JP5799752B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, a non-aqueous electrolyte containing a specific cyclic compound having a triple bond as an electrolyte and a negative electrode comprising graphite having a specific ratio of rhombohedral crystal in the negative electrode The present invention relates to a non-aqueous electrolyte secondary battery including an active material, a non-aqueous electrolyte provided in the non-aqueous electrolyte secondary battery, and a negative electrode active material.

  Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are widely used as power sources for so-called portable electronic devices such as mobile phones and notebook computers, to in-vehicle power sources for automobiles and large power sources for stationary applications. It is being put into practical use. However, with the recent high performance of electronic devices and the application to in-vehicle power supplies for driving and large power supplies for stationary applications, the demand for applied secondary batteries is increasing, and the high performance of the battery characteristics of secondary batteries is increasing. For example, it is required to achieve high levels of improvement in capacity, high temperature storage characteristics, cycle characteristics, and the like.

  The electrolyte used for the non-aqueous electrolyte lithium secondary battery is usually composed mainly of an electrolyte and a non-aqueous solvent. The main components of the non-aqueous solvent include 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. It is used.

  In addition, various nonaqueous solvents, electrolytes, auxiliaries, and the like have been proposed in order to improve battery characteristics such as load characteristics, cycle characteristics, storage characteristics, and low temperature characteristics of batteries using these nonaqueous electrolyte solutions. . For example, in a non-aqueous electrolyte using carbon as the negative electrode active material, by using vinylene carbonate and its derivatives or vinyl ethylene carbonate derivatives, the cyclic carbonate having a double bond reacts preferentially with the negative electrode surface. Patent Documents 1 and 2 disclose that a high-quality film is formed on the battery, thereby improving the storage characteristics and cycle characteristics of the battery.

  In addition, for example, in a non-aqueous electrolyte using artificial graphite as a negative electrode active material, by combining a specific ethylene carbonate derivative with a triple bond-containing compound and / or a pentafluorophenyloxy compound, gas generation is reduced and cycle characteristics are reduced. It is disclosed in Patent Document 3 that the above is improved.

JP-A-8-45545 JP-A-4-87156 WO 2006-077763

As described above, in recent years, the demand for higher performance of secondary batteries is increasing, and thus the characteristics of lithium secondary batteries have been improved, that is, higher capacity, higher temperature storage characteristics, cycle characteristics and the like have been demanded.
Under such a background, in the non-aqueous electrolyte secondary battery using carbon as the negative electrode active material described in Patent Documents 1 and 2 and using a cyclic carbonate having a double bond as the non-aqueous electrolyte, the electrode surface Although the battery durability such as storage characteristics and cycle characteristics is improved by protecting the battery, if the charged battery is left at a high temperature or subjected to continuous charge and discharge cycles, the unsaturated cyclic carbonate or derivative thereof is formed on the positive electrode. There was a problem that carbon dioxide gas was generated by oxidative decomposition. If carbon dioxide gas is generated in such a use environment, the battery itself may become unusable due to, for example, activation of a battery safety valve or expansion of the battery.

Further, in a non-aqueous electrolyte secondary battery using artificial graphite as the negative electrode active material described in Patent Document 3 and using a triple bond-containing compound as a non-aqueous electrolyte, a triple bond-containing compound or the like is used as a non-aqueous electrolyte. Although it is used, if the electrode density is increased to increase the capacity, there is a problem that the reactivity with the electrolytic solution is large and the cycle characteristics are difficult to improve.
Therefore, the present invention provides a non-aqueous electrolyte secondary battery in which the various problems expressed with respect to the required performance in recent secondary batteries are solved, and in particular, durability characteristics such as cycle and storage are improved. And providing a non-aqueous electrolyte suitable for the non-aqueous electrolyte secondary battery and a negative electrode active material.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have made a negative electrode active material composed of graphite particles having a rhombohedral crystal ratio of 0% to 35% in a negative electrode used in a non-aqueous electrolyte battery. In addition, the non-aqueous electrolyte contains at least one or more compounds selected from the group consisting of compounds represented by the following general formula (1), thereby improving durability characteristics such as cycle and storage. The present inventors have found that an aqueous electrolyte battery can be realized and have completed the present invention.

That is, the gist of the present invention is as follows.
a) a non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous solvent for dissolving the lithium salt, a negative electrode capable of occluding and releasing lithium ions, and a positive electrode, wherein the negative electrode Including a negative electrode active material composed of graphite particles having a plane crystallinity of 0% to 35%,
b) The present invention relates to a non-aqueous electrolyte battery characterized in that the non-aqueous electrolyte contains a compound represented by the following general formula ( 2 ). (Claim 1)

(Y represents C═O, S═O, S (═O) ₂ , P (═O) —R ² , P (═O) —OR ³ , where R ² is an optionally substituted carbon. It is a hydrocarbon group of the number 1 to 20. R ³ is Li, NR ⁴ ₄ or
Or it is a C1-C20 hydrocarbon group which may have a substituent. R ⁴ has a substituent
And may be the same or different from each other. )
Another gist of the present invention is that the interlayer distance d002 of the (002) plane of the graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less according to claim 1 is 0.335 nm or more and 0.339 nm. It exists in the non-aqueous electrolyte secondary battery characterized by the following. (Claim 2)
Another gist of the present invention is that the graphite particles having a rhombohedral crystal ratio of 0% to 35% according to claim 1 or 2 are graphite particles in which carbon is coated with nuclear graphite, and graphite is nuclear graphite. A non-aqueous electrolyte battery characterized by being selected from at least one of graphite particles coated with graphite and natural graphite particles. (Claim 3)
Another gist of the present invention is that the compound represented by the general formula ( 2 ) according to any one of claims 1 to 3 is represented by the following formulas (3) to (8): The present invention resides in a non-aqueous electrolyte secondary battery characterized by being at least one of the following. (Claim 4)

Also, another aspect of the present invention, the non-aqueous electrolyte solution according to any one of the claims 1 to 4, carbon - selected from a cyclic carbonate having a cyclic carbonate and a fluorine atom carbon double bond A non-aqueous electrolyte secondary battery characterized in that it contains at least one or more of the group. (Claim 5)
Another gist of the present invention is that the non-aqueous electrolyte solution according to any one of claims 1 to 5 is at least lithium monofluorophosphate (LiPO ₃ F), lithium difluorophosphate (LiPO ₂ F). ₂ ) non-aqueous electrolysis characterized by containing any one selected from the group consisting of FSO ₃ Li, lithium bis (oxalato) borate, lithium tetrafluorooxalatophosphate, and lithium difluorobis (oxalato) phosphate It resides in a liquid secondary battery. (Claim 6)
Another gist of the present invention resides in a non-aqueous electrolyte solution used in the non-aqueous electrolyte secondary battery according to any one of claims 1 to 6. (Claim 7)

  According to the present invention, a non-aqueous electrolyte battery in which durability characteristics such as battery cycle and storage are improved, particularly in a high voltage and high capacity lithium secondary battery design, a negative electrode active material used in the negative electrode, and A non-aqueous electrolyte used for an aqueous electrolyte is provided.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments, and can be arbitrarily modified and implemented.

1. Negative electrode The negative electrode active material used for the negative electrode is described below.
<Negative electrode active material>
The negative electrode active material that is one of the components of the present invention is not particularly limited as long as it includes graphite particles having a rhombohedral crystal ratio of 0% to 35%. Here, the graphite particles having a rhombohedral crystal ratio of 0% to 35% in the present invention are defined below.

[Graphite particles]
The graphite particles defined in the present invention are carbon whose d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method is usually 0.335 nm or more and less than 0.340 nm. is there. Here, the d value is preferably 0.339 nm or less, more preferably 0.337 nm or less. If the d value is too large, the crystallinity may decrease and the initial irreversible capacity may increase. On the other hand, 0.335 nm is a theoretical value of graphite.

Examples of the graphite particles include natural graphite particles and / or artificial graphite particles. Preferably, the graphite particles are selected from any one or more of graphite particles obtained by coating carbon with nuclear graphite, graphite particles obtained by coating graphite with nuclear graphite, and natural graphite particles.
Examples of natural graphite include scaly graphite, scaly graphite, and soil graphite. Examples of artificial graphite include graphite particles such as coke, needle coke, and high-density carbon material produced by high-temperature heat treatment of pitch raw materials. Of these, natural graphite particles that are spheroidized are preferable in terms of low cost and ease of electrode production.

[Rhombohedral crystal ratio]
The rhombohedral crystal ratio defined in the present invention is expressed by the following formula based on the ratio of rhombohedral structure graphite layer (ABC stacking layer) and hexagonal structure graphite layer (AB stacking layer) by X-ray wide angle diffraction (XRD). Can be obtained.
Rhombohedral crystal ratio (%) = integrated intensity of ABC (101) peak of XRD ÷
XRD AB (101) peak integrated intensity × 100
Here, the rhombohedral crystal ratio of the graphite particles of the present invention is usually 0% or more, preferably 3% or more, more preferably 5% or more, particularly preferably 12% or more, and usually 35% or less, preferably 27. % Or less, more preferably 24% or less, particularly preferably 20% or less. Here, the rhombohedral crystal ratio of 0% means that the XRD peak derived from the ABC stacking layer is hardly detected.

  If the rhombohedral crystal ratio is too large, many defects are contained in the crystal structure of the graphite particles, so that the amount of Li inserted tends to decrease and it is difficult to obtain a high capacity. In addition, since the electrolyte is decomposed during the cycle due to the defects, the cycle characteristics tend to deteriorate. On the other hand, if the rhombohedral crystal ratio is within the range of the present invention, for example, the crystal structure of the graphite particles has few defects and low reactivity with the electrolytic solution, and the consumption of the electrolytic solution during the cycle is small and the cycle characteristics. It is preferable because it is excellent.

