JP6547372B2 - Nonaqueous Electrolyte and Nonaqueous Electrolyte Secondary Battery Using the Same - Google Patents

Description

  The present invention relates to a non-aqueous electrolytic solution and a non-aqueous electrolytic solution secondary battery using the same, and more particularly, to a non-aqueous electrolyte using a non-aqueous electrolytic solution having a specific positive electrode and containing a specific component. The present invention relates to an electrolytic solution secondary battery and a non-aqueous electrolytic solution used for the same.

  With the miniaturization of electronic devices due to the rapid industrial development in modern times, there has been a strong demand for higher capacity secondary batteries. Therefore, lithium secondary batteries and the like having higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries have been developed, and efforts to improve the performance thereof have been repeated until now.

The components constituting the secondary battery are roughly classified into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Among these, in general, electrolytes such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO _{3 and the} like are used as the electrolytic solution. Cyclic carbonates such as ethylene carbonate and propylene carbonate; Linear carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; Cyclic esters such as γ-butyrolactone and γ-valerolactone; Linear esters such as methyl acetate and methyl propionate A non-aqueous electrolytic solution dissolved in a non-aqueous solvent such as the like is used.

  In recent years, with the background of global issues such as environmental problems and energy problems, great expectations have been drawn to the application of secondary batteries, particularly lithium secondary batteries, to large-sized power supplies such as automotive power supplies and stationary power supplies. However, since such batteries are generally expected to be used in an environment exposed to the open air, they are required to function in a wide temperature range. Especially in automotive applications, particularly high safety is required because the use environment is severe. In addition to this, from the application, the further high power-ization and the life performance beyond the conventional secondary battery are called for.

  Efforts have been made to add various compounds to the above-mentioned electrolytic solution as one of the efforts for further improving various characteristics of the secondary battery including the lithium secondary battery.

  For example, Patent Document 1 reports that a suitable low temperature discharge resistance and cycle characteristics can be obtained by adding a predetermined compound having a Si-Si bond and a chain compound having an NCO structure to a non-aqueous electrolyte solution. It is done.

JP 2012-178340 A

  As described above, although efforts have been made to improve the safety, output characteristics, and durability-related characteristics of the secondary battery so far, it is considered sufficient to achieve sufficient battery characteristics. However, further improvement is required.

  The present invention has been made in view of such background art, and the subject is a secondary non-aqueous electrolytic solution in which the safety is further enhanced and the output characteristics and the capacity retention rate at high temperature storage are enhanced. It is an object of the present invention to provide a battery and a non-aqueous electrolytic solution for use therein.

  As a result of intensive studies to solve the above problems, the present inventors conducted secondary studies by using a non-aqueous electrolyte containing a specific component in a non-aqueous electrolyte secondary battery provided with a specific positive electrode. The inventors have found that the battery safety, output characteristics and capacity retention rate at high temperature storage can be balanced at a high level, and the present invention has been completed.

  That is, the present invention provides the following specific embodiments and the like shown in (a) to (p).

（式中、Ｑは炭素数２〜１０の２価の有機基であり、該有機基は３級又は４級炭素を有する。）

（式中、Ｒ^１〜Ｒ^６はそれぞれ独立に水素原子、ハロゲン原子で置換されていてもよい、炭素数１〜１０のアルキル基、アルケニル基、アルキニル基又はアリール基、あるいはハロゲン原子で置換されていてもよい珪素数１〜１０の珪化水素基であり、Ｒ^１〜Ｒ^６の少なくとも二つは互いに結合して、環を形成してもよい。） (A) A current collector and lithium represented by Li x MPO ₄ (M is at least one element selected from the group consisting of metals of Groups 2 to 12 of the periodic table, x is 0 <x ≦ 1.2) A non-aqueous electrolyte secondary battery comprising: a positive electrode containing a contained phosphoric acid compound as a positive electrode active material; a negative electrode containing a negative electrode active material capable of absorbing and desorbing lithium ions; and a non-aqueous electrolytic solution A non-aqueous electrolytic solution secondary battery characterized in that the non-aqueous electrolytic solution contains at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) .

(Wherein, Q is a divalent organic group having 2 to 10 carbon atoms, and the organic group has a tertiary or quaternary carbon.)

(Wherein, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a C 1-10 alkyl group which may be substituted by a halogen atom, an alkenyl group, an alkynyl group or an aryl group, or a halogen atom And may be a silicon hydride having a silicon number of 1 to 10, and at least two of R ^{1 to} R ⁶ may be bonded to each other to form a ring.)

  (B) The non-aqueous electrolyte secondary battery according to (a), wherein Q in the general formula (1) has a cyclic skeleton.

  (C) The non-aqueous electrolyte secondary battery according to (a) or (b), wherein Q in the general formula (1) has a cyclohexane ring.

(D) The nonaqueous electrolytic solution according to any one of (a) to (c), wherein the compound represented by the general formula (1) is a compound represented by the following formula: Next battery.

(E) In the general formula (2), R ^{1 to} R ⁶ are a hydrogen atom or an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, The nonaqueous electrolytic solution secondary battery according to any one of d).

(F) The non-aqueous electrolytic solution according to any one of (a) to (e), wherein R ^{1 to} R ⁶ in the general formula (2) are a methyl group or an ethyl group. Next battery.

(G) The nonaqueous electrolytic solution according to any one of (a) to (f), wherein the compound represented by the general formula (2) is a compound represented by the following formula Secondary battery.

  (H) The compound represented by the general formula (1) is contained in an amount of 0.01 to 10% by mass based on the whole of the non-aqueous electrolyte, any of (a) to (g) The non-aqueous electrolyte secondary battery according to any one of the preceding claims.

  (I) Any one of (a) to (h), wherein the compound represented by the general formula (2) is contained in an amount of 0.01 to 10% by mass based on the whole of the non-aqueous electrolyte solution The non-aqueous electrolyte secondary battery according to any one of the preceding claims.

  (J) The nonaqueous electrolytic solution according to any one of (a) to (i), wherein the nonaqueous electrolytic solution further contains a compound which is reduced on the negative electrode at the time of initial charge of the battery. Secondary battery.

  (K) The compound to be reduced on the negative electrode is vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, lithium bis (oxalato) borate, lithium tetrafluoro oxalato phosphate, lithium difluoro bis (oxalato) phosphate and The non-aqueous electrolyte secondary battery according to (j), which is at least one selected from the group consisting of lithium tris (oxalato) phosphate.

(L) The lithium-containing phosphoric acid compound is LixMPO ₄ (M is at least one element selected from the group consisting of transition metals of Groups 4 to 11 of Periodic Table Period 4; x is 0 <x ≦ 1 The nonaqueous electrolytic solution secondary battery according to any one of (a) to (k), which is characterized by being represented by .2).

(M) The nonaqueous electrolyte secondary battery according to any one of (a) to (l), wherein the lithium-containing phosphoric acid compound is LiFePO ₄ .

  (N) The non-aqueous electrolyte secondary battery according to any one of (a) to (m), wherein the negative electrode active material contains a carbonaceous material.

  (O) The non-aqueous electrolyte secondary battery according to any one of (a) to (n), having a conductive layer of a compound composition different from that of the current collector on the surface of the current collector.

(P) a current collector, and lithium represented by LixMPO ₄ (M is at least one element selected from the group consisting of metals of Groups 2 to 12 of the periodic table, x is 0 <x ≦ 1.2) For use in a non-aqueous electrolyte secondary battery comprising a positive electrode containing a contained phosphoric acid compound as a positive electrode active material, a negative electrode containing a negative electrode active material capable of absorbing and desorbing lithium ions, and a non-aqueous electrolytic solution A non-aqueous electrolyte solution comprising at least one of a compound represented by the general formula (1) and a compound represented by the general formula (2).

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery excellent in safety, output characteristics, and capacity retention rate at high temperature storage, and a non-aqueous electrolyte for use therein.

  Hereinafter, the embodiments of the present invention will be described in detail. However, the following embodiments are exemplifications for describing the present invention, and the present invention is not limited thereto, and does not deviate from the gist of the present invention. It can be arbitrarily changed and implemented within the scope.

In the non-aqueous electrolyte secondary battery of the present invention, at least one element selected from the group consisting of a current collector and LixMPO ₄ (where M is a metal of Groups 2 to 12 of the periodic table, x is 0 <x ≦ A positive electrode containing the lithium-containing phosphoric acid compound represented by 1.2) as a positive electrode active material (hereinafter sometimes referred to as "specific positive electrode") and a negative electrode active material capable of absorbing and releasing lithium ions And a non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is a compound represented by the following general formula (1) (hereinafter, “specific NCO compound” and And at least one of the compounds represented by the following general formula (2) (hereinafter sometimes referred to as "specific Si compound").

First, the estimation mechanism of the effect of the present invention will be described. Conventionally, a positive electrode using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material (hereinafter sometimes referred to as “NMC positive electrode”) is widely used. However, the NMC positive electrode is inferior in thermal stability because the positive electrode active material has a layered rock salt type crystal structure. Therefore, at the time of overcharge or heating, the crystal structure may be destabilized, which may lead to the release of oxygen. This oxygen release causes the thermal runaway of the cell. On the other hand, the specific positive electrode of the present invention uses the lithium-containing phosphoric acid compound represented by LixMPO ₄ described above as a positive electrode active material. This lithium-containing phosphoric acid compound is excellent in thermal stability, and in particular, those having an olivine type crystal structure are particularly excellent in thermal stability. Therefore, the specific positive electrode of the present invention suppresses the thermal runaway of the cell due to the release of oxygen because the crystal structure of the lithium-containing phosphate compound is relatively stably maintained even during overcharge or heating. As a result, it is presumed that the security is enhanced.

  In addition, the specific NCO compound has an NCO group in the molecule. The NCO group is known as a highly reactive functional group, for example, it is known to react with an OH group to form a urethane bond.

  A carbonaceous material is generally used for the negative electrode material of the non-aqueous electrolyte secondary battery. It is known that there are many surface functional groups (OH group, COOH group, etc.) on the surface of the carbonaceous material. In addition, it is known that a large number of OM groups (M is Li, Na, K, H, Ca, etc.) are present in the film formed on the negative electrode due to various factors.

  The NCO group of the specific NCO compound is presumed to react with the functional group on the negative electrode or the OM group in the film to form a urethane bond. Thereby, a component derived from the specific NCO compound is formed and deposited on the negative electrode surface. It is believed that this functions as a negative electrode film and suppresses the side reaction of the non-aqueous solvent in the non-aqueous electrolyte solution (thereby forming a film on the negative electrode as described later). However, deposition of the film derived from the specific NCO compound on the negative electrode has a disadvantage that the negative electrode resistance increases to a certain extent.

  The specific NCO compound has two NCO groups in the molecule. A film can be formed more firmly on the negative electrode by reacting these two NCO groups independently with the surface functional group or the film of the negative electrode, and the side reaction of the non-aqueous solvent is effectively suppressed. However, on the other hand, the increase in negative electrode resistance is also greater. When NCO groups react, if two NCO groups react close to each other, it is considered that the density of the film on the negative electrode increases and the resistance tends to increase. In the specific NCO compound used in the present invention, the negative electrode resistance was successfully improved by adding the following measures to the molecular structure.

  The specific NCO compound is characterized by being represented by the above formula (1) and having a tertiary or quaternary carbon in Q in its structure. By branching the main chain of the specific NCO compound by this tertiary or quaternary carbon, an effect of appropriately separating the distance between the two NCO groups is expected due to the steric hindrance of the side chain. Thereby, it is considered that the increase in the film density as described above can be suppressed and the increase in resistance can be suppressed.

  Subsequently, the specific Si compound has a Si-Si bond. The Si-Si bond is known to cleave upon nucleophilic attack. Various functional groups exist on the surface of the negative electrode as described above. Those functional groups have increased nucleophilicity when charging the secondary battery. At this time, it is considered that the highly nucleophilic surface functional group reacts with the specific Si compound. By this reaction, a film of a cleaved specific Si compound is formed on the negative electrode, which has lower resistance than the film derived from the non-aqueous solvent described below, and thus can suppress the increase in resistance. Conceivable.

  Films are deposited on the surface of the negative electrode, and among these films, those formed by surface functional groups subjected to non-aqueous solvent molecules by nucleophilic attack are included. That is, the surface functional group is closely related to the resistance of the negative electrode film.

  When the surface functional group of the negative electrode reacts with the specific Si compound, the surface functional group loses activity. The nucleophilic attack of the surface functional group having lost activity to the non-aqueous solvent is significantly reduced (reactivity with the specific NCO compound is also reduced), so that the formation of a film derived from the non-aqueous solvent is suppressed. Thus, the addition of the specific Si compound can suppress the increase in the resistance of the negative electrode surface.

  In the present invention, safety, output characteristics, and capacity retention rate at high temperature storage are made compatible by using a specific positive electrode and a non-aqueous electrolytic solution containing a specific NCO compound and a specific Si compound in combination. That is, the thermal stability of the specific positive electrode is high, and the density of the negative electrode film derived from the specific NCO compound is low, the resistance of the negative electrode is small, and the film density is low, the surface functional group of the specific Si compound It is presumed that the reaction with (1) (the side reaction between the surface functional group and the non-aqueous solvent is suppressed as a result) is a factor of the effect of the present invention.

Hereinafter, each configuration of the present invention will be described.
[1. Non-aqueous electrolyte solution]
The non-aqueous electrolyte is characterized by containing a specific NCO compound and a specific Si compound.

[1-1. Specific NCO Compound and Specific Si Compound]
<1-1-1. Specific NCO compound>
As described above, the specific NCO compound used in the present invention is represented by the following general formula (1).

式中、Ｑは炭素数２〜１０の２価の有機基であり、該有機基は３級又は４級炭素を有する。

In the formula, Q is a divalent organic group having 2 to 10 carbon atoms, and the organic group has a tertiary or quaternary carbon.

  The organic group has a hydrocarbon skeleton mainly composed of carbon and hydrogen as a basic skeleton, and may have a hetero atom, and has a tertiary or quaternary carbon as described above, and is branched at that part Form a structure. In the present invention, the “branched structure” also includes a structure formed by bonding any group to a ring-constituting carbon atom of the ring structure. The organic group may have at least one tertiary or quaternary carbon, and may have two or more.

  The organic group is a linear alkylene group which may be substituted by a halogen atom having a carbon number of 2 to 10 and at least one bond with an NCO group in a portion other than the chain end (a carbon number of 2 As for the chained alkylene group (methyl methylene group), two NCO groups are bonded to the same carbon atom), a branched alkylene group which may be substituted with a halogen atom having 3 to 10 carbon atoms, the number of carbon atoms The cycloalkylene group which may be substituted by 3-10 halogen atoms, the arylene group which may be substituted by the C6-C10 halogen atom, etc. are mentioned.

  As a halogen atom which can be substituted in each of the above groups, a fluorine atom, a chlorine atom and a bromine atom can be mentioned. Among them, a fluorine atom is preferable from the viewpoint of enhancing the reactivity on the negative electrode surface.

  Among the organic groups listed above, from the viewpoint of suppressing an increase in negative electrode resistance, Q is preferably a bivalent organic group having a carbon number of 4 or more as the linear portion. The linear portion of the divalent organic group having 4 or more carbon atoms may further have a substituent. From the same viewpoint, as the organic group, one having a cyclic skeleton is preferable, for example, one having a cyclopentane skeleton or a cyclohexane skeleton is more preferable, and a cyclohexane ring is more preferable.

  The following structures are mentioned as a specific example of a C4 or more bivalent organic group whose linear part is carbon number.

なお、各構造における二つの波線は、ＮＣＯ基への結合手である。

The two wavy lines in each structure are bonds to NCO groups.

  Preferred specific examples of the specific NCO compound include compounds corresponding to the specific examples of Q described above. Among the specific NCO compounds, particularly preferred compounds are those having a cyclohexane skeleton as Q. Specifically, compounds represented by the following general formulas (1a) and (1b) can be mentioned.

