminum or an aluminum alloy, and a laminate film are preferably used.

In the case of an exterior case using metals, metals are welded to each other by laser welding, resistance welding, or ultrasonic welding to form a sealing and sealing structure, or a caulking structure using the metals through a resin gasket. Can be mentioned. In the case of an exterior case using the laminated film, resin layers are heat-sealed to form a sealed and sealed structure. In order to increase the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed through a current collecting terminal to form a sealed structure, since the metal and the resin are bonded to each other, a resin having a polar group or a modified resin in which a polar group is introduced is preferably used as the intervening resin.

<Protection element>

As a protection element, PTC (Positive Temperature Coefficient), which increases resistance when abnormal heat or excessive current flows, cuts off the current flowing through the circuit by a rapid increase in the internal pressure or internal temperature of the battery during abnormal heating. Valves (current cutoff valves), etc. can be used. It is preferable to select the protection element under a condition that does not operate under normal use of a high current, and more preferably a design that does not cause abnormal heat generation or thermal runaway even without the protection element.

<Exterior body>

The nonaqueous electrolyte secondary battery of the present invention is typically configured by housing the nonaqueous electrolyte, negative electrode, positive electrode, separator, and the like in an exterior body. This exterior body is not particularly limited, and known ones may be arbitrarily employed as long as the effect of the present invention is not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, and the like are used.

Further, the shape of the exterior body is also arbitrary, and for example, any of a cylindrical shape, a square shape, a laminate type, a coin type, and a large size may be used.

6. Battery performance

The non-aqueous electrolyte secondary battery of the present invention can be used without any particular limitation, but it can be preferably used for a high voltage or high capacity battery.

Higher voltage means, for example, in the case of a lithium ion secondary battery, usually 4.3 V or higher, preferably 4.4 V or higher, more preferably 4.5 V or higher, and still more preferably 4.6 V or higher.

In addition, in the case of an 18650 type battery, for example, high capacity|capacitance is usually 2600 mAh or more, Preferably it is 2800 mAh or more, More preferably, it is 3000 mAh or more.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Preparation of electrolyte]

In a dry argon atmosphere, ethylene carbonate (EC) or propylene carbonate (PC) as a cyclic carbonate represented by formula (1), 4-fluoroethylene carbonate (MFEC) as a fluorinated cyclic carbonate represented by formula (2) or 4,5-difluoroethylene carbonate (DFEC), (2,2,2-trifluoroethyl) methyl carbonate (TFEMC) as a fluorinated chain carbonate represented by the general formula (3), ethyl methyl carbonate as another solvent (EMC), dimethyl carbonate (DMC), hexamethylene diisocyanate (HMDI) as an auxiliary agent, 1,3-bis (isocyanatomethyl) cyclohexane (BIMCH), 1,3,5-tris (6-isocyanato) Hexyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (CTI), FSO ₃ Li, LiBF ₄ , or LiPO ₂ F ₂ in the ratio described in Table 1 Mixed. LiPF ₆ dried here was dissolved in a ratio of 1 mol/L to prepare basic electrolyte solutions 1 to 28.

[Salt Solubility Evaluation]

The prepared basic electrolyte solutions 1 to 28 were cooled, and the presence or absence of salt precipitation was visually confirmed at 0°C. The electrolytic solution in which precipitation did not occur was set to ○, and the electrolytic solution in which precipitation occurred was set to ×.

The precipitation of 210,000 electrolytic solutions composed of only cyclic carbonate and fluorinated chain carbonate was observed. By mixing the fluorinated cyclic carbonate, this precipitate is dissolved in the electrolytic solution, it was found that it is necessary to coexist the fluorinated cyclic carbonate in the mixed electrolytic solution of the non-fluorinated cyclic carbonate and the fluorinated chain carbonate.