  The XRD measurement method for determining the rhombohedral crystal ratio is as follows: a 0.2 mm sample plate is filled so that the graphite powder is not oriented, and an X-ray diffractometer (for example, CuKα ray is used with X'Pert Pro MPD manufactured by PANalytical). And an output of 45 kV and 40 mA). Using the obtained diffraction pattern, the peak integrated intensity is calculated by profile fitting using the asymmetric Pearson VII function using analysis software JADE5.0, and the rhombohedral crystal ratio is obtained from the above formula.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Solar slit 0.04 degree divergence slit 0.5 degree side divergence mask 15mm
Anti-scattering slit 1 degree ・ Measurement range and step angle / measurement time:
(101) plane: 41 ° ≦ 2θ ≦ 47.5 ° 0.3 ° / 60 sec. Background correction: connecting 42.7 to 45.5 ° with a straight line,
Subtract as background.
-Peak of rhombohedral-structure graphite particle layer: refers to a peak around 43.4 degrees.
-Peak of hexagonal structure graphite particle layer: It indicates a peak around 44.5 degrees.

  A method for obtaining graphite particles having a rhombohedral crystal ratio in the above range can employ a method of manufacturing using conventional techniques, and is not particularly limited, but the graphite particles are heat-treated at a temperature of 500 ° C. or higher. It is preferable to manufacture by this. In particular, mechanical effects such as compression, friction, shearing force, etc. including the interaction of particles are given to graphite particles mainly by impact force. In addition, the rhombohedral crystal ratio defined in the present invention can also be adjusted by changing the strength of mechanical action, processing time, presence / absence of repetition, and the like. Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives a mechanical action by circulating a carbon material, or a mechanism that does not have a circulation mechanism but connects a plurality of apparatuses. As an example of a preferable apparatus, there can be mentioned a hybridization system manufactured by Nara Machinery Co., Ltd.

Further, it is more preferable to apply a heat treatment after applying the mechanical action.
Further, it is particularly preferable that after applying the mechanical action, it is combined with a carbon precursor and subjected to heat treatment at a temperature of 700 ° C. or higher.

[Form of negative electrode active material]
The form of the negative electrode active material is not particularly limited as long as the rhombohedral crystal ratio of the graphite particles is within the above range. For example, (1) rhombohedral crystal composed of a composite and / or mixture of nuclear graphite and carbon Graphite particles having a rate of 0% to 35%, (2) graphite particles having a rhombohedral crystal ratio of 0% to 35% composed of a composite and / or mixture of nuclear graphite and graphite, and (3) rhombohedral crystal rate And graphite particles having a ratio of 0% to 35% and mixtures of (1) to (3).

Here, examples of the nuclear graphite include the aforementioned natural graphite and artificial graphite. The natural graphite as the core graphite is preferably spherical natural graphite. (In this specification, spherical natural graphite is also referred to as spheroidized graphite)
For example, in the case of a mixture obtained by combining (1) and (2), the ratio of the complex and / or mixture of (2) to the complex and / or mixture of (1) is usually 5% by mass or more, Preferably it is 10 mass% or more, More preferably, it is 15 mass% or more. Moreover, it is 95 mass% or less normally, Preferably it is 90 mass% or less, More preferably, it is 85 mass% or less. When the mixing ratio of (2) is too small, the irreversible capacity tends to increase and the battery capacity tends to decrease, and when the mixing ratio is too large, the Li acceptability at low temperatures tends to decrease.

  In the case of a mixture obtained by combining (1) and (3), the ratio of the graphite particles of (3) to the composite and / or mixture of (1) is usually 5% by mass or more, preferably 10% by mass or more. More preferably, it is 15 mass% or more. Moreover, it is 70 mass% or less normally, Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less. If the mixing ratio of (3) is too small, there is a concern that when the electrode is pressed at a high density in order to increase the battery capacity, there is a concern that the press load increases and it is difficult to increase the density, and if it is too large, the irreversible capacity increases and the battery capacity increases. May decrease.

  In the case of a mixture obtained by combining (2) and (3), the ratio of the graphite particles of (3) to the composite and / or mixture of (2) is usually 5% by mass or more, preferably 10% by mass or more. More preferably, it is 20% by mass or more. Moreover, it is 70 mass% or less normally, Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less. If the mixing ratio of (3) is too small, the electrode load tends to increase when the electrode is pressed at a high density in order to increase the battery capacity, and it tends to be difficult to increase the density. There is a tendency to decrease.

  As a combination of these, the combination of the composite of (1) and the composite of (2), the combination of the composite of (1) and (3) the graphite particles, the composite of (2) and the graphite particles of (3) The combination of (1) and (2), and the combination of (1) and (3) graphite particles facilitates the production of a high-density electrode and secures a conductive path. It is more preferable because it is easily processed and has excellent cycle characteristics.

  In addition, when the above graphite particles are mixed with other graphite having a rhombohedral crystal ratio outside the range of 0% or more and 35% or less, the other graphite is usually 2 mass relative to the mass of the graphite particles of the present invention. % Or more, preferably 5% by mass or more, more preferably 10% by mass or more. Moreover, it is 50 mass% or less normally, Preferably it is 45 mass% or less, More preferably, it is 40 mass% or less. If the amount of other graphite is too small, the effect of mixing other graphite tends to be difficult to obtain, and if it is too large, the effect of the present invention tends to be small.

  Further, when the form of the negative electrode active material includes (1) and / or (2), the rhombohedral crystal ratio of the nuclear graphite constituting these composites is usually 0% or more, preferably 3 like the graphite particles. % Or more, more preferably 5% or more, and usually 35% or less, preferably 27% or less, more preferably 24% or less, and particularly preferably 20% or less. The rhombohedral crystal ratio of the nuclear graphite constituting these composites can be determined by the same method as that for the graphite particles.

(1) Graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less composed of a composite and / or mixture of nuclear graphite and carbon. A rhombohedral crystal ratio composed of a composite and / or mixture of nuclear graphite and carbon is 0%. The graphite particles of 35% or less can be obtained, for example, by coating or bonding a carbon precursor to nuclear graphite and firing or CVD at 600 ° C. to 2200 ° C. This refers to graphite particles having a bonded rhombohedral crystal ratio within the above range. The coverage of carbon is usually 1% by mass or more, preferably 2% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less.

The coverage of the present invention can be calculated using the following formula from the mass of nuclear graphite and the mass of carbon derived from the carbon precursor after firing.
Coverage (mass%) = carbon mass ÷ (nuclear graphite mass + carbon mass) × 100
Moreover, the said mixture refers to the graphite particle whose rhombohedral crystal | crystallization ratio which consists of graphite particle | grains and carbon is 0% or more and 35% or less, for example.

(2) Graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less composed of a composite and / or a mixture of nuclear graphite and graphite. A rhombohedral crystal ratio of a composite and / or a mixture of nuclear graphite and graphite is 0%. The graphite particles of 35% or less can be obtained, for example, by coating or bonding a nuclear precursor with a carbon precursor and graphitizing at a temperature of 2300 ° C. or higher and 3200 ° C. or lower. / Or refers to graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less coated or bonded with hard graphite.

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 referred to 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 formula.
Coverage (mass%) = precursor-derived graphite mass ÷
(Nuclear graphite mass + precursor-derived graphite mass) × 100
The mixture refers to, for example, a mixture of graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less and graphite in an arbitrary ratio without being covered or bonded.

(3) Graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less The graphite particles having a rhombohedral crystal ratio of 0% or more and 35% or less do not include the structures (1) and (2). This refers to those composed of graphite particles having a rhombohedral crystal ratio of 0% to 35%. Specifically, it refers to graphite particles in which carbon and / or graphite is not combined with nuclear graphite subjected to mechanical energy treatment. Further, graphite particles obtained by firing graphite particles having a rhombohedral crystal ratio of 0% to 35% at 400 ° C. to 3200 ° C. can also be used.

  The graphite particles may be composed of one kind, or may be composed of a plurality of graphite particles having different forms and particle sizes.

<Physical properties of negative electrode active material>
The negative electrode active material preferably further has the following physical properties.
(X-ray parameters)
The crystallite size (Lc) and (La) of the graphite particles determined by X-ray diffraction by the Gakushin method of the negative electrode active material is preferably 30 nm or more, and more preferably 100 nm or more. If the crystallite size is within this range, the amount of lithium that can be charged in the negative electrode active material is increased, and a high capacity is easily obtained, which is preferable.

(Volume-based average particle size)
The volume-based average particle diameter of the negative electrode active material is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm, based on the volume-based average particle diameter (median diameter) determined by the laser diffraction / scattering method. In addition, it is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less.

If the volume-based average particle size is too small, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, if the average particle size is too large, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is carried out using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the negative electrode active material of the present invention.

(Raman R value, Raman half width)
The Raman R value of the negative electrode active 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 It is 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

If the Raman R value is too small, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers decreases with charge and discharge, which may reduce charge acceptance. On the other hand, if the Raman R value is too large, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency and gas generation may be increased.
Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of} the negative electrode active material is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and is usually 100 cm ⁻¹ or less, preferably 80 cm ⁻¹ or less. More preferably, it is 60 cm ⁻¹ or less, and particularly preferably 40 cm ⁻¹ or less.

If the Raman half-value width is too small, the crystallinity of the particle surface becomes too high, and there is a tendency that the number of sites where Li enters between the layers increases with charge / discharge. That is, there is a tendency that charge acceptance is lowered. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals tend to be oriented in a direction parallel to the electrode plate, and the load characteristics tend to be reduced. On the other hand, if the Raman half width is too large, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte increases, and the efficiency tends to decrease and the gas generation increases.

The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity I _A of the peak P _A in the vicinity of 1580 cm ^-1, and measuring the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, 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 negative electrode active material of the present invention. Further, the half width of the peak P _A in the vicinity of 1580 cm ^-1 of the resulting Raman spectrum was measured, which is defined as the Raman half-value width of the negative electrode active material of the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, Raman half width analysis: Background processing ・ Smoothing processing: Simple average, 5 points of convolution

(BET specific surface area)
The BET specific surface area of the negative electrode active material is a value of the specific surface area measured using the BET method, and is usually 0.1 m ² · g ⁻¹ or more, preferably 0.7 m ² · g ⁻¹ or more, more preferably 1 .0m ² · g ^-1 or more, particularly preferably 1.5 m ² · g ^-1 or more, and usually 100 m ² · g ^-1 or less, preferably 25 m ² · g ^-1 or less, more preferably 15 m ² · G ^-1 or less, particularly preferably 10 m ² · g ^-1 or less.