（式中、Ｌ_１及びＬ_２は、それぞれ独立して、単結合又は炭素数１〜３のアルキレン基であり、好ましくは単結合又は炭素数１〜２のアルキレン基であり、Ｒａは、それぞれ独立して、ハロゲン原子で置換されていてもよい、炭素数１〜１０のアルキル基、アルケニル基、アルキニル基又はアリール基であり、好ましくはハロゲン原子で置換されていてもよい炭素数１〜５のアルキル基、より好ましくはハロゲン原子で置換されていてもよい炭素数１〜３のアルキル基であり、ｍは、０〜５の整数であり、好ましくは０〜４の整数であり、より好ましくは０〜３の整数である。）

(Wherein, L ₁ and L ₂ are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a single bond or an alkylene group having 1 to 2 carbon atoms, and Ra is each It is independently an alkyl group having 1 to 10 carbon atoms which may be substituted by a halogen atom, an alkenyl group, an alkynyl group or an aryl group, and preferably a carbon number of 1 to 5 which may be substituted by a halogen atom Is preferably an alkyl group having 1 to 3 carbon atoms which may be substituted with a halogen atom, and m is an integer of 0 to 5, preferably an integer of 0 to 4, and more preferably Is an integer of 0 to 3.)

（式中、Ｚは、単結合又は炭素数１〜３のアルキレン基であり、好ましくは単結合又は炭素数１〜２のアルキレン基であり、Ｌ_３及びＬ_４は、それぞれ独立して、単結合又は炭素数１〜３のアルキレン基であり、Ｒａは、それぞれ独立して、ハロゲン原子で置換されていてもよい、炭素数１〜１０のアルキル基、アルケニル基、アルキニル基又はアリール基であり、好ましくはハロゲン原子で置換されていてもよい炭素数１〜５のアルキル基、より好ましくはハロゲン原子で置換されていてもよい炭素数１〜３のアルキル基であり、ｎは、０〜５の整数であり、好ましくは０〜３の整数であり、より好ましくは０〜２の整数である。）

(Wherein Z is a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a single bond or an alkylene group having 1 to 2 carbon atoms, and L ₃ and L ₄ are each independently Bond or an alkylene group having 1 to 3 carbon atoms, and each Ra independently represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an alkynyl group or an aryl group which may be substituted with a halogen atom Preferably an alkyl group of 1 to 5 carbon atoms which may be substituted by a halogen atom, more preferably an alkyl group of 1 to 3 carbon atoms which may be substituted by a halogen atom, and n is 0 to 5 And is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.)

Specific examples of the compound represented by the above general formula (1a) or (1b) are shown below.

  Among the specific NCO compounds, the reason why the compound represented by the above general formula (1a) or (1b) is particularly preferable will be described below. First, since the two NCO groups are appropriately separated from each other, when the specific NCO compound forms a film on the negative electrode, the film is less likely to be dense and the resistance is less likely to increase. Moreover, by the cyclohexane ring being arrange | positioned between two NCO groups, the approach of NCOs can be further suppressed by the influence of the steric hindrance. By these, it is expected that the increase in negative electrode resistance is suppressed more effectively.

  It is preferable that 0.01-10 mass% is contained in the whole non-aqueous electrolyte solution (100 mass%) of this invention, and the specific NCO compound demonstrated above is contained 0.1-2 mass%. Is more preferred. The reason for this is that by controlling the content of the specific NCO compound to the above range in the non-aqueous electrolytic solution, it is possible to suppress the excessive presence of these compounds in the electrolytic solution. Since these compounds are used for the purpose of modifying the interfaces such as the positive electrode / electrolyte interface, the negative electrode / electrolyte interface, etc., it is preferable to minimize the amount to which this purpose can be achieved as much as possible. If the unreacted compound is excessively present in the electrolytic solution, the battery characteristics may be deteriorated.

In the present invention, the specific NCO compounds may be used alone or in combination of two or more.

<1-1-2. Specific Si compound>
The specific Si compound used in the present invention is represented by the following general formula (2).

In the formula, R ^{1 to} R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an alkenyl group, an alkynyl group or an aryl group, or a halogen atom And may be a silicon hydride having 1 to 10 silicon atoms, and at least two of R ^{1 to} R ⁶ may be bonded to each other to form a ring.

  Examples of the halogen atom which may be substituted on the alkyl group, the alkenyl group, the alkynyl group, the aryl group and the hydrogen silicide group include a fluorine atom, a chlorine atom and a bromine atom, and among these, the reactivity on the negative electrode Fluorine atoms are preferred from the viewpoint of enhancing.

  The alkyl group is preferably an alkyl group which may be substituted by a halogen atom having 1 to 4 carbon atoms from the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode, As such an alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group and a t-butyl group can be mentioned.

  The alkenyl group has a carbon number of 2 to 10, and is an alkenyl group which may be substituted with a halogen atom having a carbon number of 2 to 3, from the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode. Is preferred. Such alkenyl groups include vinyl and allyl groups.

  The number of carbon atoms of the alkynyl group is 2 to 10, and from the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode, the alkynyl group may be substituted with a halogen atom of 2 to 3 carbon atoms Is preferred. Such alkynyl groups include ethynyl and propargyl groups.

  The carbon number of the aryl group is 6 to 10, and an aryl group which may be substituted with a halogen atom having a carbon number of 6 to 7 from the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode Is preferred. Such aryl groups include phenyl, benzyl and p-tolyl.

  From the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode, the above-mentioned hydrogen silicide group is preferably a silicon hydride having a silicon number of 1 to 2, and as such a hydrogen silicide group, Examples include silyl group, methylsilyl group, dimethylsilyl group, trimethylsilyl group and (trimethylsilyl) silyl group.

In addition, as described above, at least two of R ^{1 to} R ⁶ may be bonded to each other to form a ring (with Si-Si), and as a ring formed in such a manner, for example, cyclohexasilane It can be mentioned.

Among the various groups described above, from the viewpoint of suppressing steric hindrance when the specific Si compound reacts with the surface functional group of the negative electrode, R ^{1 to} R ⁶ is preferably a hydrogen atom or a halogen atom having 1 to 4 carbon atoms It is an alkyl group which may be substituted by In addition, preferable specific examples of R ^{1 to} R ⁶ include a hydrogen atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, vinyl group and ethynyl group. Groups, phenyl groups, benzyl groups and p-tolyl groups. Among these, methyl and ethyl are particularly preferable.

From the above, specific examples of the specific Si compound, the R ¹ it may be mentioned the number of combinations of embodiments of to R ^6, Preferred specific examples of the specific Si compound include the following.

  Further, among these, particularly preferred compounds are the following two compounds.

Among the specific Si compounds, the reason why the above compounds are particularly preferable will be described below. In general, methyl groups and ethyl groups have relatively small steric hindrance and are less likely to inhibit intermolecular reactions. Therefore, when R ^{1 to} R ⁶ are a methyl group or an ethyl group, the reaction of the specific Si compound on the negative electrode is likely to proceed, and there is an advantage that the resistance suppressing effect can be exhibited more effectively.

From the viewpoint of steric hindrance, a hydrogen atom is more preferable than a methyl group or an ethyl group, but when R ^{1 to} R ⁶ are hydrogen atoms, side reactions can occur because the activity of the Si-H bond is high. There is sex. Since the side reaction may contribute to the deterioration of the battery characteristics, it is preferable that the side reaction be small. From these reasons, among the specific Si compounds, the above two compounds are particularly preferable, and the compound on the left side (hexamethyldisilane) is most preferable.

  The specific Si compound described above is preferably contained 0.01 to 10% by mass, and 0.1 to 2% by mass in the whole (100% by mass) of the non-aqueous electrolyte solution of the present invention. Is more preferred. The reason for this is that by controlling the content of the specific Si compound to the above range in the non-aqueous electrolytic solution, it is possible to suppress the excessive presence of these compounds in the electrolytic solution. Since these compounds are used for the purpose of modifying the interfaces such as the positive electrode / electrolyte interface, the negative electrode / electrolyte interface, etc., it is preferable to minimize the amount to which this purpose can be achieved as much as possible. If the unreacted compound is excessively present in the electrolytic solution, the battery characteristics may be deteriorated.

  In addition, the specific Si compounds described above in the present invention may be used singly or in combination of two or more.

[1-2. Electrolytes〕
<Lithium salt>
The non-aqueous electrolytic solution contains an electrolyte, but in the present invention, a lithium salt is usually used as the electrolyte. The lithium salt is not particularly limited as long as it is known to be used for this application, and any lithium salt can be used. Specific examples thereof include the following.

For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
Lithium tungstates such as LiWOF ₅ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylic acid lithium salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ Sulfonic acid lithium salts such as CF ₂ CF ₂ SO ₃ Li;
_{LiN (FCO) 2, LiN (} FCO) (FSO 2), LiN (FSO 2) 2, LiN (FSO 2) (CF 3 SO 2), LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO _{2) 2,} lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic _{1,3-perfluoropropanedisulfonylimide, LiN (CF 3 SO 2)} (C 4 F 9 SO 2) lithium imide salts such as ;
Lithium methide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) _{3 and the} like;
Lithium oxalato borate salts such as lithium difluoro oxalato borate, lithium bis (oxalato) borate;
Lithium oxalato phosphate salts such as lithium tetrafluoro oxalato phosphate, lithium difluoro bis (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
Etc.

Among these, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , FSO ₃ Li, CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₄ ) 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 bisoxalato borate, lithium difluoro oxalato borate, lithium tetrafluoro oxalato phosphate, lithium difluoro bis oxalato phosphate, LiBF ₃ CF ₃ , LiBF _{3 C 2 F 5, LiPF 3} (C _{3) 3, LiPF 3 (C} 2 F 5) 3 or the like is 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 preferred example of the case of using two or more kinds, and LiPF ₆ and LiBF _4, a LiPF ₆ and _FSO 3 Li combination of such, an effect of improving the load characteristics and cycle characteristics of the secondary battery.

In this case, the concentration of LiBF ₄ or FSO ₃ Li with respect to 100% by mass of the whole non-aqueous electrolyte is not limited as long as it does not significantly impair the effect of the present invention, but the whole non-aqueous electrolyte of the present invention On the other hand, the content is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less.

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 of the secondary battery due to high temperature storage. As the organic lithium salt, CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ Lithium cyclic 1,2-perfluoroethanedisulfonyl imide lithium cyclic 1,3-perfluoropropane disulfonyl imide LiC (FSO ₂ ) ₃ LiC (CF ₃ SO ₂ ) ₃ LiC (C ₂ F ₅ SO ₂ ) ₂ ) ₃ , lithium bisoxalato borate, lithium difluoro oxalato borate, lithium tetrafluoro oxalato phosphate, lithium difluoro bis oxalato phosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _{3 and the} like are preferable.

  In this case, the ratio of the organic lithium salt is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less based on 100% by mass of the whole non-aqueous electrolyte solution. And particularly preferably 20% by mass or less.

  The concentration of the lithium salt described above in the non-aqueous electrolytic solution is not particularly limited as long as the effects of the present invention are not impaired, but the electric conductivity of the non-aqueous electrolytic solution is made into a good range. The total molar concentration of lithium in the non-aqueous electrolytic solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and still more preferably 0.5 mol / L or more, from the viewpoint of securing battery performance. Also, it is preferably 3 mol / L or less, more preferably 2.5 mol / L or less, and still more preferably 2.0 mol / L or less.

  If the total molar concentration of lithium is too low, the electrical conductivity of the non-aqueous electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to the increase in viscosity. May decrease.

[1-3. Non-aqueous solvent]
There is no restriction | limiting in particular about the non-aqueous solvent in the non-aqueous electrolyte solution of this invention, It is possible to use a well-known organic solvent. Examples of these include cyclic carbonates having no fluorine atom, linear carbonates, cyclic and linear carboxylic acid esters, ether compounds, sulfone compounds and the like.

<Cyclic carbonate having no fluorine atom>
As a cyclic carbonate which does not have the said fluorine atom, the cyclic carbonate which has a C2-C4 alkylene group is mentioned.

  As a specific example of the cyclic carbonate which does not have a fluorine atom which has a C2-C4 alkylene group, ethylene carbonate, a propylene carbonate, a butylene carbonate is mentioned. Among them, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of the improvement of the battery characteristics derived from the improvement of the lithium ion dissociation degree.

  The cyclic carbonate which does not have a fluorine atom may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The compounding amount of the cyclic carbonate having no fluorine atom is not particularly limited and is optional as long as the effects of the present invention are not significantly impaired, but the compounding amount in the case of using one kind alone is 100 volumes of nonaqueous solvent In%, it is usually 5% by volume or more, more preferably 10% by volume or more. By setting it in this range, a decrease in the electrical conductivity resulting from a decrease in the dielectric constant of the non-aqueous electrolyte solution is avoided, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery, the stability to the negative electrode, and the cycle characteristics are excellent. Range is easy. The amount is usually 95% by volume or less, more preferably 90% by volume or less, and still more preferably 85% by volume or less. By setting the viscosity in this range, the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range, the decrease in ion conductivity can be suppressed, and the load characteristics of the non-aqueous electrolyte secondary battery can be easily set in a good range.

<Linear carbonate>
As said linear carbonate, a C3-C7 linear carbonate is preferable and a C3-C7 dialkyl carbonate is more preferable.

  Specific examples of the linear carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, 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 and the like can be mentioned.

  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.

  In addition, linear carbonates having a fluorine atom (hereinafter sometimes referred to as "fluorinated linear carbonate") can also be suitably used.

  The number of fluorine atoms contained in the fluorinated linear 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 linear carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon as each other or to different carbons.

  The fluorinated linear carbonates include fluorinated dimethyl carbonate and derivatives thereof, fluorinated ethyl methyl carbonate and derivatives thereof, fluorinated diethyl carbonate and derivatives thereof and the like.

  Examples of fluorinated dimethyl carbonate and derivatives thereof include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate and the like. Be

  As fluorinated ethyl methyl carbonate and derivatives thereof, 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoro ethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2 -Trifluoroethyl methyl carbonate, 2, 2- difluoro ethyl fluoro methyl carbonate, 2- fluoro ethyl difluoro methyl carbonate, ethyl trifluoromethyl carbonate etc. are mentioned.

  As fluorinated diethyl carbonate and derivatives thereof, ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-) Trifluoroethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2, 2,2-trifluoroethyl-2 ', 2'-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, etc. are mentioned.

  The chain carbonates described above may be used alone or in any combination of two or more in any proportion.

  In addition, the amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and still more preferably 15% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this manner, the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range, the decrease in ion conductivity can be suppressed, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery can be easily set to a good range. Become. In addition, the linear carbonate is 90% by volume or less, more preferably 85% by volume or less, in 100% by volume of the non-aqueous solvent. By setting the upper limit in this manner, it is possible to avoid the decrease in the electrical conductivity resulting from the decrease in the dielectric constant of the non-aqueous electrolyte solution, and to easily set the large current discharge characteristics of the non-aqueous electrolyte secondary battery in a good range. .

<Cyclic carboxylic acid ester>
The cyclic carboxylic acid ester is preferably one having 3 to 12 carbon atoms.
Specifically, gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone and the like can be mentioned. Among them, gamma-butyrolactone is particularly preferable from the viewpoint of the improvement of the battery characteristics derived from the improvement of the lithium ion dissociation degree.

  The cyclic carboxylic acid esters may be used alone or in any combination of two or more in any proportion.

  The compounding 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. Within this range, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery can be easily improved. Further, the compounding amount of the cyclic carboxylic acid ester is preferably 50% by volume or less, more preferably 40% by volume or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is made into an appropriate range, the decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge of the non-aqueous electrolyte secondary battery It becomes easy to make a characteristic into a good range.

<Linear carboxylic acid ester>
The chain carboxylic acid ester is preferably one having 3 to 7 carbon atoms. Specifically, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyrate-n- Propyl, isopropyl isobutyrate and the like can be mentioned.

  Among these, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate etc. have viscosities. It is preferable from the point of the improvement of the ion conductivity by fall.

  The linear carboxylic acid esters described above may be used alone or in any combination and ratio of two or more.