[Example A: High-voltage battery with an open circuit voltage of 4.90 V between battery terminals]

[Selection of electrolyte]

The basic electrolyte solutions 1 to 19, 24, and 25 in which no salt precipitation was observed at 0°C were used as the electrolyte solutions used in Examples 1 to 21, and the basic electrolyte solutions 20, 22 and 26 were used as the electrolyte solutions used in Comparative Examples 1 to 3 .

[Manufacture of negative electrode]

100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose 1% by mass) and styrene-butadiene rubber as a thickener and a binder in 98 parts by mass of a natural graphite-based carbonaceous material (25% rhombohedral crystallinity) 1 part by mass of aqueous dispersion (50% by mass concentration of styrene-butadiene rubber) was added, followed by mixing with a disperger to form a slurry. The resulting slurry was applied to a copper foil having a thickness of 10 μm, dried, and rolled with a press, and cut into a shape having an uncoated portion having a width of 30 mm, a length of 40 mm, and a width of 5 mm and a length of 9 mm as the size of the active material layer. It was set as the negative electrode used for Examples 1 to 21 and Comparative Examples 1 to 3, respectively.

[Manufacture of positive electrode]

As a positive electrode active material LiNi _{0 .5} Mn _{1 .5} O ₄ with a 85% by mass, and 10 mass% of acetylene black as a conductive material, as a binder, polyvinylidene fluoride (PVdF) N- methylpyrrolidone solvent to 5% by weight It was mixed in and formed into a slurry. The resulting slurry was applied to an aluminum foil having a thickness of 15 µm, dried, and rolled with a press, and cut into a shape having an uncoated portion having a width of 30 mm, a length of 40 mm, and a width of 5 mm and a length of 9 mm as the size of the active material layer. , It was set as the positive electrode used for Examples 1-21 and Comparative Examples 1-3, respectively.

[Manufacture of lithium secondary battery]

The positive electrode, the negative electrode, and the polyethylene separator were stacked in the order of a negative electrode, a separator, and a positive electrode to manufacture a battery element. The battery element was inserted into a bag made of a laminate film in which both sides of aluminum (thickness 40 μm) were coated with a resin layer while protruding and forming the terminals of the positive electrode and the negative electrode, and then the basic electrolyte solutions described in Tables 3, 4, and 5 were added to each bag. It injected into the inside and vacuum-sealed, and a sheet-shaped battery was manufactured, and it was set as the battery used for Examples 1 -21 and Comparative Examples 1-3, respectively.

[Practice driving]

The prepared sheet-shaped lithium secondary battery was sandwiched between glass plates to increase the adhesion between the electrodes, with a constant current equivalent to 0.1 C at 25°C, and a positive electrode potential of 4.95 V based on Li/Li ⁺ , that is, opening between battery terminals. Practice operation was conducted so that the voltage was 4.90 V. Here, 1 C denotes a current value for discharging the reference capacity of the battery for 1 hour, 2 C denotes a current value twice that, and 0.1 C denotes a current value of 1/10. The battery is charged with a constant current of 1/3 C and then discharged with a constant current of 1/3 C in the range of 25° C. and the open voltage between the battery terminals in the range of 3.0 to 4.9 V, for a total of 4 cycles. I did. With the above steps, it was set as the practice operation of confirming the discharge capacity.

[Evaluation of cycle characteristics]

The process of charging and discharging the battery after the practice operation is completed with a constant current of 1/3 C in the range of 60 ℃ and the open voltage between the battery terminals is 3.0-4.9 V, and then charging and discharging with a constant current of 2 C. Was made into 1 cycle, and 200 cycles were performed. In the meantime, charging and discharging was performed with a constant current of 1/3 C at the 50, 100, and 200 cycles to check the capacity. The discharge capacity retention rate (cycle retention rate) was determined from a calculation formula of (discharge capacity at the 200th cycle) ÷ (discharge capacity at the first cycle) x 100 at a constant current of 1/3C. Further, the amount of gas generated and the resistance of the battery in which the practice operation was completed were measured. The evaluation results are shown in Tables 3, 4 and 5.

