JP6750716B2 - Lithium fluorosulfonate, non-aqueous electrolyte, and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention provides lithium fluorosulfonate containing a specific amount of carboxylic acid, lithium fluorosulfonate containing a specific amount of halogen element, lithium fluorosulfonate containing a specific amount of sulfate ion, and lithium fluorosulfonate. The present invention relates to a contained non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are being put to practical use for a wide range of applications from so-called consumer power sources such as mobile phones and laptop computers to in-vehicle power sources for automobiles and large-scale stationary power sources. is there. However, in recent years, the demand for higher performance of non-aqueous electrolyte secondary batteries has become higher and higher, and it is possible to achieve battery characteristics such as high capacity, high output, high temperature storage characteristics, and cycle characteristics at a high level. It has been demanded.

In particular, when a lithium secondary battery is used as a power source for an electric vehicle, the electric vehicle requires a large amount of energy when starting and accelerating, and a large amount of energy generated when decelerating must be efficiently regenerated. Requires high output characteristics and high input characteristics. Further, since the electric vehicle is used outdoors, the lithium secondary battery has high input/output characteristics especially at a low temperature such as −30° C. so that the electric vehicle can quickly start and accelerate even in the cold season. (Low battery internal impedance) is required. In addition, even when repeatedly charged and discharged in a high temperature environment, it is necessary for the capacity to be less deteriorated and the internal impedance of the battery to be less increased.

When using a lithium secondary battery as a large stationary power source for various backup applications, load leveling of power supply, output stabilization of natural energy generation, etc. Not only is the size increased, but many cells are connected in series and parallel. Therefore, problems of reliability and safety caused by various non-uniformities such as variations in discharge characteristics of individual cells, variations in temperature between cells, and variations in capacity and state of charge of individual cells. Is likely to occur. If the battery design and management are improper, only some of the cells that make up the battery pack as described above will be kept in a high charged state, or the temperature inside the battery will rise and fall into a high temperature state. Causes such problems.
That is, current non-aqueous electrolyte secondary batteries have high initial capacity and input/output characteristics, low battery internal impedance, high capacity retention rate after endurance tests such as high temperature storage tests and cycle tests, and durability. Items such as excellent input/output performance and impedance characteristics even after the test are required at an extremely high level.

Until now, various means such as positive and negative electrode active materials and non-aqueous electrolytes have been used as means for improving the input/output characteristics, impedance characteristics, high temperature cycle characteristics and high temperature storage characteristics of non-aqueous electrolyte secondary batteries. Many technologies have been investigated for various battery components. For example, Patent Document 1 describes that when LiFSO ₃ is used as the electrolyte, a battery having a high discharge capacity at the time of 60° C. charge/discharge cycle evaluation is obtained. According to Patent Document 1, when using the LiClO _4, LiClO ₄ is decomposed to active oxygen by noble potential generated by the cathode active material, to promote the decomposition reaction of the solvent the active oxygen to attack the solvent in the electrolyte .. When CF ₃ SO ₃ Li, LiBF ₄ and LiPF ₆ are used for the electrolyte, decomposition of the electrolyte proceeds due to the noble potential of the positive electrode active material to generate fluorine, and this fluorine attacks the solvent to cause the solvent. It is described that it accelerates the decomposition reaction of.

JP-A-7-296849

An object of the present invention is to provide an additive for a non-aqueous electrolyte solution and a non-aqueous electrolyte solution that can bring about a non-aqueous electrolyte secondary battery having excellent initial battery characteristics and durability. It is intended to provide a non-aqueous electrolyte secondary battery using this non-aqueous electrolyte solution.

That is, the present invention relates to the following lithium fluorosulfonate, non-aqueous electrolyte solution, and non-aqueous electrolyte secondary battery.
<1> Lithium fluorosulfonate in which the content of carboxylic acid is 2.5×10 ⁻² mol/kg or less based on the total amount of lithium fluorosulfonate.
<2> A non-aqueous electrolytic solution containing lithium fluorosulfonate and having a carboxylate ion content of 1.0×10 ⁻⁷ mol/L or more and 4.0×10 ⁻³ mol/L or less.
<3> Lithium fluorosulfonate having a halogen element content of 1.5×10 ⁻³ mol/kg or less.
<4> The content of halide ions containing lithium fluorosulfonate and excluding fluoride ions in the non-aqueous electrolyte solution is 1.0×10 ⁻⁷ mol/L or more and 1.0×10 ^−3. A non-aqueous electrolyte solution having a mol/L or less.
<5> Lithium fluorosulfonate having a molar content of sulfate ion of 2.5×10 ⁻¹ mol/kg or less based on the weight of lithium fluorosulfonate.
<6> Non-aqueous electrolyte containing lithium fluorosulfonate and having a sulfate ion content of 1.0×10 ⁻⁷ mol/L or more and 1.0×10 ⁻² mol/L or less. Aqueous electrolyte.
<7> The lithium fluorosulfonate according to <1>, <3>, or <5>, which is a non-aqueous electrolyte solution used for a non-aqueous electrolyte battery including a negative electrode capable of inserting and extracting lithium ions, and a positive electrode. A non-aqueous electrolyte solution containing.
<8> A non-aqueous electrolyte solution used in a non-aqueous electrolyte battery including a negative electrode capable of inserting and extracting lithium ions and a positive electrode,
The non-aqueous electrolyte contains lithium fluorosulfonate, a lithium salt other than lithium fluorosulfonate, and a non-aqueous solvent,
The molar content of lithium fluorosulfonate in the non-aqueous electrolytic solution is 0.0005 mol/L or more and 0.5 mol/L or less, and the molar content of the sulfate ion component in the non-aqueous electrolytic solution is 1.0. A nonaqueous electrolytic solution having a concentration of not less than ×10 ⁻⁷ mol/L and not more than 1.0×10 ⁻² mol/L.
<9> The non-aqueous electrolyte solution according to <7> or <8>, wherein the lithium salt other than lithium fluorosulfonate is at least one of LiPF ₆ and LiBF ₄ .
<10> The non-aqueous electrolyte solution according to any one of <7> to <9>, wherein the non-aqueous electrolyte solution contains a cyclic carbonate having a fluorine atom.
<11> The nonaqueous electrolyte solution according to <10>, wherein the cyclic carbonate having a fluorine atom is contained in the nonaqueous electrolyte solution in an amount of 0.001% by mass to 85% by mass.
<12> The non-aqueous electrolyte solution according to any one of <7> to <11>, which contains a cyclic carbonate having a carbon-carbon unsaturated bond.
<13> The non-aqueous electrolyte solution according to <12>, wherein the cyclic carbonate having a carbon-carbon unsaturated bond is contained in the non-aqueous electrolyte solution in an amount of 0.001% by mass or more and 10% by mass or less. <14> The non-aqueous electrolyte solution according to any one of <7> to <13>, which contains a cyclic sulfonic acid ester.
<15> The non-aqueous electrolyte solution according to <14>, wherein the content of the cyclic sulfonate ester in the non-aqueous electrolyte solution is 0.001% by mass or more and 10% by mass or less.
<16> The non-aqueous electrolyte solution according to any one of <7> to <15>, which contains a compound having a cyano group.
<17> The non-aqueous electrolyte solution according to <16>, wherein the content of the compound having a cyano group in the non-aqueous electrolyte solution is 0.001% by mass or more and 10% by mass or less.
<18> The non-aqueous electrolyte solution according to any one of <7> to <17>, which contains a diisocyanate compound.
<19> The non-aqueous electrolyte solution according to <18>, wherein the content of the diisocyanate compound in the non-aqueous electrolyte solution is 0.001% by mass or more and 5% by mass or less.
<20> The non-aqueous electrolyte solution according to any one of <7> to <19>, which contains lithium oxalate salts.
<21> A non-aqueous electrolyte secondary battery containing the negative electrode and the positive electrode capable of inserting and extracting lithium ions, and the non-aqueous electrolyte according to any one of <7> to <20>.
<22> The negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer is at least one of a simple substance metal of silicon, an alloy and a compound, and a simple substance metal of tin, an alloy and a compound. The non-aqueous electrolyte secondary battery according to <21>, which contains a negative electrode active material containing a seed.
<23> The negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer includes the negative electrode active material containing a carbonaceous material. Next battery.
<24> The non-aqueous electrolysis according to <21>, wherein the negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer contains a negative electrode active material containing a lithium titanium composite oxide. Liquid secondary battery.
<25> The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material layer includes a lithium-cobalt composite oxide, a lithium-cobalt-nickel composite oxide, a lithium-manganese composite oxide, From the group consisting of lithium-cobalt-manganese composite oxide, lithium-nickel composite oxide, lithium-cobalt-nickel composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel-cobalt-manganese composite oxide. The non-aqueous electrolyte secondary battery according to any one of <21> to <24>, containing at least one selected.
<26> The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material layer includes LixMPO ₄ (M is a transition metal of Group 4 to Group 11 of the 4th period of the periodic table). The non-aqueous electrolyte secondary battery according to any one of <21> to <24>, wherein at least one element selected from the group consisting of x and 0<x<1.2) is included.

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

<Lithium fluorosulfonate>
The purity is preferably high in order to exhibit higher performance when lithium fluorosulfonate is used in a battery or the like.
Among them, for example, when manufactured using lithium carboxylate, it is desirable to control the battery characteristics so that the carboxylate ions that are easily oxidized in the battery are removed so as not to dissolve in the electrolytic solution. This can be confirmed by measuring the amount of carboxylate ion when dissolved in water.

In addition, a halide ion that is easily oxidized in the battery, a chemical species that easily generates a halide ion with a small amount of water mixed in the battery, or a possibility that a halide ion may be generated by a reaction in the battery In order to control the battery characteristics, it is desirable that a certain compound containing a halogen element is removed so as not to be dissolved in the electrolytic solution. This can be confirmed by measuring the amount of halide ions when dissolved in water. On the other hand, it is also known that the performance of a battery is improved by mixing an extremely small amount of a halide salt.

The present invention also relates to lithium fluorosulfonate containing a specific amount of sulfate ion. Sulfate ions may be by-produced, for example, when producing lithium fluorosulfonate using the above lithium halide. The sulfate ion may be contained in any form of lithium sulfate, lithium hydrogen sulfate and sulfuric acid. In the lithium fluorosulfonate of the present invention, the molar content of the sulfate ion component is 1.0×10 ⁻⁵ mol/kg or more as the lower limit value with respect to the weight of lithium fluorosulfonate, and preferably 5.0. The amount is ×10 ⁻⁵ mol/kg or more, more preferably 1.0×10 ⁻⁴ mol/kg or more. Further, the molar content of the sulfate ion component contained in the lithium fluorosulfonate is 2.5×10 ⁻¹ mol/kg or less, preferably 2.0×10 ⁻¹ mol/kg or less, as the upper limit value. , And more preferably 1.5×10 ⁻¹ mol/kg or less. When the molar content of the sulfate ion component is within the above range, the effect of the sulfate ion component in the battery when added to the electrolytic solution is sufficiently exhibited, and the increase in resistance due to side reaction is suppressed.

Further, when lithium fluorosulfonate is contained in the electrolytic solution, the content of sulfate ion in the non-aqueous electrolytic solution has an upper limit value of 1.0×10 ⁻² mol/L or less, preferably 8 0.0×10 ⁻³ mol/L or less, more preferably 5.0×10 ⁻³ mol/L or less, still more preferably 1.0×10 ⁻³ mol/L or less, most preferably 5.0×10 ^{−. It is 4} mol/L or less. On the other hand, the lower limit value is 1.0×10 ⁻⁷ mol/L or more, preferably 5.0×10 ⁻⁷ mol/L or more, and more preferably 8.0×10 ⁻⁷ mol/L or more. Is. When the molar concentration of sulfate ions is within the above range, durability is more likely to be exhibited. The above value is at least one of the value calculated from the added amount and the value appropriately calculated from the content contained in the electrolytic solution by analyzing the electrolytic solution.

The method for synthesizing and obtaining the lithium fluorosulfonate of the present invention is not particularly limited, and any one synthesized or obtained can be used.
Here, as the method for synthesizing lithium fluorosulfonate, for example, a method for obtaining lithium fluorosulfonate by reacting lithium trifluoride or a lithium silicon fluoride compound with sulfur trioxide or fluorosulfonic acid, or fluorosulfonic acid and lithium To obtain lithium fluorosulfonic acid, to obtain lithium fluorosulfonic acid by reacting ammonium salt of fluorosulfonic acid with lithium, and to perform salt exchange by reacting fluorosulfonic acid with lithium carboxylate To obtain lithium fluorosulfonate, a method to obtain lithium fluorosulfonate by reacting fluorosulfonic acid with lithium halide and performing salt exchange, and other halosulfonic acids such as chlorosulfonic acid, fluorine Fluorine, hydrofluoric acid, potassium fluoride, and other acidic fluoride salts such as hydrochloric acid potassium fluoride, and non-metal inorganic fluorides and organic fluorinating agents And the like.

In these reactions, whether or not a solvent is used is not particularly limited, but when used, it can be selected from various organic solvents and inorganic solvents other than water depending on the reaction reagent. At this time, it is preferable to use a solvent that is hard to remain and has a small influence even when it remains, and examples of the organic solvent include aprotic solvents such as carbonic acid ester, and examples of the inorganic solvent include hydrofluoric acid anhydride.

<1. Non-aqueous electrolyte>
The non-aqueous electrolyte solution of the present invention contains at least lithium fluorosulfonate, a lithium salt other than lithium fluorosulfonate, and a non-aqueous solvent that dissolves these.
<1-1. Lithium fluorosulfonate>
As the lithium fluorosulfonate used in the non-aqueous electrolyte solution of the present invention, the lithium fluorosulfonate described in the preceding section can be used.

In the non-aqueous electrolytic solution of the present invention, the molar content of lithium fluorosulfonate in the non-aqueous electrolytic solution is, as a lower limit value, 0.0005 mol/L or more, and preferably 0.01 mol/L or more. , 0.02 mol/L or more is more preferable. The upper limit value is 0.5 mol/L or less, preferably 0.45 mol/L or less, and more preferably 0.4 mol/L or less. The concentration range of lithium fluorosulfonate is 0.0005 mol/L or more and 0.5 mol/L or less, preferably 0.01 mol/L or more and 0.5 mol/L or less, and 0.01 mol/L or more and 0.45 mol /L or less is more preferable, and 0.01 mol/L or more and 0.40 mol/L or less is particularly preferable. When the molar concentration of lithium fluorosulfonate is within the above range, the internal impedance of the battery becomes low, and the input/output characteristics and durability are excellent.

The above value is at least one of the value calculated from the added amount and the value appropriately calculated from the content contained in the electrolytic solution by analyzing the electrolytic solution.
Further, in the non-aqueous electrolyte solution of the present invention, the molar content of the counter anion species FSO ₃ ⁻ of lithium fluorosulfonate in the non-aqueous electrolyte solution is 0.0005 mol/L or more as the lower limit value. It is preferably 0.01 mol/L or more, more preferably 0.02 mol/L or more. The upper limit value is preferably 0.5 mol/L or less, more preferably 0.45 mol/L or less, and particularly preferably 0.4 mol/L or less. When the concentration of the counter anion species FSO ₃ ⁻ is within the above range, the internal impedance of the battery becomes low and the input/output characteristics and durability are more likely to be exhibited. The range of the concentration of the counter anion species FSO ₃ ⁻ is preferably 0.0005 mol/L or more and 0.5 mol/L or less, preferably 0.01 mol/L or more and 0.5 mol/L or less, and 0.01 mol/L or more 0 It is more preferably 0.45 mol/L or less, particularly preferably 0.01 mol/L or more and 0.40 mol/L or less. The above value is at least one of the value calculated from the added amount and the value appropriately calculated from the content contained in the electrolytic solution by analyzing the electrolytic solution.
The molar content of the counter anion species FSO ₃ ^{− in} the non-aqueous electrolyte solution can be determined, for example, by the amount of lithium fluorosulfonate used in preparing the non-aqueous electrolyte solution.