  The blending amount of the linear carboxylic acid ester is usually 10% by volume or more, preferably 15% 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 can be improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery can be easily improved. Moreover, the compounding quantity of chain | strand-shaped carboxylic acid ester is preferably 60 volume% or less, more preferably 50 volume% or less in 100 volume% of non-aqueous solvents. By setting the upper limit in this manner, an increase in negative electrode resistance can be suppressed, and the large current discharge characteristics and the cycle characteristics of the non-aqueous electrolyte secondary battery can be easily set in a favorable range.

<Ether compounds>
As said ether type compound, the C3-C10 chain | strand-shaped ether with which one part hydrogen may be substituted by the fluorine, and the C3-C6 cyclic ether are preferable.

As said C3-C10 chained ether,
Diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2, 2,2-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-tetrafluoroethyl) ether, ethyl-n-propylether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3-tet) Fluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propylether, (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-propylether, (2,2,2- Trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2,2,3 , 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-propylether, (1,1,2,2-tetrafluoroethyl) (3-fluoro-n-propyl) ether, (1,1 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-propylether, (n- Propyl) (3-fluo Ro-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-trifluoro-n-propyl) ) (2, 2, 3, 3- Trafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-pentafluoro-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-butylether, dimethoxymethane, methoxyethoxymethane, methoxy (2-fluoroethoxy) methane, methoxy (2,2,2-triyl) Fluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fluoroethoxy) 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 2,2,2-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-tetrafluoroethoxy) ethane, diethoxyethane, toki Ci (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 and the like can be mentioned.

  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 the ether compounds described above, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvation ability to lithium ions. Among these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable in view of improving the ion dissociation, and particularly preferable because they have low viscosity and give high ion conductivity.

  As such ether compounds, one type may be used alone, or two or more types may be used in combination in an optional combination and ratio.

  The compounding amount of the ether compound is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and preferably 70% by volume or less in 100% by volume of the non-aqueous solvent. More preferably, it is 60 volume% or less, more preferably 50 volume% or less.

  Within this range, the effect of improving the lithium ion dissociation degree of the chain ether and the improvement of the ion conductivity derived from the viscosity decrease can be easily secured, and when the negative electrode active material described later is a carbonaceous material, the chain ether is lithium It is easy to avoid the situation in which the battery capacity decreases due to the coinsertion with the ions.

<Sulphone type compounds>
As said sulfone type compound, a C3-C6 cyclic sulfone and a C2-C6 chain-like sulfone are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

As said C3-C6 cyclic sulfone,
Monosulfone compounds trimethylene sulfones, tetramethylene sulfones, hexamethylene sulfones;
Examples of such a disulfone compound include trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.

  Among these, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable, from the viewpoint of dielectric constant and viscosity.

  As the sulfolanes, sulfolanes and / or sulfolane derivatives (hereinafter sometimes referred to as "sulfolanes including sulfolanes") are preferable. As the sulfolane derivative, one in which at least one hydrogen atom bonded to a carbon atom constituting a sulfolane ring is 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-methylsulfolane Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methyl sulfolane, 2- Trifluoromethyl sulfolane, 3-trifluoromethyl sulfolane, 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 that they have high ion conductivity and high input / output characteristics.

Moreover, as said C2-C6 linear 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, pentafluoro Ethyl methyl sulfone, Ethyl mono fluoro methyl sulfone, Ethyl difluoro methyl sulfone, Ethyl trifluoromethyl sulfone, Perf Oroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl- n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone Trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, pentafluoroethyl- - butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

  Among these, 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 Pentafluoroethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone , Trifluoroethyl n-butyl sulfone, trifluoroethyl t-butyl sulfone, trifluoromethyl n-butyl sulfone, trifluoromethyl t-butyl sulfone, etc. have high ion conductivity and high input / output characteristics It is preferable in point.

  The sulfone-based compounds described above may be used alone or in any combination of two or more in any proportion.

  In addition, the blending amount of the sulfone compound is usually 0.3% by volume or more, preferably 1% by volume or more, more preferably 5% by volume or more in 100% by volume of the non-aqueous solvent, and preferably Is 40 volume% or less, more preferably 35 volume% or less, and still more preferably 30 volume% or less.

  Within this range, the effect of improving the durability such as cycle characteristics and storage characteristics of the secondary battery can be easily obtained, and the viscosity of the non-aqueous electrolyte solution can be made into an appropriate range to avoid the decrease in electrical conductivity. When the charge and discharge of the non-aqueous electrolyte secondary battery are performed at a high current density, it is easy to avoid the situation where the charge and discharge capacity retention rate decreases.

<When using a cyclic carbonate having a fluorine atom as a non-aqueous solvent>
In the present invention, as described above, a cyclic carbonate having no fluorine atom can be used as a non-aqueous solvent, but a cyclic carbonate having a fluorine atom can also be used as a non-aqueous solvent. In this case, as the non-aqueous solvent other than the cyclic carbonate having a fluorine atom, one of the non-aqueous solvents exemplified above may be used in combination with the cyclic carbonate having a fluorine atom, and two or more cyclic groups having a fluorine atom It may be used in combination with a carbonate.

  For example, one preferable combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having a fluorine atom and a linear carbonate. Among them, the total of the cyclic carbonate having a fluorine atom and the chain carbonate in the non-aqueous solvent is preferably 60% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more. The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a and the linear carbonate is 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and still more preferably 15% by volume or more Also preferably, it is 60% by volume or less, more preferably 50% by volume or less, still more preferably 40% by volume or less, and particularly preferably 35% by volume or less.

  When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and the high temperature storage characteristics (in particular, the residual capacity after high temperature storage and the high load discharge capacity) of a secondary battery manufactured using this can be improved is there.

For example, as a specific example of a preferable combination of cyclic carbonate having a fluorine atom and linear carbonate,
Monofluoroethylene carbonate and dimethyl carbonate, Monofluoroethylene carbonate and diethyl carbonate, Monofluoroethylene carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate and dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate and dimethyl carbonate Examples thereof include ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

  Among combinations of cyclic carbonates having a fluorine atom and linear carbonates, those containing symmetrical linear alkyl carbonates as linear carbonates are more preferable, and in particular, monofluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, mono Those containing monofluoroethylene carbonate, symmetrical linear carbonates and asymmetric linear carbonates, such as fluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and dimethyl carbonate and diethyl carbonate and ethyl methyl carbonate, are cycles It is preferable because the balance between the characteristics and the large current discharge characteristics is good. Among them, symmetrical linear carbonates are preferably dimethyl carbonate, and as the alkyl group of linear carbonate, those having 1 to 2 carbon atoms are preferable.

  The combination which added the cyclic carbonate which does not have a fluorine atom further to the combination of the cyclic carbonate which has these fluorine atoms, and linear carbonates is also mentioned as a preferable combination. Among them, the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom in the non-aqueous solvent is preferably 10% by volume or more, more preferably 15% by volume or more, still more preferably 20% by volume or more The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom is 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume % Or more, more preferably 25% by volume or more, preferably 95% by volume or less, more preferably 85% by volume or less, still more preferably 75% by volume or less, particularly preferably 60% by volume or less.

  When the cyclic carbonate containing no fluorine atom is contained in this concentration range, the electrical conductivity of the electrolytic solution can be maintained while forming a stable protective film on the negative electrode.

Specific examples of preferable combinations of cyclic carbonates having a fluorine atom, cyclic carbonates having no fluorine atom and chain carbonates are as follows:
Monofluoroethylene carbonate and ethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and ethylene carbonate and dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate Ethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl carbonate Monofluoroethylene carbonate and propylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and propylene carbonate and diethyl carbonate, monofluoroethylene carbonate and propylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and propylene carbonate and dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate Ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate and dimethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate Carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate and propylene carbonate, Examples include diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

Among the combinations of cyclic carbonates having a fluorine atom, cyclic carbonates having no fluorine atom, and chain carbonates, those containing symmetrical chain alkyl carbonates as chain carbonates are more preferable, in particular,
Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate Ethylene carbonate, ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl car , Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, mono fluoro ethylene carbonate, propylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, mono fluoro ethylene carbonate, ethylene carbonate, propylene carbonate and dimethyl carbonate Those containing carbonate, diethyl carbonate, monofluoroethylene carbonate such as ethyl methyl carbonate, symmetrical linear carbonates and asymmetric linear carbonates are preferable because the balance between the cycle characteristics and the large current discharge characteristics is good. Among them, symmetric linear carbonates are preferably dimethyl carbonate, and as the alkyl group of linear carbonate, those having 1 to 2 carbon atoms are preferable.

  When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, still more preferably 25% by volume or more, particularly Preferably, the content is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, still more preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics of the secondary battery may be improved.

  In the combination mainly composed of the cyclic carbonate having a fluorine atom and the chain carbonate, cyclic carboxylic acid esters, chain carboxylic acid esters, cyclic ethers, in addition to the cyclic carbonate having no fluorine atom, Other solvents such as chain ethers, sulfur-containing organic solvents, phosphorus-containing organic solvents, and fluorine-containing aromatic solvents may be mixed.

<When using a cyclic carbonate having a fluorine atom as an auxiliary agent>
As described later, an auxiliary agent can be added to the non-aqueous electrolyte solution of the present invention, but when a cyclic carbonate having a fluorine atom is used as an auxiliary, the above-mentioned nonaqueous solvent other than the cyclic carbonate having a fluorine atom One of the exemplified non-aqueous solvents may be used alone, or two or more thereof may be used in any combination and ratio.

  For example, one preferable combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having no fluorine atom and a linear carbonate.

  Among them, the total of the cyclic carbonate having no fluorine atom in the non-aqueous solvent and the linear carbonate is preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more. And the ratio of the cyclic carbonate having no fluorine atom to the total of the cyclic carbonate and the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and still more preferably 15% by volume or more. The content is preferably 50% by volume or less, more preferably 35% by volume or less, still more preferably 30% by volume or less, and particularly preferably 25% by volume or less.

  When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and the high temperature storage characteristics (in particular, the residual capacity after high temperature storage and the high load discharge capacity) of a battery manufactured using the combination may be improved.

For example, as a specific example of a preferable combination of cyclic carbonate and linear carbonate which does not have a fluorine atom,
Ethylene carbonate and dimethyl carbonate, Ethylene carbonate and diethyl carbonate, Ethylene carbonate and ethyl methyl carbonate, Ethylene carbonate and dimethyl carbonate and diethyl carbonate, Ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, Ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, Ethylene carbonate And dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

  Among the combinations of cyclic carbonates having no fluorine atom and linear carbonates, those containing asymmetric linear alkyl carbonates as linear carbonates are more preferable, and in particular, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Those containing ethylene carbonate, symmetrical linear carbonates and asymmetric linear carbonates, such as ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate and ethyl methyl carbonate, have cycle characteristics and large current discharge It is preferable because the balance of the characteristics is good.

  Among these, those in which the asymmetric linear carbonates are ethyl methyl carbonate are preferable, and those having 1 to 2 carbon atoms are preferable as the alkyl group of the linear carbonate.

  The combination which added the propylene carbonate further to the combination of these ethylene carbonate and linear carbonates is also mentioned as a preferable combination.

  When containing propylene carbonate, 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 proportion of propylene carbonate in the whole nonaqueous solvent is preferably 0.1% by volume or more, more preferably 1% by volume or more, still more preferably 2% by volume or more, and preferably 20% by volume or less, more preferably Is 8 volume% or less, more preferably 5 volume% or less.

  It is preferable to contain propylene carbonate in this concentration range because the low temperature characteristics may be further excellent while maintaining the characteristics of the combination of ethylene carbonate and linear carbonate.

  When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, still more preferably 25% by volume or more, particularly Preferably, it is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, still more preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics of the secondary battery may be improved.

  In the combination mainly composed of the cyclic carbonate having no fluorine atom and the linear carbonate, cyclic carboxylic acid esters, linear carboxylic acid esters, cyclic ethers, linear ethers, sulfur-containing organic solvent, Other solvents such as a phosphorus organic solvent and an aromatic fluorine-containing solvent may be mixed.

<About the volume of non-aqueous solvent>
In addition, in this specification, although the volume of a non-aqueous solvent is a measured value at 25 degreeC, what is a solid at 25 degreeC like ethylene carbonate uses the measured value in melting | fusing point.

[1-4. Auxiliary agent]
In the non-aqueous electrolyte solution of the present invention, an auxiliary may be appropriately used according to the purpose. Examples of the assistant include the compounds shown below, which are reduced on the negative electrode at the time of initial charge of the battery, overcharge inhibitors, other assistants and the like.

  The compound to be reduced on the negative electrode is reduced to form a film on the negative electrode, which is preferable in terms of stably protecting the negative electrode-electrolyte interface. Examples of the compound include cyclic carbonates having a carbon-carbon unsaturated bond, cyclic carbonates having a fluorine atom, and unsaturated cyclic carbonates having a fluorine atom (hereinafter sometimes referred to as "fluorinated unsaturated cyclic carbonate"), Examples thereof include carboxylic acid anhydrides and art-type complex compounds.

<Cyclic carbonate having a carbon-carbon unsaturated bond>
The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes referred to as “unsaturated cyclic carbonate”) may be a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond, There is no particular limitation, and any unsaturated carbonate can be used. In addition, the cyclic carbonate which has an aromatic ring shall also be included by unsaturated cyclic carbonate.

Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, And catechol carbonates.
As vinylene carbonates,
Vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate, 4,5-divinylvinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene carbonate Etc.

As specific examples of ethylene carbonates substituted by a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond,
Vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5 -Ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl -5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate and the like.

Among them, preferred unsaturated cyclic carbonates are
Vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene 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-5-allyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5 -Diethynyl ethylene carbonate, 4-methyl 5- ethynyl ethylene carbonate, 4-vinyl 5- ethynyl ethylene carbonate are mentioned.

In addition, vinylene carbonate, vinyl ethylene carbonate and ethynyl ethylene carbonate are particularly preferable because they form a more stable surface protective film.
The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary unless the effects of the present invention are significantly impaired. The molecular weight is preferably 80 or more and 250 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolytic solution can be easily secured, and the effects of the present invention can be sufficiently exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more, and more preferably 150 or less. The method for producing the unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production.

  The unsaturated cyclic carbonates may be used alone or in any combination of two or more in any proportion. Further, the compounding amount of the unsaturated cyclic carbonate is not particularly limited and is arbitrary unless the effects of the present invention are significantly impaired. However, it is usually 0.001% by mass or more, preferably 0% in 100% by mass of the non-aqueous electrolytic solution. .01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient improvement in cycle characteristics, and also the high temperature storage characteristics deteriorate, the amount of gas generation increases, and the discharge capacity retention rate decreases. It is easy to avoid the situation.

<Cyclic carbonate having a fluorine atom>
As a cyclic carbonate which has the said fluorine atom, the fluoride of the cyclic carbonate which has a C2-C6 alkylene group, and its derivative are mentioned, For example, the fluoride of ethylene carbonate, and its derivative are mentioned. As a derivative of the fluorinated product of ethylene carbonate, for example, fluorinated products of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms) can be mentioned. Among them, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferable.

In particular,
Fluoroethylene 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-methyl ethylene 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-dimethylethylene car Sulfonates, 4,4-difluoro-5,5-dimethylethylene carbonate.

  Among them, at least one selected from the group consisting of fluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate gives high ion conductivity and preferably forms an interfacial protective film. More preferable.

  The cyclic carbonates having a fluorine atom may be used alone or in any combination of two or more in any proportion.

  The cyclic carbonates having a fluorine atom may be used alone or in any combination of two or more in any proportion. There is no restriction | limiting in the compounding quantity of the fluorinated cyclic carbonate with respect to the whole non-aqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually 0.001 mass% in 100 mass% of non-aqueous electrolytes The content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

<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 one or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2.

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

  As fluorinated vinylene carbonate derivatives, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-5-fluorovinylene carbonate And vinyl vinylene carbonate and the like.