From Table 3, the non-aqueous electrolyte solution (Examples 1 to 13) containing more than 15% by volume of EC or a mixed cyclic carbonate of EC and PC according to the present invention is a nonaqueous electrolyte solution having 15% by volume or less of cyclic carbonate. With respect to (Comparative Examples 1 and 2), it can be seen that the cycle retention rate under high voltage is excellent.

In Comparative Example 1 that did not contain the cyclic carbonate represented by the general formula (1), the cycle retention rate was significantly lowered before 200 cycles of charging and discharging, and charging and discharging was not possible at the time of 200 cycles (therefore, Table The number in indicates the retention rate at 100 cycles). Further, it was suggested that Comparative Example 1 containing no cyclic carbonate represented by the general formula (1) had a very large initial amount of generated gas and insufficient stability under high voltage. In Comparative Example 2 containing 15% by volume of the cyclic carbonate represented by the general formula (1), the amount of gas generated at the initial stage was reduced, and charging and discharging was possible even after 200 cycles, but the capacity retention rate was 32%, indicating that the stability under high voltage was insufficient. It was suggested. On the other hand, in Examples 1 to 13 containing more than 15% by volume of the cyclic carbonate represented by the general formula (1), gas generation was also suppressed and the cycle retention rate was also improved. It is surprising that the generation of gas during durability was suppressed and the cycle characteristics were improved by coexisting a certain amount of EC or PC in the electrolytic solution under high voltage conditions, which generally has less oxidation resistance compared to the fluorinated solvent. This result suggests the specificity of EC and PC in a high voltmeter.

In addition, when HMDI, CTI, FSO ₃ Li, LiBF ₄ , LiPO ₂ F ₂ , BIMCH, or a combination thereof was added as an auxiliary agent, the cycle retention rate was further excellent (Examples 5 to 11). Although this effect is not particularly limited, it was speculated that it originated from the protective effect of the electrode surface by various auxiliary agents.

Moreover, it can be seen from Table 4 that a composition containing more cyclic carbonates represented by General Formula (1) also exhibits a good cycle retention rate. Instead of increasing the ratio of the cyclic carbonate represented by the general formula (1), the ratio of the fluorinated chain carbonate was reduced, but the fluorinated chain carbonate operated satisfactorily even when it was reduced to 10% by volume.

In addition, for an electrolyte solution having a composition containing a large amount of cyclic carbonate represented by the general formula (1), when BIMCH and LiBF ₄ were added as auxiliary agents, the cycle retention rate was further excellent (Examples 17, 18, 19). Although this effect is not particularly limited, it was speculated that it originated from the effect of protecting the electrode surface by BIMCH.

Even when DFEC was used as the fluorinated cyclic carbonate, the cycle retention was further improved by mixing the cyclic carbonate EC, which is a characteristic of the present invention, similarly to MFEC (Examples 20 and 21). Moreover, it is also possible to suppress the amount of generated gas by adding EC. That is, regardless of the type of fluorinated cyclic carbonate, the effect of adding EC is confirmed, and from the viewpoint of suppression of gas generation during durability and improvement of cycle characteristics in a high-voltage battery system, General Formula (1) It has been shown that the cyclic carbonate represented by is acting specifically and effectively.

[Example B: Upper limit operating potential dependence]

[Manufacture of lithium secondary battery]

Using the same negative electrode and positive electrode as in Example A, and using the same method as in Example A, a lithium secondary battery was manufactured.

[Practice driving]

The prepared sheet-shaped lithium secondary battery is sandwiched between glass plates to increase the adhesion between the electrodes, and the positive electrode potential is 4.95 V, 4.90 V, 4.85 V based on Li/Li ⁺ with a constant current equivalent to 0.1 C at 25°C. , 4.75 V, 4.65 V, that is, the open voltage between the battery terminals was in the range of 4.90 V, 4.85 V, 4.80 V, 4.70 V, and 4.60 V. The battery was charged with a constant current of 1/3 C, and then discharged with a constant current of 1/3 C in the range of 25° C. and the open-circuit voltage between the respective battery terminals as 1 cycle, followed by 4 cycles. With the above steps, it was set as the practice operation of confirming the discharge capacity. Table 6 shows the discharge current capacity of each sheet-shaped lithium secondary battery after exercise driving at 25°C and 1/3 C constant current discharge.

