JP2009170146A - Electrolyte solution and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of obtaining superior cycle characteristic, load characteristic, bulge characteristic and security. <P>SOLUTION: A positive electrode 21 and anode 22 are provided together with an electrolyte solution, while a separator 23 provided between the positive electrode 21 and the anode 22 is impregnated with an electrolyte solution. The solvents of the electrolyte solution include: a first solvent of ethylene carbonate or the like, a second solvent of diethyl carbonate or the like, a third solvent of 4,5-difluoro-1,3-dioxolane, and a fourth solvent of 4-fluoro-1,3-dioxolane or the like. The content of the respective solvents is as follows: the first solvent having 5% or more of the weight and 45% of the weight or less; the second solvent having 40% of the weight or more and 70% of the weight or less; the third solvent having 1% of the weight or more and 15% of the weight or less; the fourth solvent having 3% of the weight or more and 24% of the weight or less; the total of the third and fourth solvents having 4% of the weight or more and 25% of the weight or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrolytic solution containing a solvent and a secondary battery using the same.

  In recent years, portable electronic devices such as a camera-integrated VTR (Video Tape Recorder), a mobile phone, or a laptop computer have been widely used, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is lightweight and capable of obtaining a high energy density is in progress.

  Among them, secondary batteries that use the insertion and release of lithium (Li) in charge and discharge reactions (so-called lithium ion secondary batteries) and secondary batteries that use precipitation and dissolution of lithium (so-called lithium metal secondary batteries) Since a higher energy density is obtained than lead batteries and nickel cadmium batteries, it is highly expected.

  Lithium ion secondary batteries that use lithium storage and release have better charge / discharge capacity reproducibility than lithium metal secondary batteries that use precipitation and dissolution of lithium, so that stable charge / discharge characteristics can be obtained. It is thought that you can. This lithium ion secondary battery includes an electrolyte solution together with a positive electrode and a negative electrode, the negative electrode has a negative electrode active material layer on a negative electrode current collector, and the electrolytic solution contains a solvent and an electrolyte salt.

  Carbon materials such as graphite are widely used as the negative electrode active material included in the negative electrode active material layer of the lithium ion secondary battery. Recently, since further improvement in battery capacity has been demanded as portable electronic devices have higher performance and multi-functions, the use of silicon or tin instead of carbon materials has been studied. This is because the theoretical capacity of silicon (4199 mAh / g) and the theoretical capacity of tin (994 mAh / g) are much larger than the theoretical capacity of graphite (372 mAh / g), so that a significant improvement in battery capacity can be expected.

  However, in a lithium ion secondary battery, the negative electrode active material that occludes lithium during charge and discharge becomes highly active, and the electrolytic solution is easily decomposed and lithium is easily deactivated. It is difficult to obtain. In addition, gas is generated during the decomposition reaction of the electrolytic solution, and the secondary battery tends to swell, so that the swell characteristic tends to decrease. In particular, the former problem becomes noticeable when high theoretical capacity silicon or the like is used as the negative electrode active material, while the latter problem becomes noticeable when a film-like exterior member is used as the exterior member of the secondary battery. It becomes.

Therefore, various studies have been made to solve various problems of lithium ion secondary batteries. Specifically, in order to improve cycle characteristics, a chain carbonate ester having a halogen, a cyclic carbonate ester having a halogen, or both of them are used as the solvent of the electrolytic solution, and the content thereof is specified. Techniques have been proposed (see, for example, Patent Documents 1 to 5). In this case, cyclic carbonates such as ethylene carbonate and chain carbonates such as diethyl carbonate are used in combination as other solvents.
JP 2007-019010 A JP 2007-019011 A International Publication No. 2006/033358 Pamphlet JP 2006-172811 A JP 2006-261092 A

  In recent years, portable electronic devices have become more sophisticated and multifunctional, and their power consumption tends to increase. Therefore, charging and discharging of secondary batteries are frequently repeated, and their cycle characteristics and load characteristics tend to deteriorate. Is in the situation. In addition, portable electronic devices are widely used in various fields, and secondary batteries are likely to swell because they may be exposed to a high temperature atmosphere during transportation, use, or carrying. Furthermore, recently, in order to guarantee the safe use of portable electronic devices, there is an increasing demand for improving the safety of secondary batteries.

  The present invention has been made in view of such problems, and an object thereof is to provide an electrolytic solution and a secondary battery capable of obtaining excellent cycle characteristics, load characteristics, swelling characteristics and safety.