<1-2. Lithium salts other than lithium fluorosulfonate>
The non-aqueous electrolyte in the present invention contains lithium fluorosulfate containing a specific amount of sulfate ion, and preferably further contains one or more other lithium salts.
The other lithium salt is not particularly limited as long as it is known to be used for this purpose, and specific examples 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;
LiPO ₃ F, LiPO ₂ F _{2 and} other lithium fluorophosphate salts other than LiPF ₆ ;
Lithium tungstate salts 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 and CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ 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 CF 2 CF 2 Lithium sulfonates such as SO ₃ Li;

_{LiN (FCO 2) 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, lithium imide such as LiN(CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ). salts;
LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) _{3 and} other lithium methide salts;

Lithium oxalate salts such as lithium difluorooxalatoborate, lithium bis(oxalato)borate, lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, lithium tris(oxalato)phosphate;
_{Other, LiPF 4 (CF 3) 2} , LiPF 4 (C 2 F 5) 2, LiPF 4 (CF 3 SO 2) 2, LiPF 4 (C 2 F 5 SO 2) 2, LiBF 3 CF 3, LiBF 3 C _{2 F 5, LiBF 3 C 3} F 7, LiBF 2 (CF 3) 2, LiBF 2 (C 2 F 5) 2, LiBF 2 (CF 3 SO 2) 2, LiBF 2 (C 2 F 5 SO 2) 2 Fluorine-containing organic lithium salts such as;

Among the _{above, LiPF 6, LiBF 4, LiSbF} 6, LiTaF 6, LiPO 2 F 2, CF 3 SO 3 Li, LiN (FSO 2) 2, LiN (FSO 2) (CF 3 SO 2), LiN (CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO ₂ ) ₃ , _{LiC (CF 3 SO 2) 3} , LiC (C 2 F 5 SO 2) 3, lithium Bisuo Kisara oxalatoborate, lithium difluoro oxalatoborate, lithium tetrafluoro-oxa Lato phosphate, lithium difluoro bis oxa Lato 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. Further, among these, LiPF ₆ and LiBF ₄ are preferable, and LiPF ₆ is most preferable.

In the non-aqueous electrolyte solution of the present invention, the counter anion species of the lithium salt other than fluoro lithium sulfonate nonaqueous electrolytic solution (e.g., PF 6 when lithium salts other than lithium fluorosulfonic acid is LiPF _{6 ^-)} of The lower limit of the molar content is preferably 0.5 mol/L or more, more preferably 0.6 mol/L or more, and particularly preferably 0.7 mol/L or more. Further, the upper limit value is preferably 3.0 mol/L or less, more preferably 2.0 mol/L or less, and particularly preferably 1.5 mol/L or less. The concentration range of the counter anion species of the lithium salt other than lithium fluorosulfonate is preferably 0.5 mol/L or more and 3.0 mol/L or less, and 0.5 mol/L or more and 2.0 mol/L or less. It is more preferably 0.5 mol/L or more and 1.5 mol/L or less. When the concentration of the counter anion species of the lithium salt other than lithium fluorosulfonate is within the above range, the total ion content in the non-aqueous electrolyte solution has a proper balance between the existing amount and the viscosity of the electrolyte solution, and thus the ionic conduction The internal impedance of the battery is lowered without lowering the temperature, and the effect of the input/output characteristics is easily exhibited.

In the present invention, the molar content of lithium fluorosulphonate relative to the molar content of lithium in the lithium salt other than lithium fluorosulphonate [lithium salt other than lithium fluorosulphonate] in the non-aqueous electrolyte [lithium fluorosulphonate ] ([Lithium fluorosulfonate]/[lithium salt other than lithium fluorosulfonate]) is preferably 0.001 or more and 1.2 or less.

When the ratio of [lithium fluorosulfonate]/[lithium salt other than lithium fluorosulfonate] is within the above range, the input/output characteristics and durability characteristic of the fluorosulfonate are easily exhibited. In order to exert the effect of the present invention more remarkably, [lithium fluorosulfonate]/[lithium salt other than lithium fluorosulfonate] is preferably 0.01 or more, more preferably 0.02 or more, Further, it is preferably 1.1 or less, more preferably 1.0 or less, and further preferably 0.7 or less. The range of [lithium fluorosulfonate]/[lithium salt other than lithium fluorosulfonate] is preferably 0.001 or more and 1.2 or less, more preferably 0.01 or more and 1.1 or less, and 0.01 It is more preferably 1.0 or more and 1.0 or less, and particularly preferably 0.01 or more and 0.7 or less.

In addition to these, from the viewpoint of improving output characteristics, high rate charge/discharge characteristics, high temperature storage characteristics, cycle characteristics, etc., lithium fluorophosphate salts other than LiPF ₆ described above, lithium imide salts, lithium oxalates. It may be preferable to include a lithium salt selected from salts. Specific examples of these lithium salts include LiPO ₂ F ₂ , LiBF ₄ , LiN(CF ₃ SO ₂ ) ₂ , LiN(FSO ₂ ) ₂ , lithium difluorooxalatoborate, lithium bisoxalatoborate, and lithium difluorobisbis. A lithium salt selected from oxalatophosphate and lithium tetrafluorobisoxalate phosphate is preferable.

In the present invention, LiPO ₂ F ₂ , LiBF ₄ , LiN(CF ₃ SO ₂ ) ₂ , LiN(FSO ₂ ) ₂ , lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, lithium. The content of the lithium salt selected from the tetrafluorobisoxalate phosphate is arbitrary as long as the effect of the present invention is not significantly impaired, but the lower limit is preferably 0.0005 mol/L or more, It is more preferably 0.001 mol/L or more, and particularly preferably 0.01 mol/L or more. The upper limit value is preferably 0.5 mol/L or less, more preferably 0.45 mol/L or less, and particularly preferably 0.4 mol/L or less.

Among this, the preparation of the electrolyte solution in the case of incorporating the LiPO ₂ F ₂ in the electrolyte solution, the LiPO ₂ F ₂ which is separately synthesized by a known method, Ya methods and active material to be added to the electrolytic solution containing LiPF ₆ There is a method in which water is allowed to coexist in a battery constituent element such as an electrode plate, and LiPO ₂ F ₂ is generated in the system when a battery is assembled using an electrolyte solution containing LiPF _6, and in the present invention, You may use the method of.
The method for measuring the content of LiPO ₂ F ₂ in the non-aqueous electrolyte solution and the non-aqueous electrolyte solution battery is not particularly limited, and any known method can be used, Examples include ion chromatography and F nuclear magnetic resonance spectroscopy (hereinafter, sometimes abbreviated as NMR).

<1-3. Non-aqueous solvent>
In the present invention, typical examples of non-aqueous solvents for dissolving lithium fluorosulfonate and lithium salts other than lithium fluorosulfonate are listed below. In the present invention, these non-aqueous solvents are used alone or as a mixed solution in which a plurality of solvents are mixed at an arbitrary ratio, but are not limited to these examples as long as the effects of the present invention are not significantly impaired.

<Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate that can be used as the non-aqueous solvent in the present invention include those having an alkylene group having 2 to 4 carbon atoms.
Specifically, examples of the saturated cyclic carbonate having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Among them, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving the battery characteristics resulting from the improvement in the degree of lithium ion dissociation.
As the saturated cyclic carbonate, one kind may be used alone, and two kinds or more may be used in optional combination and ratio.

The amount of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the lower limit of the amount of the compound when one kind is used alone is 3% in 100% by volume of the non-aqueous solvent. It is at least volume%, more preferably at least 5 volume%. By setting this range, it is possible to avoid a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and to improve the large-current discharge characteristics of the non-aqueous electrolyte secondary battery, the stability against the negative electrode, and the cycle characteristics. It becomes easy to set the range. The upper limit is 90% by volume or less, more preferably 85% by volume or less, and further preferably 80% by volume or less. Within this range, the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range, the decrease in ionic conductivity can be suppressed, and the load characteristics of the non-aqueous electrolyte secondary battery can be easily set to a good range.

Further, the saturated cyclic carbonate can be used in an arbitrary combination of two or more kinds. One of the preferred combinations is a combination of ethylene carbonate and propylene carbonate. In this case, the volume ratio of ethylene carbonate and propylene carbonate is preferably 99:1 to 40:60, and particularly preferably 95:5 to 50:50. Further, the amount of propylene carbonate in the whole non-aqueous solvent is 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and the upper limit is usually 20% by volume or less, preferably 8% by volume or less. , And more preferably 5% by volume or less. It is preferable to contain propylene carbonate within this range because the low-temperature characteristics are further excellent while maintaining the characteristics of the combination of ethylene carbonate and dialkyl carbonates.

<Chain carbonate>
Examples of chain carbonates that can be used as the non-aqueous solvent in the present invention include those having 3 to 7 carbon atoms.
Specifically, as the chain carbonate having 3 to 7 carbon atoms, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, Examples thereof include n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate.

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

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

Examples of the fluorinated diethyl carbonate derivative include ethyl-(2-fluoroethyl)carbonate, ethyl-(2,2-difluoroethyl)carbonate, bis(2-fluoroethyl)carbonate, ethyl-(2,2,2-trifluoro). Ethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2,2,2. 2-trifluoroethyl-2',2'-difluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate and the like can be mentioned.

As the chain carbonate, one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
The chain carbonate is preferably 15% by volume or more in 100% by volume of the non-aqueous solvent. By adjusting the content to 15% by volume or more, the viscosity of the non-aqueous electrolyte solution can be adjusted to an appropriate range, the decrease in ionic conductivity can be suppressed, and the large-current discharge characteristics of the non-aqueous electrolyte secondary battery can be easily adjusted to a good range. .. The chain carbonate content is preferably 90% by volume or less in 100% by volume of the non-aqueous solvent. By setting the content to 90% by volume or less, it is possible to avoid a decrease in electric conductivity due to a decrease in dielectric constant of the non-aqueous electrolyte solution, and it is easy to set the large current discharge characteristics of the non-aqueous electrolyte secondary battery in a good range. The content of the chain carbonate is more preferably 20% by volume or more, further preferably 25% by volume or more, more preferably 85% by volume or less, further preferably 80% by volume or less.

Furthermore, the battery performance can be significantly improved by combining ethylene carbonate with a specific chain carbonate in a specific blending amount.
For example, when dimethyl carbonate and ethyl methyl carbonate are selected as the specific chain carbonates, the blending amount of ethylene carbonate is 15 vol% or more and 40 vol% or less, and the blending amount of dimethyl carbonate is 20 vol% or more and 50 vol% or less. It is preferable that the blending amount of ethyl methyl carbonate is 20% by volume or more and 50% by volume or less. By selecting such a blending amount, it is possible to lower the low temperature deposition temperature of the electrolyte, reduce the viscosity of the non-aqueous electrolyte solution, improve the ionic conductivity, and obtain a high output even at a low temperature. Particularly preferably, the blending amount of ethylene carbonate is 25 vol% or more and 35 vol% or less, the blending amount of dimethyl carbonate is 30 vol% or more and 40 vol% or less, and the blending amount of ethyl methyl carbonate is 30 vol% or more, 40 vol% or less. % Or less.

<Cyclic carbonate having a fluorine atom>
The cyclic carbonate having a fluorine atom that can be used as the non-aqueous solvent in the present invention (hereinafter sometimes abbreviated as “fluorinated cyclic carbonate”) is not particularly limited as long as it is a cyclic carbonate having a fluorine atom. ..
Examples of the fluorinated cyclic carbonate include derivatives of cyclic carbonates having an alkylene group having 2 to 6 carbon atoms, such as ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and among them, those having 1 to 8 fluorine atoms. Is preferred.

Specifically, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4- Fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4-(fluoromethyl)-ethylene carbonate, 4-(difluoromethyl)-ethylene carbonate, 4-(trifluoromethyl)-ethylene carbonate , 4-(fluoromethyl)-4-fluoroethylene carbonate, 4-(fluoromethyl)-5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethyl Examples thereof include ethylene carbonate and 4,4-difluoro-5,5-dimethylethylene carbonate.

Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate has high ionic conductivity. It is more preferable in terms of imparting properties and suitably forming an interface protective film.
The fluorinated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio. The blending amount of the fluorinated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but in 100 mass% of the non-aqueous electrolyte solution, preferably 0.001 mass% or more, and more preferably Is 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 85% by mass or less, more preferably 80% by mass or less, further preferably 75% by mass or less. And as a range of the density|concentration of a fluorinated cyclic carbonate, 0.001 mass% or more and 85 mass% or less are preferable, 0.01 mass% or more and 80 mass% or less are more preferable, 0.1 mass% or more and 75 mass% or less Is more preferable.

The fluorinated cyclic carbonate may be used as a main solvent or a sub solvent of the non-aqueous electrolyte solution. The blending amount of the fluorinated cyclic carbonate when used as the main solvent is preferably 8% by mass or more, more preferably 10% by mass or more, and further preferably 12% by mass in 100% by mass of the non-aqueous electrolyte solution. % Or more, preferably 85% by mass or less, more preferably 80% by mass or less, and further preferably 75% by mass or less. Within this range, it is easy for the non-aqueous electrolyte secondary battery to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid a decrease in discharge capacity retention rate. The amount of the fluorinated cyclic carbonate when used as a secondary solvent is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, in 100% by mass of the non-aqueous electrolyte solution. Further preferably, it is 0.1% by mass or more, preferably 8% by mass or less, more preferably 6% by mass or less, and further preferably 5% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit sufficient output characteristics.

<Chain carboxylic acid ester>
Examples of the chain carboxylic acid ester that can be used as the non-aqueous solvent in the present invention include those having a total carbon number of 3 to 7 in the structural formula.
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, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, acetic acid-n-propyl, acetic acid-n-butyl, methyl propionate, ethyl propionate, propionic acid-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improving ionic conductivity.
The chain carboxylic acid ester content is preferably 5% by volume or more in 100% by volume of the non-aqueous solvent. When the content is 5% by volume or more, the electric conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily improved. Further, the chain carboxylic acid ester is preferably 80% by volume or less in 100% by volume of the non-aqueous solvent. When the content is 80% by volume or less, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery are likely to be in good ranges. The content of the chain carboxylic acid ester is more preferably 8% by volume or more, and further preferably 70% by volume or less.

<Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester that can be used as the non-aqueous solvent in the present invention include those having a total carbon atom number of 3 to 12 in the structural formula.
Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone. Among them, gamma-butyrolactone is particularly preferable from the viewpoint of improving the battery characteristics resulting from the improvement in the degree of lithium ion dissociation.

The cyclic carboxylic acid ester is preferably 3% by volume or more in 100% by volume of the non-aqueous solvent. When the content is 3% by volume or more, the electric conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily improved. The cyclic carboxylic acid ester content is preferably 60% by volume or less. By adjusting the content to 60% by volume or less, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in electric conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are suppressed. Can be easily set to a good range. The content of the cyclic carboxylic acid ester is more preferably 5% by volume or more, and further preferably 50% by volume or less.

<Ether compound>
Examples of ether compounds that can be used as the non-aqueous solvent in the present invention include chain ethers having 3 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms.
As the chain ether having 3 to 10 carbon atoms, diethyl ether, di(2-fluoroethyl)ether, di(2,2-difluoroethyl)ether, di(2,2,2-trifluoroethyl)ether, ethyl (2-Fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -Trifluoroethyl)ether, (2-fluoroethyl)(1,1,2,2-tetrafluoroethyl)ether, (2,2,2-trifluoroethyl)(1,1,2,2-tetrafluoro Ethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3-). Tetrafluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl ether, (2-fluoroethyl) (3-fluoro -N-propyl)ether, (2-fluoroethyl)(3,3,3-trifluoro-n-propyl)ether, (2-fluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ) Ether, (2-fluoroethyl)(2,2,3,3,3-pentafluoro-n-propyl)ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2 -Trifluoroethyl)(3-fluoro-n-propyl)ether, (2,2,2-trifluoroethyl)(3,3,3-trifluoro-n-propyl)ether, (2,2,2- Trifluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ) Ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl)(3-fluoro-n-propyl)ether, (1,1,2) ,2-Tetrafluoroethyl)(3,3,3-trifluoro-n-propyl)ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3-tetrafluoro-n- Propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-propyl Ether, (n-propyl)(3-fluoro-n-propyl)ether, (n-propyl)(3,3,3-trifluoro-n-propyl)ether, (n-propyl)(2,2,3 ,3-tetrafluoro-n-propyl)ether, (n-propyl)(2,2,3,3,3-pentafluoro-n-propyl)ether, di(3-fluoro-n-propyl)ether, ( 3-fluoro-n-propyl)(3,3,3-trifluoro-n-propyl)ether, (3-fluoro-n-propyl)(2,2,3,3-tetrafluoro-n-propyl)ether , (3-fluoro-n-propyl)(2,2,3,3,3-pentafluoro-n-propyl)ether, di(3,3,3-trifluoro-n-propyl)ether, (3,3 3,3-trifluoro-n-propyl)(2,2,3,3-tetrafluoro-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-butyl ether, dimethoxymethane, methoxyethoxy Methane, methoxy(2-fluoroethoxy)methane, methoxy(2,2,2-trifluoroethoxy)methane methoxy(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-tetrafluoroethoxy)methane, di(1,1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, methoxyethoxyethane, methoxy(2-fluoroethoxy) Ethane, methoxy(2,2,2-trifluoroethoxy)ethane, methoxy(1,1,2,2-tetrafluoroeth) Xy)ethane, diethoxyethane, ethoxy(2-fluoroethoxy)ethane, ethoxy(2,2,2-trifluoroethoxy)ethane, ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, di(2 -Fluoroethoxy)ethane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)ethane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(2,2 2,2-trifluoroethoxy)ethane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(1,1,2,2-tetrafluoroethoxy) Examples thereof include ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

As the cyclic ether having 3 to 6 carbon atoms, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvation ability to lithium ions and improve ionic dissociation. From the viewpoint, it is preferable to use dimethoxymethane, diethoxymethane and ethoxymethoxymethane since they have low viscosity and high ionic conductivity.