Even if the upper limit operating potential was in the range of the high positive electrode potential of 4.75-4.95 V, there was no significant difference in the discharge capacity after the practice operation, but the discharge capacity at 4.65 V was almost reduced by half. This is because if the upper limit operating potential is too low, charging to a sufficient depth is not possible and capacity cannot be obtained. Therefore, the durability evaluation of Example B was performed in the range of 4.75 V or more of the upper limit operating potential capable of taking out a large discharge capacity.

[Example B: Cycle durability evaluation]

[Selection of electrolyte]

Basic electrolytic solution 3 in which no salt precipitation was observed at 0°C was used as the electrolytic solution used in Examples 22 to 24, and basic electrolytic solution 7 was used as the electrolytic solution for Examples 25 and 26, and basic electrolytic solution 27 was used for Comparative Example 4. It was set as the electrolyte solution.

[Example 22]

[Manufacture of negative electrode]

It was manufactured by the same method as the negative electrode used in Example A, and was set as the negative electrode used in Example 22.

[Manufacture of positive electrode]

It was manufactured by the same method as the positive electrode used in Example A, and was set as the positive electrode used in Example 22.

[Manufacture of lithium secondary battery]

Regarding the manufacture of a lithium secondary battery, a lithium secondary battery was manufactured using the same method as in Example A using the electrolyte 3 shown in Table 1 as a basic electrolyte.

[Practice driving]

The prepared sheet-shaped lithium secondary battery was sandwiched between glass plates to increase the adhesion between the electrodes, and the positive electrode potential was 4.75 V, that is, the open voltage between the battery terminals was 4.70 V at a constant current equivalent to 0.1 C at 25°C. Practice driving was carried out. The battery was charged with a constant current of 1/3 C in the range of 25° C. and 3.0-4.70 V as an open voltage between the battery terminals, and then discharged at a constant current of 1/3 C as 1 cycle, and 4 cycles were performed. . It was set as the practice operation of Example 22 with the above process.

[Evaluation of cycle characteristics]

The process of charging and discharging the battery after the practice operation is completed with a constant current of 1/3 C in the range of 3.0-4.70 V as an open voltage between the battery terminals at 60° C., and then charging and discharging with a constant current of 2 C. Was made into 1 cycle, and 200 cycles were performed. In the meantime, charging and discharging with a constant current of 1/3 C was performed at the 50, 100, and 200 cycles to check the capacity. From the calculation formula of (discharge capacity at the 200th cycle) ÷ (discharge capacity at the first cycle) × 100 at a constant current of 1/3 C, the discharge capacity retention rate (cycle retention rate) was calculated as the evaluation result of Example 22. I did. Table 7 shows the evaluation results.

[Example 23]

Regarding practice operation and evaluation of cycle characteristics, manufacturing, practice operation, and evaluation of cycle characteristics were performed in the same manner as in Example 22, except that the positive upper limit potential was set to 4.85 V, that is, the open voltage between battery terminals was 4.80 V. I did. Table 7 shows the evaluation results.

[Example 24]

Regarding practice operation and evaluation of cycle characteristics, manufacturing, practice operation, and evaluation of cycle characteristics were performed in the same manner as in Example 22, except that the positive upper limit potential was set to 4.90 V, that is, the open voltage between battery terminals was 4.85 V. I did. Table 7 shows the evaluation results.

[Example 25]

Regarding the manufacture of a lithium secondary battery, in the same manner as in Example 23, except that the electrolyte 7 shown in Table 1 was used as the basic electrolyte, production, training operation, and evaluation of cycle characteristics were performed. Table 7 shows the evaluation results.