As a fluorinated ethylene carbonate derivative substituted by a substituent having an aromatic ring or a carbon-carbon double bond,
4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene Carbonate, 4,4-difluoro-4-allyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate, 4,5-difluoro-4-allyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate, 4-fluoro-4-phenyl ethylene carbonate, 4-f Oro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate.

Among the above, particularly preferable fluorinated unsaturated cyclic carbonates are
4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro- 4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,4-difluoro-4-allyl ethylene carbonate, 4,5-Difluoro-4-vinyl ethylene carbonate, 4,5-Difluoro-4-allyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate 4,5-difluoro-4,5-divinyl ethylene carbonate, and 4,5-difluoro-4,5-diallyl carbonate. These are more preferably used because they form a stable interfacial protective film.

  The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary unless the effects of the present invention are significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the fluorinated unsaturated cyclic carbonate in the non-aqueous electrolytic solution can be easily secured, and the effects of the present invention can be easily exhibited.

  The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

  The fluorinated unsaturated cyclic carbonates may be used alone or in any combination of two or more in any proportion. In addition, the blending amount of the fluorinated unsaturated cyclic carbonate is not particularly limited, and is arbitrary unless the effects of the present invention are significantly impaired.

  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, still more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolytic solution. Also, it is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less.

  Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient improvement in cycle characteristics, and the high-temperature storage characteristics are degraded, so that the amount of gas generation increases and the discharge capacity retention rate is decreased. It is easy to avoid the situation.

<Carboxylic anhydride>
The compounding amount of the above-mentioned carboxylic acid anhydride is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass in 100% by mass of the non-aqueous electrolytic solution. It is the above, and is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less.

  Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient improvement in cycle characteristics, and the high temperature storage characteristics are degraded, the amount of gas generation is increased, and the discharge capacity retention rate is decreased. It is easy to avoid.

  Examples of such carboxylic acid anhydrides include succinic acid anhydride, maleic acid anhydride and phthalic acid anhydride.

<Art-type complex compound>
The compounding amount of the art-type complex compound is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass in 100% by mass of the non-aqueous electrolytic 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 improvement in cycle characteristics, and the high temperature storage characteristics are degraded, the amount of gas generation is increased, and the discharge capacity retention rate is decreased. It is easy to avoid.

  As such an ate-type complex compound, for example, lithium difluoro oxalato borate, lithium bis (oxalato) borate, lithium tetrafluoro oxalato phosphate, lithium difluoro bis (oxalato) phosphate and lithium tris (oxalato) phosphate can be mentioned.

  Although the compound reduced on the negative electrode at the time of initial charge of the battery, which can be used as an auxiliary in the non-aqueous electrolyte solution of the present invention, has been described above, the negative electrode-electrolyte solution interface is stably protected among them, side reactions From the viewpoint of suppressing, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, lithium bis (oxalato) borate, lithium tetrafluorooxalato phosphate, lithium difluoro bis (oxalato) phosphate and lithium tris (oxalato) phosphate preferable.

<Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an anti-overcharge agent can be used in order to effectively suppress battery rupture and ignition when the non-aqueous electrolyte secondary battery is in a state of overcharge and the like. .

As an overcharge inhibitor,
Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like;
Partially fluorinated products of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene and the like;
And fluorine-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like.

Among these,
Preferred are aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like.

  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, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, The combined use of at least one selected from oxygen-free aromatic compounds such as t-amyl benzene and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran is the overcharge preventing property and high temperature storage It is preferable from the point of balance of the characteristics.

  The compounding amount of the overcharge inhibitor is not particularly limited, and is optional unless the effects of the present invention are significantly impaired. The overcharge inhibitor is blended in a proportion of preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effect of the overcharge preventing agent can be easily exhibited sufficiently, and the situation in which the battery characteristics such as the high temperature storage characteristics are degraded can be easily avoided.

  The overcharge inhibitor is more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, more preferably Preferably, it is blended in a proportion of 2% by mass or less.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. As other adjuvants,
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate etc .; glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentadicarboxylic acid anhydride Carboxylic acid anhydrides such as pentanetetracarboxylic acid dianhydride and phenylsuccinic acid anhydride;
Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane;
Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenyl sulfone, N, N-dimethyl methane sulfonamide, N, N-diethyl methane sulfonamide, etc. Sulfur-containing compounds;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methyl succinimide;
Hydrocarbon compounds such as heptane, octane, nonane, decane and cycloheptane;
Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride;
Etc. These may be used alone or in combination of two or more. By adding these assistants, capacity retention characteristics and cycle characteristics after high temperature storage of the secondary battery can be improved.

  The amount of the other auxiliary agent is not particularly limited, and is optional unless the effects of the present invention are significantly impaired. The compounding amount of 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 the other auxiliary agents can be sufficiently exhibited, and situations in which battery characteristics such as high load discharge characteristics are degraded can be easily avoided.

  The compounding amount of the other auxiliary agent is more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and more preferably 3% by mass or less, still more preferably 1% by mass or less .

  As mentioned above, the above-mentioned non-aqueous electrolyte solution also contains the thing which exists inside the non-aqueous electrolyte solution secondary battery of this invention.

  Specifically, components of the non-aqueous electrolytic solution such as a lithium salt, a solvent, and an auxiliary are separately synthesized, and the non-aqueous electrolytic solution is prepared from those substantially isolated, and the method described below is used. In the case of a non-aqueous electrolytic solution in a non-aqueous electrolytic solution secondary battery obtained by pouring into a separately assembled battery, or the components of the non-aqueous electrolytic solution of the present invention are separately put in the battery; When the same composition as the non-aqueous electrolytic solution of the present invention is obtained by mixing in a battery, a compound constituting the non-aqueous electrolytic solution of the present invention is further generated in the non-aqueous electrolyte secondary battery, The case of obtaining the same composition as the non-aqueous electrolyte solution of the present invention is also included.

[2. Non-aqueous electrolyte secondary battery]
Next, the non-aqueous electrolyte secondary battery of the present invention will be described. The secondary battery includes a specific positive electrode, a negative electrode containing a negative electrode active material capable of absorbing and releasing lithium ions, and a non-aqueous electrolytic solution. Each of these configurations will be described below.

[2-1. Non-aqueous electrolyte solution]
The non-aqueous electrolyte of the present invention described above is used as the non-aqueous electrolyte. In addition, it is also possible to mix | blend and use another non-aqueous electrolyte solution with respect to the non-aqueous electrolyte solution of this invention in the range which does not deviate from the meaning of this invention.

[2-2. Positive electrode]
The positive electrode used for the lithium secondary battery of the present invention will be described below.

<Composition>
The non-aqueous electrolyte battery of the present invention is represented by LixMPO ₄ (M is at least one element selected from the group consisting of metals of Groups 2 to 12 of the periodic table, x is 0 <x ≦ 1.2). And a positive electrode active material having a lithium-containing phosphoric acid compound as a basic composition.

As the above-mentioned lithium-containing phosphate compound, Li x MPO ₄ (M is at least one element selected from the group consisting of transition metals of Groups 4 to 11 of Period 4 of the periodic table, x is 0 <x ≦ 1. What is represented by 2) is preferable.

Further, M of LixMPO ₄ is preferably at least one element selected from the group consisting of Mg, Zn, Ca, Cd, Sr, Ba, Co, Ni, Fe, Mn and Cu, and Co, Ni More preferably, it is at least one element selected from the group consisting of Fe, Fe, and Mn. Among these, lithium iron phosphate having an olivine structure having LiFePO ₄ as a basic composition is particularly preferably used because metal elution hardly occurs in a high temperature / charged state and it is inexpensive.

The above-mentioned "having LixMPO ₄ as a basic composition" includes not only one having the composition represented by the composition formula but also one having some of the sites such as Fe in the crystal structure replaced with another element It means that. Furthermore, it is meant to include not only stoichiometric compositions but also non-stoichiometric compositions in which some elements are deficient or the like. The other element to be substituted is preferably an element such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, or Si. When performing said other element substitution, 0.1 mol% or more and 5 mol% or less are preferable, More preferably, they are 0.2 mol% or more and 2.5 mol% or less.

Moreover, although the said positive electrode active material has the said LixMPO ₄ as a main component, In addition, for example, lithium manganese complex oxide, lithium cobalt complex oxide, lithium nickel complex oxide, lithium nickel cobalt complex oxide, lithium nickel Lithium transition metal complex oxides such as manganese complex oxide and lithium nickel manganese cobalt complex oxide can be used in combination. The lithium transition metal-based compound is a compound having a structure capable of releasing and inserting lithium ions, and examples thereof include a sulfide, a silicic acid compound, and a boric acid compound. As the sulfide, a strong compound represented by a compound having a two-dimensional layered structure such as TiS ₂ or MoS ₂ or a general formula MxMo ₆ S ₈ (M is various transition metals such as Pb, Ag, and Cu) The Shubrel compound etc. which have a three-dimensional frame structure are mentioned. Examples of the silicate compound include LiMSiO ₄ , and examples of the boric acid compound include LiMBO ₄ . Preferably, the positive electrode active material may contain 20 wt% or more of the LixMPO ₄ . In this case, the charge / discharge cycle characteristics of the non-aqueous electrolyte battery can be further improved. More preferably, the content of LixMPO ₄ is 40 wt% or more.

Moreover, two or more types of LixMPO ₄ can be used in combination. Preferred combinations when used in _combination, can be cited LixFePO ₄ and LixMnPO _4, LixFePO 4 and LixCoPO _4, LixFePO ₄ and LixNiPO _4, thereby improving the battery operating voltage while maintaining safety. Particularly preferred combination among these are LixFePO ₄ and LixMnPO _4, in addition to the improvement of the safety and the battery operating voltage, preferably for excellent durability such as high-temperature storage characteristics and cycle characteristics.

<Surface coating>
In addition, as the positive electrode active material, a material in which a substance having a composition different from this may be attached to the surface of LixMPO ₄ may be used. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.

  These surface adhesion substances are, for example, dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and dried, or the surface adhesion substance precursor is dissolved or suspended in a solvent and impregnated into 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 it to the positive electrode active material precursor and simultaneously baking it. In addition, when making carbon adhere, the method of making carbon quality adhere mechanically later, for example, in the form of activated carbon etc. can also be used.

  The amount of the surface adhesion substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and preferably 20% or less as an upper limit, based on the mass of the positive electrode active material. Is used at 10% or less, more preferably 5% or less. By the surface adhesion substance, the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material can be suppressed, the battery life can be improved, and when the adhesion amount is appropriate, the effect is more exhibited.

In the present invention, a substance in which a substance having a composition different from this adheres to the surface of the LixMPO ₄ positive electrode active material is also referred to as a "positive electrode active material".

<Shape>
As the shape of the particles of the positive electrode active material in the present invention, lumps, polyhedrons, spheres, oval spheres, plates, needles, columns, etc. which are conventionally used are used, among which primary particles are aggregated. It is preferable that the secondary particles be formed into a secondary particle, and the shape of the secondary particle is spherical or elliptical. Usually, since the active material in the electrode expands and contracts with the charge and discharge of the electrochemical element, the active material is likely to be broken due to the stress, or deterioration such as breakage of the conductive path may occur. Therefore, it is preferable that primary particles are aggregated and secondary particles are formed rather than a single particle active material consisting of only primary particles, because stress of expansion and contraction is alleviated and deterioration is prevented. In addition, since spherical or elliptic spherical particles have less orientation at the time of molding of the electrode than plate-like equiaxially oriented particles, expansion and contraction of the electrode at the time of charge and discharge are also small, and the electrode is prepared Even in the mixing with the conductive material at the time, it is preferable because it is easily mixed uniformly.

<Tap density>
The tap density of the positive electrode active material is preferably 0.1 g / cm ³ or more, more preferably 0.2 g / cm ³ or more, still more preferably 0.3 g / cm ³ or more, and most preferably 0.4 g / cm ³ It is above. When the tap density of the positive electrode active material is below the above lower limit, the necessary amount of dispersion medium increases at the time of forming the positive electrode active material layer, and the required amount of the conductive material and the binder increases, and the positive electrode to the positive electrode active material layer The filling rate of the active material may be limited, and the battery capacity may be limited. By using a composite oxide powder with a high tap density, a high density positive electrode active material layer can be formed. Generally, the tap density is preferably as high as possible, and there is no particular upper limit. However, if it is too large, diffusion of lithium ions in the positive electrode active material layer through the electrolyte may be limited, and load characteristics may be easily degraded. The upper limit is preferably 2.0 g / cm ³ or less, more preferably 1.8 g / cm ³ or less.

  In the present invention, the tap density is defined as 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 particles of the positive electrode active material (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.1 μm or more, more preferably 0.2 μm or more, More preferably, it is 0.3 μm or more, most preferably 2 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, most preferably 15 μm or less. Below the lower limit, high tap density products may not be obtained. When the upper limit is exceeded, it takes time to diffuse lithium in the particles, resulting in deterioration of battery performance, or battery positive electrode preparation, ie, active material When a conductive material, a binder or the like is slurried with a solvent and applied in a thin film, problems such as streaking may occur. Here, by mixing two or more types of the positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of preparation of the positive electrode can be further improved.

The median diameter d ₅₀ in the present invention is measured by a known laser diffraction / scattering type particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA is used as a particle size distribution analyzer, a 0.1 mass% sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a 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 0.02 μm or more, more preferably 0.03 μm or more, and still more preferably 0. The upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. If it is within the above range, spherical secondary particles are likely to be formed, which adversely affects the powder packing property or the specific surface area is greatly reduced, and the possibility of deterioration of battery performance such as output characteristics is increased. It is easy to avoid such situations. Furthermore, since crystals are underdeveloped, problems such as poor reversibility of charge and discharge are less likely to occur.

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

<BET specific surface area>
The BET specific surface area of the positive electrode active material to be used for the secondary battery of the present invention is preferably 0.4 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 0.6 m ² / g or more. The upper limit is 50 m ² / g or less, preferably 40 m ² / g or less, and more preferably 30 m ² / g or less. The fall of battery performance can be suppressed as a BET specific surface area is in the said range, and the coating property at the time of positive electrode active material layer formation is also favorable.

  The BET specific surface area is determined by using a surface area meter (for example, Okura Riken fully automatic surface area measurement device) and subjecting the sample to predrying at 150 ° C. for 30 minutes under nitrogen flow, and then relative pressure of nitrogen to atmospheric pressure It is defined as a value measured by a nitrogen adsorption BET one-point method by a gas flow method using a nitrogen-helium mixed gas which is accurately adjusted to have a value of 0.3.

<Manufacturing method>
As a method for producing the positive electrode active material, a general method can be used as a method for producing an inorganic compound. In particular, various methods can be considered to form a spherical or elliptical spherical active material. For example, a phosphorus source material such as phosphoric acid and a M source material in LixMPO ₄ are dissolved or pulverized and dispersed in a solvent such as water The pH is adjusted while stirring to prepare a spherical precursor, which is dried if necessary, and then added with a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ and calcined at high temperature And the like, and the like.

For the production of the positive electrode in the present invention, the positive electrode active material of LixMPO ₄ and / or the positive electrode active material of LixMPO ₄ coated with the surface adhesion material may be used alone, and one or more of different compositions may be used. You may use together in arbitrary combinations or ratios. Here, the positive electrode active material of LixMPO ₄ and / or the positive electrode active material of LixMPO ₄ coated with the surface adhesion material is preferably 30% by mass or more of the entire positive electrode active material, and is 50% by mass or more. Is more preferred. When it is within the proportion above range of the positive electrode active material and / or positive electrode active material of which the surface adhesion LixMPO ₄ coated with substance LixMPO _4, it is possible to provide a suitable battery capacity.

Note that "the positive electrode active material of LixMPO ₄ and / or the positive electrode active material of LixMPO ₄ coated with the surface adhesion material" and "the positive electrode active material of LixMPO ₄ and / or the positive electrode of LixMPO ₄ coated with the surface adhesion material. The positive electrode active material other than the active material is generically referred to as "positive electrode active material".

[Configuration of positive electrode]
The configuration of the positive electrode used in the present invention will be described below.