The blending amount of the ether compound is usually preferably 3% by volume or more, more preferably 4% by volume or more, further preferably 5% by volume or more, and preferably 70% by volume or less in 100% by volume of the non-aqueous solvent. It is more preferably 65% by volume or less, and further preferably 60% by volume or less. Within this range, it is easy to ensure the effect of improving the ionic conductivity resulting from the decrease in the degree of lithium ion dissociation of the chain ether and the decrease in viscosity, and when the negative electrode active material is a carbonaceous material, the chain ether together with the lithium ion It is easy to avoid the situation where capacity is reduced due to co-insertion.

<Sulfone compounds>
Examples of the sulfone compounds that can be used as the non-aqueous solvent in the present invention include cyclic sulfones having 3 to 6 carbon atoms and chain sulfones having 2 to 6 carbon atoms. The number of sulfonyl groups in one molecule is preferably 1 or 2.
Examples of the cyclic sulfone include trimethylene sulfone, tetramethylene sulfone and hexamethylene sulfone which are monosulfone compounds; trimethylenedisulfone, tetramethylenedisulfone and hexamethylenedisulfone which are disulfone compounds. Among them, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

As the sulfolane, at least one of sulfolane and a sulfolane derivative (hereinafter sometimes abbreviated as “sulfolane” including sulfolane) is preferable. The sulfolane derivative is preferably a sulfolane derivative in which one or more hydrogen atoms bonded to carbon atoms constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.
Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methyl Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3-(trifluoromethyl)sulfolane, 3-fluoro-3-(trifluoromethyl)sulfolane, 4-fluoro-3-( Trifluoromethyl)sulfolane, 5-fluoro-3-(trifluoromethyl)sulfolane and the like are preferable because of high ionic conductivity and high input/output.

As the chain sulfone, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di(tri Fluoroethyl) 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, penta Examples thereof include fluoroethyl-n-butyl sulfone and pentafluoroethyl-t-butyl sulfone.

Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone. , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t -Butyl sulfone and the like are preferable because of high ionic conductivity and high input/output.

The sulfone compound is preferably 0.3% by volume or more and 80% by volume or less in 100% by volume of the non-aqueous solvent. Within this range, the effect of improving durability such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte solution can be set in an appropriate range to prevent a decrease in electric conductivity. When charging/discharging the aqueous electrolyte secondary battery at a high current density, it is easy to avoid a situation in which the charge/discharge capacity retention rate decreases. The content of the sulfone compound is more preferably 0.5% by volume or more, further preferably 1% by volume or more, more preferably 75% by volume or less, and further preferably 70% by volume or less.

<1-4. Auxiliary>
In the present invention, the following auxiliaries can be contained in the non-aqueous solvent, but they are not particularly limited to these as long as the effects of the present invention are not significantly impaired.
<Cyclic carbonate having a carbon-carbon unsaturated bond>
In the non-aqueous electrolytic solution of the present invention, a film is formed on the negative electrode surface of the non-aqueous electrolytic solution battery, and in order to achieve a long service life of the battery, a cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter, referred to as "unsaturated Abbreviated as “cyclic carbonate”).

The cyclic carbonate having a carbon-carbon unsaturated bond is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond, and any carbonate having a carbon-carbon unsaturated bond can be used. The cyclic carbonate having a substituent having an aromatic ring is also included in the cyclic carbonate having a carbon-carbon unsaturated bond.
Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, allyl carbonates and the like.

Examples of the vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate and allylvinylene carbonate.
Specific examples of the ethylene carbonate substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, Examples thereof include ethynyl ethylene carbonate and 4,5-diethynyl ethylene carbonate.

Among them, vinylene carbonates, ethylene rings substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond are preferable, and particularly vinylene carbonate, 4,5-diphenylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinyl. Ethylene carbonate and ethynyl ethylene carbonate are more preferably used because they form a stable interface protective film.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution can be easily ensured, and the effects of the present invention can be sufficiently exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less. The method for producing the unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected and produced.

The unsaturated cyclic carbonates may be used alone or in combination of two or more in any combination and ratio. The amount of the unsaturated cyclic carbonate compounded is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The unsaturated cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 100% by mass in the non-aqueous electrolyte solution. Is 0.2% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less. And as a range of the density|concentration of unsaturated cyclic carbonate, 0.001 mass% or more and 10 mass% or less are preferable, 0.001 mass% or more and 8 mass% or less are more preferable, 0.001 mass% or more and 5 mass% or less Is more preferable.
Within the above range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristic improving effect, and the high temperature storage characteristic is deteriorated, the gas generation amount is increased, and the discharge capacity maintenance ratio is decreased. It is easy to avoid the situation.

<Fluorinated unsaturated cyclic carbonate>
As the fluorinated cyclic carbonate, it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”). The fluorinated unsaturated cyclic carbonate is not particularly limited. Of these, one having one or two fluorine atoms is preferable.
Examples of the fluorinated unsaturated cyclic carbonate include a vinylene carbonate derivative, an ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, and the like.
Examples of the vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, and 4,5-difluoroethylene carbonate.

Examples of the ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate and 4,4-difluoro-4. -Vinylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-fluoro-4-phenyl Examples thereof include ethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate and 4,5-difluoro-4-phenylethylene carbonate.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the fluorinated cyclic carbonate in the non-aqueous electrolyte solution can be easily secured, and the effect of the present invention can be easily exhibited. The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected and produced. The molecular weight is more preferably 80 or more, and more preferably 150 or less.

As the fluorinated unsaturated cyclic carbonate, one kind may be used alone, and two kinds or more may be used in optional combination and ratio. The blending amount of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired. The fluorinated unsaturated cyclic carbonate is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. In this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving cycle characteristics, the high temperature storage characteristics are deteriorated, the gas generation amount is increased, and the discharge capacity maintenance ratio is decreased. Easy to avoid. The content of the fluorinated unsaturated cyclic carbonate is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 4% by mass or less, further preferably 3% by mass or less. Is.

<Cyclic sulfonate compound>
The cyclic sulfonic acid ester compound that can be used in the non-aqueous electrolyte solution of the present invention is not particularly limited in type, and examples thereof include compounds represented by the general formula (1).

(In the formula, R ⁵ and R ⁶ are each independently an organic atom composed of at least one atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom. Represents a group, and R ⁵ and R ⁶ may contain an unsaturated bond together with —O—SO ₂ —.
R ⁵ and R ⁶ are preferably organic groups composed of carbon atoms, hydrogen atoms, oxygen atoms, and sulfur atoms, and among them, hydrocarbon groups having 1 to 3 carbon atoms, —O—SO. It is preferably an organic group having _2- .

The molecular weight of the cyclic sulfonic acid ester compound is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 100 or more and 250 or less. Within this range, the solubility of the cyclic sulfonate compound in the non-aqueous electrolyte solution can be easily ensured, and the effect of the present invention can be easily exhibited. The method for producing the cyclic sulfonate compound is not particularly limited, and a known method can be arbitrarily selected and produced.

Specific examples of the compound represented by the general formula (1) include, for example,
1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone , 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene- 1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2- Fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene-1, 3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl- 2-propene-1,3-sultone,

1,4-butanesultone, 1-fluoro-1,4-butanesultone, 2-fluoro-1,4-butanesultone, 3-fluoro-1,4-butanesultone, 4-fluoro-1,4-butanesultone, 1-methyl- 1,4-butanesultone, 2-methyl-1,4-butanesultone, 3-methyl-1,4-butanesultone, 4-methyl-1,4-butanesultone, 1-butene-1,4-sultone, 2-butene- 1,4-Sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone, 3-fluoro-1- Butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-fluoro-2-butene-1,4-sultone, 2-fluoro-2-butene-1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2-butene-1,4-sultone, 1-fluoro-3-butene-1,4-sultone, 2-fluoro-3-butene- 1,4-sultone,

3-fluoro-3-butene-1,4-sultone, 4-fluoro-3-butene-1,4-sultone, 1-methyl-1-butene-1,4-sultone, 2-methyl-1-butene- 1,4-sultone, 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone, 1-methyl-2-butene-1,4-sultone, 2- Methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4-methyl-2-butene-1,4-sultone, 1-methyl-3-butene-1, 4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-1,4-sultone, 1,5- Pentane sultone, 1-fluoro-1,5-pentane sultone, 2-fluoro-1,5-pentane sultone, 3-fluoro-1,5-pentane sultone, 4-fluoro-1,5-pentane sultone, 5-fluoro -1,5-pentanesultone, 1-methyl-1,5-pentanesultone, 2-methyl-1,5-pentanesultone,

3-methyl-1,5-pentanesultone, 4-methyl-1,5-pentanesultone, 5-methyl-1,5-pentanesultone, 1-pentene-1,5-sultone, 2-pentene-1,5 -Sultone, 3-pentene-1,5-sultone, 4-pentene-1,5-sultone, 1-fluoro-1-pentene-1,5-sultone, 2-fluoro-1-pentene-1,5-sultone , 3-fluoro-1-pentene-1,5-sultone, 4-fluoro-1-pentene-1,5-sultone, 5-fluoro-1-pentene-1,5-sultone, 1-fluoro-2-pentene -1,5-sultone, 2-fluoro-2-pentene-1,5-sultone, 3-fluoro-2-pentene-1,5-sultone, 4-fluoro-2-pentene-1,5-sultone, 5 -Fluoro-2-pentene-1,5-sultone, 1-Fluoro-3-pentene-1,5-sultone, 2-Fluoro-3-pentene-1,5-sultone, 3-Fluoro-3-pentene-1 , 5-sultone, 4-fluoro-3-pentene-1,5-sultone, 5-fluoro-3-pentene-1,5-sultone,

1-fluoro-4-pentene-1,5-sultone, 2-fluoro-4-pentene-1,5-sultone, 3-fluoro-4-pentene-1,5-sultone, 4-fluoro-4-pentene- 1,5-Sultone, 5-Fluoro-4-pentene-1,5-sultone, 1-Methyl-1-pentene-1,5-sultone, 2-Methyl-1-pentene-1,5-sultone, 3- Methyl-1-pentene-1,5-sultone, 4-methyl-1-pentene-1,5-sultone, 5-methyl-1-pentene-1,5-sultone, 1-methyl-2-pentene-1, 5-sultone, 2-methyl-2-pentene-1,5-sultone, 3-methyl-2-pentene-1,5-sultone, 4-methyl-2-pentene-1,5-sultone, 5-methyl-
2-pentene-1,5-sultone, 1-methyl-3-pentene-1,5-sultone, 2-methyl-3-pentene-1,5-sultone, 3-methyl-3-pentene-1,5- Sultone, 4-methyl-3-pentene-1,5-sultone, 5-methyl-3-pentene-1,5-sultone, 1-methyl-4-pentene-1,5-sultone, 2-methyl-4- Pentene-1,5-sultone,

Sultone compounds such as 3-methyl-4-pentene-1,5-sultone, 4-methyl-4-pentene-1,5-sultone, 5-methyl-4-pentene-1,5-sultone;
Sulfate compounds such as methylene sulphate, ethylene sulphate, propylene sulphate;
Disulfonate compounds such as methylene methane disulfonate and ethylene methane disulfonate;
1,2,3-oxathiazolidine-2,2-dioxide, 3-methyl-1,2,3-oxathiazolidine-2,2-dioxide, 3H-1,2,3-oxathiazole-2,2-dioxide ,

5H-1,2,3-oxathiazole-2,2-dioxide, 1,2,4-oxathiazolidine-2,2-dioxide, 4-methyl-1,2,4-oxathiazolidine-2,2-dioxide 3H-1,2,4-oxathiazole-2,2-dioxide, 5H-1,2,4-oxathiazole-2,2-dioxide, 1,2,5-oxathiazolidine-2,2-dioxide, 5-methyl-1,2,5-oxathiazolidine-2,2-dioxide, 3H-1,2,5-oxathiazole-2,2-dioxide, 5H-1,2,5-oxathiazole-2,2 -Dioxide, 1,2,3-oxathiazinane-2,2-dioxide, 3-methyl-1,2,3-oxathiazinane-2,2-dioxide,

5,6-dihydro-1,2,3-oxathiazine-2,2-dioxide, 1,2,4-oxathiazinane-2,2-dioxide, 4-methyl-1,2,4-oxathiazinane-2,2- Dioxide, 5,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,4-dihydro-1, 2,4-oxathiazine-2,2-dioxide, 1,2,5-oxathiazinane-2,2-dioxide, 5-methyl-1,2,5-oxathiazinane-2,2-dioxide, 5,6-dihydro- 1,2,5-oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,5-oxathiazine-2, 2-dioxide, 1,2,6-oxathiazinane-2,2-dioxide, 6-methyl-1,2,6-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine- Nitrogen-containing compounds such as 2,2-dioxide, 3,4-dihydro-1,2,6-oxathiazine-2,2-dioxide and 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide ;

1,2,3-oxathiaphoslane-2,2-dioxide, 3-methyl-1,2,3-oxathiaphoslane-2,2-dioxide, 3-methyl-1,2,3-oxathi Aphoslane-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiaphoslane-2,2,3-trioxide, 1,2,4-oxathiaphoslane-2,2-dioxide , 4-methyl-1,2,4-oxathiaphoslane-2,2-dioxide, 4-methyl-1,2,4-oxathiaphoslane-2,2,4-trioxide, 4-methoxy-1 ,2,4-oxathiaphoslane-2,2,4-trioxide, 1,2,5-oxathiaphoslane-2,2-dioxide, 5-methyl-1,2,5-oxathiaphoslane- 2,2-dioxide, 5-methyl-1,2,5-oxathiaphoslane-2,2,5-trioxide, 5-methoxy-1,2,5-oxathiaphoslane-2,2,5- Trioxide, 1,2,3-oxathiaphosphinan-2,2-dioxide, 3-methyl-1,2,3-oxathiaphosphinan-
2,2-dioxide, 3-methyl-1,2,3-oxathiaphosphinane-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiaphosphinane-2,2,3- Trioxide,

1,2,4-oxathiaphosphinane-2,2-dioxide, 4-methyl-1,2,4-oxathiaphosphinane-2,2-dioxide, 4-methyl-1,2,4-oxathia Phosphinane-2,2,3-trioxide, 4-methyl-1,5,2,4-dioxathiaphosphinane-2,4-dioxide, 4-methoxy-1,5,2,4-dioxathia Phosphinane-2,4-dioxide, 3-methoxy-1,2,4-oxathiaphosphinane-2,2,3-trioxide, 1,2,5-oxathiaphosphinane-2,2-dioxide, 5 -Methyl-1,2,5-oxathiaphosphinan-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinan-2,2,3-trioxide, 5-methoxy-1,2 ,5-oxathiaphosphinane-2,2,3-trioxide, 1,2,6-oxathiaphosphinane-2,2-dioxide, 6-methyl-1,2,6-oxathiaphosphinane-2, 2-dioxide, 6-methyl-1,2,6-oxathiaphosphinane-2,2,3-trioxide, 6-methoxy-1,2,6-oxathiaphosphinane-2,2,3-trioxide, etc. Phosphorus-containing compound;

Of these,
1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1,4-butanesultone, methylenemethane Disulfonate and ethylene methane disulfonate are preferable from the viewpoint of improving storage characteristics, and 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, and 3-fluoro-1. , 3-propane sultone and 1-propene-1,3-sultone are more preferable.