  If the value of the BET specific surface area is too small, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, and lithium is likely to precipitate on the electrode surface, which may reduce the stability. On the other hand, if the value of the BET specific surface area is too large, the reactivity with the non-aqueous electrolyte increases when used as a negative electrode material, gas generation tends to increase, and a preferable battery tends to be difficult to obtain.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the negative electrode active material of the present invention.

(Tap density)
The tap density of the negative electrode active 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 particularly preferably 1 g · cm ⁻³ or more. Moreover, it is 2 g * cm <^-3> or less normally, Preferably it is 1.8 g * cm < ^-3 > or less, More preferably, it is 1.6 g * cm <^-3> or less. If the tap density is too small, when used as a negative electrode, the packing density is difficult to increase, and there is a tendency that a high-capacity battery cannot be obtained. On the other hand, if the tap density is too high, there are too few voids between the particles in the electrode, and it is difficult to ensure conductivity between the particles, and it is difficult to obtain preferable battery characteristics.

The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap 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 negative electrode active material of the present invention.

(Orientation ratio)
The orientation ratio of the negative electrode active material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is too small, the high-density charge / discharge characteristics tend to decrease. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities 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 negative electrode active material of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) 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)
The aspect ratio (major axis / minor axis) of graphite having a rhombohedral crystal ratio of 0% to 35% is usually 0.05 or more, preferably 0.07 or more, more preferably 0.10 or more, and particularly preferably 0. .14 or more, usually 20 or less, preferably 15 or less, more preferably 10 or less, and particularly preferably 7 or less. If the aspect ratio is too small (or too large), the graphite particles become flat or scaly, and the graphite particles are easily oriented in the electrode, and the electrode expansion due to charge / discharge is large, so it is difficult to increase the battery capacity. , Cycle characteristics tend to deteriorate.

The aspect ratio of the spheroidized graphite particles can be measured using the negative electrode according to the following procedure.
Take a photo of the negative electrode surface (or polish or cut it in a plane parallel to the film surface of the current collector and take a cross-sectional photograph thereof), and analyze the photographed image to determine the surface of the graphite particles (cross-section). ) Is measured at 50 points or more. In addition, the negative electrode was cut and polished perpendicularly to the film surface of the current collector, a cross-sectional photograph thereof was taken, and image analysis of the photographed photograph revealed that the short diameter (particle thickness) of the graphite particle cross section was 50 points. Measure above. An average value is obtained for each of the measured major axis and minor axis, and the ratio of the average major axis to the average minor axis is defined as an aspect ratio (major axis / minor axis).

In addition, when the negative electrode active material does not maintain the negative electrode form (for example, in powder form), the negative electrode active material particles are embedded in a resin in a state where they are arranged on a flat plate serving as a substrate such as glass, and the surface is parallel to the flat plate. Polish and cut and measure the major axis from the cross-sectional photograph as described above. Similarly, the minor axis of the graphite particle cross section can be measured to determine the aspect ratio.
Here, since the plate-like particles usually tend to be arranged so that the thickness direction of the particles is perpendicular to the flat plate, the above-mentioned method obtains characteristic long and short diameters of the particles. I can do it.

In addition, the cross-sectional (or surface) photograph of the particle is generally a scanning electron microscope (Scanning).
Photograph using Electron Microscope (SEM). However, when the shape of the spheroidized graphite cannot be specified by the SEM photograph, by taking a cross-sectional (surface) photograph in the same manner as described above using a polarizing microscope or a transmission electron microscope (TEM), The aspect ratio can be obtained.

  The method for obtaining the spheroidized graphite particles having the aspect ratio in the above range is not particularly limited, but for example, mechanical effects such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force are repeatedly applied to the particles. It is preferred to use an apparatus for feeding. Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives a mechanical action by circulating a carbon material, or a mechanism that does not have a circulation mechanism but connects a plurality of apparatuses. As an example of a preferable apparatus, there can be mentioned a hybridization system manufactured by Nara Machinery Co., Ltd.

<Configuration and production method of negative electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector described later, dried, and then pressed. can do.

(Current collector)
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both 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 is 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, and conversely if it is too thin, handling may be difficult.

(Thickness ratio between current collector and negative electrode active material layer)
The ratio of the thickness of the current collector to 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 the nonaqueous electrolyte injection) / (thickness of the current collector)” However, 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 or more is more preferable, and 1 or more is particularly preferable. If the ratio of the thickness of the current collector to the negative electrode active material layer is too large, the current collector tends to generate heat due to Joule heat during high current density charge / discharge. On the other hand, if the ratio of the thickness of the current collector to the negative electrode active material layer is too small, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity tends to 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 the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or 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, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10% by mass or less is further preferable, and 8% by mass or less is particularly preferable. When the ratio of the binder to the negative electrode active material is too large, the binder ratio in which the binder amount does not contribute to the battery capacity increases, and the battery capacity tends to decrease. Moreover, when the ratio of a binder is too small, there exists a tendency which causes the strength reduction of a negative electrode.

  In particular, when a rubbery polymer typified by SBR is contained as a 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 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, 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. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

(Slurry forming solvent)
The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

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

(Thickener)
A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when 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, Moreover, it is 5 mass% or less normally, 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 too small, applicability tends to be remarkably lowered. Moreover, when there are too many ratios of a thickener, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and there exists a tendency for the capacity | capacitance of a battery to fall and the resistance between negative electrode active materials to increase.

(Electrode density)
The electrode structure when the negative electrode active material is converted 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, and 1.2 g · cm ⁻³ or more. but more preferably, particularly preferably 1.3 g · cm ^-3 or more, preferably 2.2 g · cm ^-3 or less, more preferably 2.1 g · cm ^-3 or less, 2.0 g · cm ^-3 or less Further preferred is 1.9 g · cm ⁻³ or less. If the density of the negative electrode active material present on the current collector is too large, the negative electrode active material particles will be destroyed, increasing the initial irreversible capacity, and the non-aqueous electrolyte solution near the current collector / negative electrode active material interface. There is a tendency for high current density charge / discharge characteristics to deteriorate due to a decrease in permeability. On the other hand, if the density is too small, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume tends to decrease.

(Thickness of negative electrode plate)
The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

(Surface coating of negative electrode plate)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include 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 and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

2. Non-aqueous electrolyte 1-1. 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 lithium salt can be used. Specific examples include the following.

For example, inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ and LiWF ₇ ; Lithium fluorophosphates such as LiPO ₃ F and LiPO ₂ F ₂ ; Tungstic acids such as LiWOF ₅ Lithium; 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 CO ₂ Li, CF ₃
Carboxylic acid lithium salts such as 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 Sulfonic acid lithium salts such as Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ 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 imide salts such as lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) Lithium lithium salt such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ; lithium oxalate borate such as lithium difluorooxalatoborate and lithium bis (oxalato) borate salts;
Lithium oxalate phosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, 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 ) ₂ Fluorine-containing organic lithium salts such as;

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-perfluoroethanedisulfonylimide, 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, LiBF 3 C 2} F 5, LiPF 3 (CF 3) 3, LiPF 3 (C 2 F 5) 3 There the output characteristics and high-rate discharge characteristics, high-temperature storage characteristics, particularly preferred from the viewpoint that an effect of improving the cycle characteristics and the like.

These lithium salts may be used alone or in combination of two or more. A preferable example in the case of using two or more kinds in combination is a combination of LiPF ₆ and LiBF ₄ , LiPF ₆ and FSO ₃ Li, LiPF ₆ and LiPO ₂ F _2, etc., and has an effect of improving load characteristics and cycle characteristics. . Among these, the combined use of LiPF ₆ and FSO ₃ Li and LiPF ₆ and LiPO ₂ F ₂ is preferable because the effect is remarkable, and among them, the combined use of LiPF ₆ and LiPO ₂ F ₂ is a remarkable effect with a small amount of addition. Is particularly preferred because

When LiPF ₆ and LiBF ₄ , LiPF ₆ and FSO ₃ Li are used in combination, the concentration of LiBF ₄ or FSO ₃ Li with respect to 100% by mass of the entire non-aqueous electrolyte is not limited, and the effects of the present invention are not significantly impaired. As long as it is optional, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, and the upper limit is usually 30% by mass or less, preferably 20% with respect to the non-aqueous electrolyte solution of the present invention. It is below mass%. On the other hand, even when LiPF ₆ and LiPO ₂ F ₂ are used in combination, the concentration of LiPO ₂ F ₂ with respect to 100% by mass of the total amount of the non-aqueous electrolyte is not limited as long as the effect of the present invention is not significantly impaired. However, with respect to the non-aqueous electrolyte solution of the present invention, it is usually 0.001% by mass or more, preferably 0.01% by mass or more, while its upper limit is usually 10% by mass or less, preferably 5% by mass or less. is there. Within 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 it is too much, it may be deposited at low temperature to deteriorate the battery characteristics, and if it is too little, the effect of improving the low temperature characteristics, cycle characteristics, high temperature storage characteristics, etc. may be reduced.

Here, the preparation of the electrolyte solution in the case of incorporating the LiPO ₂ F ₂ in the electrolyte solution, Ya separately active material method and later be added to the electrolytic solution containing LiPF ₆ and LiPO ₂ F ₂ synthesized by a known method A method of generating LiPO ₂ F ₂ in the system when water is allowed to coexist in a battery component such as an electrode plate and assembling a battery using an electrolyte containing LiPF ₆ is used. You may use the method of.

The method for measuring the content of LiPO ₂ F ₂ in the non-aqueous electrolyte and the non-aqueous electrolyte battery is not particularly limited, and any known method can be used. Examples include ion chromatography and F nuclear magnetic resonance spectroscopy (hereinafter sometimes abbreviated as NMR).
Another example is the combined use of an inorganic lithium salt and an organic lithium salt, and the combined use of both has the effect of suppressing deterioration due to high-temperature storage. Examples of the organic lithium salt include 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-perfluoroethanedisulfonylimide, 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 bis (oxalato) borate, Lithium difluorooxalatoborate, Lithium tetrafluorooxalatophosphate, Lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , 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 organic lithium salt to 100% by mass of the whole non-aqueous electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, preferably 30% by mass or less, particularly preferably. It is 20 mass% or less.