<Electrode structure and manufacturing method>
The positive electrode for a lithium secondary battery of the present invention is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. That is, the positive electrode for a lithium secondary battery of the present invention is produced by forming a positive electrode active material layer containing the above 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 carried out by a conventional method. That is, a positive electrode active material, a binder, and optionally a conductive material, a thickener and the like mixed in a dry state to form a sheet is pressure bonded to a positive electrode current collector, or a liquid medium of these materials A positive electrode can be obtained by forming a positive electrode active material layer on a current collector by applying it as a slurry by dissolving or dispersing it as a slurry and drying it.

  The content of the positive electrode active material used in the positive electrode of the lithium secondary battery of the present invention in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, particularly preferably 84% by mass or more is there. The upper limit is preferably 97% by mass or less, more preferably 95% by mass or less. When the content of the positive electrode active material in the positive electrode active material layer is within the above range, the balance between the electric capacity and the strength of the positive electrode is excellent.

In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press, or the like. Filling density of the positive electrode active material layer is preferably 1.3 g / cm ³ or more as a lower limit, more preferably 1.4 g / cm ³ or more, more preferably 1.5 g / cm ³ or more, the upper limit, preferably Is preferably in the range of 3.0 g / cm ³ or less, more preferably 2.5 g / cm ³ or less, and still more preferably 2.3 g / cm ³ or less.

  Within the above range, the permeability of the electrolyte to the vicinity of the current collector / active material interface is reduced, and in particular, the charge / discharge characteristics at high current density are reduced, and a high output can not be obtained, or the active material In the meantime, it is easy to avoid the situation that the battery resistance decreases and high output can not be obtained.

<Conductive material>
As the conductive material, any known conductive material can be used. Specific examples thereof include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon blacks such as acetylene black; carbon materials such as amorphous carbon such as needle coke and the like. 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 that 30 mass% or less, more preferably 15 mass% or less is contained. Conductivity can fully be ensured as content is in the said range, and a suitable battery capacity can be provided.

<Binding agent>
The binder used to manufacture 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 at the time of electrode manufacture may be used. Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber Rubber-like polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or a hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymers such as isoprene / styrene block copolymers or their hydrogenated products; Syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymer Soft resinous polymers such as coalescing agents; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer etc .; alkali metal ions (especially lithium ion) And the like, and the like. One of these substances may be used alone, or two or more of these substances may be used in any combination and ratio.

  The proportion 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 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60 It is at most mass%, more preferably at most 40 mass%, most preferably at most 10 mass%. When the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained, so that a suitable positive electrode mechanical strength can be provided, and the cycle characteristics can be achieved without causing a decrease in battery capacity or conductivity. Etc. It becomes possible to provide excellent battery performance.

<Liquid medium>
As a liquid medium for forming a slurry, any kind of solvent can be used so long as it can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used if necessary. There is no particular limitation, 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 methyl naphthalene; 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) And amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphaamide and dimethylsulfoxide.

  In particular, when an aqueous medium is used, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to make a slurry. Thickeners are usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One of these may be used alone, or two or more of these may be used in any combination and ratio. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. Within the above range, the coatability becomes good, and the ratio of the active material to the positive electrode active material layer does not become too low, causing a problem that the capacity of the battery decreases or a problem that the resistance between the positive electrode active materials increases. It is easy to avoid such situations.

<Current collector>
There is no restriction | limiting in particular as a material of a positive electrode collector, A well-known thing can be used arbitrarily. Specific examples thereof include metal materials such as aluminum, stainless steel, nickel plating, titanium and tantalum; and carbon materials such as carbon cloth and carbon paper. Among them, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foils, metal cylinders, metal coils, metal coils, metal plates, metal thin films, expanded metals, punched metals, foamed metals and the like in the case of metal materials, and in the case of carbon materials, carbon plates and carbons A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. The thin film may be formed in a mesh shape as appropriate. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. When the thin film is in the above range, the strength necessary for the current collector can be provided, and the handling becomes easy.

  In addition, it is preferable to use one in which a conductive layer is formed on the surface of the current collector with a compound composition different from that of the current collector, from the viewpoint of reducing the electron contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive layer formed of a compound composition different from that of the current collector include conductive materials formed of a carbonaceous material, a conductive polymer, and noble metals such as gold, platinum, and silver.

  The ratio of the thickness of the current collector to the thickness of the positive electrode active material layer is not particularly limited, but the value of (thickness of positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of current collector) is 20 The following is preferable, more preferably 15 or less, and 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. Within the above range, the current collector is heated by Joule heat during high current density charge and discharge, and the volume ratio of the current collector to the positive electrode active material is increased, thereby avoiding a decrease in battery capacity. It will be easier.

<Electrode area>
When the non-aqueous electrolyte solution of the present invention is used, it is preferable to make the area of the positive electrode active material layer larger than the outer surface area of the battery case from the viewpoint of enhancing the stability at high output and high temperature. Specifically, the sum of the electrode area of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more in area ratio, and more preferably 40 times or more. The external surface area of the outer case means, in the case of a rectangular shape with a bottom, the total area obtained by calculation from the dimensions of the length, width and thickness of the case portion filled with the power generating element excluding the protruding portion of the terminal. . In the case of a bottomed cylindrical shape, it is a geometric surface area which approximates the case part filled with the power generation element excluding the protruding part of the terminal as a cylinder. The sum of the 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 formed by forming the positive electrode mixture layer on both sides via the current collector foil. , The sum of the area to calculate each face separately.

<Thickness of positive electrode plate>
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture layer obtained by subtracting the metal foil thickness of the core material is one side of the current collector. The lower limit is preferably 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 400 μm or less.

<Surface coating of positive electrode plate>
Moreover, you may use that to which the substance of the composition different from this adhered on the surface of the said positive electrode plate. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as 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.

[2-3. Negative electrode]
The negative electrode active material used for the negative electrode of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited as long as it can electrochemically absorb and release metal ions. Specific examples thereof include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. Among these, it is most preferable to use a carbonaceous material in terms of good cycle characteristics and safety, and also excellent continuous charging characteristics. One of these may be used alone, or two or more of these may be used in combination as desired.

<Carbonaceous material>
Examples of carbonaceous materials include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, (6) resin-coated graphite, etc. .

  (1) Examples of natural graphite include scale-like graphite, scale-like graphite, soil graphite and / or graphite particles obtained by subjecting such graphite to a treatment such as spheroidization or densification. Among these, spherical or ellipsoidal graphite having a spheroidizing treatment is particularly preferable from the viewpoint of particle filling property and charge / discharge rate characteristics.

  As an apparatus used for the spheroidizing process, for example, an apparatus which repeatedly gives mechanical action such as compression, friction, shear force and the like including impact force and particle interaction can be used. Specifically, it has a rotor having a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, and shear force is performed on the carbon material introduced inside. And a device for performing the spheronization process is preferred. In addition, it is preferable to have a mechanism in which the mechanical action is repeatedly given by circulating the carbon material.

  For example, when spheroidizing treatment is performed using the above-mentioned apparatus, the peripheral velocity of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and further preferably 50 to 100 m / sec. It is more preferable to do. Further, the treatment can be performed simply by passing the carbon material, but it is preferable to treat by circulating or staying in the device for 30 seconds or more, and it is preferable to treat by circulating or staying in the device for 1 minute or more. More preferable.

  (2) As artificial graphite, coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are generally in the range of 2500 ° C. or more, usually 3200 ° C. or less What is graphitized at temperature, and grind | pulverized and / or classified as needed, and what is manufactured is mentioned.

  Under the present circumstances, a silicon containing compound, a boron containing compound, etc. can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch may be mentioned. Furthermore, artificial graphite of granulated particles consisting of primary particles can also be mentioned. For example, by mixing mesograph microbeads, graphitizable carbonaceous material powder such as coke, graphitizable binder such as tar and pitch, and graphitization catalyst, graphitizing, and grinding as necessary A plurality of flat particles can be obtained, and graphite particles assembled or combined such that the orientation planes are not parallel may be mentioned.

  (3) Amorphous carbon which is heat-treated once or more in a non-graphitizing temperature range (range of 400 to 2200 ° C.) using a graphitizable carbon precursor such as tar or pitch as a raw material as the amorphous carbon Non-graphitizable carbon precursors such as particles and resins may be used as the raw material to heat-treat amorphous carbon particles.

  (4) As carbon-coated graphite, it can be obtained by mixing natural graphite and / or artificial graphite and a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treating at a temperature of 400 to 2300 ° C. once or more. Examples thereof include carbon-graphite composites in which natural graphite and / or artificial graphite are core graphite and amorphous carbon covers the core graphite. The form of the composite may be a whole or a part of the surface, or a plurality of primary particles composited with carbon derived from the carbon precursor as a binder. Also, carbon can be deposited (CVD) on the surface of graphite by reacting natural graphite and / or artificial graphite with hydrocarbon-based gas such as benzene, toluene, methane, propane, volatiles of aromatic series at high temperature, etc. Graphite composites can also be obtained.

  (5) Graphite-coated graphite is prepared by mixing natural graphite and / or artificial graphite and a carbon precursor of a graphitizable organic compound such as tar or pitch, resin, etc., once in the range of about 2400 to 3200 ° C. The graphite coated graphite which makes natural graphite and / or artificial graphite which are obtained by heat processing above and / or artificial graphite as core graphite, and the graphitization coats the whole surface or a part of core graphite is mentioned.

  (6) As the resin-coated graphite, natural graphite and / or artificial graphite are mixed with a resin etc. and dried at a temperature of less than 400 ° C. Natural graphite and / or artificial graphite obtained as core graphite are used as the resin. Resin-coated graphite which is coated with

  Moreover, the carbonaceous material of (1)-(6) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  As organic compounds such as tars, pitches and resins used for producing the carbonaceous materials of the above (2) to (5), coal-based heavy oil, direct current-based heavy oil, cracking-based petroleum heavy oil, aromatic Examples thereof include carbonizable organic compounds selected from the group consisting of hydrocarbons, N-ring compounds, S-ring compounds, polyphenylenes, organic synthetic polymers, natural polymers, thermoplastic resins and thermosetting resins. Moreover, in order to adjust the viscosity at the time of mixing, the raw material organic compound may be dissolved in a low molecular weight organic solvent and used.

  Moreover, as natural graphite used as a raw material of nuclear graphite and / or artificial graphite, natural graphite subjected to a spheroidizing treatment is preferable.

<Physical properties of carbonaceous materials>
The carbonaceous material as a negative electrode active material in the present invention satisfies at least one of the characteristics such as physical properties and shape shown in the following (1) to (9) in addition to the above-described requirements. It is particularly preferable to satisfy a plurality of items at the same time.

(1) X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction of the carbonaceous material by X-ray diffraction is preferably 0.335 nm or more, and usually 0. It is 360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, more preferably 1.5 nm or more, and particularly preferably 2 nm or more. It is further preferred that

(2) Volume-Based Average Particle Size In the present invention, the volume-based average particle size of the carbonaceous material is a volume-based average particle size (median diameter d50) determined by laser diffraction / scattering method, and is usually 1 μm or more. The thickness is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, particularly preferably 25 μm or less.

  When the volume-based average particle diameter is in the above-mentioned range, it is possible to suppress an initial loss of battery capacity due to an increase in irreversible capacity, and enable uniform electrode application when including a step of electrode preparation by application.

  The measurement of the volume-based average particle diameter is carried out by dispersing the powder of carbonaceous material in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate which is a surfactant, and laser diffraction / scattering. It can carry out using a formula particle size distribution analyzer (LA-700 made by Horiba, Ltd.). The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.

(3) Raman R value, Raman half value width The Raman R value of the carbonaceous material is a value measured using argon ion laser Raman spectroscopy, and is usually 0.01 or more, preferably 0.03 or more, 0 1 or more is more preferable, and usually 1.5 or less, 1.2 or less is preferable, 1 or less is more preferable, and 0.5 or less is particularly preferable.

The Raman half value width in the vicinity of 1580 cm ^{-1 of the} carbonaceous material is not particularly limited, but is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and usually 100 cm ^-1 or less, 80 cm ^-1 or less Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.

  The Raman R value and the Raman half value width are indices indicating the crystallinity of the surface of the carbonaceous material, but the carbonaceous material has appropriate crystallinity from the viewpoint of chemical stability, while the interlayer into which lithium is introduced by charge and discharge. It is preferable that it is crystalline to such an extent that the site of. In the case where the density of the negative electrode is increased by pressing after application to a current collector, it is preferable to take account of the fact that crystals tend to be oriented in a direction parallel to the electrode plate.

  While being able to suppress reaction of a carbonaceous material and a non-aqueous electrolyte solution as a Raman R value or a Raman half value width is the said range, the fall of the load characteristic by the loss | disappearance of a site can be suppressed.

The measurement of the Raman spectrum is carried out by naturally dropping the sample into the measuring cell and filling it using a Raman spectrometer (Raman spectrometer manufactured by JASCO), and irradiating the sample surface in the cell with argon ion laser light, It is performed by rotating the cell in a plane perpendicular to the laser light. The resulting Raman spectrum, the intensity IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material. Moreover, the half value width of peak PA around 1580 cm < ^-1 > of the obtained Raman spectrum is measured, and this is defined as the Raman half value width of carbonaceous material.

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

(4) BET specific surface area The BET specific surface area of the carbonaceous material is a value of the specific surface area measured by using the BET method, and is usually 0.1 m ² · g ^-1 or more, 0.7 m ² · g ^-1 The above is preferable, 1.0 m ² · g ^-1 or more is more preferable, 1.5 m ² · g ^-1 or more is particularly preferable, and usually 100 m ² · g ^-1 or less, 25 m ² · g ^-1 or less 15 m ² · g ^-1 or less is more preferable, and 10 m ² · g ^-1 or less is particularly preferable.

  While precipitation of lithium on the electrode surface can be suppressed when the value of the BET specific surface area is in the above range, gas generation due to reaction with the non-aqueous electrolyte can be suppressed.

  Measurement of the specific surface area by the BET method is carried out by using a surface area meter (total surface area measurement device manufactured by Okura Riken) and predrying the sample under flowing nitrogen at 350 ° C. for 15 minutes and then using nitrogen of atmospheric pressure. It is carried out by the nitrogen adsorption BET one-point method according to the gas flow method, using a nitrogen-helium mixed gas which is accurately adjusted so that the value of relative pressure is 0.3. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material.

(5) Degree of Circularity When the degree of circularity is measured as the degree of spherical shape of the carbonaceous material, it is preferable to fall within the following range. The circularity is defined as "circularity = (peripheral length of equivalent circle having the same area as the particle projection shape) / (actual peripheral length of the particle projection shape)", and when the circularity is 1, it is theoretical It becomes a true sphere.
The circularity of particles having a particle diameter of the carbonaceous material in the range of 3 to 40 μm is preferably as close to 1 as possible, preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more. 0.85 or more is more preferable, and 0.9 or more is especially preferable.

  As the degree of circularity of the carbonaceous material is larger, the filling property is improved and the resistance between particles can be suppressed, so the high current density charge / discharge characteristics are improved. Therefore, the higher the degree of circularity as in the above range, the better.

  The measurement of the degree of circularity is performed using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate which is a surfactant, and irradiated with ultrasonic waves of 28 kHz for 1 minute at a power of 60 W The detection range is specified to 0.6 to 400 μm, and measurement is performed on particles having a particle size in the range of 3 to 40 μm. The degree of circularity determined by the measurement is defined as the degree of circularity of the carbonaceous material.

  The method for improving the degree of circularity is not particularly limited, but it is preferable to use a sphericization treatment to make it spherical since the shape of the interparticle voids when the electrode body is formed can be obtained. As an example of the spheroidizing process, a mechanical force or a mechanical processing method in which a plurality of fine particles are granulated by a binder or the adhesive force of the particles themselves by mechanically applying a shear force or a compressive force to a spherical shape Can be mentioned.