The cyclic sulfonate compound may be used alone or in combination of two or more in any combination and ratio. There is no limitation on the amount of the cyclic sulfonic acid ester compound to be added to the entire non-aqueous electrolyte solution of the present invention, and any amount may be used as long as the effects of the present invention are not significantly impaired. 001 mass% or more, preferably 0.1 mass% or more, more preferably 0.3 mass% or more, and usually 10 mass% or less, preferably 5 mass% or less, more preferably 3 mass% or less Let When the above range is satisfied, the effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

<Compound having a cyano group>
In the non-aqueous electrolyte solution of the present invention, the compound having a cyano group that can be used is not particularly limited as long as it is a compound having a cyano group in the molecule, and is represented by the general formula (2). The compound to be mentioned is mentioned.

(In the formula, T represents an organic group composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom, and U has a substituent. It may be a V-valent organic group having 1 to 10 carbon atoms. V is an integer of 1 or more, and when V is 2 or more, Ts may be the same or different from each other.)
The molecular weight of the compound having a cyano group is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more, more preferably 80 or more, still more preferably 100 or more, and 200 or less. Within this range, the solubility of the compound having a cyano group in the non-aqueous electrolyte solution can be easily ensured and the effect of the present invention can be easily exhibited. The method for producing the compound having a cyano group is not particularly limited, and a known method can be arbitrarily selected and produced.

Specific examples of the compound represented by the general formula (2) include, for example,
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, 2,2-dimethylbutyronitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile , Acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile , 2-hexenenitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3, 3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, 1 Compounds having one cyano group, such as 2,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile and pentafluoropropionitrile;

Malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, methylmalononitrile, ethylmalononitrile, i-propylmalononitrile, t-butylmalononitrile, methylsuccinonitrile. Cinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, trimethylsuccinonitrile, tetramethylsuccinonitrile, 3,3′-(ethylenedioxy)dipropionitrile, 3,3′ A compound having two cyano groups such as -(ethylenedithio)dipropionitrile;
Compounds having three cyano groups such as 1,2,3-tris(2-cyanoethoxy)propane and tris(2-cyanoethyl)amine;

Cyanate compounds such as methyl cyanate, ethyl cyanate, propyl cyanate, butyl cyanate, pentyl cyanate, hexyl cyanate and heptyl cyanate;
Methyl thiocyanate, ethyl thiocyanate, propyl thiocyanate, butyl thiocyanate, pentyl thiocyanate, hexyl thiocyanate, heptyl thiocyanate, methanesulfonyl cyanide, ethanesulfonylcyanide, propanesulfonylcyanide, butanesulfonylcyanide, pentanesulfonylcyanide, hexanesulfonylcyanide , Heptanesulfonyl cyanide, methylsulfurocyanidate, ethylsulfurocyanidate, propylsulfurocyanidate, butylsulfurocyanidate, pentylsulfurocyanidate, hexylsulfurocyanidate, heptylsulfur Sulfur-containing compounds such as furocyanidates;

Cyanodimethylphosphine, cyanodimethylphosphine oxide, methyl cyanomethylphosphinate, methyl cyanomethylphosphinate, cyanide dimethylphosphinic acid, cyanide dimethylphosphinate, dimethyl cyanophosphonate, dimethylcyanophosphonate, cyanomethyl methylphosphonate, methylphosphonate Phosphorus-containing compounds such as cyanomethyl phosphate, cyanodimethyl phosphate, and cyanodimethyl phosphite;
Etc.

Of these,
Acetonitrile, propionitrile, butyronitrile, i-butyronitrile, valeronitrile, i-valeronitrile, lauronitrile, crotononitrile, 3-methylcrotononitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, Azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile are preferable from the viewpoint of improving storage characteristics, and cyano such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile. A compound having two groups is more preferable.

As the compound having a cyano group, one type may be used alone, or two or more types may be used together in any combination and ratio. The compounding amount of the cyano group-containing compound with respect to the whole non-aqueous electrolyte solution of the present invention is not limited and may be any amount as long as the effect of the present invention is not significantly impaired. 001 mass% or more, preferably 0.1 mass% or more, more preferably 0.3 mass% or more, and usually 10 mass% or less, preferably 5 mass% or less, more preferably 3 mass% or less Let When the above range is satisfied, the effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

<Diisocyanate compound>
The diisocyanate compound that can be used in the non-aqueous electrolyte solution of the present invention is not particularly limited as long as it is a compound having two isocyanato groups in the molecule, but a compound represented by the following general formula (3) is preferable.

(In the formula, X is a hydrocarbon group having 1 to 16 carbon atoms which may be substituted with fluorine)
In the above general formula (3), X is a hydrocarbon group having 1 to 16 carbon atoms which may be substituted with fluorine. The carbon number of X is preferably 2 or more, more preferably 3 or more, particularly preferably 4 or more, and preferably 14 or less, more preferably 12 or less, particularly preferably 10 or less, most preferably 8 or less. The type of X is not particularly limited as long as it is a hydrocarbon group. It may be any of an aliphatic chain alkylene group, an aliphatic cyclic alkylene group and an aromatic ring-containing hydrocarbon group, but an aliphatic chain alkylene group or an aliphatic cyclic alkylene group is preferable.

Specific examples of the diisocyanate in the present invention,
Linear polymethylene diisocyanates such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, etc.;
1-methylhexamethylene diisocyanate, 2-methylhexamethylene diisocyanate, 3-methylhexamethylene diisocyanate, 1,1-dimethylhexamethylene diisocyanate, 1,2-dimethylhexamethylene diisocyanate, 1,3-dimethylhexamethylene diisocyanate, 1, Branched alkylene diisocyanates such as 4-dimethylhexamethylene diisocyanate, 1,5-dimethylhexamethylene diisocyanate, 1,6-dimethylhexamethylene diisocyanate, 1,2,3-trimethylhexamethylene diisocyanate;

1,4-diisocyanato-2-butene, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-3-pentene, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, Diisocyanatoalkenes such as 1,8-diisocyanato-2-octene, 1,8-diisocyanato-3-octene, 1,8-diisocyanato-4-octene, and the like;
1,3-diisocyanato-2-fluoropropane, 1,3-diisocyanato-2,2-difluoropropane, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,2-difluorobutane, 1, 4-diisocyanato-2,3-difluorobutane, 1,6-diisocyanato-2-fluorohexane, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-2,2-difluorohexane, 1,6- Diisocyanato-2,3-difluorohexane, 1,6-diisocyanato-2,4-difluorohexane, 1,6-diisocyanato-2,5-difluorohexane, 1,6-diisocyanato-3,3-difluorohexane, 1, 6-diisocyanato-3,4-difluorohexane, 1,8-diisocyanato-2-fluorooctane, 1,8-diisocyanato-3-fluorooctane, 1,8-diisocyanato-4-fluorooctane, 1,8-diisocyanato- 2,2-Difluorooctane, 1,8-Diisocyanato-2,3-difluorooctane, 1,8-Diisocyanato-2,4-difluorooctane, 1,8-Diisocyanato-2,5-difluorooctane, 1,8- Fluorine-substituted diisocyanatoalkanes such as diisocyanato-2,6-difluorooctane and 1,8-diisocyanato-2,7-difluorooctane;

1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4'. A cycloalkane ring-containing diisocyanate such as diisocyanate, dicyclohexylmethane-3,3′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate;

1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene-2,3-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,5-diisocyanate, tolylene-2,6 -Diisocyanate, tolylene-3,4-diisocyanate, tolylene-3,5-diisocyanate, 1,2-bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)benzene, 1,4-bis(isocyanate) Natomethyl)benzene, 2,4-diisocyanatobiphenyl, 2,6-diisocyanatobiphenyl, 2,2'-diisocyanatobiphenyl, 3,3'-diisocyanatobiphenyl, 4,4'-diisocyanato- 2-Methylbiphenyl, 4,4'-diisocyanato-3-methylbiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanato-2 -Methyldiphenylmethane, 4,4'-diisocyanato-3-methyldiphenylmethane, 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane, 1,5-diisocyanatonaphthalene, 1,8-diisocyanatonaphthalene, 2 ,3-Diisocyanatonaphthalene, 1,5-bis(isocyanatomethyl)naphthalene, 1,8-bis(isocyanatomethyl)naphthalene, 2,3-bis(isocyanatomethyl)naphthalene, etc. ; And the like.

Among these,
Linear polymethylene diisocyanates such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, etc.;
1-methylhexamethylene diisocyanate, 2-methylhexamethylene diisocyanate, 3-methylhexamethylene diisocyanate, 1,1-dimethylhexamethylene diisocyanate, 1,2-dimethylhexamethylene diisocyanate, 1,3-dimethylhexamethylene diisocyanate, 1, Branched alkylene diisocyanates such as 4-dimethylhexamethylene diisocyanate, 1,5-dimethylhexamethylene diisocyanate, 1,6-dimethylhexamethylene diisocyanate, 1,2,3-trimethylhexamethylene diisocyanate;

1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4'. A cycloalkane ring-containing diisocyanate such as diisocyanate, dicyclohexylmethane-3,3′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate;
Is preferred.

Furthermore,
Linear polymethylene diisocyanates selected from tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate;
1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 4-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate A cycloalkane ring-containing diisocyanate selected from dicyclohexylmethane-3,3′-diisocyanate and dicyclohexylmethane-4,4′-diisocyanate;
Is particularly preferable.

The above-mentioned diisocyanates in the present invention may be used alone or in any combination of two or more at any ratio.
In the non-aqueous electrolytic solution of the present invention, the content of diisocyanate that can be used is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably based on the total mass of the non-aqueous electrolytic solution. Is 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 4.0% by mass or less, more preferably 3.0% by mass or less, further preferably 2% by mass. % Or less. When the content is within the above range, durability such as cycle and storage can be improved, and the effects of the present invention can be sufficiently exhibited.

<Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress the rupture and ignition of the battery when the non-aqueous electrolyte secondary battery is in a state of overcharge or the like. ..
As the overcharge preventing agent, an aromatic compound such as biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partial fluorinated compounds of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole, etc. And a fluorine-containing anisole compound of Among them, biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated terphenyl, and aromatic compounds such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. In the case of using two or more kinds in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, It is desirable to use at least one selected from oxygen-free aromatic compounds such as t-amylbenzene and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran in combination with overcharge prevention characteristics and high-temperature storage characteristics. Is preferable from the standpoint of balance.

The blending amount of the overcharge inhibitor is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired. The overcharge inhibitor is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effect of the overcharge preventing agent can be sufficiently exhibited, and a situation in which the characteristics of the battery such as high temperature storage characteristics are deteriorated can be easily avoided. The overcharge inhibitor is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, further preferably Is 2% by mass or less.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. Other auxiliary agents include erythritan carbonate, spiro-bis-dimethylene carbonate, carbonate compounds such as methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydrous. Carboxylic acid anhydrides such as itaconic acid, diglycolic acid anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentanetetracarboxylic acid dianhydride and phenylsuccinic acid anhydride; 2,4,8,10-tetraoxaspiro[5.5 ] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane; ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, Sulfur-containing compounds such as ethyl methanesulfonate, busulfan, sulfolene, ethylene sulfate, vinylene sulfate, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1 -Nitrogen-containing compounds such as methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; carbonization of heptane, octane, nonane, decane, cycloheptane, etc. Fluorine-containing aromatic compounds such as hydrogen compounds, fluorobenzene, difluorobenzene, hexafluorobenzene, and benzotrifluoride; tris(trimethylsilyl)borate, tris(trimethoxysilyl)borate, tris(trimethylsilyl)phosphate, trisphosphate (Trimethoxysilyl), dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytriethoxysilane, dipropoxyaluminoxytriethoxysilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetrakis (trimethylsiloxy) ), silane compounds such as titanium tetrakis (triethylsiloxide), and the like. These may be used alone or in combination of two or more. By adding these auxiliary agents, it is possible to improve the capacity retention characteristics after high temperature storage and the cycle characteristics.

The amount of the other auxiliary compounded is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. Other auxiliaries are 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 auxiliaries are easily exhibited sufficiently, and it is easy to avoid a situation in which the characteristics of the battery such as the high load discharge characteristics are deteriorated. The amount of the other auxiliary compounded is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. ..

The non-aqueous electrolyte solution described above also includes those present inside the non-aqueous electrolyte battery described in the present invention. Specifically, by separately synthesizing the components of the non-aqueous electrolytic solution such as a lithium salt, a solvent, and an auxiliary agent, adjusting the non-aqueous electrolytic solution from the substantially isolated one, and using the method described below. Non-aqueous electrolyte solution obtained by injecting into a separately assembled battery If the non-aqueous electrolyte solution in the battery, or if the components of the non-aqueous electrolyte solution of the present invention are put in the battery individually, In the case of obtaining the same composition as the non-aqueous electrolyte solution of the present invention by mixing in, further, by generating a compound constituting the non-aqueous electrolyte solution of the present invention in the non-aqueous electrolyte battery, The case where the same composition as the aqueous electrolytic solution is obtained is also included.

<2. Non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode capable of inserting and extracting ions, and the non-aqueous electrolyte solution of the present invention.
<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery for the configuration other than the negative electrode and the non-aqueous electrolyte, and usually the non-aqueous electrolyte of the present invention is The positive electrode and the negative electrode are laminated via an impregnated porous film (separator), and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of cylindrical type, prismatic type, laminate type, coin type, large size and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolytic solution, the above-mentioned non-aqueous electrolytic solution of the present invention is used.
<2-3. Negative electrode>
The negative electrode has a negative electrode active material layer on the current collector, and the negative electrode active material will be described below.

The negative electrode active material is not particularly limited as long as it can electrochemically store and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. These may be used alone or in any combination of two or more.

<2-3-1. Carbonaceous material>
As the carbonaceous material used as the negative electrode active material,
(1) Natural graphite,
(2) A carbonaceous material obtained by heat-treating an artificial carbonaceous substance and an artificial graphite substance at least once in the range of 400°C to 3200°C.
(3) A carbonaceous material in which the negative electrode active material layer is made of at least two kinds of carbonaceous materials having different crystallinity and/or has an interface in which the carbonaceous materials having different crystallinity are in contact with each other.
(4) A carbonaceous material in which the negative electrode active material layer is made of at least two kinds of carbonaceous materials having different orientations and/or has an interface where the carbonaceous materials having different orientations are in contact with each other.
A material selected from the following is preferable because it has a good balance of initial irreversible capacity and high current density charge/discharge characteristics.
The carbonaceous materials (1) to (4) may be used alone or in any combination of two or more at any ratio.

Specific examples of the artificial carbonaceous material and artificial graphite material of the above (2) include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, Needle coke, pitch coke and carbon material partially graphitized thereof, furnace black, acetylene black, thermal decomposition products of organic matter such as pitch-based carbon fiber, carbonizable organic matter, and these carbides, or carbonizable organic matter Examples thereof include solutions dissolved in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and their carbides.

<2-3-2. Configuration, physical properties, and preparation method of carbonaceous negative electrode>
Regarding the properties of the carbonaceous material, the negative electrode containing the carbonaceous material, the electrode forming method, the current collector, and the non-aqueous electrolyte secondary battery, any one of the following (1) to (13) or It is desirable that multiple items be satisfied at the same time.
(1) X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction of the carbonaceous material by the Gakushin method is usually 0.335 to 0.340 nm, and particularly 0.335. It is preferably 0.338 nm, especially 0.335 to 0.337 nm. The crystallite size (Lc) determined by X-ray diffraction by Gakushin method is usually 1.0 nm or more, preferably 1.5 nm or more, and particularly preferably 2 nm or more.