[Example 26]

Regarding the manufacture of a lithium secondary battery, in the same manner as in Example 24, except for using the electrolyte 7 shown in Table 1 as the basic electrolyte, production, training operation, and evaluation of cycle characteristics were performed. Table 7 shows the evaluation results.

[Comparative Example 4]

Regarding the manufacture of a lithium secondary battery, in addition to using the electrolyte solution 27 shown in Table 1 as a basic electrolyte solution, manufacturing, practice operation, and evaluation of cycle characteristics were performed using the same method as in Example 22. Table 7 shows the evaluation results. Table 7 also shows Example 7 in which the upper limit potential of the positive electrode was 4.95 V.

It is understood that the high-voltage design cells (Examples 22, 23, and 24) in which the upper limit potential of the positive electrode was 4.75 V, 4.85 V, and 4.90 V exhibited a high cycle retention rate.

For example, in Example 22 in which the upper limit potential of the positive electrode was set to 4.75 V using the non-aqueous electrolyte according to the present invention, the capacity retention rate after 200 cycles was high to 82.0%, and by applying this design, high durability in a high voltage design cell On the other hand, in the case of using a non-aqueous electrolyte solution containing no fluorinated solvent according to the present invention in the cycle test at the same upper limit potential of the positive electrode, the capacity retention rate is greatly reduced to 55.7% (Comparative Example 4 ). As described above, even in a high-voltage design cell in which the open circuit voltage between battery terminals exceeds 4.7 V, a lithium secondary battery having high durability can be obtained by using the non-aqueous electrolyte according to the present invention.

Moreover, when CTI was added as an auxiliary agent, a more excellent cycle retention rate was shown (Examples 25, 26, 7). Although this effect is not particularly limited, it was speculated that it originated from the protective effect of the electrode surface by CTI.

[Example C]

[Selection of electrolyte]

The basic electrolyte solution 2 and the basic electrolyte solution 28 in which no salt precipitation was observed at 0°C were used as the electrolyte solutions used in Example 27 and Comparative Example 5, respectively.

[Manufacture of negative electrode]

It was manufactured by the same method as the negative electrode used for Examples A and B, and was set as the negative electrode used for Example 27 and Comparative Example 5.

[Manufacture of positive electrode]

As the positive electrode active material Li _{1 .1} (Ni Mn _{0 .45 0 .45 0 .10} Co) and the O ₂ 85% by mass, and 10 mass% of acetylene black as a conductive material, a polyvinylidene fluoride 5 wt% as a binder It was mixed in an N-methylpyrrolidone solvent to make a slurry. The resulting slurry was applied to an aluminum foil having a thickness of 15 µm coated with a conductive aid in advance, dried, and rolled with a press, as the size of the active material layer, as the size of the active material layer, with a width of 30 mm, a length of 5 mm, and a length of 9 mm. It cut out into the shape which had and was set as the positive electrode used for Example 27 and Comparative Example 5.

[Manufacture of lithium secondary battery]

A sheet-like battery was produced in the same manner as in Examples A and B, except that the electrolyte solution, the negative electrode, and the positive electrode were used, and a battery used in Example 27 and Comparative Example 5 was obtained.

[Practice driving]

The manufactured lithium secondary battery is sandwiched between glass plates to increase the adhesion between the electrodes, with a constant current equivalent to 0.2 C at 25°C, and the upper limit operating potential of the positive electrode is 4.65 V based on Li/Li ⁺ , that is, between the battery terminals. Practice operation was carried out in the range of voltage 3.0-4.6 V so that the open circuit voltage was 4.60 V.

[Evaluation of cycle characteristics]

The battery on which the practice operation was completed was charged with a constant current of 2 C in the range of 60° C. and an open voltage between the battery terminals of 3.0 to 4.6 V, and then discharged with a constant current of 2 C as 1 cycle, and 200 cycles were performed. . The discharge capacity retention rate (cycle retention rate) was determined from the calculation formula of (discharge capacity at the 200th cycle) ÷ (discharge capacity at the first cycle) x 100. Table 8 shows the evaluation results.