  The electrolytic solution of the present invention comprises at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and 4-trifluoromethyl-1,3-dioxolan-2-one. A first solvent comprising, a second solvent comprising at least one member selected from the group consisting of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolan-2-one A fourth solvent comprising at least one member selected from the group consisting of a third solvent and 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and vinylene carbonate; And the content of the first solvent in the solvent is 5% by weight or more and 45% by weight or less, and the second solvent in the solvent is contained in the solvent. The content of the medium is 40% by weight or more and 70% by weight or less, the content of the third solvent in the solvent is 1% by weight or more and 15% by weight or less, and the content of the fourth solvent in the solvent is 3%. The total content of the third and fourth solvents is 4% by weight or more and 25% by weight or less.

  The secondary battery of the present invention includes an electrolyte solution together with a positive electrode and a negative electrode, and the electrolyte solution includes ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and 4-trifluoromethyl- A first solvent comprising at least one member selected from the group consisting of 1,3-dioxolan-2-one; and a second solvent comprising at least one member selected from the group consisting of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate. A third solvent composed of 4,5-difluoro-1,3-dioxolan-2-one, 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate And a solvent containing a fourth solvent consisting of at least one member selected from the group consisting of vinylene carbonate, and containing the first solvent in the solvent The amount is 5 wt% or more and 45 wt% or less, the content of the second solvent in the solvent is 40 wt% or more and 70 wt% or less, and the content of the third solvent in the solvent is 1 wt% or more. 15 wt% or less, the content of the fourth solvent in the solvent is 3 wt% or more and 24 wt% or less, and the sum of the contents of the third and fourth solvents is 4 wt% or more and 25 wt% or less It is what is.

  According to the electrolytic solution of the present invention, the solvent is ethylene carbonate, which is the first solvent, diethyl carbonate, which is the second solvent, and 4,5-difluoro-1,3-, which is the third solvent. It contains dioxolan-2-one and the fourth solvent 4-fluoro-1,3-dioxolan-2-one, etc., and the content in the solvent is 5 wt% or more and 45 wt% in the first solvent. % Or less, 40 to 70% by weight in the second solvent, 1 to 15% by weight in the third solvent, 3 to 24% by weight in the fourth solvent, the third and fourth Since the total amount of the solvent is 4% by weight or more and 25% by weight or less, the chemical stability is improved. As a result, when the electrolytic solution is used in an electrochemical device such as a battery, the state of the electrode reactant is stabilized and the decomposition reaction of the electrolytic solution is suppressed. Thereby, according to the secondary battery using the electrolytic solution of the present invention, excellent cycle characteristics, load characteristics, swelling characteristics and safety can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An electrolytic solution according to an embodiment of the present invention is used for an electrochemical device such as a secondary battery, and includes a solvent and an electrolyte salt dissolved in the solvent.

  The solvent contains the 1st-4th solvent. The kind of 1st-4th solvent and the ratio (content) which occupy in a solvent are as follows.

  The first solvent is at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and 4-trifluoromethyl-1,3-dioxolan-2-one. . The content of the first solvent in the solvent is 5% by weight or more and 45% by weight or less.

  The second solvent is at least one member selected from the group consisting of diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. The content of the second solvent in the solvent is 40% by weight or more and 70% by weight or less.

  The third solvent is 4,5-difluoro-1,3-dioxolan-2-one. This 4,5-difluoro-1,3-dioxolan-2-one may be a cis isomer or a trans isomer. The content of the third solvent in the solvent is 1% by weight or more and 15% by weight or less.

  The fourth solvent is at least one member selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and vinylene carbonate. The content of the fourth solvent in the solvent is 3% by weight or more and 24% by weight or less.

  However, the total content of the third and fourth solvents is 4% by weight or more and 25% by weight or less.

  The solvent contains the above-mentioned first to fourth solvents, and the contents in those solvents are within the above-mentioned range. By combining these four types of solvents in appropriate amounts, the electrolyte solution This is because the chemical stability is improved.

  In addition, the solvent may contain any 1 type or 2 types or more of non-aqueous solvents, such as another organic solvent, with the above-mentioned 1st-4th solvent as needed.

  As such a non-aqueous solvent, for example, a cyclic carbonate having an unsaturated bond (excluding vinylene carbonate which is a fourth solvent) can be mentioned. This is because the chemical stability of the electrolytic solution is further improved. Examples of the cyclic carbonate having an unsaturated bond include vinylene carbonate compounds, vinyl ethylene carbonate compounds, and methylene ethylene carbonate compounds.

  Examples of the vinylene carbonate compound include methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), ethyl vinylene carbonate (4-ethyl-1,3-dioxol-2-one), 4,5- Dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3-dioxol-2-one, or 4-trifluoromethyl-1 , 3-dioxol-2-one.