(2) Volume-Based Average Particle Diameter The volume-based average particle diameter of the carbonaceous material is usually 1 μm or more, preferably 3 μm or more, as the volume-based average particle diameter (median diameter) obtained by the laser diffraction/scattering method. It is 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, further preferably 30 μm or less, particularly preferably 25 μm or less. If the volume-based average particle diameter is less than the above range, the irreversible capacity may increase, which may lead to a loss of the initial battery capacity. On the other hand, when the amount exceeds the above range, an uneven coating surface is likely to be formed when an electrode is formed by coating, which may be undesirable in the battery manufacturing process.

The volume-based average particle size is measured by dispersing carbon powder in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and using a laser diffraction/scattering particle size distribution. It is performed using a total (LA-700 manufactured by Horiba Ltd.). The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.
[Rhombohedral crystal ratio]
For the rhombohedral crystal ratio defined in the present invention, the following formula is used from the ratio of the rhombohedral crystal structure graphite layer (ABC stacking layer) and the hexagonal structure graphite layer (AB stacking layer) by X-ray wide angle diffraction (XRD). Can be asked.

Rhombohedral crystal ratio (%)=integrated intensity of ABC(101) peak of XRD÷
XRD AB(101) peak integrated intensity x 100
Here, the rhombohedral crystal ratio of the graphite particles of the present invention is usually 0% or more, preferably more than 0%, more preferably 3% or more, further preferably 5% or more, particularly preferably 12% or more, and It is usually 35% or less, preferably 27% or less, more preferably 24% or less, particularly preferably 20% or less. Here, the rhombohedral crystal ratio of 0% means that the XRD peak derived from the ABC stacking layer is not detected at all. In addition, “more than 0%” means that even a small amount of XRD peaks derived from the ABC stacking layer is detected.

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

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

The X-ray diffraction measurement conditions are as follows. In addition, "2θ" indicates a diffraction angle.
・Target: Cu (Kα ray) graphite monochromator ・Slit:
Solar slit 0.04 degrees Divergence slit 0.5 degrees Horizontal divergence mask 15mm
Anti-scatter slit 1 degree, measurement range and step angle/measurement time:
(101) plane: 41 degrees ≤ 2θ ≤ 47.5 degrees 0.3 degrees/60 seconds ・Background correction: Connect a line between 42.7 and 45.5 degrees with a straight line and subtract it as the background.
-Rhombohedral graphite particle layer peak: Refers to a peak near 43.4 degrees.
-Peak in hexagonal structure graphite particle layer: Refers to a peak near 44.5 degrees.

As a method for obtaining graphite particles having a rhombohedral crystal ratio in the above range, a method of manufacturing using a conventional technique can be adopted, and the method is not particularly limited, but the graphite particles are heat-treated at a temperature of 500° C. or higher. It is preferable to manufacture by this. It is also preferable to give mechanical effects such as compression, friction, shearing force, etc. to the graphite particles, including impact force as a main component and particle interaction. In addition, the rhombohedral crystal ratio can be adjusted by changing the strength of mechanical action, the treatment time, the presence or absence of repetition. As a specific device for adjusting the rhombohedral crystal ratio, it has a rotor in which a large number of blades are installed inside the casing, and the rotor rotates at high speed, thereby impacting the carbon material introduced inside. An apparatus for applying a mechanical action such as compression, friction, shearing force, etc. to perform surface treatment is preferable. In addition, it is preferable that the carbon material has a mechanism that repeatedly gives a mechanical action by circulating the carbon material, or a mechanism that does not have a circulation mechanism but has a mechanism for connecting a plurality of devices and processing. An example of a preferable apparatus is a hybridization system manufactured by Nara Machinery Co., Ltd.
Further, it is more preferable to apply heat treatment after applying the mechanical action.
Further, it is particularly preferable that after the mechanical action is applied, the carbon precursor is made into a composite and heat treatment is performed at a temperature of 700° C. or higher.

(3) Raman R value, Raman half-value width The Raman R value of the carbonaceous material is usually 0.01 or more, preferably 0.03 or more, and preferably 0.03 or more, as measured by an argon ion laser Raman spectrum method. One 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.
If the Raman R value is less than the above range, the crystallinity of the particle surface may become too high, and the number of sites where Li enters between layers may decrease with charge and discharge. That is, charge acceptability may decrease. Further, when the negative electrode is densified by pressing after applying it to the current collector, the crystals are likely to be oriented in the direction parallel to the electrode plate, which may cause deterioration of load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface may be lowered, the reactivity with the non-aqueous electrolyte may be increased, and the efficiency may be lowered and the gas generation may be increased.

Further, the Raman half-value width near 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. It is preferably 60 cm ⁻¹ or less, more preferably 40 cm ⁻¹ or less.
When the Raman full width at half maximum is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters the layers may decrease with charge and discharge. That is, charge acceptability may decrease. Further, when the negative electrode is densified by pressing after applying it to the current collector, the crystals are likely to be oriented in the direction parallel to the electrode plate, which may cause deterioration of load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface may be lowered, the reactivity with the non-aqueous electrolyte may be increased, and the efficiency may be lowered and the gas generation may be increased.

The Raman spectrum is measured by using a Raman spectroscope (Raman spectroscope manufactured by JASCO Corporation) to spontaneously drop and fill the sample into the measurement cell, while irradiating the sample surface in the cell with an argon ion laser beam, It is performed by rotating the cell in a plane perpendicular to the laser beam. 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 in the present invention. Further, the full width at half maximum of the peak PA around 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half width of the carbonaceous material in the present invention.

The Raman measurement conditions are as follows.
・Argon ion laser wavelength: 514.5 nm
・Laser power on sample: 15-25mW
・Resolution: 10-20 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 As for the BET specific surface area of the carbonaceous material, the value of the specific surface area measured by the BET method is usually 0.1 m ² ·g ⁻¹ or more, and 0.7 m ² ·g ⁻¹ or more. 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 and 25 m ² ·g ⁻¹ or less is preferable. It is preferably 15 m ² ·g ⁻¹ or less, more preferably 10 m ² ·g ⁻¹ or less.
When the value of the BET specific surface area is less than this range, the acceptability of lithium during charging when used as a negative electrode material is likely to be poor, lithium is likely to be deposited on the electrode surface, and the stability may be reduced. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte solution increases when it is used as a negative electrode material, and gas generation tends to increase, and it may be difficult to obtain a preferable battery.

The specific surface area is measured by the BET method using a surface area meter (Full automatic surface area measuring device manufactured by Okura Riken Co., Ltd.), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then nitrogen of atmospheric pressure is measured. A nitrogen adsorption BET one-point method by a gas flow method is performed by using a nitrogen-helium mixed gas that is accurately adjusted so that the value of the relative pressure is 0.3. The specific surface area obtained by the measurement is defined as the BET specific surface area of the carbonaceous material in the present invention.

(5) Circularity When the circularity is measured as the degree of spherical shape of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity=(perimeter of equivalent circle having the same area as the particle projection shape)/(actual perimeter of particle projection shape)”, and theoretically when the circularity is 1. 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 closer to 1, and is 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 particularly preferable.

The high current density charge/discharge characteristics improve as the circularity increases. Therefore, if the circularity is less than the above range, the filling property of the negative electrode active material may be deteriorated, the resistance between particles may be increased, and the short-time high current density charge/discharge characteristics may be deteriorated.
The circularity is measured using a flow-type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of the sample was dispersed in a 0.2 mass% aqueous solution of polyoxyethylene (20) sorbitan monolaurate (about 50 mL) which is a surfactant, and after irradiating with an ultrasonic wave of 28 kHz at an output of 60 W for 1 minute. The detection range is specified to 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the carbonaceous material in the present invention.

The method of improving the circularity is not particularly limited, but a spherical shape obtained by subjecting to a spherical shape is preferable because the shape of interparticle voids is adjusted when the electrode body is formed. Examples of the spheroidizing treatment include a method of mechanically approaching a spherical shape by applying a shearing force or a compressing force, a mechanical/physical treatment method of granulating a plurality of fine particles with a binder or the adhesive force of the particles themselves, etc. Is mentioned.

(6) Tap Density The tap density of the carbonaceous material is usually 0.1 g·cm ⁻³ or higher, preferably 0.5 g·cm ⁻³ or higher, more preferably 0.7 g·cm ⁻³ or higher, and 1 g· cm ⁻³ or more is particularly preferable, 2 g·cm ⁻³ or less is preferable, 1.8 g·cm ⁻³ or less is further preferable, and 1.6 g·cm ⁻³ or less is particularly preferable.

When the tap density is less than the above range, the packing density is difficult to increase when used as a negative electrode, and it may not be possible to obtain a high capacity battery. On the other hand, when the amount exceeds the above range, voids between particles in the electrode become too small, it becomes difficult to secure conductivity between particles, and it may be difficult to obtain preferable battery characteristics.
The tap density is measured by passing it through a sieve with an opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ to fill the sample to the upper end surface of the cell, and then measuring the powder density (for example, manufactured by Seishin Enterprise Co., Ltd.). Tapping is performed 1000 times with 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 in the present invention.

(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. If the orientation ratio is less than the above range, the high density charge/discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressing the sample. A molded body obtained by filling 0.47 g of a sample in a molding machine having a diameter of 17 mm and compressing it with 58.8 MN·m ⁻² was set with clay so as to be flush with the surface of the sample holder for measurement. X-ray diffraction is measured. A ratio represented by (110) diffraction peak intensity/(004) diffraction peak intensity is calculated from the peak intensity of (110) diffraction and (004) diffraction of the obtained carbon. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material in the present invention.

The X-ray diffraction measurement conditions are as follows. In addition, "2θ" indicates a diffraction angle.
・Target: Cu (Kα ray) graphite monochromator ・Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree, measurement range and step angle/measurement time:
(110) plane: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree/60 seconds (004) plane: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree/60 seconds

(8) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more, and is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the aspect ratio exceeds the above range, streaks may not occur when a plate is formed, a uniform coated surface may not be obtained, and high current density charge/discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.
The aspect ratio is measured by magnifying and observing particles of the carbonaceous material with a scanning electron microscope. A carbonaceous material when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed on the end surface of a metal having a thickness of 50 microns or less and rotating and tilting the stage on which the sample is fixed for each. 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 obtained. The aspect ratio (A/B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material in the present invention.

(9) Production of Electrode For production of the electrode, any known method can be used unless the effect of the present invention is significantly limited. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. You can

The thickness of the negative electrode active material layer per one surface immediately before the step of injecting the non-aqueous electrolyte solution of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less. , 120 μm or less is preferable, and 100 μm or less is more preferable. This is because if the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution is unlikely to penetrate into the vicinity of the interface of the current collector, and the high current density charge/discharge characteristics may deteriorate. Also, if it is less than this range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-formed into a sheet electrode, or compression-molded into a pellet electrode.

(10) Current Collector As a current collector for holding the negative electrode active material, any known current collector can be used. Examples of the current collector of the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, and copper is particularly preferable from the viewpoint of workability and cost.
When the current collector is made of a metal material, examples of the shape of the current collector include a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.
Further, when the thickness of the copper foil is thinner than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

(10-1) Thickness of Current Collector Although the thickness of the current collector is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less and 100 μm or less. Is preferable, and 50 μm or less is more preferable. If the thickness of the metal coating is less than 1 μm, the strength may be reduced and the coating may be difficult. If it is thicker than 100 μm, the shape of the electrode such as winding may be deformed. The current collector may have a mesh shape.

(11) Thickness Ratio of Current Collector and Negative Electrode Active Material Layer The thickness ratio of the current collector and the negative electrode active material layer is not particularly limited. The value of (material layer thickness)/(current collector thickness)” is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, and preferably 0.1 or more and 0.4 or more. More preferably, 1 or more is particularly preferable.
When the thickness ratio of the current collector and the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge/discharge. On the other hand, if it is less than the above range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease.

(12) Electrode Density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g·cm ⁻³ or more, and 1. 2 g·cm ⁻³ or more is more preferable, 1.3 g·cm ⁻³ or more is particularly preferable, 2.2 g·cm ⁻³ or less is preferable, 2.1 g·cm ⁻³ or less is more preferable, 2.0 g · ^{cm -3} more preferably less, 1.9 g · ^{cm -3} or less are particularly preferred. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous system near the current collector/negative electrode active material interface. High current density charge/discharge characteristics may be deteriorated due to a decrease in electrolyte permeability. On the other hand, if it is less than the above range, the conductivity between the negative electrode active materials may be lowered, the battery resistance may be increased, and the capacity per unit volume may be lowered.

(13) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in the production of the electrode.
Specific examples thereof include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose and nitrocellulose; SBR (styrene/butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR( Acrylonitrile/butadiene rubber), rubber-like polymers such as ethylene/propylene rubber; styrene/butadiene/styrene block copolymers or hydrogenated products thereof; EPDM (ethylene/propylene/diene terpolymer), styrene/ethylene/ Thermoplastic elastomer polymer such as butadiene/styrene copolymer, styrene/isoprene/styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymer Polymers, soft resin-like polymers such as propylene/α-olefin copolymers; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene/ethylene copolymers and other fluoropolymers; alkali Examples thereof include polymer compositions having ion conductivity of metal ions (particularly lithium ions). These may be used alone or in any combination of two or more at any ratio.

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

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and form a slurry using a latex such as SBR. These solvents may be used alone or in any combination of two or more at any ratio.
The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is particularly preferable. When the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder in which the amount of the binder does not contribute to the battery capacity increases, and the battery capacity may decrease. On the other hand, if it is less than the above range, the strength of the negative electrode may be lowered.

In particular, when a rubber-like polymer represented by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, The content is more preferably 0.6% by mass or more, usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
When a fluorine-containing polymer represented by polyvinylidene fluoride is contained as a main component, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more. It is preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 8% by mass or less.

Thickeners are commonly used to adjust the viscosity of slurries. The thickener is not particularly limited, and specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. These may be used alone or in any combination of two or more at any ratio.

When a thickener is further used, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, It is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is less than the above range, the coatability may be significantly reduced. On the other hand, when the amount exceeds the above range, the ratio of the negative electrode active material in the negative electrode active material layer decreases, which may cause a problem of decreasing the battery capacity and increase the resistance between the negative electrode active materials.

<2-3-3. Composition, physical properties, and preparation method of metal compound-based material, and negative electrode using metal compound-based material>
The metal compound-based material used as the negative electrode active material may be a single metal or an alloy forming a lithium alloy, or an oxide, a carbide, a nitride, a silicide, a sulfide, if capable of inserting and extracting lithium, There is no particular limitation on the compound such as phosphide. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Of these, a simple metal or alloy forming a lithium alloy is preferable, a material containing a metal/metalloid element of group 13 or group 14 (that is, excluding carbon) is more preferable, and further, a silicon (Si ), tin (Sn), or lead (Pb) (hereinafter, these three types of elements may be referred to as “specific metal elements”), elemental metals or alloys containing these atoms, or those metals (specific metal elements) Are preferable, and elemental metals, alloys and compounds of silicon, and elemental metals, alloys and compounds of tin are particularly preferable. These may be used alone or in any combination of two or more at any ratio.

Examples of the negative electrode active material having at least one atom selected from the specific metal elements include a simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, and one or more kinds. Of the above-mentioned specific metal element and one or more other metal elements, and a compound containing one or more specific metal elements, or an oxide/carbide/nitride of the compound -Compound compounds such as silicide, sulfide, and phosphide are included. By using these metal simple substances, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

Moreover, the compound which these complex compounds combined with several kinds of elements, such as a simple metal, an alloy, or a nonmetallic element, can also be mentioned as an example. More specifically, for example, for silicon or tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. Further, for example, in the case of tin, a complex compound containing 5 to 6 elements in combination with a metal other than tin and silicon that acts as a negative electrode, a metal that does not work as a negative electrode, and a non-metal element can also be used. ..

Among these negative electrode active materials, since the capacity per unit mass is large when made into a battery, any one kind of a specific metal element metal simple substance, two or more kinds of specific metal element alloys, and a specific metal element oxidation Materials, carbides, nitrides and the like are preferable, and particularly, simple metals of silicon and tin, and alloys, oxides, carbides, nitrides thereof, etc. are preferable from the viewpoint of capacity per unit mass and environmental load.