(6) The tap density of the tap density carbonaceous material is usually 0.1 g · ^{cm -3} or higher, preferably 0.5 g · ^{cm -3} or more, more preferably 0.7 g · ^{cm -3} or more, 1 g · Particularly, cm ³ or more is preferable, 2 g · cm ³ or less is preferable, 1.8 g · cm ³ or less is more preferable, and 1.6 g · cm ³ or less is particularly preferable. While being able to ensure battery capacity as a tap density is the said range, the increase in the resistance between particle | grains can be suppressed.

The tap density is measured by passing the sample through a 300 μm mesh screen and dropping the sample into a 20 cm ³ tapping cell to fill the sample to the top end face of the cell, and then using a powder density measuring instrument (eg, Seishin Enterprise Co., Ltd.) Tap tapping is performed 1000 times using a stroke length of 10 mm, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material.

(7) Orientation ratio The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is in the above range, excellent high density charge / discharge characteristics can be secured. 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. A molded body obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing it at 58.8 MN · m ⁻² is set using clay to be flush with the surface of the sample holder for measurement. Measure X-ray diffraction. From the obtained peak intensities of (110) diffraction and (004) diffraction of carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material.

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 Photo acceptance 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

(8) Aspect Ratio The aspect ratio of the carbonaceous material is usually 1 or more, and usually 10 or less, preferably 8 or less, and more preferably 5 or less. When the aspect ratio is in the above range, streaking at the time of electrode plate formation can be suppressed, and uniform coating can be performed, so that excellent high current density charge / discharge characteristics can be ensured. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

  The measurement of the aspect ratio is performed by magnifying and observing particles of the carbonaceous material with a scanning electron microscope. Carbon material material particles when selecting arbitrary 50 graphite particles fixed to the end face of metal having a thickness of 50 μm or less, rotating and tilting the stage on which the sample is fixed for each, and observing it three-dimensionally The longest diameter A and the shortest diameter B orthogonal to that are measured, and the average value of A / B is determined. The aspect ratio (A / B) determined by the measurement is defined as the aspect ratio of the carbonaceous material.

(9) Secondary Material Mixing The secondary material mixing means that two or more kinds of carbonaceous materials having different “properties” are contained in the negative electrode and / or the negative electrode active material. The “properties” mentioned here are selected from the group of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Show one or more characteristics.

  Particularly preferable examples of mixing of these additives are that the volume-based particle size distribution does not become symmetrical when centering on the median diameter, and contains two or more kinds of carbonaceous materials having different Raman R values, And different X-ray parameters.

  As an example of the effect of mixing the auxiliary material, carbon materials such as natural graphite, graphite such as artificial graphite (graphite), carbon black such as acetylene black, amorphous carbon such as needle coke, etc. are contained as a conductive material , To reduce the electrical resistance.

  When the conductive material is mixed as the auxiliary material mixture, one kind may be mixed alone, or two or more kinds may be mixed in any combination and ratio. In addition, the mixing ratio of the conductive material to the carbonaceous material is usually 0.1 mass% or more, preferably 0.5 mass% or more, more preferably 0.6 mass% or more, and usually 45 mass% or less. 40 mass% or less is preferable. While being able to ensure an electrical resistance reduction effect as a mixing ratio is the said range, the increase in an initial stage irreversible capacity | capacitance can be suppressed.

<Alloy-based material>
As an alloy-based material used as a negative electrode active material, lithium alone, lithium single metal and alloy forming lithium alloy, or oxides, carbides, nitrides, silicides, sulfide thereof as long as lithium can be absorbed and released It may be any of compounds or compounds such as phosphides and is not particularly limited. The single metal and alloy forming the lithium alloy is preferably a material containing Group 13 and Group 14 metal / metalloid elements (ie excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ A single metal) and an alloy or compound containing these atoms. One of these may be used alone, or two or more of these may be used in any combination and ratio.

  As a negative electrode active material having at least one kind of atom selected from specific metal elements, a metal simple substance of any one kind of specific metal element, an alloy composed of two or more kinds of specific metal elements, one kind or two kinds or more of specification Alloy consisting of metal element and one or more other metal elements, compound containing one or more specified metal elements, and oxide, carbide, nitride, silicide of the compound And complex compounds such as sulfides and phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the secondary battery.

  Moreover, the compound which these composite compounds couple | bonded with several types of elements, such as a simple metal, an alloy, or a nonmetallic element, etc. is also mentioned. Specifically, for example, in silicon and tin, an alloy of these elements and a metal which does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 elements in combination of a metal other than tin and silicon and acting as a negative electrode, a metal not acting as a negative electrode and a nonmetallic element may also be used it can.

  Among these negative electrode active materials, since the capacity per unit mass is large when made into a secondary battery, a metal simple substance of any one specific metal element, an alloy of two or more specific metal elements, a specific metal element Oxides, carbides, nitrides and the like are preferable, and in particular, silicon and / or tin single metals, alloys, oxides, carbides, nitrides and the like are preferable from the viewpoint of capacity per unit mass and environmental load.

Lithium-containing metal composite oxide material
The lithium-containing metal complex oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable in terms of high current density charge and discharge characteristics, More preferably, a lithium-containing composite metal oxide material containing titanium is mentioned, and more preferably a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as "lithium-titanium composite oxide") can be mentioned. That is, it is particularly preferable to use a lithium-titanium composite oxide having a spinel structure by incorporating it into a negative electrode active material for a non-aqueous electrolyte secondary battery, since the output resistance is greatly reduced.

  In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. It is also preferred that one element be substituted. The metal oxide is a lithium titanium composite oxide represented by the following general formula (C), and in the general formula (C), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3 It is preferable that 0 ≦ z ≦ 1.6, because the structure at the time of lithium ion doping / dedoping is stable.

LixTiyMzO ₄ (C)
[In the general formula (C), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. ]

Among the compositions represented by the above general formula (C),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
Is particularly preferable because the battery performance is well balanced.

Particularly preferable representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ In addition, for the structure of z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is mentioned as a preferable one.

  The method for producing the lithium-titanium composite oxide is not particularly limited as long as the scope of the present invention is not exceeded, but several methods can be mentioned, and a general method can be used as a method for producing an inorganic compound.

For example, a method of uniformly mixing titanium source materials such as titanium oxide, source materials of other elements if necessary, and Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ and firing at high temperature to obtain an active material Can be mentioned.

In particular, various methods can be considered to produce a spherical or elliptical spherical active material. As an example, titanium starting materials such as titanium oxide and, if necessary, starting materials of other elements are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to prepare a spherical precursor After recovering this and drying it as needed, a method of adding a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ and firing at a high temperature to obtain a negative electrode active material may be mentioned.

Further, as another example, a titanium raw material such as titanium oxide and, if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water, and dried and formed by a spray dryer or the like to form a sphere Or a spheroid spherical precursor, to which a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ is added, followed by firing at a high temperature to obtain a negative electrode active material.

Further, as another method, a titanium source material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ and, if necessary, source materials of other elements are dissolved or pulverized in a solvent such as water It is dispersed and dried and formed by a spray drier or the like to form a spherical or elliptical spherical precursor, which is calcined at high temperature to obtain an active material.

  In addition, during these steps, elements other than Ti, for example, Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn It is also possible that Ag is present in the titanium-containing metal oxide structure and / or in contact with the titanium-containing oxide. By containing these elements, it becomes possible to control the operating voltage and capacity of the battery.

<Physical properties of lithium titanium composite oxide>
The lithium-titanium composite oxide as a negative electrode active material in the present invention satisfies at least one of characteristics such as physical properties and shape shown in the following (1) to (7) in addition to the above-mentioned requirements. It is particularly preferable to satisfy a plurality of items at the same time.

(1) BET Specific Surface Area The BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material is preferably 0.5 m ² · g ⁻¹ or more of the specific surface area measured using the BET method, and 0. 7 m ² · g ^-1 or more is more preferable, 1.0 m ² · g ^-1 or more is more preferable, 1.5 m ² · g ^-1 or more is particularly preferable, and 200 m ² · g ^-1 or less is preferable, 100 m ² * g <^-1> or less is more preferable, 50 m < ² > * g <^-1> or less is further more preferable, and 25 m < ² > * g <^-1> or less is especially preferable.

  If the BET specific surface area falls below the above range, the reaction area in contact with the non-aqueous electrolyte solution when used as a negative electrode material may decrease, and the output resistance may increase. On the other hand, beyond the above range, the surface and end face portions of the titanium oxide-containing metal oxide crystal increase, and this also causes distortion of the crystal, making irreversible capacity non-negligible, which is preferable. It may be difficult to obtain a secondary battery.

  The specific surface area of the lithium-titanium composite oxide was measured by BET method using a surface area meter (Okura Riken fully automatic surface area measuring device), the sample was predried at 350 ° C. for 15 minutes under nitrogen flow. Thereafter, using a nitrogen-helium mixed gas which is accurately adjusted so that the value of the relative pressure of nitrogen to the atmospheric pressure is 0.3, the nitrogen adsorption BET one-point method by the gas flow method is performed. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium titanium composite oxide in the present invention.

(2) Volume-Based Average Particle Size The volume-based average particle size of lithium titanium composite oxide (secondary particle size when primary particles are aggregated to form secondary particles) is determined by laser diffraction / scattering method. It is defined by the volume-based average particle diameter (median diameter) determined.

  The volume-based average particle diameter of the lithium titanium composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 0.7 μm or more, and preferably 50 μm or less, more preferably 40 μm or less, 30 μm The following is more preferable, and 25 μm or less is particularly preferable.

  Specifically, the measurement of the volume-based average particle diameter of the lithium-titanium composite oxide can be performed by using a 0.2 mass% aqueous solution (10 mL) of a surfactant polyoxyethylene (20) sorbitan monolaurate as a lithium-titanium composite oxide The powder is dispersed and carried out using a laser diffraction / scattering particle size distribution analyzer (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the lithium titanium composite oxide.

  When the volume average particle diameter of the lithium titanium composite oxide is below the above range, a large amount of binder is required at the time of preparation of the negative electrode, and as a result, the battery capacity may be reduced. Moreover, when it exceeds the said range, it will be easy to become a non-uniform coated surface at the time of negative electrode plate-making, and it may be undesirable on the battery manufacture process.

(3) Average Primary Particle Size When primary particles are aggregated to form secondary particles, the average primary particle size of the lithium titanium composite oxide is preferably 0.01 μm or more, and more preferably 0.05 μm or more. Preferably, 0.1 μm or more is more preferable, 0.2 μm or more is particularly preferable, 2 μm or less is preferable, 1.6 μm or less is more preferable, 1.3 μm or less is more preferable, and 1 μm or less is particularly preferable. When the volume-based average primary particle size exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder packing property or significantly reduces the specific surface area. Performance may be reduced. Moreover, if it is less than the said range, since the reversibility of charging / discharging is inferior in general because a crystal | crystallization becomes undeveloped, the performance of a secondary battery may be reduced.

  The average primary particle size of the lithium titanium composite oxide is measured by observation using a scanning electron microscope (SEM). Specifically, the magnification at which the particle can be confirmed, for example, a photograph with a magnification of 10,000 to 100,000 times, the longest value of the intercepts by the left and right boundaries of the primary particle with respect to the horizontal straight line, arbitrary 50 The primary particles are determined by taking the average value.

(4) Shape The shape of the particles of lithium titanium composite oxide may be any of conventionally used lumps, polyhedrons, spheres, oval spheres, plates, needles, columns, etc. Among them, primary particles are aggregated. Preferably, secondary particles are formed, and the shape of the secondary particles is spherical or elliptical.

  Usually, since the active material in the electrode expands and contracts with the charge and discharge of the electrochemical element, the active material is likely to be broken due to the stress, or deterioration such as breakage of the conductive path may occur. Therefore, it is possible to alleviate the stress of expansion and contraction and to prevent deterioration if the primary particles are aggregated to form the secondary particles rather than being a single particle active material of only primary particles.

  In addition, since spherical or elliptical spherical particles have less orientation at the time of molding of the electrode than particles having plate-like equiaxial orientation, expansion and contraction of the electrode at the time of charge and discharge are less, and the electrode is prepared Also in the mixing with the conductive material at the time of mixing, it is preferable because it is easily mixed uniformly.

(5) Tap Density Tap density lithium-titanium composite oxide is preferably from 0.05 g · ^{cm -3} or more, 0.1 g · ^{cm -3} or more, and more preferably 0.2 g · ^{cm -3} or more, 0.4 g · cm ⁻³ or more is particularly preferable, 2.8 g · cm ⁻³ or less is preferable, 2.4 g · cm ⁻³ or less is more preferable, and 2 g · cm ⁻³ or less is particularly preferable. When the tap density of the lithium titanium composite oxide is below the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between particles decreases, so the resistance between particles increases and the output resistance May increase. Moreover, when the said range is exceeded, the space | gap between particle | grains in an electrode may decrease too much, and the flow path of non-aqueous electrolyte solution may decrease, and output resistance may increase.

To measure the tap density of lithium titanium composite oxide, a sample is dropped to a 20 cm ³ tapping cell by passing through a 300 μm sieve, and the sample is filled up to the upper end face of the cell, and then a powder density measuring device Tapping with a stroke length of 10 mm is performed 1000 times using (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.), and the 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 lithium titanium composite oxide in the present invention.

(6) Circularity When the circularity is measured as the degree of spherical shape of the lithium titanium composite oxide, it is preferable to fall within the following range. The circularity is defined as "circularity = (peripheral length of equivalent circle having the same area as the particle projection shape) / (actual peripheral length of the particle projection shape)", and when the circularity is 1, it is theoretical It becomes a true sphere.

  The circularity of the lithium-titanium composite oxide is preferably as close to one as possible. Preferably, it is 0.10 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and particularly preferably 0.90 or more. The high current density charge / discharge characteristics generally improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material may be reduced, the resistance between particles may be increased, and the high current density charge / discharge characteristics may be deteriorated for a short time.

  The measurement of the circularity of the lithium titanium composite oxide is performed using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). Specifically, about 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate which is a surfactant, and ultrasonic waves of 28 kHz are output at 60 W. After irradiation for a minute, the detection range is specified to 0.6 to 400 μm, and measurement is performed on particles having a particle size in the range of 3 to 40 μm. The degree of circularity determined by the measurement is defined as the degree of circularity of the lithium titanium composite oxide in the present invention.

(7) Aspect Ratio The aspect ratio of the lithium titanium composite oxide is preferably 1 or more, 5 or less, more preferably 4 or less, still more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking during electrode plate formation and a uniform coated surface can not be obtained, and the high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the lithium titanium composite oxide.

  The measurement of the aspect ratio of the lithium-titanium composite oxide is performed by observing the particles of the lithium-titanium composite oxide with a scanning electron microscope. When arbitrary 50 lithium titanium complex oxide particles fixed to the end face of metal with a thickness of 50 μm or less are selected, the stage on which the sample is fixed is rotated and tilted for each, and observed three-dimensionally The longest diameter A of the particle and the shortest diameter B orthogonal to it are measured, and the average value of A / B is determined. The aspect ratio (A / B) determined by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

<Structure of negative electrode and preparation method>
For production of the negative electrode, any known method can be used as long as the effects of the present invention are not significantly impaired. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler and the like are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried and pressed to form a negative electrode active material layer It can be formed by

  In addition, in the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a method such as vapor deposition method, sputtering method, plating method is also used.

<Current collector>
As the current collector for holding the negative electrode active material layer, any known one can be used. Examples of the current collector of the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, nickel plated steel and the like, but copper is particularly preferable in terms of ease of processing and cost.

The current collector of the negative electrode may be roughened in advance.
Furthermore, when the current collector is a metal material, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, foamed metal and the like. Among them, preferably metal foil, more preferably copper foil, more preferably rolled copper foil by rolling method and electrolytic copper foil by electrolytic method, both of which can be used as a current collector.

  The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less, from the viewpoint of securing the battery capacity and handling.

(The ratio of the thickness of the current collector to the negative electrode active material layer)
The ratio of the thickness of the current collector to the thickness of the negative electrode active material layer is not particularly limited, but the “(thickness of the negative electrode active material layer on one side immediately before pouring of the non-aqueous electrolyte solution) / (thickness of current collector)” The value is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, 0.1 or more, preferably 0.4 or more, and particularly preferably 1 or more. When the thickness ratio of the current collector to the negative electrode active material layer is in the above range, the battery capacity can be secured, and heat generation of the current collector at the time of high current density charge and discharge can be suppressed.