  Examples of the vinyl ethylene carbonate compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4-ethyl- 4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2-one ON, 4,4-divinyl-1,3-dioxolan-2-one, 4,5-divinyl-1,3-dioxolan-2-one, and the like.

  Examples of the methylene ethylene carbonate compound include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl- 5-methylene-1,3-dioxolan-2-one and the like.

  The cyclic ester carbonate having an unsaturated bond may be catechol carbonate (catechol carbonate) having a benzene ring in addition to the above-described vinylene carbonate compound.

  These may be single and multiple types may be mixed. The content of the cyclic carbonate having an unsaturated bond in the solvent can be arbitrarily set. For example, the content is 0.01% by volume or more and 5% by volume.

  The intrinsic viscosity of the solvent is preferably 10.0 mPa · s or less at 25 ° C. This is because the dissociation property of the electrolyte salt and the ion mobility are improved. Note that the intrinsic viscosity of the electrolyte salt dissolved in the solvent (so-called intrinsic viscosity of the electrolytic solution) is preferably 10.0 mPa · s or less at 25 ° C. for the same reason.

The electrolyte salt contains, for example, one or more light metal salts such as a lithium salt. As this lithium salt, for example, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetraphenylborate (LiB (C ₆ H ₅ ) ₄ ), Lithium methanesulfonate (LiCH ₃ SO ₃ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium tetrachloroaluminate (LiAlCl ₄ ), dilithium hexafluorosilicate (Li ₂ SiF ₆ ), lithium chloride ( LiCl) or lithium bromide (LiBr). This is because it contributes to the improvement of the electrical performance of the electrochemical device. Among these, at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate is preferable, and lithium hexafluorophosphate is more preferable. This is because the resistance of the electrolytic solution decreases. In particular, it is preferable to use lithium hexafluorophosphate and lithium tetrafluoroborate in combination. This is because a higher effect can be obtained.

  This electrolyte salt may contain at least one selected from the group consisting of compounds represented by Chemical Formulas 1 to 3. This is because a higher effect can be obtained when used together with the above-described lithium hexafluorophosphate or the like. In addition, R11 and R13 in Chemical Formula 1 may be the same or different. The same applies to R21 to R23 in Chemical Formula 2 and R31 and R32 in Chemical Formula 3.

（Ｘ１１は長周期型周期表における１族元素あるいは２族元素、またはアルミニウムである。Ｍ１１は遷移金属、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒ１１はハロゲン基である。Ｙ１１は−ＯＣ−Ｒ１２−ＣＯ−、−ＯＣ−Ｃ（Ｒ１３）₂ −あるいは−ＯＣ−ＣＯ−である。ただし、Ｒ１２はアルキレン基、ハロゲン化アルキレン基、アリーレン基あるいはハロゲン化アリーレン基である。Ｒ１３はアルキル基、ハロゲン化アルキル基、アリール基あるいはハロゲン化アリール基である。なお、ａ１は１〜４の整数であり、ｂ１は０、２あるいは４の整数であり、ｃ１、ｄ１、ｍ１およびｎ１は１〜３の整数である。）

(X11 is a group 1 element or group 2 element in the long-period periodic table, or aluminum. M11 is a transition metal, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R11 is Y11 is —OC—R12—CO—, —OC—C (R13) ₂ — or —OC—CO—, wherein R12 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated group. R13 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, wherein a1 is an integer of 1 to 4, b1 is an integer of 0, 2 or 4, and c1 , D1, m1 and n1 are integers of 1 to 3.)

（Ｘ２１は長周期型周期表における１族元素あるいは２族元素である。Ｍ２１は遷移金属、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｙ２１は−ＯＣ−（Ｃ（Ｒ２１）₂ ）_b2−ＣＯ−、−（Ｒ２３）₂ Ｃ−（Ｃ（Ｒ２２）₂ ）_c2−ＣＯ−、−（Ｒ２３）₂ Ｃ−（Ｃ（Ｒ２２）₂ ）_c2−Ｃ（Ｒ２３）₂ −、−（Ｒ２３）₂ Ｃ−（Ｃ（Ｒ２２）₂ ）_c2−ＳＯ₂ −、−Ｏ₂ Ｓ−（Ｃ（Ｒ２２）₂ ）_d2−ＳＯ₂ −あるいは−ＯＣ−（Ｃ（Ｒ２２）₂ ）_d2−ＳＯ₂ −である。ただし、Ｒ２１およびＲ２３は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、それぞれのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。Ｒ２２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。なお、ａ２、ｅ２およびｎ２は１あるいは２の整数であり、ｂ２およびｄ２は１〜４の整数であり、ｃ２は０〜４の整数であり、ｆ２およびｍ２は１〜３の整数である。）