As can be seen from Table 8, by using the non-aqueous electrolyte according to the present invention, a high cycle retention rate exceeding 70% was exhibited even under severe conditions of 60°C and 200 cycles.

[Example D]

[Selection of electrolyte]

Basic electrolytic solution 3 and basic electrolytic solution 20 in which no salt precipitation was observed at 0°C were used as electrolytic solutions used in Example 28 and Comparative Example 6, respectively.

[Manufacture of negative electrode]

A lithium titanium composite oxide as a negative electrode active material, carbon black as a conductive material, a binder, and a binder were mixed in a solvent to form a slurry. Using the obtained slurry, it was set as the negative electrode used for Example 28 and Comparative Example 6 by the method similar to Examples A, B, and C.

[Manufacture of positive electrode]

It was manufactured by the same method as the positive electrode used for Examples A and B, and was set as the positive electrode used for Example 28 and Comparative Example 6.

[Manufacture of lithium secondary battery]

A sheet-like battery was produced in the same manner as in Examples A, B, and C, except that the electrolyte solution, the negative electrode, and the positive electrode were used, and a battery for use in Example 28 and Comparative Example 6 was obtained.

[Practice driving]

The prepared sheet-shaped lithium secondary battery was sandwiched between glass plates to increase the adhesion between the electrodes, with a constant current equivalent to 0.1 C at 25°C, and a positive electrode potential of 4.95 V based on Li/Li ⁺ , that is, opening between battery terminals. Practice operation was conducted so that the voltage became 3.50 V. The battery is charged with a constant current of 1/3 C, and discharged with a constant current of 1/3 C in the range of 25° C. and the open voltage between the battery terminals in the range of 1.50 to 3.50 V. I did. With the above steps, it was set as the practice operation of confirming the discharge capacity.

[Evaluation of cycle characteristics]

The process of charging and discharging the battery after the practice operation is completed at 60°C and the open voltage between the battery terminals in the range of 1.5-3.5 V with a constant current of 1/3 C, and then charging and discharging with a constant current of 2 C. Was made into 1 cycle, and 200 cycles were performed. In the meantime, charging and discharging with a constant current of 1/3 C was performed at the 50, 100, and 200 cycles to check the capacity. The discharge capacity retention rate (cycle retention rate) was determined from a calculation formula of (discharge capacity at the 200th cycle) ÷ (discharge capacity at the first cycle) x 100 at a constant current of 1/3C. Further, the amount of gas generated and the resistance of the battery in which the practice operation was completed were measured. Table 9 shows the evaluation results.

As can be seen from Table 9, by using the non-aqueous electrolyte according to the present invention, a high cycle retention rate exceeding 70% was exhibited even under severe conditions of 60°C and 200 cycles, and further gas generation was also suppressed. That is, even in the case of using a lithium titanium composite oxide as the negative electrode, as in the case of using carbon as the negative electrode, by coexisting a certain amount of EC in the electrolytic solution under high voltage conditions, gas generation during durability was suppressed and the cycle characteristics were also improved. This is one result and suggests the specificity of EC in a high voltmeter.

Industrial availability

The non-aqueous electrolyte secondary battery of the present invention can be used for various known applications. As a specific example, for example, a notebook PC, a pen input PC, a mobile PC, an electronic book player, a mobile phone, a smartphone, a mobile fax, a mobile copy, a mobile printer, a headphone stereo, a video movie, a LCD TV, a handy cleaner, Portable CD, mini disc, transceiver, electronic notebook, electronic desk calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, motorcycle, motorized bicycle, bicycle, lighting equipment, toys, game equipment, clock, electric Tools, strobes, cameras, load leveling power supplies, and natural energy storage power supplies.