  The concentration of these lithium salts in the non-aqueous electrolyte solution is not particularly limited as long as the effects of the present invention are not impaired, but the electric conductivity of the electrolyte solution is in a good range, and good battery performance is ensured. Therefore, the total molar concentration of lithium in the non-aqueous electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and further preferably 0.5 mol / L or more. Preferably it is 3 mol / L or less, More preferably, it is 2.5 mol / L or less, More preferably, it is 2.0 mol / L or less. If it is this range, effects, such as a low temperature characteristic, cycling characteristics, and a high temperature characteristic, will improve. On the other hand, if the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity. May decrease.

1-2. Solvent As the non-aqueous solvent, a saturated cyclic carbonate, a cyclic carbonate having a fluorine atom, a chain carbonate, a cyclic and chain carboxylic acid ester, an ether compound, a sulfone compound, and the like can be used.

<Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate include those having an alkylene group having 2 to 4 carbon atoms.
Specifically, examples of the saturated cyclic carbonate having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.
A saturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.

The blending amount of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The lower limit of the blending amount when one kind is used alone is 5% in 100% by volume of the non-aqueous solvent. Volume% or more, more preferably 10 volume% or more. By setting this range, the decrease in electrical conductivity resulting from the decrease in the dielectric constant of the non-aqueous electrolyte is avoided, and the large current discharge characteristics, negative electrode stability, and cycle characteristics of the non-aqueous electrolyte secondary battery are good. It becomes easy to be in a range. Moreover, an upper limit is 95 volume% or less, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less. By setting it as this range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in ionic conductivity is suppressed, and as a result, the load characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range.

  Moreover, one of the preferable combinations when using 2 or more types of saturated cyclic carbonates by arbitrary combinations is a combination to ethylene carbonate and propylene carbonate. In this case, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, and particularly preferably 95: 5 to 50:50. Furthermore, the amount of propylene carbonate in the entire non-aqueous solvent is 0.1% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and the upper limit is usually 20% by volume or less, preferably 8% by volume. % Or less, more preferably 5% by volume or less. When propylene carbonate is contained within this range, it is preferable because the low temperature characteristics are further excellent while maintaining the combination characteristics of ethylene carbonate and dialkyl carbonates.

<Cyclic carbonate having a fluorine atom>
The cyclic carbonate having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated cyclic carbonate”) is not particularly limited as long as it is a cyclic carbonate having a fluorine atom.
Examples of the fluorinated cyclic carbonate include derivatives of cyclic carbonates having an alkylene group having 2 to 6 carbon atoms, such as ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include fluorinated products of ethylene carbonate or ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and particularly those having 1 to 8 fluorine atoms. Is preferred.

  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- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethyl Le ethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and 4,5-difluoro-4,5-dimethylethylene carbonate has high ionic conductivity. It is more preferable in terms of imparting properties and suitably forming an interface protective film.
A fluorinated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios. The blending amount of the fluorinated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but in 100% by volume of the non-aqueous solvent, preferably 0.01% by volume or more, more preferably 0.8%. It is 1 volume% or more, More preferably, it is 0.2 volume% or more, Preferably it is 95 volume% or less, More preferably, it is 90 volume% or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit a sufficient cycle characteristic improvement effect, and avoids a decrease in discharge capacity maintenance rate due to a decrease in high-temperature storage characteristics or an increase in the amount of gas generated. Cheap.

  In addition, the cyclic carbonate which has a fluorine atom expresses an effective function not only as a solvent but also as an auxiliary agent described in the following 1-3. There is no clear boundary in the blending amount when used as a cyclic carbonate solvent / auxiliary having a fluorine atom, and the blending amount described in the previous paragraph can be followed as it is.

<Chain carbonate>
As a chain carbonate, a C3-C7 thing is preferable.

  Specifically, as the chain carbonate having 3 to 7 carbon atoms, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, Examples include n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
Further, chain carbonates having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated chain carbonate”) can also be suitably used. The number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.

Examples of the fluorinated dimethyl carbonate derivative include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like.
Fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

  Fluorinated diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-trifluoro). Ethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, the decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily set to a favorable range. Become. Further, the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, in 100% by volume of the nonaqueous solvent. By setting the upper limit in this way, it is easy to avoid a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte and to make the large current discharge characteristics of the non-aqueous electrolyte secondary battery in a favorable range. .

The battery performance can be remarkably improved by combining ethylene carbonate at a specific blending amount with respect to the specific chain carbonate.
For example, when dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate is selected as the specific chain carbonate, the blending amount of ethylene carbonate is 10% by volume or more and 80% by volume or less, dimethyl carbonate, ethyl methyl carbonate, or diethyl It is preferable that the blending amount of carbonate is 20% by volume or more and 90% by volume or less. By selecting such a blending amount, the low-temperature deposition temperature of the electrolyte is lowered, the viscosity of the nonaqueous electrolytic solution is also lowered to improve the ionic conductivity, and a high output can be obtained even at a low temperature.

  It is also preferable to use two or more types of specific chain carbonates in combination. When dimethyl carbonate and ethyl methyl carbonate are used in combination with a specific chain carbonate, the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less, and the blending amount of dimethyl carbonate is 10% by volume or more and 70% by volume or less. Particularly preferred are those in which the amount of ethyl methyl carbonate is 10% by volume or more and 80% by volume or less. When a specific chain carbonate is used in combination with dimethyl carbonate and diethyl carbonate, the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less, and the blending amount of dimethyl carbonate is 10% by volume or more and 70% by volume. Hereinafter, it is particularly preferable that the amount of diethyl carbonate is 10% by volume or more and 70% by volume or less. Further, when ethyl methyl carbonate and diethyl carbonate are used in combination with a specific chain carbonate, the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less, the blending amount of ethyl methyl carbonate is 10% by volume or more, 80% Those having a volume% or less and a blending amount of diethyl carbonate of 10 vol% or more and 70 vol% or less are particularly preferable.

<Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester include those having 3 to 12 total carbon atoms in the structural formula.
Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

  The amount of the cyclic carboxylic acid ester is usually 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent. By setting the lower limit in this manner, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily improved. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 50 volume% or less, More preferably, it is 40 volume% or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and a large current discharge of the non-aqueous electrolyte secondary battery is performed. It becomes easy to make a characteristic into a favorable range.

<Chain carboxylic acid ester>
Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in the structural formula.
Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl acetate-n-butyl acetate, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improvement of ionic conductivity.
The compounding amount of the chain carboxylic acid ester is usually 10% by volume or more, more preferably 15% by volume or more, in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily improved. Moreover, the compounding quantity of chain | strand-shaped carboxylic acid ester is 60 volume% or less preferably in 100 volume% of nonaqueous solvents, More preferably, it is 50 volume% or less. By setting the upper limit in this manner, 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 in a favorable range.

<Ether compound>
As the ether compound, a chain ether having 3 to 10 carbon atoms in which part of hydrogen may be substituted with fluorine, and a cyclic ether having 3 to 6 carbon atoms are preferable.
Examples of the chain ether having 3 to 10 carbon atoms include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -Trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoro) Ethyl) 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-fluoroethyl-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, (2,2,2-trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (3,3,3-trifluoro Olo-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2 , 2,3,3,3-pentafluoro-n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl) (3 -Fluoro-n-propyl) 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, (1,1,2,2-tetrafluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) Ether, di-n-propyl Ether, (n-propyl) (3-fluoro-n-propyl) ether, (n-propyl) (3,3,3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3 , 3-tetrafluoro-n-propyl) ether, (n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3-fluoro-n-propyl) ether, ( 3-Fluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether , (3-fluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3,3,3-trifluoro-n-propyl) ether, (3 3,3-triflu (Ro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-penta Fluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,3 3,3-pentafluoro-n-propyl) ether, di (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy (2 -Fluoroethoxy) methane, methoxy (2,2,2-trifluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fur Roethoxy) methane, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2-fluoroethoxy) ( 2,2,2-trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2, 2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ) Ethane, methoxy (2,2,2-trifluoroethoxy) ethane, methoxy (1,1,2,2-tetrafluoroeth) Xyl) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2 -Fluoroethoxy) ethane, (2-fluoroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (2, 2,2-trifluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) Ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, etc. And the like.

Examples of the cyclic ether having 3 to 6 carbon atoms include 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 to lithium ions and improve ion dissociation. Of these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable because they have low viscosity and give high ionic conductivity.

The compounding amount of the ether compound is usually in 100% by volume of the non-aqueous solvent, preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably 70% by volume or less. More preferably, it is 60 volume% or less, More preferably, it is 50 volume% or less. If it is this range, it is easy to ensure the improvement effect of the lithium ion dissociation degree of chain ether, and the improvement of the ionic conductivity derived from a viscosity fall, and when a negative electrode active material is a carbonaceous material, a chain ether with lithium ion It is easy to avoid a situation where the capacity is reduced due to co-insertion.

<Sulfone compound>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.
Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds. Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

  The sulfolane is preferably sulfolane and / or a sulfolane derivative (hereinafter sometimes abbreviated as “sulfolane” including sulfolane). As the sulfolane derivative, one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable. 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-methyl Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methyl sulfolane, 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.

  As the chain sulfone, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trif Oromethylsulfone, perfluoroethylmethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoroethylsulfone, di (trifluoroethyl) sulfone, perfluorodiethylsulfone, fluoromethyl-n-propylsulfone, difluoromethyl-n-propylsulfone Trifluoromethyl-n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, Pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone Emissions, pentafluoroethyl -n- butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, tri Ruoroechiru -n- butyl sulfone, trifluoroethyl -t- butyl sulfone, trifluoromethyl -n- butyl sulfone, trifluoromethyl -t- butyl sulfone is preferred because a higher high output ionic conductivity.

  The compounding amount of the sulfone compound is usually 0.3% by volume or more, more preferably 0.5% by volume or more, and further preferably 1% by volume or more in 100% by volume of the nonaqueous solvent. Is 40% by volume or less, more preferably 35% by volume or less, and still more preferably 30% by volume or less. Within this range, durability improvement effects such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte can be set to an appropriate range to avoid a decrease in electrical conductivity. When charging / discharging an aqueous electrolyte secondary battery at a high current density, it is easy to avoid a situation in which the charge / discharge capacity retention rate decreases.