Further, the following compounds containing at least one of silicon and tin are also preferable because they have excellent cycle characteristics, although the capacity per unit mass is inferior to that of using a simple metal or an alloy.
-The element ratio of at least one of silicon and tin to oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably "Oxide of at least one of silicon and tin" of 1.3 or less, more preferably 1.1 or less.
The element ratio of at least one of silicon and tin to nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably "Nitride of at least one of silicon and tin" of 1.3 or less, more preferably 1.1 or less.
-The element ratio of at least one of silicon and tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably "Carbides of at least one of silicon and tin" of 1.3 or less, more preferably 1.1 or less.
Any one of the above-mentioned negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured by any known method. Specifically, as a method for producing a negative electrode, for example, a method in which a negative electrode active material to which a binder, a conductive material, or the like is added as described above is roll-formed into a sheet electrode, or compression-molded into a pellet electrode. The above-mentioned negative electrode is usually formed on the current collector for the negative electrode (hereinafter may be referred to as “negative electrode current collector”) by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method. A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, a binder, a thickener, a conductive material, a solvent, etc. are added to the above-mentioned negative electrode active material to form a slurry, which is applied to a negative electrode current collector, dried, and then pressed to increase the density. A negative electrode active material layer is formed on the negative electrode current collector.

Examples of the material of the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, stainless steel and the like. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.
The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may decrease too much, and if it is too thin, handling may become difficult.

In order to improve the binding effect with the negative electrode active material layer formed on the surface, it is preferable that the surface of these negative electrode current collectors be roughened in advance. As the surface roughening method, blasting, rolling with a rough surface roll, a polishing cloth paper with abrasive particles fixed, a grindstone, an emery buff, a machine for polishing the current collector surface with a wire brush equipped with a steel wire, etc. Polishing method, electrolytic polishing method, chemical polishing method and the like.

Further, in order to reduce the mass of the negative electrode current collector and improve the energy density per mass of the battery, a perforated type negative electrode current collector such as expanded metal or punching metal can be used. The mass of the negative electrode current collector of this type can be changed to white by changing the aperture ratio. Further, when the negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the rivet effect through the hole makes the negative electrode active material layer less likely to peel off. However, when the aperture ratio is too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, which may rather reduce the adhesive strength.

The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener and the like to the negative electrode material. Note that the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.
The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, particularly preferably 95% by mass or less. When the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and when the content is too large, the content of the binder or the like is relatively insufficient, which is obtained. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may be set within the above range.

Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used alone or in any combination of two or more at any ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material also acts as an active material. The content of the conductive material in the negative electrode material is usually 3% by mass or more, particularly 5% by mass or more, and usually 30% by mass or less, particularly 25% by mass or less. This is because if the content of the conductive material is too small, the conductivity tends to be insufficient, and if the content is too large, the content of the negative electrode active material or the like is relatively insufficient, and thus the battery capacity or strength tends to decrease. .. When two or more conductive materials are used together, the total amount of the conductive materials may be set within the above range.

As the binder used for the negative electrode, any material can be used as long as it is a material that is safe for the solvent and the electrolytic solution used during the production of the electrode. For example, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene/butadiene rubber/isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene/methacrylic acid copolymer and the like can be mentioned. These may be used alone or in any combination of two or more at any ratio. The content of the binder is usually 0.5 parts by mass or more, particularly 1 part by mass or more, and usually 10 parts by mass or less, particularly 8 parts by mass or less, relative to 100 parts by mass of the negative electrode material. If the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient, and if the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and the battery capacity and conductivity tend to be insufficient. This is because When two or more binders are used in combination, the total amount of the binders may be set within the above range.

Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch and casein. These may be used alone or in any combination of two or more at any ratio. The thickener may be used as necessary, but when used, the content of the thickener in the negative electrode active material layer is usually 0.5% by mass or more and 5% by mass or less. Is preferred.

A slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive material, a binder, and a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. .. Water is usually used as the aqueous solvent, but a solvent other than water, such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone, is used together in a proportion of about 30% by mass or less with respect to water. You can also As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N,N-dimethylformamide and N,N-dimethylacetamide, aromatic carbons such as anisole, toluene and xylene are used. Examples thereof include hydrogens, butanols and alcohols such as cyclohexanol. Among them, cyclic amides such as N-methylpyrrolidone and linear amides such as N,N-dimethylformamide and N,N-dimethylacetamide are preferable. .. Any one of these may be used alone, or two or more of them may be used in any combination and ratio.

The viscosity of the slurry is not particularly limited as long as it can be applied onto the current collector. The amount of the solvent used and the like may be changed at the time of preparing the slurry so that the viscosity can be applied, and the slurry may be appropriately prepared.
The obtained negative electrode current collector is coated with the slurry, dried, and then pressed to form a negative electrode active material layer. The coating method is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and known methods such as natural drying, heat drying, and vacuum drying can be used.

The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material existing on the current collector is preferably 1 g·cm ⁻³ or more, and 1.2 g·cm. ^-3 or more is more preferable, 1.3 g·cm ⁻³ or more is particularly preferable, 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.
If the density of the active material existing on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector/active material interface is removed. In some cases, deterioration of high current density charge/discharge characteristics may be caused due to a decrease in permeability. On the other hand, when the content is less than the above range, the conductivity between the active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

<2-3-4. Lithium-containing metal composite oxide material, and constitution, physical properties, and preparation method of negative electrode using the lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can store and release lithium, but a lithium-containing composite metal oxide material containing titanium is preferable, and a lithium-titanium composite oxide is preferable. (Hereinafter, abbreviated as “lithium titanium composite oxide”) is particularly preferable. That is, it is particularly preferable to use the lithium titanium composite oxide having a spinel structure in the negative electrode active material for a non-aqueous electrolyte secondary battery, since the output resistance is greatly reduced.

Further, lithium or titanium of the lithium-titanium composite oxide is at least selected from the group consisting of other metal elements, for example, Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. Those substituted with one kind of element are also preferable.
The metal oxide is a lithium titanium composite oxide represented by the general formula (3), and in the general formula (3), 0.7≦x≦1.5, 1.5≦y≦2.3, It is preferable that 0≦z≦1.6 because the structure during lithium ion doping/dedoping is stable.

LixTiyMzO ₄ (3)
[In the general formula (3), 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 (3),
(A) 1.2≦x≦1.4, 1.5≦y≦1.7, z=0
(B) 0.9≦x≦1.1, 1.9≦y≦2.1, z=0
(C) 0.7≦x≦0.9, 2.1≦y≦2.3, z=0
The structure (1) is particularly preferable because it has a good balance of battery performance.

Particularly preferable typical 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). It is ₄ . Regarding the structure of Z≠0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.
The lithium titanium composite oxide as the negative electrode active material in the present invention satisfies at least one of the following characteristics (1) to (13) such as physical properties and shape, in addition to the above requirements. Is preferable, and it is particularly preferable to satisfy two or more types at the same time.

(1) BET Specific Surface Area As for the BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material, the value of the specific surface area measured by the BET method is preferably 0.5 m ² ·g ⁻¹ or more, 7 m ² ·g ⁻¹ or more is more preferable, 1.0 m ² ·g ⁻¹ or more is further preferable, 1.5 m ² ·g ⁻¹ or more is particularly preferable, and 200 m ² ·g ⁻¹ or less is preferable, 100 m more preferably ² · ^{g -1} or less, more preferably ^{50 m} 2 · ^{g -1} or less, particularly preferably ^{25 m} 2 · ^{g -1} or less.

If the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolyte solution used as the negative electrode material may decrease, and the output resistance may increase. On the other hand, when it exceeds the above range, the surface and end face portions of the crystal of the metal oxide containing titanium increase, and due to this, strain of the crystal also occurs, so that the irreversible capacity cannot be ignored, which is preferable. It may be difficult to obtain a battery.

The specific surface area is measured by the BET method using a surface area meter (Okura Riken's fully automatic surface area measuring device), and the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow. A nitrogen adsorption BET one-point method by a gas flow method is performed using a nitrogen-helium mixed gas that is precisely adjusted so that the value of the relative pressure is 0.3. The specific surface area obtained 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 Diameter The volume-based average particle diameter (secondary particle diameter when primary particles aggregate to form secondary particles) of the lithium-titanium composite oxide is determined by laser diffraction/scattering method. It is defined by the obtained volume-based average particle diameter (median diameter).
The volume-based average particle diameter of the lithium titanium composite oxide is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more, and usually 50 μm or less, preferably 40 μm or less, 30 μm The following is more preferable, and 25 μm or less is particularly preferable.

The volume-based average particle size is measured by dispersing a carbon powder in a 0.2 mass% aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and using a laser diffraction/scattering particle size distribution meter. (LA-700 manufactured by HORIBA, Ltd.) is used. The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material in the present invention.
If the volume average particle diameter of the lithium-titanium composite oxide is less than the above range, a large amount of binder is required at the time of producing the electrode, and as a result, the battery capacity may decrease. On the other hand, if it exceeds the above range, a non-uniform coating surface is likely to be formed when the electrode plate is formed, which may be undesirable in the battery manufacturing process.

(3) Average Primary Particle Diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the lithium titanium composite oxide is usually 0.01 μm or more, and 0.05 μm or more. It is preferably 0.1 μm or more, more preferably 0.2 μm or more, usually 2 μm or less, preferably 1.6 μm or less, more preferably 1.3 μm or less, particularly preferably 1 μm or less. When the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that the battery having output characteristics or the like There is a high possibility that performance will decrease. On the other hand, when the amount is less than the above range, the performance of the secondary battery may be deteriorated, such that the crystal is usually undeveloped and the reversibility of charge and discharge is deteriorated.
The primary particle size is measured by observation with a scanning electron microscope (SEM). Specifically, in a photograph at a magnification at which particles can be confirmed, for example, at a magnification of 10,000 to 100,000, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is calculated for any 50 primary particles. It is calculated by taking the average value.

(4) Shape The shape of the particles of the lithium-titanium composite oxide may be lumps, polyhedra, spheres, ellipsoids, plates, needles, pillars, etc., which are conventionally used. Among them, primary particles are aggregated. It is preferable that the secondary particles are formed into secondary particles, and the secondary particles have a spherical shape or an elliptic spherical shape.
Usually, in an electrochemical device, the active material in the electrode expands and contracts as it is charged and discharged, and the stress is likely to cause the active material to be broken or the conductive path to be broken. Therefore, the primary particles are aggregated to form the secondary particles rather than the single-particle active material having only the primary particles, so that the stress of expansion and contraction is alleviated and deterioration is prevented.
Further, spherical or elliptic spherical particles have less orientation during molding of the electrode than particles having plate-like equiaxed orientation, so that expansion/contraction of the electrode during charge/discharge is small, and the electrode is produced. Also in mixing with the conductive material at the time of performing, it is easy to mix uniformly, which is preferable.

(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 further preferable, and 2 g·cm ⁻³ or less is particularly preferable. When the tap density is less than the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between particles decreases, so that the resistance between particles may increase and the output resistance may increase. On the other hand, when the amount exceeds the above range, the voids between the particles in the electrode become too small and the flow path of the non-aqueous electrolyte solution decreases, which may increase the output resistance.

The tap density is measured by passing through a sieve with a mesh opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ to fill the sample up to the upper end surface of the cell, and then measuring the powder density (for example, manufactured by Seishin Enterprise Co., Ltd.). Tapping is performed 1000 times with a stroke length of 10 mm, 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 spherical degree of the lithium titanium composite oxide, it is preferably within the following range. The circularity is defined as “circularity=(perimeter of equivalent circle having the same area as the particle projection shape)/(actual perimeter of particle projection shape)”, and when the circularity is 1, a theoretical sphere Becomes
The circularity of the lithium titanium composite oxide is preferably as close to 1 as possible, usually 0.10 or higher, preferably 0.80 or higher, more preferably 0.85 or higher, and particularly preferably 0.90 or higher. The higher current density charge/discharge characteristics improve as the circularity increases. Therefore, if the circularity is less than the above range, the filling property of the negative electrode active material may be deteriorated, the resistance between particles may be increased, and the short-time high current density charge/discharge characteristics may be deteriorated.

The circularity is measured using a flow-type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of the sample was dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and after irradiating with an ultrasonic wave of 28 kHz at an output of 60 W for 1 minute. The detection range is specified to 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the lithium titanium composite oxide in the present invention.

(7) Aspect Ratio The aspect ratio of the lithium titanium composite oxide is usually 1 or more and usually 5 or less, preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking may not occur when a plate is formed, a uniform coated surface may not be obtained, and the high current density charge/discharge characteristics may deteriorate 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 aspect ratio is measured by magnifying and observing particles of lithium titanium composite oxide with a scanning electron microscope. Select arbitrary 50 particles fixed to the end face of metal having a thickness of 50 μm or less, and rotate and tilt the stage on which the sample is fixed for each, and the particle becomes the longest in three-dimensional observation. The diameter A and the shortest diameter B orthogonal to the diameter A are measured, and the average value of A/B is obtained. The aspect ratio (A/B) obtained by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

(8) Manufacturing Method of Negative Electrode Active Material The manufacturing method of the lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. Conventional methods are used.
For example, a method of uniformly mixing a titanium source material such as titanium oxide, a source material of another element and a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ if necessary, and firing at high temperature to obtain an active material. Is mentioned.

In particular, various methods can be considered for producing a spherical or elliptic spherical active material. As an example,
Titanium raw materials 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 the pH is adjusted with stirring to prepare and recover a spherical precursor, After drying this as needed, a method of adding an Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and firing at high temperature to obtain an active material can be mentioned.

Further, as another example, titanium raw materials 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 molded by a spray dryer or the like to obtain spherical particles. Alternatively, a method of obtaining an active material by using an ellipsoidal precursor as a precursor, adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ to the precursor and firing the precursor at a high temperature is mentioned.
As still another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and, if necessary, a raw material of another element are dissolved or pulverized in a solvent such as water. A method is available in which the active material is dispersed and dried and molded with a spray dryer or the like to give a spherical or ellipsoidal precursor, which is then baked at a high temperature to obtain an active material.

Further, 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. , Ag can be present in the titanium-containing metal oxide structure and/or in contact with the titanium-containing oxide. By containing these elements, the operating voltage and capacity of the battery can be controlled.

(9) Production of Electrode Any known method can be used for production of the electrode. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. You can
The thickness of the negative electrode active material layer per one surface immediately before the step of injecting the non-aqueous electrolyte solution of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm. Or less, more preferably 100 μm or less.
When it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, so that the high current density charge/discharge characteristics may deteriorate. If it is less than this range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-formed into a sheet electrode, or may be compression-formed into a pellet electrode.

(10) Current Collector As a current collector for holding the negative electrode active material, any known current collector can be used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among them, copper is particularly preferable from the viewpoint of workability and cost.
When the current collector is made of a metal material, examples of the shape of the current collector include a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal. Among them, a metal foil film containing at least one of copper (Cu) and aluminum (Al) is preferable, a copper foil and an aluminum foil are more preferable, and a rolled copper foil by a rolling method and an electrolytic method are more preferable. There are electrolytic copper foils, both of which can be used as current collectors.

Further, when the thickness of the copper foil is thinner than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used. Further, since the aluminum foil has a low specific gravity, it can reduce the mass of the battery when used as a current collector, and can be preferably used.
Since a current collector made of a copper foil produced by a rolling method has copper crystals arranged in the rolling direction, it is hard to crack even if the negative electrode is densely rolled or sharply rounded, and is suitable for a small cylindrical battery. be able to.

Electrolytic copper foil is, for example, by immersing a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and by passing an electric current while rotating this, copper is deposited on the surface of the drum and peeled off. It is obtained by doing. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One or both surfaces of the copper foil may be roughened or surface-treated (for example, a chromate treatment with a thickness of about several nm to 1 μm, a base treatment with Ti or the like).
Further, the collector substrate is desired to have the following physical properties.

(10-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate specified by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more. Further, it is usually 1.5 μm or less, preferably 1.3 μm or less, and more preferably 1.0 μm or less.
This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge/discharge cycle characteristics can be expected. Also, the area of the interface with the active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) of more than 1.5 μm are generally available as foils of practical thickness for batteries. Since it is difficult, a film having a thickness of 1.5 μm or less is usually used.