Claims (12)

A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a lithium salt and a non-aqueous solvent dissolving the same, a negative electrode capable of storing and discharging lithium ions, and a positive electrode,
The upper limit operating potential of the positive electrode is 4.5 V or more based on Li/Li ⁺ ,
The non-aqueous electrolyte solution contains a cyclic carbonate represented by the following general formula (1), a fluorinated cyclic carbonate represented by the following general formula (2), and a fluorinated chain carbonate represented by the following general formula (3), The total amount of carbonates represented by 1), (2) and (3) is 100% by volume or less of the nonaqueous solvent, and the cyclic carbonate represented by the general formula (1) is more than 15% by volume and 70% by volume in the nonaqueous solvent. % Or less, and the total amount of carbonates represented by the general formulas (1) and (2) is 25% by volume or more and 98% by volume or less of the nonaqueous solvent.
[Formula 1]

(In General Formula (1), R ₁ represents hydrogen or a hydrocarbon group, and may be the same or different from each other)
[Formula 2]

(In General Formula (2), R ₂ represents hydrogen, fluorine, or a hydrocarbon group, and may be the same or different from each other)
[Formula 3]

(In general formula (3), R ₃ may have a substituent and a hydrocarbon group containing at least one fluorine, R ₄ represents a hydrocarbon group which may have a substituent, and R ₃ and R ₄ may be the same or different. do) The method of claim 1,
In the non-aqueous electrolyte solution, the total amount of carbonates represented by the general formulas (1) to (3) is 50 vol% or more and 100 vol% or less of the non-aqueous solvent. The method of claim 1,
In the non-aqueous electrolyte solution, a fluorinated chain carbonate represented by the general formula (3) is contained in a non-aqueous solvent in an amount of 5% by volume or more and 75% by volume or less. The method of claim 1,
In the nonaqueous electrolyte solution, a cyclic carbonate represented by the general formula (1) is contained in a nonaqueous solvent in an amount of 20% by volume or more and 70% by volume or less. The method of claim 1,
In the general formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The method according to any one of claims 1 to 5,
Non-aqueous electrolyte secondary battery, characterized in that the cyclic carbonate represented by the general formula (1) is at least one selected from ethylene carbonate and propylene carbonate. The method according to any one of claims 1 to 5,
A nonaqueous electrolyte secondary battery, wherein the fluorinated cyclic carbonate represented by the general formula (2) is at least one selected from 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate. The method according to any one of claims 1 to 5,
A non-aqueous electrolyte secondary battery, wherein the fluorinated chain carbonate represented by the general formula (3) contains trifluoroethylmethylcarbonate. The method according to any one of claims 1 to 5,
The non-aqueous electrolyte secondary battery, wherein the positive electrode contains a positive electrode active material containing at least one selected from the group consisting of lithium transition metal compounds represented by the following general formulas (4) to (6).
Li[Li _a M _x Mn _2-xa ]O _4+δ … (4)
(In formula (4), 0 ≤ a ≤ 0.3, 0.4 <x <1.1, -0.5 <δ <0.5 is satisfied, and M is at least one of transition metals selected from Ni, Cr, Fe, Co, and Cu. Indicate)
Li _x M1 _y M2 _z O _2-δ ... (5)
(In formula (5), 1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 0.3, -0.1 ≤ δ ≤ 0.1 is satisfied, M1 represents Ni, Co and/or Mn, and M2 represents Fe , Cr, V, Ti, Cu, Ga, Bi, Sn, B, P, Zn, Mg, Ge, Nb, W, Ta, Be, Al, Ca, Sc, and at least one of the elements selected from Zr )
αLi ₂ MO ₃ ·(1-α)LiM'O ₂ … (6)
(In formula (6), 0<α<1 is satisfied, M represents at least one metal element with an average oxidation number of +4, and M'represents at least one metal element with an average oxidation number of +3) The method according to any one of claims 1 to 5,
The non-aqueous electrolyte secondary battery, wherein the negative electrode contains a negative electrode active material made of graphite particles. delete delete