1-3. The present invention relates to a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous solvent that dissolves the lithium salt, a negative electrode capable of occluding and releasing lithium ions, and a non-electrode provided with a positive electrode. An aqueous electrolyte secondary battery is characterized in that the nonaqueous electrolyte contains at least one or more compounds selected from the group consisting of compounds represented by the following general formula (1).

(Wherein X and Z represent CR ¹ ₂ , C═O, C═N—R ¹ , C═P—R ¹ , O, S, N—R ¹ , P—R ¹ , and are the same or different. Y represents CR ¹ ₂ , C═O, S═O, S (═O) ₂ , P (═O) —R ² , P (═O) —OR ³ , wherein R and R ¹ is 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, and R ² has a substituent. Or a hydrocarbon group having 1 to 20 carbon atoms, R ³ is Li, NR ⁴ ₄ or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms, and R ⁴ is a substituent group. And may be the same or different from each other, n and m each represents an integer of 0 or more, and W has the same meaning as R above, Same as R above It may be made to.)

<Compound represented by the general formula (1)>
In the formula, X and Z are not particularly limited as long as they are in the range described in the general formula (1), but CR ¹ ₂ , O, S, and N—R ¹ are more preferable. Y is not particularly limited as long as it is within the range described in the general formula (1), but preferably C═O, S═O, S (═O) ₂ , P (═O) —R ² , P ( ═O) —OR ³ is more preferred. R and R ¹ are not particularly limited as long as they are within the range described in the general formula (1), but preferably have hydrogen, fluorine, a saturated aliphatic hydrocarbon group which may have a substituent, or a substituent. Examples thereof may include an unsaturated aliphatic hydrocarbon group which may be substituted, and an aromatic hydrocarbon group which may have a substituent.

R ² and R ⁴ are not particularly limited as long as they are within the range described in the general formula (1), but are preferably a saturated aliphatic hydrocarbon group that may have a substituent or a substituent. Examples thereof include unsaturated aliphatic hydrocarbons and optionally substituted aromatic hydrocarbons / aromatic heterocycles.
R ³ is not particularly limited as long as it is within the range described in the general formula (1), but preferably Li, a saturated aliphatic hydrocarbon which may have a substituent, or an unsaturated which may have a substituent Examples thereof include an aliphatic hydrocarbon and an aromatic hydrocarbon / aromatic heterocycle which may have a substituent.

  Substituents of saturated aliphatic hydrocarbons which may have substituents, unsaturated aliphatic hydrocarbons which may have substituents, aromatic hydrocarbons and aromatic heterocycles which may have substituents Is not particularly limited, but preferably has a saturated aliphatic hydrocarbon group, which may have a substituent such as halogen, carboxylic acid, carbonic acid, sulfonic acid, phosphoric acid, phosphorous acid, etc. And an unsaturated aliphatic hydrocarbon group that may be substituted, an ester of an aromatic hydrocarbon group that may have a substituent, and the like, more preferably halogen, and most preferably fluorine.

  Preferable saturated aliphatic hydrocarbons include, 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 A phenyl group, a cyclopentyl group, and a cyclohexyl group are preferred.

Specific preferred unsaturated aliphatic hydrocarbons include ethenyl, 1-fluoroethenyl, 2-fluoroethenyl, 1-methylethenyl, 2-propenyl, and 2-fluoro-2-propenyl. 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 preferable.

Preferred aromatic heterocycles are 2-furanyl group, 3-furanyl group, 2-thiophenyl group, 3-thiophenyl group, 1-methyl-2-pyrrolyl group, and 1-methyl-3-pyrrolyl group.
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.
n and m are not particularly limited as long as they are within the range described in the general formula (1), but are preferably 0 or 1, and more preferably n = m = 1 or n = 1 and m = 0.
The molecular weight is preferably 50 or more. Moreover, Preferably it is 500 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will fully be expressed easily. Specific examples of these preferred compounds include

  Among these, it is preferable that R is hydrogen, a fluorine, or an ethynyl group from both the reactivity and the stability. In the case of other substituents, the reactivity is lowered, and the expected properties may be lowered. Moreover, when it is halogen other than fluorine, there is a possibility that the reactivity is too high and the side reaction increases.

The number of fluorine or ethynyl groups in R is preferably within 2 in total. If the number is too large, the compatibility with the electrolytic solution may be deteriorated, and the reactivity may be too high to increase the side reaction.
Among these, n = 1 and m = 0 are preferable. When both are 0, stability deteriorates from the distortion of the ring, the reactivity becomes too high, and there is a possibility that side reactions increase. Further, even if n = 2 or more, or n = 1, when m = 1 or more, there is a possibility that the chain is more stable than the ring and the initial characteristics may not be exhibited.

Further, in the formula, X and Z are more preferably CR ¹ ₂ or O. In cases other than these, the reactivity may be too high and side reactions may increase.
The molecular weight is more preferably 100 or more, and more preferably 200 or less. If it is this range, it will be easy to ensure further the solubility of General formula (1) with respect to a non-aqueous electrolyte solution, and the effect of this invention will be further fully expressed easily.

Among these, specific examples of more preferable compounds are shown below.

More preferably, R is all hydrogen. In this case, the side reaction is most likely to be suppressed while maintaining the expected characteristics. Further, when Y is C═O or S═O, one of X and Z is O, indicating that Y is S (═O) ₂ , P (═O) —R ² , P (═O ) In the case of —OR ³ , it is preferred that both X and Z are 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, if both X and Z are CH ₂ , the reactivity may be too high and side reactions may increase.

Specific examples of these compounds are shown below.

  Of the compounds represented by the general formula (1), the compound represented by the general formula (2) is preferable from the viewpoint of ease of industrial production.

In the above formula (2), Y represents C═O, S═O, S (═O) ₂ , P (═O) —R ² , P (═O) —OR ³ . R ² is an optionally substituted hydrocarbon group having 1 to 20 carbon atoms. R ³ is Li, NR ⁴ ₄ or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent. R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and may be the same or different.
Specific examples of these compounds having preferable conditions are shown below.

一般式（１）であらわされる化合物は、１種を単独で用いても、２種以上を任意の組み合わせ及び比率で併有してもよい。また、一般式（１）であらわされる化合物の配合量は、特に制限されず、本発明の効果を著しく損なわない限り任意である。一般式（１）であらわされる化合物の配合量は、非水系電解液１００質量％中、好ましくは、０．００１質量％以上、より好ましくは０．０１質量％以上、さらに好ましくは０．１質量％以上であり、また、好ましくは５質量％以下、より好ましくは４質量％以下、さらに好ましくは３質量％以下である。この範囲であれば、非水系電解液二次電池が十分なサイクル特性向上効果を発現しやすく、また、高温保存特性が低下し、ガス発生量が多くなり、放電容量維持率が低下するといった事態を回避しやすい。一方で少なすぎると、本発明における効果が十分に発揮しにくい場合があり、また多すぎると、抵抗が増加して出力や負荷特性が低下する場合がある。

The compound represented by General formula (1) may be used individually by 1 type, or may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of the compound represented by General formula (1) is not restrict | limited especially, unless the effect of this invention is impaired remarkably. The compounding amount of the compound represented by the general formula (1) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass in 100% by mass of the non-aqueous electrolyte solution. % Or 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 cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exerted. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.

1-4. Auxiliary agent In the non-aqueous electrolyte battery of the present invention, an auxiliary agent may be appropriately used according to the purpose in addition to the compound of the general formula (1). Examples of the auxiliary agent include a cyclic carbonate having an unsaturated bond shown below, an unsaturated cyclic carbonate having a fluorine atom, an overcharge inhibitor, and other auxiliary agents.

<Cyclic carbonate having an unsaturated bond>
In the non-aqueous electrolyte solution of the present invention, in order to form a film on the negative electrode surface of the non-aqueous electrolyte battery and to extend the life of the battery, in addition to the compound of the general formula (1), the general formula (1) A cyclic carbonate having an unsaturated bond from which the above compound is removed (hereinafter sometimes abbreviated as “unsaturated cyclic carbonate”) may be used.

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. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.
Examples of the unsaturated cyclic carbonate 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, and the like. It is done.

  Examples of vinylene carbonates include 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 and the like.

  Specific examples of ethylene carbonates substituted with an aromatic ring or a substituent having a carbon-carbon double bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 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 Examples thereof include carbonate and 4-methyl-5-allylethylene carbonate.

  Among them, particularly preferable unsaturated cyclic carbonates for use in combination with the compound of the general formula (1) include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, Allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl- Since 5-allylethylene carbonate and 4-allyl-5-vinylethylene carbonate form a stable interface protective film, they are more preferably used.

  The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will fully be expressed easily. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less. The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

  An unsaturated cyclic carbonate may be used individually by 1 type, or may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The amount of the unsaturated cyclic carbonate is 100% by mass in the non-aqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more. Moreover, Preferably it is 5 mass% or less, More preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exhibited. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.

<Fluorinated unsaturated cyclic carbonate>
As the fluorinated cyclic carbonate, it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”). The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms 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 an aromatic ring or a substituent having a carbon-carbon double bond.
Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

  Examples of the fluorinated ethylene carbonate derivative 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, 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-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

Among them, particularly preferred fluorinated unsaturated cyclic carbonates to be used in combination with the compound of the general formula (1) include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate. 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 -Full B-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate Since a stable interface protective film is formed, it is more preferably used.

  The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

  A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The compounding amount of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, in 100% by mass of the nonaqueous electrolytic solution. Moreover, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exhibited. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.

<Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress battery explosion / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like. .
As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

  The amount of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The overcharge inhibitor is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. If it is this range, it will be easy to fully express the effect of an overcharge inhibiting agent, and it will be easy to avoid the situation where the battery characteristics, such as a high temperature storage characteristic, fall. The overcharge inhibitor is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, still more preferably. Is 2% by mass or less.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydrous Carboxylic anhydrides such as itaconic acid, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; 2,4,8,10-tetraoxaspiro [5.5 ] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite, 1,3-propane sultone, 1-fluoro-1,3- Propane sultone, 2-fluoro-1,3-propane sultone, 3-ph Oro-1,3-propane sultone, 1-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, 1,4-butanesultone, 1-butene-1,4-sultone, 3-butene-1,4-sultone, methyl fluorosulfonate, ethyl fluorosulfonate, methanesulfonic acid Sulfur-containing compounds such as methyl, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2 -Piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-me Nitrogen-containing compounds such as Rusukushin'imido; heptane, octane, nonane, decane, hydrocarbon compounds cycloheptane, etc., fluorobenzene, difluorobenzene, hexafluorobenzene, fluorinated aromatic compounds such as benzotrifluoride, and the like. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

  The blending amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effects of other auxiliaries can be sufficiently exhibited, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics deteriorate. The blending amount of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. .