(10-2) Tensile Strength Tensile strength is the maximum tensile force required to break the test piece divided by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by an apparatus and method similar to those described in JISZ2241 (Metallic material tensile test method).
The tensile strength of the current collector substrate is not particularly limited, it is generally 50 N · ^{mm -2} or more, preferably 100 N · ^{mm -2} or more, more preferably 150 N · ^{mm -2} or more. The higher the tensile strength is, the more preferable it is, but from the viewpoint of industrial availability, the tensile strength is usually preferably 1000 N·mm ⁻² or less.
If the current collector substrate has high tensile strength, cracks in the current collector substrate due to expansion/contraction of the active material thin film due to charging/discharging can be suppressed, and good cycle characteristics can be obtained.

(10-3) 0.2% proof stress 0.2% proof stress is the magnitude of load required to give 0.2% plastic (permanent) strain, and is removed after applying a load of this magnitude. It means that even if loaded, it is deformed by 0.2%. The 0.2% proof stress is measured by the same device and method as the tensile strength.
0.2% proof stress of the current collector substrate is not particularly limited, normally 30 N · ^{mm -2} or more, preferably 100 N · ^{mm -2} or more, particularly preferably 150 N · ^{mm -2} or more. The higher the 0.2% proof stress is, the more preferable it is, but from the viewpoint of industrial availability, it is usually desirable that the yield strength be 900 N·mm ⁻² or less.
If the current collector substrate has a high 0.2% proof stress, it is possible to suppress plastic deformation of the current collector substrate due to expansion/contraction of the active material thin film due to charging/discharging, and obtain good cycle characteristics. Because you can.

(10-4) Thickness of Current Collector Although the thickness of the current collector is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less and 100 μm or less. Is preferable, and 50 μm or less is more preferable.
If the thickness of the metal coating is less than 1 μm, the strength may be reduced and the coating may be difficult. If it is thicker than 100 μm, the shape of the electrode such as winding may be deformed.
The metal thin film may have a mesh shape.

(11) Ratio of Thickness of Current Collector and Active Material Layer Although the ratio of thickness of the current collector and active material layer is not particularly limited, “(the thickness of the active material layer on one surface immediately before the non-aqueous electrolyte solution injection) The value of (thickness)/(thickness of current collector)” is usually 150 or less, preferably 20 or less, more preferably 10 or less, and usually 0.1 or more, preferably 0.4 or more. 1 or more is more preferable.
If the thickness ratio of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge/discharge. On the other hand, if it is less than the above range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease.

(12) Electrode Density The electrode structure of the negative electrode active material when formed into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g·cm ⁻³ or more, and 1.2 g · ^{cm -3} or more, and more preferably 1.3 g · ^{cm -3} or more, particularly preferably 1.5 g · ^{cm -3} or more, preferably 3 g · ^{cm -3} or less, 2.5 g · cm ^{- 3} or less is more preferable, 2.2 g·cm ⁻³ or less is further preferable, and 2 g·cm ⁻³ or less is particularly preferable.
When the density of the active material existing on the current collector exceeds the above range, the binding between the current collector and the negative electrode active material is weakened, and the electrode and the active material may be separated from each other. On the other hand, if it is less than the above range, the conductivity between the negative electrode active materials may be lowered, and the battery resistance may be increased.

(13) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in the production of the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethylmethacrylate, polyimide, aromatic polyamide, cellulose and nitrocellulose; SBR (styrene/butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber-like polymers such as NBR (acrylonitrile-butadiene rubber) and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and hydrogenated products thereof; EPDM (ethylene-propylene-diene terpolymer), styrene- Thermoplastic elastomeric polymers such as ethylene/butadiene/styrene copolymers, styrene/isoprene/styrene block copolymers and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate Soft resin-like polymers such as copolymers and propylene/α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride and polytetrafluoroethylene/ethylene copolymers A polymer composition having ion conductivity of alkali metal ions (particularly lithium ions) and the like. These may be used alone or in any combination of two or more at any ratio.

As the solvent for forming the slurry, the negative electrode active material, the binder, the thickener and the conductive material used as necessary, if the solvent can dissolve or disperse, the type is not particularly limited. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N. , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamerylphosphamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. Particularly when an aqueous solvent is used, a dispersant or the like is added to the above-mentioned thickener, and a latex such as SBR is used to form a slurry. These may be used alone or in any combination of two or more in any ratio.

The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 20% by mass or less, 15% by mass. % Or less is 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 negative electrode active material exceeds the above range, the binder ratio in which the binder amount does not contribute to the battery capacity increases, and the battery capacity may decrease. On the other hand, when the amount is less than the above range, the strength of the negative electrode may be deteriorated, which may not be preferable in the battery manufacturing process.

In particular, when a rubber-like polymer represented by SBR is contained as a main component, the ratio of the binder to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0.1% by mass or more. 6 mass% or more is more preferable, it is usually 5 mass% or less, 3 mass% or less is preferable, and 2 mass% or less is more preferable.
Further, when the main component contains a fluoropolymer represented by polyvinylidene fluoride, the ratio to the active material is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, It is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

Thickeners are commonly used to adjust the viscosity of slurries. The thickener is not particularly limited, and specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. These may be used alone or in any combination of two or more at any ratio.

When using a thickener, the ratio of the thickener to the negative electrode active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and It is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is less than the above range, the coatability may be significantly reduced. On the other hand, when the amount exceeds the above range, the ratio of the active material in the negative electrode active material layer decreases, which may cause a problem of decreasing the battery capacity and increase the resistance between the negative electrode active materials.

<2-4. Positive electrode>
The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material will be described below.
<2-4-1. Positive electrode active material>
The positive electrode active material used for the positive electrode will be described below.

(1) Composition The positive electrode active material is not particularly limited as long as it can occlude and release lithium ions electrochemically. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

The transition metal of the lithium-transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof are lithium-cobalt composite oxides such as LiCoO ₂ , LiMnO ₂ , LiMn. Examples thereof include lithium-manganese composite oxides such as ₂ O ₄ and Li ₂ MnO ₄ , lithium-nickel composite oxides such as LiNiO ₂ . In addition, some of the transition metal atoms that are the main constituents of these lithium-transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si. Those substituted with other metals such as, and the like, as specific examples, lithium-cobalt-nickel composite oxide,
Examples thereof include lithium/cobalt/manganese composite oxide, lithium/nickel/manganese composite oxide, and lithium/nickel/cobalt/manganese composite oxide.

Specific examples of the substituted ones are, for example, Li _1+a Ni _0.5 Mn _0.5 O ₂ , Li _1+a Ni _0.8 Co _0.2 O ₂ , Li _1+a Ni _0.85 Co _0.10 Al _{0. 05} O ₂ , Li _1+a Ni _0.33 Co _0.33 Mn _0.33 O ₂ , Li _1+a Ni _0.45 Co _0.45 Mn _0.1 O ₂ , Li _1+a Mn _1.8 Al _0.2 O ₄ , Li _1+a Mn _1.5 Ni _0.5 O ₄ , xLi ₂ MnO _{3 .} (1-x)Li _1+a MO ₂ (M=transition metal) and the like (a=0<a≦3.0).

The lithium-containing transition metal phosphate compound is LixMPO ₄ (M=one element selected from the group consisting of Group 4 to Group 11 transition metals in the 4th period of the periodic table, x is 0<x<1.2). And the transition metal (M) is at least one selected from the group consisting of V, Ti, Cr, Mg, Zn, Ca, Cd, Sr, Ba, Co, Ni, Fe, Mn and Cu. Is more preferable, and at least one element selected from the group consisting of Co, Ni, Fe, and Mn is more preferable. For _{example, LiFePO 4, Li 3 Fe 2} (PO 4) 3, LiFeP 2 O 7 , etc. of phosphorus Santetsurui, cobalt phosphate such as LiCoPO _4, manganese phosphate such as LiMnPO _4, phosphoric acids such as LiNiPO ₄ Nickel, some of the transition metal atoms that are the main constituents of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Examples include those substituted with other metals such as Nb and Si. Among these, particularly lithium-manganese composite oxides such as LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ MnO ₄ , and iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ and LiFeP ₂ O _7. However, metal elution at a high temperature and in a charged state does not easily occur, and it is inexpensive, and therefore, it is preferably used.

In addition, the above-mentioned "having LixMPO ₄ as a basic composition" includes not only a composition represented by the composition formula but also a composition in which a part of the site such as Fe in the crystal structure is replaced with another element. Means that. Further, it is meant to include not only the stoichiometric composition but also the non-stoichiometric composition in which some elements are defective. Other elements to be replaced are preferably elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr and Si. When other element substitution is performed, the content is preferably 0.1 mol% or more and 5 mol% or less, and more preferably 0.2 mol% or more and 2.5 mol% or less.
The positive electrode active material may be used alone or in combination of two or more kinds.

(2) Surface coating It is also possible to use a material having a composition different from that of the constituent material of the positive electrode active material (hereinafter referred to as "surface-adhered material" as appropriate) on the surface of the positive electrode active material. .. Examples of surface-adhering substances include 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, Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

These surface-adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material and then dried, and the surface-adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. After that, it can be attached to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the precursor of the positive electrode active material and simultaneously firing.
The mass of the surface-adhering substance adhering to the surface of the positive electrode active material is usually 0.1 ppm or more, preferably 1 ppm or more, more preferably 10 ppm or more, and usually 20% with respect to the mass of the positive electrode active material. It is below, preferably 10% or less, more preferably 5% or less.
The surface-adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, if the adhesion amount is less than the above range, the effect is not sufficiently exhibited, and if it exceeds the above range, the resistance may increase due to the obstruction of the entry and exit of lithium ions, so the above range is preferable.

(3) Shape The shape of the positive electrode active material particles may be lumps, polyhedra, spheres, ellipsoids, plates, needles, pillars, etc., which are conventionally used. It is preferable that secondary particles are formed and the shape of the secondary particles is spherical or ellipsoidal.
Usually, in an electrochemical device, the active material in the electrode expands and contracts as it is charged and discharged, and the stress is likely to cause the active material to be broken or the conductive path to be broken. Therefore, the primary particles are aggregated to form the secondary particles, rather than the single particle active material having only the primary particles, because the stress of expansion and contraction is alleviated and deterioration is prevented.
In addition, since spherical or elliptic spherical particles have less orientation during molding of the electrode than plate-like particles having equiaxial orientation, expansion and contraction of the electrode during charging and discharging are less, and when forming the electrode. Also in the case of mixing with the conductive material, it is easy to mix uniformly, which is preferable.

(4) Tap Density The tap density of the positive electrode active material is usually 0.4 g·cm ⁻³ or more, preferably 0.6 g·cm ⁻³ or more, more preferably 0.8 g·cm ⁻³ or more, and 1. 0 g · ^{cm -3} or more are particularly preferred, and generally not more than ^{4.0g · cm -3, 3.8g · cm} -3 or less.
By using the metal composite oxide powder having a high tap density, a high density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium required at the time of forming the positive electrode active material layer is increased, and the required amount of the conductive material and the binder is increased, so The filling rate of the positive electrode active material may be restricted, and the battery capacity may be restricted. Further, the tap density is generally preferably as large as possible, but there is no particular upper limit, but if it is less than the above range, diffusion of lithium ions in the positive electrode active material layer using the non-aqueous electrolyte as a medium becomes rate-determining, and load characteristics are likely to deteriorate. There are cases.

The tap density is measured by passing through a sieve with a mesh opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ to fill the cell volume, and then using a powder density measuring instrument (for example, Seiden Enterprise Tap Denser). Using this, tapping with a stroke length of 10 mm is performed 1000 times, 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 positive electrode active material in the present invention.

(5) Median diameter d50
The median diameter d50 of the particles of the positive electrode active material (the secondary particle diameter when primary particles aggregate to form secondary particles) should also be measured using a laser diffraction/scattering particle size distribution analyzer. You can
The median diameter d50 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 3 μm or more, and usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. , 15 μm or less is particularly preferable. If the median diameter d50 is less than the above range, it may not be possible to obtain a high bulk density product, and if it exceeds the above range, it takes time to diffuse lithium in the particles, resulting in deterioration of battery characteristics and production of a battery positive electrode. That is, when the active material, the conductive material, the binder and the like are slurried with a solvent and applied as a thin film, streaks may occur.

By mixing two or more kinds of positive electrode active materials having different median diameters d50 at an arbitrary ratio, it is possible to further improve the filling property at the time of producing the positive electrode.
The median diameter d50 was measured by using a 0.1 mass% sodium hexametaphosphate aqueous solution as a dispersion medium and using a LA-920 manufactured by Horiba, Ltd. as a particle size distribution meter to measure a refractive index of 1.24 after ultrasonic dispersion for 5 minutes. Set and measure.

(6) Average Primary Particle Diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.03 μm or more, preferably 0.05 μm or more, and 0.1. 08 μm or more is more preferable, 0.1 μm or more is particularly preferable, and usually 5 μm or less, 4 μm or less is preferable, 3 μm or less is more preferable, and 2 μm or less is particularly preferable. If it exceeds the above range, it is difficult to form spherical secondary particles, and the powder filling property is adversely affected, or the specific surface area is greatly reduced, so that there is a high possibility that the battery performance such as output characteristics is deteriorated. is there. On the other hand, when the amount is less than the above range, the performance of the secondary battery may be deteriorated, such that the reversibility of charge and discharge is usually poor because the crystal is not developed yet.
The average primary particle diameter is measured by observation with 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 particles with respect to the horizontal straight line is obtained for any 50 primary particles, and the average value is obtained. To be

(7) BET Specific Surface Area As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured by the BET method is usually 0.1 m ² ·g ⁻¹ or more, and 0.2 m ² ·g ⁻¹ or more. Is preferred, 0.3 m ² ·g ⁻¹ or more is more preferred, and usually 50 m ² ·g ⁻¹ or less, 40 m ² ·g ⁻¹ or less is preferred, and 30 m ² ·g ⁻¹ or less is more preferred. If the value of the BET specific surface area is less than the above range, the battery performance tends to deteriorate. On the other hand, when the content exceeds the above range, the tap density becomes difficult to increase, and the coatability at the time of forming the positive electrode active material may decrease.

The BET specific surface area is measured using a surface area meter (Okura Riken full automatic surface area measuring device). After predrying the sample for 30 minutes at 150° C. under a nitrogen flow, a gas was prepared using a nitrogen-helium mixed gas that was accurately adjusted so that the value of the relative pressure of nitrogen with respect to the atmospheric pressure was 0.3. Nitrogen adsorption by flow method BET One-point method. The specific surface area obtained by the measurement is defined as the BET specific surface area of the anode active material in the present invention.

(8) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the scope of the present invention, but some methods are mentioned, and are generally used as a method for producing an inorganic compound. A method is used.
Various methods are conceivable in particular for producing a spherical or elliptic spherical active material. For example, one of them is a transition metal raw material such as a transition metal nitrate or sulfate, and if necessary, a raw material of another element. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted with stirring to prepare and recover a spherical precursor, which is dried if necessary, and then LiOH, Li ₂ CO ₃ , LiNO _A method of adding an Li source such as ₃ and baking at a high temperature to obtain an active material can be mentioned.

In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, and oxides, and, if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it is subjected to dry molding with a spray dryer or the like to obtain a spherical or elliptic spherical precursor, and a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ is added to the precursor, and the mixture is baked at a high temperature to obtain an active material. Is mentioned.
As an example of still another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, and oxides, a Li source such as LiOH, Li ₂ CO ₃ , and LiNO ₃ , and other elements as necessary. The raw material of is dissolved or pulverized and dispersed in a solvent such as water, and dried and molded with a spray dryer or the like to give a spherical or elliptic spherical precursor, which is then baked at a high temperature to obtain an active material. Can be mentioned.

<2-4-2. Electrode structure and fabrication method>
The constitution of the positive electrode used in the present invention and the method for producing the same will be described below.
(1) Method for Producing Positive Electrode A positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The positive electrode using the positive electrode active material can be manufactured by any known method. That is, a positive electrode active material, a binder, and optionally a conductive material, a thickener, etc. are dry mixed to form a sheet, which is then pressure-bonded to a positive electrode current collector, or these materials are used as a liquid medium. A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by dissolving or dispersing it in a slurry to form a slurry, which is applied to the positive electrode current collector and dried.