<Binding agent>
The binder (binding agent) for binding the negative electrode active material is not particularly limited as long as it is a material stable to the non-aqueous electrolytic solution and the solvent used at the time of production of the electrode.

  Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, nitrocellulose, etc .; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber-like polymers such as NBR (acrylonitrile butadiene rubber), ethylene propylene rubber, etc .; styrene butadiene styrene block copolymer or its hydrogenated substance; EPDM (ethylene propylene diene terpolymer), styrene ス チ レ ンThermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or their hydrogenated products; syndiotactic-1,2-polybutadiene, polyacetic acid vinyl Soft resin-like polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. Fluorinated polymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. One of these may be used alone, or two or more of these may be used in any combination and ratio.

  The proportion of the binder in the slurry obtained by mixing the negative electrode active material and the binder, and further, the following solvent, thickener and the like as required is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more 0.6% by mass or more is particularly preferable, 20% by mass or less is preferable, 15% by mass or less is more preferable, 10% by mass or less is more preferable, and 8% by mass or less is particularly preferable. When the ratio of the binder to the slurry exceeds the above range, the binder ratio in which the amount of binder does not contribute to the battery capacity may increase, which may lead to a decrease in the battery capacity. Moreover, if it is less than the said range, strength reduction of a negative electrode may be caused.

  In particular, when a rubbery polymer represented by SBR is contained in the main component, the ratio of the binder to the slurry 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 usually 5% by mass or less, 3% by mass or less is preferable, and 2% by mass or less is more preferable. Moreover, when the fluorine-based polymer represented by polyvinylidene fluoride is contained in the main component, the ratio of the binder to the slurry is usually 1% by mass or more, preferably 2% by mass or more, and 3% by mass or more. Further, it is usually 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 far 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 needed. Instead, either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methyl pyrrolidone (NMP), dimethylformamide, dimethyl acetamide, methyl acetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyl triamine, N, N- Dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like can be mentioned.

  In particular, when an aqueous solvent is used, it is preferable to use a latex such as SBR to make a slurry by combining a thickener with a dispersing agent and the like. These solvents may be used alone or in any combination of two or more with any proportion.

<Thickener>
Thickeners are usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples thereof include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One of these may be used alone, or two or more of these may be used in any combination and ratio.

  Furthermore, when a thickener is used, the ratio of the thickener to the slurry is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. Usually, it is 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. While the fall of a battery capacity and the increase in resistance can be suppressed as the ratio of the thickener with respect to a slurry is the said range, appropriate coating property is securable.

<Electrode density>
The electrode structure when making the negative electrode active material into an electrode is not particularly limited, but the density of the negative electrode active material layer present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ The above is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, and 2.2 g · cm ⁻³ or less is preferable, 2.1 g · cm ⁻³ or less is more preferable, and 2.0 g · cm ⁻³ or less Is more preferable, and 1.9 g · cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material layer present on the current collector is in the above range, the destruction of the negative electrode active material particles is prevented, and the initial irreversible capacity is increased, or the vicinity of the current collector / negative electrode active material interface While the deterioration of the high current density charge / discharge characteristics due to the decrease in the permeability of the non-aqueous electrolyte solution can be suppressed, the decrease in battery capacity and the increase in resistance can be suppressed.

<Thickness of negative electrode plate>
The thickness of the negative electrode plate in which the negative electrode active material layer is formed on the current collector as described above is designed according to the positive electrode plate to be used and is not particularly limited, but the metal foil thickness of the core material The thickness of the mixture layer obtained by subtracting is usually 15 μm or more, preferably 20 μm or more, more preferably 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 that to which the substance of the composition different from this adhered on the surface of the said negative electrode plate. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as 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.

<Area of negative electrode plate>
The area of the negative electrode plate is not particularly limited, but from the viewpoint of suppressing cycle life after repeated charging and discharging and deterioration due to high temperature storage, an electrode ratio that works more uniformly and effectively as close to the area as possible to the positive electrode It is preferable because the properties are improved by enhancing. In particular, when used at a large current, the design of the area of the negative electrode plate is important.

[2-4. Separator]
In order to prevent a short circuit, a separator is usually interposed between the positive electrode and the negative electrode. In this case, the non-aqueous electrolytic solution of the present invention is usually used by impregnating this separator.

  The material and shape of the separator are not particularly limited, and any known ones can be adopted as long as the effects of the present invention are not significantly impaired. Among them, resins, glass fibers, inorganic substances, etc., which are made of a material stable to the non-aqueous electrolyte solution of the present invention, are used, and porous sheet or non-woven fabric-like articles etc. excellent in liquid retention are used. Is preferred.

<Material>
As materials of resin and glass fiber separator, for example, polyolefin such as polyethylene and polypropylene, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, polyimide, polyester, polyoxyalkylene, glass filter and the like can be used. Among them, preferred are glass filters and polyolefins, more preferred are polyolefins, and particularly preferred are polyethylene and polypropylene. One of these materials may be used alone, or two or more of these materials may be used in any combination and ratio. Further, the above materials may be laminated and used.

<Thickness>
The thickness of the separator is arbitrary but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less. If the separator is thinner than the above range, the insulation and mechanical strength may be reduced. When the thickness is more than the above range, not only the battery performance such as rate characteristics may be degraded, but also the energy density of the whole non-aqueous electrolyte secondary battery may be degraded.

<Porosity>
When a porous sheet such as a porous sheet or non-woven fabric is used as the separator, the porosity of the separator is optional, but is usually 20% or more, preferably 35% or more, and more preferably 45% or more. Usually 90% or less, preferably 85% or less, and more preferably 75% or less. When the porosity is smaller than the above range, the film resistance tends to be increased and the rate characteristic tends to be deteriorated. Moreover, when it is larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

<Average pore size>
The average pore diameter of the separator is also optional, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. When the average pore size exceeds the above range, a short circuit is likely to occur. If the above range is exceeded, the film resistance may increase and the rate characteristics may deteriorate.

<Inorganic separator>
On the other hand, as the inorganic material, for example, oxides such as alumina and titania and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Are used.

<Form>
Examples of the form of the separator include thin film shapes such as non-woven fabric, woven fabric and microporous film. In the thin film form, one having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is suitably used. A separator formed by forming a composite porous layer containing particles of the above-mentioned inorganic material on the surface layer of the positive electrode and / or the negative electrode using a binder made of resin other than the above-mentioned independent thin film shape can be used. For example, forming a porous layer using alumina particles with a 90% particle diameter of less than 1 μm on both sides of a positive electrode and a fluorocarbon resin such as PVdF as a binder can be mentioned.

<Air permeability>
The characteristics of the separator in the non-aqueous electrolyte secondary battery can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passing through in the film thickness direction, and since 100 ml of air is represented by the number of seconds required to pass through the film, smaller numbers are easier to pass through and larger numbers are larger. It means that one is more difficult to pass through. That is, the smaller the value, the better the communication in the thickness direction of the film, and the larger the value, the worse the communication in the thickness direction of the film. The communication property is the degree of connection of the holes in the film thickness direction. If the separator Gare value is low, it can be used in various applications. For example, when it is used as a separator of a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily moved, which is preferable because the battery performance is excellent. The Gurley value of the separator is optionally but preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and still more preferably 20 to 500 seconds / 100 ml. If the Gurley value is 1000 seconds / 100 ml or less, the electric resistance is substantially low and it is preferable as a separator.

<Manufacturing method>
Specific examples of the method for obtaining the separator body and the porous film include the following methods.

(1) A low molecular weight substance which is compatible with the polyolefin resin and can be extracted in a later step is added to the polyolefin resin to melt and knead it into a sheet, and the low molecular weight substance is extracted after stretching or before stretching. Extraction method to make porous (2) Stretching method to make porous by adding low temperature stretch and high temperature stretch to a high elastic sheet made by making crystalline resin into a sheet with high draft ratio Stretching method (3) Inorganic or organic to thermoplastic resin Filler is added and melt-kneaded, sheeted, and interfacial peeling method to peel off the interface of resin and filler by stretching to make porous (4) Melt-kneaded, sheeted by adding β crystal nucleating agent to polypropylene resin .Beta. Crystal nucleating agent method in which a sheet in which .beta. Crystals are formed is stretched and made porous by utilizing crystal transition. A method of production may be either wet or dry.

[2-5. Battery design]
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate described above are intervened by the separator, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound through the separator. Any one may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less .

  When the electrode group occupancy rate falls below the above range, the battery capacity decreases. Further, when the above range is exceeded, the void space is small, the battery becomes high temperature, the members expand, the vapor pressure of the liquid component of the electrolyte becomes high, and the internal pressure rises, and the charge and discharge repetition performance as the battery Or, the characteristics such as high temperature storage may be lowered, and furthermore, a gas release valve may be actuated to release the internal pressure to the outside.

<Current collection structure>
When the electrode group has the above-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminal 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 above-described wound structure, the internal resistance can be reduced by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.

<Protective element>
As a protection element, PTC (Positive Temperature Coefficient) thermistor, whose resistance increases when abnormal heat generation or excessive current flows, thermal fuse, shut off current flowing in the circuit due to sudden increase of internal pressure of battery and internal temperature at abnormal heat generation. A valve (current cutoff valve) or the like can be used. The protective element is preferably selected under conditions which do not operate under normal use of high current, and it is more preferable to design it so as not to lead to abnormal heat generation or thermal runaway without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually constructed by housing the above non-aqueous electrolyte, the negative electrode, the positive electrode, the separator and the like in an outer package (outer case). The outer package is not limited, and any known one can be adopted as long as the effects of the present invention are not significantly impaired.

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

  In the outer case using the above metals, the metals are welded together by laser welding, resistance welding, ultrasonic welding to form a hermetically sealed structure, or a caulking structure using the above metals via a resin gasket. The thing to do is mentioned. In the outer case using the above-mentioned laminated film, those having a sealing and sealing structure by thermally fusing the resin layers to each other may be mentioned. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, in the case where the resin layer is heat-sealed through the current collection terminal to form a sealed structure, the metal and the resin are joined, and therefore, a resin having a polar group or a modification having a polar group introduced as an intervening resin Resin is preferably used.

<Shape>
The shape of the outer case is also arbitrary, and may be, for example, cylindrical, square, laminate, coin or large size.

  EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples and reference examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[Preparation of secondary battery]
<Production of Positive Electrode 1>
Lithium iron phosphate (LiFePO ₄ , manufactured by Tatung) 83.5% by mass as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 6.5% by mass of polyvinylidene fluoride (PVdF) as a binder Were mixed in N-methyl pyrrolidone solvent and slurried. The obtained slurry is uniformly coated on one side of a 15 μm thick aluminum foil coated with a carbonaceous material in advance and dried, and the coated amount of the positive electrode active material layer after drying is 13.8 mg · cm ⁻² I made it. Thereafter, the density of the positive electrode active material layer is pressed so as to be 1.85 g · cm ⁻³ , and cut into a shape having an uncoated portion of 30 mm wide, 40 mm long, and 5 mm wide and 9 mm long. And

<Fabrication of Positive Electrode 2>
90 parts by mass of lithium manganese manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, 7 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride are mixed, N-methyl -2-Pyrrolidone was added to make a slurry. The slurry was uniformly applied on one side of a 15 μm thick aluminum foil, dried, and the coated amount of the positive electrode active material layer after drying was 11.85 mg · cm ⁻² . Thereafter, the density of the positive electrode active material layer is pressed so as to be 2.6 g · cm ⁻³ , and the positive electrode 2 is cut out into a shape having an uncoated portion of 30 mm wide, 40 mm long, and 5 mm wide and 9 mm long. And

<Fabrication of negative electrode>
To graphite, an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and an aqueous dispersion of styrene-butadiene rubber (concentration of 50% by mass of styrene-butadiene rubber) as a binder are added, It mixed by a disperser and it slurried. The obtained slurry was uniformly coated on one surface of a copper foil with a thickness of 12 μm, dried, and the coated amount of the negative electrode active material layer after drying was made to be 6.0 mg · cm ⁻² . Thereafter, the density of the negative electrode active material layer is pressed so as to be 1.36 g · cm ⁻³ , and cut into a shape having an uncoated portion of 32 mm in width, 42 mm in length, and 5 mm in width and 9 mm in length. did.

The used graphite has a d50 value of 10.9 μm, a BET specific surface area of 3.41 m ² / g, and a tap density of 0.985 g / cm ³ . In addition, the slurry was prepared so that the weight ratio of graphite: sodium carboxymethylcellulose: styrene-butadiene rubber = 97.5: 1.5: 1 in the dried negative electrode.

<Production of Nonaqueous Electrolyte Secondary Battery 11>
The positive electrode 1 and the negative electrode, and the separator were laminated in the order of the negative electrode, the separator and the positive electrode. As a separator, one made of polypropylene, having a thickness of 20 μm and a porosity of 54% was used. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, and after injecting a non-aqueous electrolytic solution described later, vacuum sealing was performed, and a sheet-like non-aqueous electrolytic solution secondary battery 11 was produced. Furthermore, in order to enhance the adhesion between the electrodes, the sheet battery was sandwiched between the glass plates and pressurized.

<Production of Nonaqueous Electrolyte Secondary Battery 21>
A non-aqueous electrolyte secondary battery 21 was produced in the same manner as the above except that the positive electrode 1 was replaced with the positive electrode 2. Furthermore, in order to enhance the adhesion between the electrodes, the sheet battery was sandwiched between the glass plates and pressurized.

[Evaluation of battery]
<Initial charge / discharge test of non-aqueous electrolyte secondary battery 11>
The sheet-like non-aqueous electrolyte secondary battery 11 was charged at 0.05 C for 10 hours in a thermostat at 25 ° C., then rested for 3 hours, and then charged at 0.2 C constant current to 3.8 V. After an additional 3 hours of rest, constant current-constant voltage charging at 0.2 C to 3.8 V and then constant current discharging to 2.5 V at 1/3 C. The ratio of the discharge capacity to the sum of the charge capacities in this series of charging was taken as the initial efficiency (%).

  Thereafter, two charge / discharge cycles were performed, each cycle including 1/3 C constant current-constant voltage charge up to 3.8 V and subsequent 1/3 C constant current discharge up to 2.5 V.

  Furthermore, the battery was stabilized by storing the battery at 60 ° C. for 12 hours after performing constant current-constant voltage charging at 1/3 C to 3.8 V. Thereafter, charge and discharge cycles of 1/3 C constant current-constant voltage charge up to 3.8 V at 25 ° C. and subsequent 1/3 C constant current discharge up to 2.5 V were performed twice. The final discharge capacity at this time was taken as the initial capacity. Here, 1 C is a current value in the case of discharging the entire capacity of the battery in one hour.

<Capacity Maintenance Ratio Test of Non-aqueous Electrolyte Secondary Battery 11 at High Temperature Storage>
The non-aqueous electrolyte secondary battery 11 after the above initial charge / discharge test was adjusted to 3.8 V and stored at 60 ° C. for one week. Perform post charge / discharge cycle of 1/3 C constant current-constant voltage charge up to 3.8 V at 25 ° C and 1/3 C constant current discharge up to 2.5 V at 25 ° C for the battery after storage The The final discharge capacity at this time was taken as the capacity after high temperature storage, and the ratio of the capacity after high temperature storage to the initial capacity obtained in the above initial charge / discharge test was taken as the capacity retention ratio (%) during high temperature storage.

<Low-Temperature Characteristic Evaluation Test of Nonaqueous Electrolyte Secondary Battery 11>
The non-aqueous electrolyte secondary battery 11 is adjusted to 3.8 V at 25 ° C. after the initial charge / discharge test and after the capacity retention test at high temperature storage, and from that state 2.5 V at 25 ° C. and −20 ° C. respectively. 1 C constant current discharge was performed. The ratio (%) of 1 C discharge capacity at -20 ° C. to 1 C discharge capacity at 25 ° C. was defined as the low temperature characteristics of the non-aqueous electrolyte secondary battery 21. In addition, the ratio of the low temperature characteristics after storage to the initial low temperature characteristics was defined as the low temperature characteristics retention rate (%).