  The non-aqueous electrolyte solution described above includes those existing inside the non-aqueous electrolyte battery according to the present invention. Specifically, the components of the non-aqueous electrolyte solution such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte solution is prepared from what is substantially isolated by the method described below. In the case of a nonaqueous electrolyte solution in a nonaqueous electrolyte battery obtained by pouring into a separately assembled battery, the components of the nonaqueous electrolyte solution of the present invention are individually placed in the battery, In order to obtain the same composition as the non-aqueous electrolyte solution of the present invention by mixing in a non-aqueous electrolyte battery, the compound constituting the non-aqueous electrolyte solution of the present invention is further generated in the non-aqueous electrolyte battery. The case where the same composition as the aqueous electrolyte is obtained is also included.

3. Battery Configuration The non-aqueous electrolyte battery of the present invention is suitable for use as an electrolyte for a secondary battery, for example, a lithium secondary battery, among non-aqueous electrolyte batteries. Hereinafter, a non-aqueous electrolyte battery using the non-aqueous electrolyte of the present invention will be described.
The non-aqueous electrolyte secondary battery of the present invention can adopt a known structure. Typically, the negative electrode and the positive electrode capable of occluding and releasing ions (for example, lithium ions), and the non-aqueous electrolyte of the present invention described above. An aqueous electrolyte solution.

4). Positive electrode <Positive electrode active material>
The positive electrode active material used for the positive electrode is described below.
(composition)
The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples include lithium / cobalt composite oxide such as LiCoO ₂ or LiNiO ₂ . Lithium / nickel composite oxides, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and} other lithium / manganese composite oxides, part of transition metal atoms that are the main components of these lithium transition metal composite oxides are Na, K , B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc. And the like. Specific examples of the substituted ones include, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.45 Co _0.10 Al _0.45 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like.

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, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other elements.

  In addition, it is preferable to include lithium phosphate in the positive electrode active material because continuous charge characteristics are improved. Although there is no restriction | limiting in the use of lithium phosphate, It is preferable to mix and use the said positive electrode active material and lithium phosphate. The lower limit of the amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.5% by mass with respect to the total of the positive electrode active material and lithium phosphate. %, And the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.

(Surface coating)
Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. Surface adhering substances include 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.

  For example, these surface adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

  The amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably, as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently manifested. If it is too high, the resistance may increase in order to inhibit the entry and exit of lithium ions.

In the present invention, a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.
(shape)
Examples of the shape of the particles of the positive electrode active material include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape as conventionally used. 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 further preferably 1.0 g / cm ³ or more. If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of conductive material and binder increases, so that the positive electrode to the positive electrode active material layer The filling rate of the active material is restricted, and the battery capacity may be restricted. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, and there is no particular upper limit, but if it is too large, diffusion of lithium ions using the electrolytic solution in the positive electrode active material layer as a medium is rate-limiting, and load characteristics may be easily reduced. The upper limit is preferably 4.0 g / cm ³ or less, more preferably 3.7 g / cm ³ or less, and still more preferably 3.5 g / cm ³ or less.

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

(Median diameter d ₅₀ )
The median diameter d ₅₀ of the positive electrode active material particles (secondary particle diameter when the primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, The upper limit is preferably 30 μm or less, more preferably 27 μm or less, still more preferably 25 μm or less, and most preferably 22 μm or less. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time to diffuse lithium in the particles. When a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of forming the positive electrode can be further improved.

In the present invention, the median diameter d ₅₀ is measured by a known laser diffraction / scattering particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium used for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

(Average primary particle size)
When primary particles are aggregated 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, and still more preferably 0.8 μm. The upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

  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 the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

(BET specific surface area)
The BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more, more preferably 0.2 m ² / g or more, still more preferably 0.3 m ² / g or more, and the upper limit is 50 m ² / g or less. , Preferably 40 m ² / g or less, more preferably 30 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered. If the BET specific surface area is larger, the tap density is difficult to increase, and a problem may occur in applicability when forming the positive electrode active material layer.

  In the present invention, the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 150 ° C. for 30 minutes under nitrogen flow, and then atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3.

(Method for producing positive electrode active material)
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for preparing a spherical or elliptical active material. For example, a transition metal source material is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring. And a spherical precursor is prepared and recovered, and after drying as necessary, a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 and the} like is added and fired at a high temperature to obtain an active material. .

For the production of the positive electrode, the positive electrode active material may be used alone, or one or more of the different compositions may be used in any combination or ratio. A preferable combination in this case is a combination of LiCoO ₂ and LiMn ₂ O ₄ such as LiNi _0.33 Co _0.33 Mn _0.33 O ₂ or a part of this Mn substituted with another transition metal or the like, or LiCoO ₂ or The combination with what substituted a part of Co with other transition metals etc. is mentioned.

<Configuration and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. 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. The production of the positive electrode using the 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 mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  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, an upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more as a lower limit, more preferably 2 g / cm ³ , further preferably 2.2 g / cm ³ or more, and preferably 5 g / cm ³ as an upper limit. ^{It is 3} or less, more preferably 4.5 g / cm ³ or less, and 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 the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

(Conductive material)
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. 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 in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

(Binder)
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode production may be used. Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymer such as isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Soft resinous polymers such as polymers; Fluoropolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkali metal ions (especially lithium ions) And a polymer composition having ion conductivity. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

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 Is 6
It is 0 mass% or less, More preferably, it is 40 mass% or less, Most preferably, it is 10 mass% or less. When the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

(Slurry forming solvent)
As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent that can dissolve or disperse the thickener that is used as necessary are particularly suitable for the type. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. 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); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

  In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. When a thickener is further added, 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. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.

(Current collector)
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. Although the thickness of the thin film is arbitrary, it 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 μm or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.

Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.
The ratio of the thickness of the current collector to 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 20 The lower limit is preferably 15 or less, 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. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.

(Electrode area)
When using the non-aqueous electrolyte of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

(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 composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 450 μm or less.

(Positive electrode surface coating)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. Surface adhering substances include 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.

5. Separator Normally, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  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, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

  As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the 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-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

6). 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 shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Current collection structure>
The current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the non-aqueous electrolyte solution of the present invention, a structure that reduces the resistance of the wiring part and the joint part is used. It is preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.

In the case where the electrode group has the above laminated structure, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

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

  In an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

<Protective element>
As a protection element, PTC (Positive Temperature Coefficient) increases in resistance when abnormal heat generation or excessive current flows, thermal fuse, thermistor, shuts off current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature in abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are 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, or the like is used.

  The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

7). Battery Performance The battery obtained in the present invention can be used without particular limitation, but can be preferably used for a battery with a higher voltage or a higher capacity.

For example, in the case of a lithium ion secondary battery, the increase in voltage is usually 4.25 V or more, preferably 4.3 or more.
The increase in capacity is usually 2600 mAh or more, preferably 2800 mAh or more, more preferably 3000 mAh or more in the case of an 18650 type battery, for example.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Example 1>
[Negative electrode]
A spheroidized natural graphite mixture having the following physical properties was used as the negative electrode active material. Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 25%, the aspect ratio is 8.4, the d value (interlayer distance) of the lattice plane (002 plane) is 0.336 nm, the crystal Child size Lc, La is 100 nm or more, volume-based average particle diameter is 21.8 μm, BET specific surface area is 5.0 m ² / g, tap density is 1.00 g · cm ⁻³ , Raman R value is 0.21, powder A spherical natural graphite mixture having a body orientation ratio of 0.25 was used. Here, as the spheroidized natural graphite mixture, a mixture obtained by mixing spheroidized natural graphite particles and spheroidized natural graphite particles at 1000 ° C. in a mass ratio of 1: 1 was used.

98 parts by mass of the negative electrode active material, 100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) and an aqueous dispersion of styrene-butadiene rubber (styrene 1 part by mass of a butadiene rubber concentration of 50% by mass was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 18 μm, dried, rolled to an electrode density of 1.7 g / cm ³ with a press, and the cut out was used as the negative electrode.

[Positive electrode]
A slurry is prepared by mixing 90% by mass of LiCoO ₂ as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder in an N-methylpyrrolidone solvent. did. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, rolled with a press, and the cut out was used as a positive electrode.

[Electrolyte]
Under a dry argon atmosphere, dried LiPF ₆ was dissolved in a mixture of ethylene carbonate and dimethyl carbonate (volume ratio 30:70) to a ratio of 1 mol / L to prepare a basic electrolyte. A compound described in Table 1 was mixed with this basic electrolytic solution and used as an electrolytic solution.

[Lithium secondary battery]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
The battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and each of the electrolyte solutions shown in Table 1 was placed in the bag. And sealed in a vacuum to produce a sheet-like battery.

[Run-in operation]
The lithium secondary battery was conditioned with a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve the adhesion between the electrodes.

[Evaluation of cycle characteristics]
The battery after the break-in operation was charged at 45 ° C. with a constant current of 0.5 C, and then discharged with a constant current of 0.5 C as one cycle, and 100 cycles were performed. Here, 1C represents a current value that discharges the reference capacity of the battery in one hour, 5C represents a current value that is five times that of the battery, and 0.2C represents a current value that is 1/5 of the current value. The capacity retention rate was calculated from the formula of (discharge capacity at the 100th cycle) ÷ (discharge capacity at the first cycle) × 100.

[Evaluation of high-temperature storage characteristics]
The battery after the break-in operation was charged at a constant current of 0.2 C at 25 ° C., and then stored at 85 ° C. for 24 hours. After the battery was cooled to room temperature, it was immersed in an ethanol bath to measure the volume. The amount of gas generated from the volume change before and after high temperature storage was determined.

<Example 2>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the compounds contained in the electrolytic solution shown in Table 1 were changed, and the battery characteristics (capacity retention rate only) were similarly determined.