The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. The upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. When the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. On the other hand, if the content is too high, the strength of the positive electrode may be insufficient. The positive electrode active material powder in the present invention may be used alone, or two or more kinds having different compositions or different powder properties may be used in any combination and ratio.

(2) 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 such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may be used together by 2 or more types in arbitrary combinations and ratios.
In the positive electrode active material layer, the conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less. , And more preferably 15% by mass or less. If the content is less than the above range, the conductivity may be insufficient. If it exceeds the above range, the battery capacity may decrease.

(3) Binder The binder used in the production of the positive electrode active material layer is not particularly limited as long as it is a material stable to the non-aqueous electrolyte solution and the solvent used in the production of the electrode.
In the case of the coating method, any material can be used as long as it can be dissolved or dispersed in the liquid medium used for manufacturing the electrode, and specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethylmethacrylate, aromatic polyamide, cellulose, nitro. Resin-based polymers such as cellulose; rubber-like polymers such as SBR (styrene/butadiene rubber), NBR (acrylonitrile/butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene/propylene rubber; styrene/butadiene/styrene block Such as copolymers or hydrogenated products thereof, EPDM (ethylene/propylene/diene terpolymer), styrene/ethylene/butadiene/ethylene copolymers, styrene/isoprene/styrene block copolymers or hydrogenated products thereof Thermoplastic elastomer-like polymer; Soft resin-like polymer such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymer, propylene/α-olefin copolymer; polyvinylidene fluoride (PVdF) ), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene/ethylene copolymers and other fluorine-based polymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. To be These substances may be used alone or in any combination of two or more at any 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 usually 50% by mass or less, 30% by mass. % Or less is preferable, 10% by mass or less is more preferable, and 8% by mass or less is particularly preferable. If the proportion of the binder is less than the above range, the positive electrode active material cannot be sufficiently retained and the mechanical strength of the positive electrode is insufficient, which may deteriorate the battery performance such as cycle characteristics. On the other hand, if it exceeds the above range, the battery capacity and conductivity may be lowered.

(4) Liquid Medium The liquid medium for forming the slurry may be a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. For example, the kind is not particularly limited, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methylethylketone and cyclohexanone. Esters such as methyl acetate and methyl acrylate; Amines such as diethylenetriamine and N,N-dimethylaminopropylamine; Ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphamide, dimethylsulfoxide, and the like. In addition, these may be used individually by 1 type and may be used together by 2 or more types in arbitrary combinations and ratios.

(5) Thickener When a water-based medium is used as the liquid medium for forming the slurry, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to make a slurry. Thickeners are commonly used to adjust the viscosity of slurries.
The thickener is not limited unless the effects of the present invention are significantly limited, but specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. Etc. These may be used alone or in any combination of two or more at any ratio.

When a thickener is further used, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and It is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it is less than the above range, applicability may be significantly reduced, and if it is more than the above range, the proportion of the active material in the positive electrode active material layer is reduced, which causes a problem of reduction in battery capacity and resistance between the positive electrode active materials. May increase.

(6) Consolidation The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1 g·cm ⁻³ or more, more preferably 1.5 g·cm ⁻³ or more, particularly preferably 2 g·cm ⁻³ or more, and preferably 4 g·cm ⁻³ or less, 3.5 g·cm ⁻³ or less is more preferable, and 3 g·cm ⁻³ or less is particularly preferable.
When the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution near the current collector/active material interface may be reduced, and the charge/discharge characteristics may be reduced particularly at high current density. On the other hand, if it is less than the above range, the conductivity between the active materials may decrease, and the battery resistance may increase.

(7) Current collector The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples thereof include metal materials such as aluminum, stainless steel, nickel plating, titanium and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metallic materials, particularly aluminum are preferable.
Examples of the shape of the current collector include a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal in the case of a metal material, and a carbon plate in the case of a carbonaceous material, Examples thereof include carbon thin films and carbon cylinders. Of these, metal thin films are preferred. The thin film may be appropriately formed in a mesh shape.
Although the thickness of the current collector is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, 100 μm or less, preferably 50 μm or less. If the thin film is thinner than the above range, the strength required as a current collector may be insufficient. If the thin film is thicker than the above range, the handling property may be impaired.

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 the positive electrode active material layer on one surface immediately before the electrolyte injection)/(thickness of the current collector) is 20. It is preferably the following or less, more preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during high current density charging/discharging. Below this range, the volume ratio of the current collector to the positive electrode active material may increase, and the battery capacity may decrease.

<2-5. Separator>
A separator is usually interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the non-aqueous electrolytic solution of the present invention is usually used by impregnating this separator.
There is no particular limitation on the material and shape of the separator, and any known material can be used as long as the effects of the present invention are not significantly impaired. Among them, formed of a material stable to the non-aqueous electrolyte of the present invention, a resin, glass fiber, an inorganic substance or the like is used, and a porous sheet or a non-woven fabric-like substance excellent in liquid retention is used. Is preferred.

As the material of the resin and the glass fiber separator, for example, polyolefin such as polyethylene and polypropylene, polytetrafluoroethylene, polyether sulfone, and glass filter can be used. Of these, glass filters and polyolefins are preferable, and polyolefins are more preferable. These materials may be used alone or in any combination of two or more in any ratio.
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, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating property and mechanical strength may decrease. If the thickness is more than the above range, not only the battery performance such as rate characteristics may deteriorate, but also the energy density of the entire non-aqueous electrolyte secondary battery may decrease.

Furthermore, when using a porous material such as a porous sheet or a non-woven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, It is usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is smaller than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is larger than the above range, the mechanical strength of the separator tends to decrease, and the insulating property tends to decrease.
The average pore size of the separator is also arbitrary, 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, short circuit is likely to occur. On the other hand, if it is less than the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Things are used.

As the form, a non-woven fabric, a woven fabric, or a thin film-shaped one such as a microporous film is used. In the form of a thin film, one having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the particles of the inorganic material on at least one of the positive electrode and the negative electrode using a resin binder can be used. For example, it is possible to form alumina layers having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and to form a porous layer using a fluororesin as a binder.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure including the positive electrode plate and the negative electrode plate with the separator interposed therebetween, and has a structure in which the positive electrode plate and the negative electrode plate are spirally wound with the separator interposed therebetween. Either 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 is below the above range, the battery capacity becomes small. In addition, if it exceeds the above range, the void space is small, the internal pressure rises because the member expands or the vapor pressure of the liquid component of the electrolyte increases due to the high temperature of the battery, and the repeated charge and discharge performance as a battery In some cases, various characteristics such as high temperature storage may be deteriorated, and further, a gas release valve that releases the internal pressure to the outside may be activated.

[Current collecting structure]
Although the current collecting structure is not particularly limited, in order to more effectively realize the improvement of the discharge characteristics by the non-aqueous electrolyte solution of the present invention, a structure in which the resistance of the wiring portion or the joint portion is reduced is used. preferable. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolyte solution of the present invention is particularly well exhibited.
When the electrode group has the above-described laminated structure, a structure formed by bundling the metal core portions of the electrode layers and welding the terminals is preferably used. Since the internal resistance increases when the area of one electrode increases, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the above-mentioned wound structure, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode and bundling them into the terminals.

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

In the outer case using the metals, laser welding, resistance welding, ultrasonic welding to weld the metals to each other to form a hermetically sealed structure, or a caulking structure using the metals via a resin gasket. There are things to do. Examples of the outer case using the laminate film include those having a hermetically sealed structure by heat-sealing resin layers. 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, when a resin layer is heat-sealed via a collector terminal to form a hermetically sealed structure, a metal and a resin are joined, so a resin having a polar group as a resin to intervene or a modification in which a polar group is introduced. Resin is preferably used.

[Protective element]
As the above-mentioned protection element, PTC (Positive Temperature Coefficient) whose resistance increases when abnormal heat generation or excessive current flows, thermal fuse, thermistor, current flowing in the circuit due to abrupt increase of battery internal pressure or internal temperature during abnormal heat generation A valve for shutting off (current cutoff valve) and the like can be mentioned. It is preferable to select the protective element under the condition that it does not operate in normal use with high current, and from the viewpoint of high output, it is more preferable to design so as not to cause abnormal heat generation or thermal runaway without the protective element.

[Exterior body]
The non-aqueous electrolyte secondary battery of the present invention is usually constituted by accommodating the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator and the like in an outer casing. There is no limitation on the outer package, and any known package can be used as long as the effects of the present invention are not significantly impaired.
Specifically, the material of the outer package is arbitrary, but, typically, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
Moreover, the shape of the outer package is also arbitrary, and may be, for example, any of a cylindrical type, a rectangular type, a laminated type, a coin type, a large size, and the like.

EXAMPLES Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples, but the present invention is not limited to these Examples, and is carried out by arbitrarily modifying it without departing from the gist of the present invention. can do.
<Examples 1 to 15, Comparative Examples 1 to 9>
[Test Example A]
[Measurement of sulfate ion content]
Sulfate ion contained in lithium fluorosulfonate was measured by ion chromatography. The measurement results are shown in Table 1.
[Battery manufacturing]

[Preparation of negative electrode]
To 98 parts by mass of the carbonaceous material, 100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose of 1% by mass) and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene) as a thickener and a binder, respectively. 1 part by mass of rubber (concentration of rubber: 50% by mass) was added and mixed with a disperser to form a slurry. The obtained slurry is applied to a copper foil having a thickness of 10 μm, dried, and rolled with a press to obtain an active material layer having a width of 30 mm, a length of 40 mm, and an uncoated width of 5 mm and a length of 9 mm. It was cut out into a shape having a part, and used as the negative electrodes used in Examples and Comparative Examples, respectively.

[Preparation of positive electrode]
90 mass% of lithium cobalt oxide as a positive electrode active material, 5 mass% of acetylene black as a conductive material, and 5 mass% of polyvinylidene fluoride (PVdF) as a binder were mixed in a N-methylpyrrolidone solvent. And made into a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and rolled with a press to obtain an active material layer having a width of 30 mm, a length of 40 mm, and an uncoated width of 5 mm and a length of 9 mm. It was cut into a shape having a processed portion, and used as positive electrodes used in Examples and Comparative Examples, respectively.

[Production of electrolyte]
Under a dry argon atmosphere, dry LiPF ₆ was dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 30:70) at a ratio of 1 mol/L to prepare a basic electrolyte solution. did. This basic electrolytic solution was mixed so as to contain 5% by mass of lithium fluorosulfonate containing sulfate ion.

[Manufacture of lithium secondary battery]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in this order on the negative electrode, the separator, and the positive electrode to prepare a battery element. This battery element was inserted into a bag made of a laminated film in which both sides of aluminum (thickness 40 μm) were coated with a resin layer while protruding the terminals of the positive electrode and the negative electrode, and then an electrolytic solution containing the compound shown in the table was mixed. Each was injected into a bag and vacuum-sealed to produce a sheet-shaped battery, which was used as a battery used in Example 1 and Comparative Example 1, respectively.

[Initial capacity evaluation]
The lithium secondary battery was charged to a constant current of 0.2 C at a constant current of 0.2 C at 25° C. while being sandwiched between glass plates in order to enhance the adhesion between the electrodes. It was discharged to 3.0V. Do this for 2 cycles to stabilize the battery, and in the 3rd cycle, charge to 4.2V with a constant current of 0.2C and then charge to a current value of 0.05C with a constant voltage of 4.2V. , And was discharged to 3.0 V at a constant current of 0.2 C. After that, in the fourth cycle, the battery was charged with a constant current of 0.2C to 4.2V, and then charged with a constant voltage of 4.2V until the current value became 0.05C. The initial discharge capacity was obtained by discharging to 0V. The evaluation results are shown in Table 1. Note that 1C represents a current value at which the reference capacity of the battery is discharged in 1 hour, 2C represents a current value twice that, and 0.2C represents a current value of 1/5 thereof.

[High temperature storage blistering evaluation]
The battery for which the initial discharge capacity evaluation test was completed was charged to a constant current of 0.2 C up to 4.2 V, and then charged to a constant voltage of 4.2 V until the current value reached 0.05 C. This was stored at 85° C. for 24 hours, and after cooling the battery, it was immersed in an ethanol bath to measure the volume, and the amount of gas generated from the volume change before and after high temperature storage was determined. The evaluation results are shown in Table 1.

From Table 1, in the battery using the electrolytic solution containing the same amount of lithium fluorosulfonate, the smaller the amount of sulfate ion contained in lithium fluorosulfonate, the higher the initial discharge capacity and the storage time at high temperature. It can be seen that the battery characteristics are excellent because the gas generation amount of is low.

[Test Example B]
[Production of electrolyte]
Under a dry argon atmosphere, dry LiPF ₆ was dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 30:70) at a ratio of 1 mol/L to prepare a basic electrolyte solution. did. Lithium fluorosulfonate containing sulfate ions was mixed with this basic electrolyte solution in the proportions shown in Table 2.

[Manufacture of lithium secondary battery]
A sheet-like battery was prepared in the same manner as in Example 1 and Comparative Example 1, and the initial capacity evaluation and the high temperature storage swelling evaluation were performed. The evaluation results are shown in Table 2.

From Table 2, when the amount of sulfate ions in the produced electrolytic solution is in the range of 1.00×10 ⁻⁷ ×mol/L to 1.00×10 ⁻² mol/L, the initial discharge capacity is improved. It can be seen that the battery characteristics are improved because the amount of gas generated during high temperature storage is reduced.

Although the present invention has been described in detail and with reference to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

INDUSTRIAL APPLICABILITY The non-aqueous electrolyte solution of the present invention and the non-aqueous electrolyte secondary battery using the same can be used for various known applications. Specific examples include, for example, laptop computers, pen input computers, mobile computers, e-book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini disks. , Walkie-talkie, electronic organizer, calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, motorcycle, motorbike, bicycle, lighting equipment, toys, game equipment, clock, electric tool, strobe, camera, load A power supply for leveling, a natural energy storage power supply, etc. can be mentioned.

Claims (16)

A positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte solution is enclosed in an outer case, the non-aqueous electrolyte solution containing lithium fluorosulfonate and sulfate ions. The content of sulfate ions in the non-aqueous electrolyte solution is 1.0×10 ⁻⁷ mol/L or more and 1.0×10 ⁻² mol/L or less, and the positive electrode is on the current collector. It has a positive electrode active material layer, and the positive electrode active material layer is a lithium-cobalt composite oxide, a lithium-cobalt-nickel composite oxide, a lithium-manganese composite oxide, a lithium-cobalt-manganese composite oxide, a lithium-nickel. Non-aqueous electrolysis containing at least one selected from the group consisting of composite oxide, lithium-cobalt-nickel composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel-cobalt-manganese composite oxide. Liquid secondary battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the positive electrode active material in the positive electrode active material layer of the positive electrode is 80% by mass or more. The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material layer in the positive electrode contains a binder. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains a lithium salt other than lithium fluorosulfonate. The non-aqueous electrolyte secondary battery according to claim 4, wherein the lithium salt other than lithium fluorosulfonate is at least one of LiPF ₆ and LiBF ₄ . The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains a cyclic carbonate having a fluorine atom. The non-aqueous electrolyte secondary battery according to claim 6, wherein the cyclic carbonate having a fluorine atom is contained in the non-aqueous electrolyte in an amount of 0.001% by mass or more and 85% by mass or less. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the non-aqueous electrolyte contains a cyclic carbonate having a carbon-carbon unsaturated bond. The non-aqueous electrolyte secondary battery according to claim 8, wherein the cyclic carbonate having a carbon-carbon unsaturated bond is contained in the non-aqueous electrolyte in an amount of 0.001% by mass or more and 10% by mass or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains a cyclic sulfonate ester. The non-aqueous electrolyte secondary battery according to claim 10, wherein the content of the cyclic sulfonate ester in the non-aqueous electrolyte is 0.001 mass% or more and 10 mass% or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains a compound having a cyano group. The non-aqueous electrolyte secondary battery according to claim 12, wherein the content of the compound having a cyano group in the non-aqueous electrolyte is 0.001% by mass or more and 10% by mass or less. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 13, wherein the non-aqueous electrolyte solution contains a diisocyanate compound. The non-aqueous electrolyte secondary battery according to claim 14, wherein the content of the diisocyanate compound in the non-aqueous electrolyte solution is 0.001% by mass or more and 5% by mass or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains a lithium oxalate salt.