<Initial charge / discharge test of non-aqueous electrolyte secondary battery 21>
The sheet-like non-aqueous electrolyte secondary battery 21 was charged at 0.05 C for 10 hours in a thermostat at 25 ° C., then rested for 3 hours, and then constant current charge at 4.1 C to 0.2 V. After an additional 3 hours of rest, constant current-constant voltage charging at 0.2 C to 4.1 V and then constant current discharging to 3.0 V at 1/3 C. The ratio of the discharge capacity to the sum of the charge capacities in this series of charging was taken as the initial efficiency (%).

  Thereafter, two charge / discharge cycles were performed, each cycle consisting of 1/3 C constant current-constant voltage charge up to 4.1 V and subsequent 1/3 C constant current discharge up to 3.0 V.

  Furthermore, the battery was stabilized by storing the battery at 60 ° C. for 12 hours after constant current-constant voltage charging to 4.2 V at 1/3 C. Thereafter, charge and discharge cycles of 1/3 C constant current-constant voltage charging up to 4.2 V at 25 ° C. and subsequent 1/3 C constant current discharge up to 3.0 V were performed twice. The final discharge capacity at this time was taken as the initial capacity. Here, 1 C is a current value in the case of discharging the entire capacity of the battery in one hour.

<Capacity Maintenance Ratio Test of Non-aqueous Electrolyte Secondary Battery 21 at High Temperature Storage>
The non-aqueous electrolyte secondary battery 21 after the initial charge-discharge test was adjusted to 4.2 V and stored at 60 ° C. for one week. Perform post charge / discharge cycle of 1/3 C constant current-constant voltage charge up to 4.2 V at 25 ° C and 1/3 C constant current discharge up to 3.0 V at 25 ° C to the battery after storage The The final discharge capacity at this time was taken as the capacity after high temperature storage, and the ratio of the capacity after high temperature storage to the initial capacity obtained in the above initial charge / discharge test was taken as the capacity retention ratio (%) during high temperature storage.

<Low-Temperature Characteristic Evaluation Test of Nonaqueous Electrolyte Secondary Battery 21>
The non-aqueous electrolyte secondary battery 21 was adjusted to 3.72 V after the initial charge / discharge test and after the capacity retention test at high temperature storage, and constant current discharge was performed at -30 ° C. for 10 seconds at various current values from that state. . The voltage after 10 seconds was plotted against these various current values, and the current value was determined such that the voltage after 10 seconds was 3V. The area of a triangle surrounded by the points thus determined, the initial value (open circuit state), and the three points of 3 V (current value = 0 mA) represents the low temperature characteristics of the non-aqueous electrolyte secondary battery 11 and Defined. In addition, the ratio of the low temperature characteristics after storage to the initial low temperature characteristics was defined as the low temperature characteristics retention rate (%).

Example 1
Fully dry LiPF ₆ in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4) in a dry argon atmosphere so as to be 1 mol / L in the total volume of the non-aqueous electrolyte It was made to melt | dissolve (Hereafter, this electrolyte solution may be called "reference | standard electrolyte solution").

  A compound represented by the following formula (i) was added to the reference electrolyte so that the content in the non-aqueous electrolyte was 0.5% by mass, to prepare a non-aqueous electrolyte.

  The non-aqueous electrolytic solution secondary battery 11 was manufactured by the above-mentioned method using this electrolytic solution, and the capacity retention rate during high temperature storage was measured. The ratio of the capacity retention rate when the capacity retention rate of Comparative Example 1 to be described later was set to a reference value (100%) (hereinafter, this ratio may be referred to as “capacity retention rate improvement rate”) was calculated. Further, the ratio of the initial efficiency when the initial efficiency of Comparative Example 1 to be described later was used as the reference value (100%) (hereinafter, this ratio may be referred to as “initial efficiency improvement rate”) was calculated. Also in the following Examples 2 to 10, the capacity retention rate improvement rate and the initial efficiency improvement rate were similarly calculated. The results are shown in Table 1.

Example 2
A compound represented by the following formula (ii) was added to the reference electrolyte so that the content in the non-aqueous electrolyte was 0.5% by mass to prepare a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

[Example 3]
A compound represented by the following formula (iii) was added to the reference electrolyte so that the content in the non-aqueous electrolyte was 0.5% by mass, to prepare a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

Example 4
A compound represented by the following formula (iv) was added to the reference electrolyte so that the content in the non-aqueous electrolyte was 0.5% by mass to prepare a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1 except that this non-aqueous electrolyte was used. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

[Example 5]
A non-aqueous electrolytic solution secondary battery 11 was produced in the same manner as in Example 1 except that the content of the compound represented by the above formula (i) was changed to 1.0% by mass. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

[Example 6]
A non-aqueous electrolytic solution secondary battery 11 was produced in the same manner as in Example 2 except that the content of the compound represented by the above formula (ii) was changed to 1.0% by mass. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

[Example 7]
In the same manner as in Example 1 except that 0.5 mass% of the compound represented by the above formula (i) and 0.5 mass% of the compound represented by the above formula (ii) are blended in the reference electrolytic solution. The non-aqueous electrolyte secondary battery 11 was produced. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 1.

Comparative Example 1
A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1 except that the reference electrolyte was used as the non-aqueous electrolyte. The capacity retention rate and the initial efficiency at high temperature storage were measured, and these values were used as reference values (100%).

[Comparative Examples 2 to 6]
Using the non-aqueous electrolyte solutions of Examples 1 to 4 and Comparative Example 1, a non-aqueous electrolyte secondary battery 21 was produced by the method described above. In addition, the capacity retention rate and the initial efficiency at high temperature storage are measured, and the capacity retention rate and the initial efficiency ratio when the capacity retention rate and the initial efficiency of Comparative Example 6 are respectively set to the reference value (100%) The maintenance rate improvement rate and the initial efficiency improvement rate may be called. The results are shown in Table 1.

As shown in Table 1, in the non-aqueous electrolyte secondary battery 21 of Comparative Examples 2, 4 and 5 in which LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material, the blending of the specific NCO compound The improvement effect of the capacity retention ratio by-was -1.9%-0.9%. On the other hand, in the non-aqueous electrolyte secondary batteries 11 of Examples 1, 3, 4, 5 and 7 using LixMPO ₄ as the positive electrode active material, the improvement effect of the capacity retention ratio by the blending of the specific NCO compound is 3. It was 6-12%. From this, it is understood that the improvement effect of the capacity retention rate by the blending of the specific NCO compound appears notably when LixMPO ₄ is used as the positive electrode active material.

In addition, as shown in Table 1, in the non-aqueous electrolyte secondary battery 21 of Comparative Example 3 using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material, the capacity by the combination of the specific Si compound The maintenance rate improvement effect was 0.3%. On the other hand, in the non-aqueous electrolyte secondary batteries 11 of Examples 2, 6 and 7 using LixMPO ₄ as the positive electrode active material, the improvement effect of the capacity retention ratio by the blending of the specific Si compound is 4.4%- It was 12.1%. From this, it is understood that the improvement effect of the capacity retention rate by the compounding of the specific Si compound appears notably when LixMPO ₄ is used as the positive electrode active material.

In addition, as shown in Table 1, in the non-aqueous electrolyte secondary battery 11 of Examples 1 to 7 using LixMPO ₄ as a positive electrode active material, excellent initial efficiency is maintained. In particular, in the non-aqueous electrolyte secondary battery 11 of Example 7 in which the specific NCO compound and the specific Si compound are blended, the improvement effect of the capacity retention ratio appears remarkably as 12.1% without impairing the initial efficiency. .

[Examples 8 to 10]
Non-aqueous system in the same manner as in Examples 1, 2 and 7 except that vinylene carbonate (hereinafter also referred to as “VC”) is further added so that the content in the non-aqueous electrolytic solution is 0.5% by mass. An electrolyte was prepared. A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1 except that these non-aqueous electrolytes were used. In addition, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated. The results are shown in Table 2.

[Comparative Examples 7-9]
The non-aqueous electrolyte secondary battery 21 was manufactured by the above-mentioned method using the non-aqueous electrolyte of Examples 8-10. Further, the capacity retention rate improvement rate and the initial efficiency improvement rate were calculated in the same manner as in Comparative Examples 2 to 6. The results are shown in Table 2.

Comparative Example 10
Using the non-aqueous electrolyte solution of Example 7, a non-aqueous electrolyte secondary battery 21 was produced by the method described above.

As shown in Table 2, in the non-aqueous electrolyte secondary battery 21 of Comparative Examples 7 to 9 using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material, the improvement effect of the capacity retention rate is It was 0.5% to 1.5%. On the other hand, in the nonaqueous electrolyte secondary batteries 11 of Examples 8 to 10 in which LixMPO ₄ was used as a positive electrode active material, the improvement effect of the capacity retention rate was 12.8 to 14.5%. From this, when LixMPO ₄ is used as a positive electrode active material, the effect of improving the capacity retention rate is particularly remarkable without impairing the initial efficiency by further blending vinylene carbonate with the specific NCO compound and / or the specific Si compound. It was shown to appear in

  Initial low temperature characteristics were determined for the non-aqueous electrolyte secondary batteries of Examples 1, 4 and 6 and Comparative Examples 1, 2, 5 and 6, respectively. For the non-aqueous electrolyte secondary battery 11, the ratio of the initial low temperature characteristics when the initial low temperature characteristics of Comparative Example 1 are set to the reference value (100%) (hereinafter, this ratio is referred to as "low temperature characteristic improvement rate" Yes) was calculated. In addition, for the non-aqueous electrolyte secondary battery 21, the ratio of the initial low temperature characteristics when the initial low temperature characteristics of Comparative Example 6 are set to the reference value (100%) (hereinafter, this ratio is referred to as "low temperature characteristics improvement rate" There is a case. Table 3 shows the initial low temperature characteristic improvement rates.

As shown in Table 3, the nonaqueous electrolytic solution secondary batteries 11 of Examples 1, 4 and 6 using LixMPO ₄ as a positive electrode active material have an initial low temperature characteristic improvement ratio of -4.8% to 6.0%. The The initial low temperature characteristic improvement ratio of the non-aqueous electrolyte secondary battery 21 of Comparative Examples 2 and 5 using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material is −15.5% to −5 The comparison with .2% indicates that the non-aqueous electrolyte secondary battery of the present invention is also excellent in initial low temperature characteristics.

  For the non-aqueous electrolyte secondary batteries of Examples 1, 4, 5, and 6 and Comparative Examples 1, 2, 4, 5, 6, 7, and 10, the low temperature characteristics and the low temperature characteristics retention ratio after storage were determined, respectively. For the non-aqueous electrolyte secondary battery 11, the ratio of the low temperature characteristics after storage to the low temperature characteristics maintenance ratio when the low temperature characteristics after storage and the low temperature characteristics maintenance ratio of Comparative Example 1 are respectively set to the reference value (100%) These ratios may be referred to as “post-storage low temperature characteristics improvement rate” and “low temperature characteristics retention rate improvement rate”, respectively. In the non-aqueous electrolyte secondary battery 21, the ratio of the low temperature characteristics after storage to the low temperature characteristics maintenance ratio when the low temperature characteristics after storage and the low temperature characteristics maintenance ratio of Comparative Example 6 are respectively set to the reference value (100%) Hereinafter, these ratios may be referred to as “post-storage low temperature characteristic improvement rate” and “low temperature characteristic maintenance rate improvement rate”, respectively. Table 4 shows the low temperature characteristics improvement rate after storage and the low temperature characteristics maintenance rate improvement rate.

As shown in Table 4, the non-aqueous electrolyte secondary batteries 11 of Examples 1, 4, 5 and 6 using LixMPO ₄ as a positive electrode active material have a low-temperature characteristic improvement ratio of −0.8% to 11.1 after storage. It was 1%, and the low temperature characteristic maintenance rate was -2.9% to 44.8%. The non-aqueous electrolyte secondary batteries 21 of Comparative Examples 2, 4, 5, 7 and 10 using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material show improvement in low temperature characteristics after storage From the comparison with -54.3% to -7.8% and the low temperature characteristic maintenance rate being -27.2% to -9.3%, the non-aqueous electrolyte secondary battery of the present invention It is shown that the low temperature characteristic improvement rate after storage and the low temperature characteristic maintenance rate are also excellent.

  From the above results, the non-aqueous electrolyte secondary battery of the present invention can be used for safety, output characteristics and high temperature by using a specific positive electrode and a non-aqueous electrolyte containing a specific NCO compound and / or a specific Si compound. It can be seen that the capacity retention rate during storage can be compatible at a high level.

  The non-aqueous electrolyte secondary battery and the non-aqueous electrolyte of the present invention are excellent in safety, output characteristics, and capacity retention rate at high temperature storage, and thus can be suitably used for various known applications. Moreover, it can utilize suitably also in electric field capacitors, such as a lithium ion capacitor which uses a non-aqueous electrolyte solution.

  Specific examples of these applications are, for example, laptop computers, pen-input PCs, mobile computers, e-book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, headphone movies, video movies, LCD TVs, handy cleaners, portables CD, mini disk, transceiver, electronic organizer, calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, bike, motorized bicycle, bicycle, lighting equipment, toy, game machine, watch, electric tool, strobe , Cameras, load leveling power sources, natural energy storage power sources, lithium ion capacitors, and the like.

Claims (13)

A current collector, a positive electrode containing lithium iron phosphate of olivine structure as a positive electrode active material having a basic composition of LiFePO ₄ , a negative electrode containing a negative electrode active material capable of absorbing and releasing lithium ions, and a non-aqueous electrolyte A non-aqueous electrolyte secondary battery comprising
The non-aqueous electrolytic solution is characterized by containing at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2):

(Wherein, Q is a divalent organic group having 2 to 10 carbon atoms, and the organic group has a tertiary or quaternary carbon).

(Wherein, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a C 1-10 alkyl group which may be substituted by a halogen atom, an alkenyl group, an alkynyl group or an aryl group, or a halogen atom And may be a silicon hydride having a silicon number of 1 to 10, and at least two of R ^{1 to} R ⁶ may be bonded to each other to form a ring.)
Nonaqueous electrolyte secondary battery. In the above formula (1), Q is characterized by having a cyclic skeleton,
The non-aqueous electrolyte secondary battery according to claim 1. In the general formula (1), Q is characterized by having a cyclohexane ring,
The non-aqueous electrolyte secondary battery according to claim 1. The compound represented by the said General formula (1) is a compound represented by a following formula, The non-aqueous electrolyte-liquid secondary battery as described in any one of the Claims 1 thru | or 3 characterized by the above-mentioned.

In the above general formula (2), R ^{1 to} R ⁶ are a hydrogen atom or an alkyl group which may be substituted by a halogen atom having 1 to 4 carbon atoms,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4. In the general formula (2), R ^{1 to} R ⁶ are a methyl group or an ethyl group,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 5. The compound represented by the general formula (2) is a compound represented by the following formula:
The nonaqueous electrolytic solution secondary battery according to any one of claims 1 to 6.

The compound represented by the general formula (1) is contained in an amount of 0.01 to 10% by mass based on the whole of the non-aqueous electrolyte solution,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 7. The compound represented by the general formula (2) is contained in 0.01 to 10% by mass with respect to the whole of the non-aqueous electrolyte solution,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 8. The non-aqueous electrolyte further comprises a compound to be reduced on the negative electrode upon initial charge of the battery,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 9. The compound to be reduced on the negative electrode is vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, lithium bis (oxalato) borate, lithium tetrafluoro oxalato phosphate, lithium difluoro bis (oxalato) phosphate and lithium tris ( Characterized by being at least one selected from the group consisting of oxalato phosphates,
The non-aqueous electrolyte secondary battery according to claim 10. The negative electrode active material includes a carbonaceous material,
The nonaqueous electrolytic solution secondary battery according to any one of claims 1 to 11. Having a conductive layer of a compound composition different from the current collector on the surface of the current collector,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 12 .