<Example 3>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the compounds contained in the electrolytic solution shown in Table 1 were changed, and the battery characteristics (capacity retention rate only) were similarly determined.

<Example 4>
Assembling the battery using the same positive electrode and electrolyte (including the compound) as in Example 1 except that the composite of spheroidized natural graphite described below and a mixture of spheroidized natural graphite and a mixture of spheroidized natural graphite was used as the negative electrode active material, Similarly, the battery characteristics were obtained.

Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 26%, the aspect ratio is 8.0, the d value (interlayer distance) of the lattice plane (002 plane) is 0.336 nm, the crystal Child size Lc, La of 100 nm or more, volume-based average particle diameter of 18.8 μm, BET specific surface area of 3.8 m ² / g, tap density of 1.03 g · cm ⁻³ , Raman R value of 0.22, powder A mixture having a body orientation ratio of 0.36 (consisting of a composite of spheroidized natural graphite coated with carbon and spheroidized natural graphite) was used.

  Here, for a composite in which spheroidized natural graphite is coated with carbon, a material obtained by coating the carbon precursor with spheroidized natural graphite so as to be 3% by mass (coverage) after firing and firing at 1300 ° C. is used. It was. Furthermore, a mixture obtained by mixing the carbon-coated composite with spheroidized natural graphite at a mass ratio of 1: 1 was used as the negative electrode active material.

<Example 5>
Example 2 Aside from using a composite of a spheroidized natural graphite having a rhombohedral crystal ratio of 7% and a spheroidized natural graphite having a rhombohedral crystal ratio of 21%, as described below, as the negative electrode active material, coated with graphite on spheroidized natural graphite. A battery was assembled using the same positive electrode and electrolyte solution (including the compound) as above, and the battery characteristics were similarly determined.
Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 13%, the aspect ratio is 4.1, the d value (interlayer distance) of the lattice plane (002 plane) is 0.336 nm, the crystal Child size Lc, La is 100 nm or more, volume-based average particle diameter is 19.1 μm, BET specific surface area is 4.3 m ² / g, tap density is 1.10 g · cm ⁻³ , and Raman R value is 0.17. A mixture (consisting of a composite of spheroidized natural graphite coated with graphite and spheroidized natural graphite) was used.

  Here, for a composite in which spheroidized natural graphite is coated with graphite, a material obtained by coating the carbon precursor with spheroidized natural graphite so as to be 15% by mass (coverage) after firing and firing at 3000 ° C. is used. It was. Further, a mixture obtained by mixing spheroidized natural graphite in a mass ratio of 6: 4 to the graphite-coated composite was used as the negative electrode active material.

<Reference Example 1>
A battery was assembled using the same positive electrode and electrolyte (including the compound) as in Example 1 except that natural graphite described below was used as the negative electrode active material, and battery characteristics (capacity retention rate only) were similarly determined.
Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 38%, the aspect ratio is 5.6, the d value (interlayer distance) of the lattice plane (002 plane) is 0.336 nm, the crystal Natural graphite having a child size Lc, La of 100 nm or more, a volume-based average particle size of 7.0 μm, a BET specific surface area of 11.2 m ² / g, and a Raman R value of 0.37 was used.

<Comparative Example 1>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the compounds contained in the electrolytic solution shown in Table 1 were changed, and the battery characteristics (capacity retention rate only) were similarly determined.

<Comparative Example 2>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the compounds contained in the electrolytic solution shown in Table 1 were changed, and the battery characteristics (capacity retention rate only) were similarly determined.

<Comparative Example 3>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the compounds contained in the electrolytic solution shown in Table 1 were changed, and battery characteristics were similarly determined.

  Table 1 shows the powder physical properties of the negative electrode active materials used in Examples 1 to 5, Comparative Examples 1 to 3, and Reference Example 1, the compounds contained in the electrolyte, and the battery characteristics.

As is clear from Table 1, in a battery using a negative electrode having a rhombohedral crystal ratio within the range of the present invention, when a nonaqueous electrolytic solution containing a compound of the general formula (1) was used (Example 1) To 5), when a non-aqueous electrolyte containing no compound of general formula (1) is used (Comparative Example 1) or when a non-aqueous electrolyte containing a compound other than the compound of general formula (1) is used ( Compared to Comparative Examples 2 and 3), the cycle capacity retention rate and the gas generation rate during high temperature storage are excellent. The reason for exhibiting such excellent battery durability is that the compound of the general formula (1) in the non-aqueous electrolyte during charging / discharging is on the negative electrode surface using a negative electrode active material having a specific rhombohedral crystal ratio. It is presumed that an effective film capable of preventing deterioration of battery characteristics is formed.
Even when the nonaqueous electrolytic solution containing the compound of the general formula (1) is used in combination with a negative electrode whose rhombohedral crystal ratio falls outside the scope of the present invention, there is an effect of the cycle capacity retention rate. (Reference Example 1). However, it can be seen that the present invention is excellent in cycle capacity retention and gas generation suppression during high-temperature storage as compared with the case where a negative electrode having a rhombohedral crystal ratio within the range of the present invention is used (Example 1).

<Example 6 and Comparative Examples 4 and 5>
[Negative electrode]
A negative electrode produced by the same method as in Example 1 was used except that spheroidized graphite particles having the following physical properties were used as the negative electrode active material. Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 4%, the aspect ratio is 4.9, the d value (interlayer distance) of the lattice plane (002 plane) is 0.3354 nm, the crystal Graphite particles having a child size Lc, La of 100 nm or more, a volume-based average particle size of 22 μm, a BET specific surface area of 4.2 m ² / g, a tap density of 1.09 g · cm ⁻³ , and a Raman R value of 0.04 Was used.

[Positive electrode]
A positive electrode produced by the same method as in Example 1 was used.

[Electrolyte]
Under a dry argon atmosphere, dried LiPF ₆ was dissolved in a mixture of ethylene carbonate and dimethyl carbonate (volume ratio 30:70) to a ratio of 1 mol / L to prepare a basic electrolyte. A compound described in Table 2 was mixed with this basic electrolytic solution and used as an electrolytic solution.

[Lithium secondary battery]
It was produced by the same method as in Example 1.

[Evaluation of durability characteristics]
A battery that has been run-in under the same conditions as in Example 1 was charged at a constant current of 0.2 C at 25 ° C., then stored at 85 ° C. for 24 hours, and then at a constant temperature of 0.5 C at 45 ° C. The process of discharging at a constant current of 0.5 C after charging with a current was carried out for 6 cycles. From the calculation formula of (discharge capacity at the nth cycle) ÷ (discharge capacity at the first cycle) × 100, the capacity retention rate at the nth cycle was obtained. The evaluation results are shown in Table 2.

As is clear from Table 2, even in the lithium secondary battery that has finished the high-temperature storage test, the nonaqueous electrolytic solution containing the compound of the general formula (1) and the rhombohedral crystal ratio are within the scope of the present invention. By using the negative electrode, the capacity retention rate was not significantly reduced (Example 6). On the other hand, even when a negative electrode that is within the scope of the present invention is used, when a compound other than the general formula (1) is used or when an additive is not included, with an increase in the cycle of charge and discharge, The capacity retention rate was significantly reduced (Comparative Examples 4 and 5).
Thus, even under the harsh conditions after the high-temperature storage test, the reason for exhibiting a very excellent effect as shown in Example 6 is that the general formula (1) in the non-aqueous electrolyte during charge / discharge It is presumed that this compound forms an effective film capable of preventing deterioration of battery characteristics on the negative electrode surface using a negative electrode active material having a specific rhombohedral crystal ratio.

<Examples 7 to 9 and Comparative Examples 6 and 7>
[Negative electrode]
As the negative electrode active material, a composite in which amorphous natural carbon was coated on spherical natural graphite described below was used. Specifically, the rhombohedral crystal ratio of the negative electrode active material measured by the above method is 30%, the aspect ratio is 4.2, the d value (interlayer distance) of the lattice plane (002 plane) is 0.3355 nm, the crystal Child size Lc, La is 100 nm or more, volume-based average particle diameter is 11.6 μm, BET specific surface area is 3.4 m ² / g, tap density is 0.99 g · cm ⁻³ , and Raman R value is 0.32. Then, graphite particles obtained by coating graphite on natural graphite were used.

  Here, for the composite in which spheroidized natural graphite is coated with carbon, a material obtained by coating the carbon precursor with spheroidized natural graphite so as to be 3% by mass (coverage) after firing, and firing at 1100 ° C. is used. It was.

98 parts by mass of the negative electrode active material, 100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) and an aqueous dispersion of styrene-butadiene rubber (styrene 1 part by mass of a butadiene rubber concentration of 50% by mass was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 18 μm, dried, rolled to an electrode density of 1.45 g / cm ³ with a press, and the cut out was used as the negative electrode.

[Positive electrode]
90% by mass of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder, -Mixed in a methylpyrrolidone solvent and slurried. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, rolled with a press, and the cut out was used as a positive electrode.

[Electrolyte]
In a dry argon atmosphere, the basic electrolyte solution was prepared by dissolving LiPF ₆ in a mixture of monofluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 30:40:30) to a ratio of 1 mol / L. Prepared. A compound described in Table 3 was mixed with this basic electrolytic solution at a ratio shown in Table 3 and used as the electrolytic solution.

[Lithium secondary battery]
It was produced by the same method as in Example 1.

[Evaluation of cycle characteristics]
A battery that had been subjected to a break-in operation under the same conditions as in Example 1 was charged at 60 ° C. with a constant current of 2 C, and then discharged with a constant current of 2 C, and 300 cycles were performed. The capacity retention rate was calculated from the formula of (discharge capacity at the 100th cycle) ÷ (discharge capacity at the first cycle) × 100. The evaluation results are shown in Table 3.

  As is clear from Table 3, in the battery using the negative electrode having a rhombohedral crystal ratio within the range of the present invention, the non-aqueous electrolytes containing the compound of the general formula (1) (Examples 7 to 9) When a non-aqueous electrolyte containing no compound of general formula (1) is used (Comparative Example 7) or when a non-aqueous electrolyte containing a compound other than the compound of general formula (1) is used (Comparative Example 6) Compared to, the high temperature cycle capacity retention rate is excellent. As described above, any compound represented by the general formula (1) exhibits a characteristic effect on battery durability regardless of which compound is used. However, even in the case of a compound having a multiple bond site outside the ring as in the general formula (1), when a compound having a carbon-carbon double bond outside the ring (Comparative Example 6) is used, Even if a negative electrode having a plane crystal ratio in the range of the present invention is used, the durability improvement effect is greatly inferior to Examples 7-9. The reason why such an excellent cycle capacity retention rate is exhibited is that the compound of the general formula (1) in the non-aqueous electrolyte during charge / discharge is on the negative electrode surface using a negative electrode active material having a specific rhombohedral crystal ratio. Thus, it is presumed that an effective film capable of preventing deterioration of battery characteristics is formed.

<Examples 10 to 13 and Comparative Examples 8 and 9>
[Electrolyte]
In a dry argon atmosphere, a basic electrolyte was prepared by dissolving LiPF ₆ dried in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 30:30:40) to a ratio of 1 mol / L. . A compound described in Table 4 was mixed with this basic electrolytic solution at a ratio shown in Table 4 and used as the electrolytic solution.

[Manufacture of lithium secondary batteries]
Using a positive electrode similar to Example 7 and a negative electrode similar to Example 7, a sheet-like battery was produced in the same manner as in Example 1.

[Evaluation of high-temperature storage characteristics]
After confirming the capacity of a battery that has been run-in under the same conditions as in Example 1 at a constant current corresponding to 0.2 C at 25 ° C., the battery was charged with a constant current corresponding to 0.2 C, and 120 ° C. at 75 ° C. Saved for hours. After cooling the battery to room temperature, discharge at a constant current equivalent to 0.2C to obtain the discharge capacity, and maintain the capacity from the formula of (discharge capacity after storage) ÷ (discharge capacity before storage) x 100 The rate was determined. The results are shown in Table 4.

  As is clear from Table 4, in the battery using the negative electrode having a rhombohedral crystal ratio within the range of the present invention, the nonaqueous electrolytic solution containing the compound of the general formula (1) (Examples 10 to 13) Compared with the case where the non-aqueous electrolyte solution not containing the compound of the general formula (1) is used (Comparative Examples 8 and 9), the high temperature storage capacity retention rate is excellent. The reason for exhibiting such an excellent high-temperature storage capacity retention ratio is that the compound of the general formula (1) in the non-aqueous electrolyte solution during charge / discharge uses a negative electrode active material having a specific rhombohedral crystal ratio. From the above, it is presumed that an effective film capable of preventing deterioration of battery characteristics is formed.

<Examples 14 and 15 and Comparative Examples 10 to 14>
[Positive electrode]
85% by mass of Li _1.1 (Ni _0.45 Mn _0.45 Co _0.10 ) O ₂ as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder, N-methyl Mix in a pyrrolidone solvent to make a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, rolled with a press, and the cut out was used as a positive electrode.

[Manufacture of lithium secondary batteries]
The same negative electrode as in Example 7 was used. For Example 14 and Comparative Examples 12 and 13, the same basic electrolyte as in Example 10 was used. For Example 15 and Comparative Examples 10, 11, and 14, the same basic electrolyte as in Example 7 was used. Next, using these positive electrode, negative electrode, and electrolytic solution, a sheet-like battery was produced in the same manner as in Example 1.

[Evaluation of cycle characteristics]
A battery that had been subjected to a break-in operation under the same conditions as in Example 1 was charged at 60 ° C. with a constant current of 2 C, and then discharged with a constant current of 2 C, and 300 cycles were performed. The discharge capacity retention ratio was calculated from the formula of (discharge capacity at 300th cycle) ÷ (discharge capacity at the first cycle) × 100. The evaluation results are shown in Table 5.

  As is clear from Table 5, in the battery using the negative electrode having a rhombohedral crystal ratio within the range of the present invention, the nonaqueous electrolytic solution containing the compound of the general formula (1) (Examples 14 and 15) Compared with the case of using a non-aqueous electrolyte solution that does not contain the compound of general formula (1) (Comparative Examples 10 to 14), the high temperature cycle capacity retention rate is excellent. The reason for exhibiting such an excellent high-temperature storage capacity retention ratio is that the compound of the general formula (1) in the non-aqueous electrolyte solution during charge / discharge uses a negative electrode active material having a specific rhombohedral crystal ratio. From the above, it is presumed that an effective film capable of preventing deterioration of battery characteristics is formed.

<Example 16 and Comparative Example 15>
[Production of negative electrode]
98 parts by mass of the negative electrode active material used in Example 7, 100 parts by mass of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of carboxymethylcellulose sodium) and an aqueous solution of styrene-butadiene rubber, respectively, as a thickener and a binder 1 part by weight of dispersion (styrene-butadiene rubber concentration 50% by weight) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 10 μm, dried, and rolled with a press. The active material layer was 30 mm wide, 40 mm long, 5 mm wide, and 9 mm long uncoated. It cut out into the shape which has a part, and it was set as the negative electrode used for Example 16 and Comparative Example 15, respectively.

[Production of positive electrode]
85% by mass of Li _1.1 (Ni _0.45 Mn _0.45 Co _0.10 ) O ₂ as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder, N-methyl Mix in a pyrrolidone solvent to make a slurry. The obtained slurry was applied to a 15 μm-thick aluminum foil previously coated with a conductive additive, dried, and rolled with a press machine. The active material layer size was 30 mm wide, 40 mm long, and 5 mm wide. The positive electrode used in Example 16 and Comparative Example 15 was cut into a shape having an uncoated part with a length of 9 mm.

[Manufacture of electrolyte]
In a dry argon atmosphere, LiPF ₆ , ethylene carbonate (EC), monofluoroethylene carbonate (MFEC), 2,2,2-trifluoroethyl methyl carbonate (TFEMC) and general formula (1 The electrolyte solution used for Example 16 and Comparative Example 15 was prepared using the compound represented by this. The concentration of LiPF ₆ was adjusted to 1.0 mol / L with respect to the solvent composition obtained by mixing EC, MFEC, TFEMC and the compound represented by the general formula (1).

[Manufacture of lithium secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. The battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and each electrolyte solution shown in Table 6 was then placed in the bag. And then sealed in a vacuum to produce a sheet-like battery, which were used for Example 16 and Comparative Example 15, respectively.

[Evaluation of initial discharge capacity]
The lithium secondary battery was conditioned with a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve the adhesion between the electrodes. The battery that had been conditioned was charged with a constant current corresponding to 0.2 C at 25 ° C., and then discharged with a constant current corresponding to 0.2 C to obtain an initial discharge capacity. The results are shown in Table 2. Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and 0.2C represents a current value of 1/5 thereof.

[Evaluation of cycle characteristics]
The lithium secondary battery for which the initial discharge capacity was evaluated was charged at 60 ° C. with a constant current of 2 C, and then discharged with a constant current of 2 C, and 100 cycles were performed. The discharge capacity retention rate was determined from the formula of (discharge capacity at the 100th cycle) ÷ (discharge capacity at the first cycle) × 100.

  As is clear from Table 6, in a battery using a negative electrode having a rhombohedral crystal ratio within the range of the present invention, when a nonaqueous electrolytic solution containing a compound of the general formula (1) was used (Example 16) Compared with the case where the non-aqueous electrolyte not containing the compound represented by the general formula (1) is used (Comparative Example 15), the cycle capacity retention rate is excellent. This is presumed that the compound represented by the general formula (1) is highly cross-linked so that the electrode surface durability is remarkably improved, and as a result, the above-mentioned remarkable battery durability is improved. Is done.

  According to the combination of the negative electrode and the non-aqueous electrolyte solution of the present invention, the non-aqueous electrolyte secondary battery has a high capacity retention rate and is useful even after a durability test such as a high-temperature storage test or a cycle test. Therefore, the negative electrode active material, the non-aqueous electrolyte solution, and the non-non-aqueous electrolyte secondary battery using the negative electrode active material of the present invention can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, etc. , Walkie Talkie, Electronic Notebook, Calculator, Memory Card, Portable Tape Recorder, Radio, Backup Power Supply, Motor, Automobile, Motorcycle, Motorbike, Bicycle, Lighting Equipment, Toy, Game Equipment, Clock, Electric Tool, Strobe, Camera, Load Examples include leveling power sources and natural energy storage power sources.

Claims (7)

A non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous solvent that dissolves the lithium salt, a negative electrode capable of occluding and releasing lithium ions, and a positive electrode. Characterized in that it contains a negative electrode active material composed of graphite particles having a plane crystallinity of 0% or more and 35% or less, and the non-aqueous electrolyte contains a compound represented by the following general formula ( 2 ). Non-aqueous electrolyte secondary battery.

(Y represents C═O, S═O, S (═O) ₂ , P (═O) —R ² , P (═O) —OR ³ , where R ² is an optionally substituted carbon. It is a hydrocarbon group of the number 1 to 20. R ³ is Li, NR ⁴ ₄ or
Or it is a C1-C20 hydrocarbon group which may have a substituent. R ⁴ has a substituent
And may be the same or different from each other. )   The non-aqueous electrolyte secondary battery according to claim 1, wherein an interlayer distance d002 of the graphite particles is 0.335 nm or more and 0.339 nm or less.   The graphite particles according to claim 1 or 2, wherein the graphite particles are selected from any one or more of graphite particles obtained by coating carbon with nuclear graphite, graphite particles obtained by coating graphite with nuclear graphite, and natural graphite particles. Non-aqueous electrolyte battery. 4. The compound represented by the general formula ( 2 ) is any one or more of compounds represented by the following formulas (3) to (8). The non-aqueous electrolyte secondary battery described in 1.

  The non-aqueous electrolyte solution contains at least one or more members selected from the group consisting of a cyclic carbonate having a carbon-carbon double bond and a cyclic carbonate having a fluorine atom. The non-aqueous electrolyte secondary battery according to claim 1. The non-aqueous electrolyte solution is at least lithium monofluorophosphate (LiPO ₃ F), lithium difluorophosphate (LiPO ₂ F ₂ ), FSO ₃ Li, lithium bis (oxalato) borate, lithium tetrafluorooxalatophosphate, lithium The nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, comprising any one selected from the group of difluorobis (oxalato) phosphates.   A non-aqueous electrolyte solution that is used in the non-aqueous electrolyte secondary battery according to claim 1.