(X21 is a group 1 element or group 2 element in the long-period periodic table. M21 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Y21 is -OC-. _{(C (R21) 2) b2} -CO -, - (R23) 2 C- (C (R22) 2) c2 -CO -, - (R23) 2 C- (C (R22) 2) c2 -C (R23 ) ₂ -,-(R23) ₂ C- (C (R22) ₂ ) _c2 -SO _2- , -O ₂ S- (C (R22) ₂ ) _d2 -SO ₂ -or -OC- (C (R22) ₂ ) _d2 —SO ₂ —, wherein R21 and R23 are a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, and at least one of each is a halogen group or a halogenated alkyl group. R22 is hydrogen group, alkyl group, halogen Or a halogenated alkyl group, wherein a2, e2 and n2 are integers of 1 or 2, b2 and d2 are integers of 1 to 4, c2 is an integer of 0 to 4, and f2 and m2 are It is an integer from 1 to 3.)

（Ｘ３１は長周期型周期表における１族元素あるいは２族元素である。Ｍ３１は遷移金属、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒｆはフッ素化アルキル基あるいはフッ素化アリール基であり、いずれの炭素数も１〜１０である。Ｙ３１は−ＯＣ−（Ｃ（Ｒ３１）₂ ）_d3−ＣＯ−、−（Ｒ３２）₂ Ｃ−（Ｃ（Ｒ３１）₂ ）_d3−ＣＯ−、−（Ｒ３２）₂ Ｃ−（Ｃ（Ｒ３１）₂ ）_d3−Ｃ（Ｒ３２）₂ −、−（Ｒ３２）₂ Ｃ−（Ｃ（Ｒ３１）₂ ）_d3−ＳＯ₂ −、−Ｏ₂ Ｓ−（Ｃ（Ｒ３１）₂ ）_e3−ＳＯ₂ −あるいは−ＯＣ−（Ｃ（Ｒ３１）₂ ）_e3−ＳＯ₂ −である。ただし、Ｒ３１は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。Ｒ３２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、そのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。なお、ａ３、ｆ３およびｎ３は１あるいは２の整数であり、ｂ３、ｃ３およびｅ３は１〜４の整数であり、ｄ３は０〜４の整数であり、ｇ３およびｍ３は１〜３の整数である。）

(X31 is a group 1 element or group 2 element in the long-period periodic table. M31 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Rf is a fluorinated alkyl. Or a fluorinated aryl group, each having 1 to 10 carbon atoms, Y31 is —OC— (C (R31) ₂ ) _d3 —CO—, — (R32) ₂ C— (C (R31) _{2 D3} —CO—, — (R32) ₂ C— (C (R31) ₂ ) _d3 —C (R32) ₂ —, — (R32) ₂ C— (C (R31) ₂ ) _d3 —SO ₂ —, — O ₂ S— (C (R 31) ₂ ) e ₃ —SO ₂ — or —OC— (C (R 31) ₂ ) e ₃ —SO ₂ —, wherein R 31 is a hydrogen group, an alkyl group, a halogen group or a halogenated group. R32 represents a hydrogen group, an alkyl group, or a halogen. Or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a3, f3 and n3 are integers of 1 or 2, and b3, c3 and e3 are 1 to 4; (It is an integer, d3 is an integer of 0 to 4, and g3 and m3 are integers of 1 to 3.)

  The long-period periodic table is represented by a revised inorganic chemical nomenclature proposed by IUPAC (International Pure and Applied Chemistry Association). Specifically, group 1 elements are hydrogen, lithium, sodium, potassium, rubidium, cesium and francium. Group 2 elements are beryllium, magnesium, calcium, strontium, barium and radium. Group 13 elements are boron, aluminum, gallium, indium and thallium. Group 14 elements are carbon, silicon, germanium, tin and lead. Group 15 elements are nitrogen, phosphorus, arsenic, antimony and bismuth.

  Examples of the compound represented by Chemical Formula 1 include compounds represented by Chemical Formulas (1) to (6). Examples of the compound shown in Chemical Formula 2 include compounds represented by Chemical Formulas (1) to (8). Examples of the compound represented by Chemical Formula 3 include the compound represented by Chemical Formula 6 and the like. It is needless to say that the compound having the structure shown in Chemical Formula 1 to Chemical Formula 3 is not limited to the compound shown in Chemical Formula 4 to Chemical Formula 6.

  The electrolyte salt may contain at least one selected from the group consisting of compounds represented by Chemical Formulas 7 to 9. This is because a higher effect can be obtained when used together with the above-described lithium hexafluorophosphate or the like. Note that m and n in Chemical Formula 7 may be the same or different. The same applies to p, q and r in Chemical formula 9.

（ｍおよびｎは１以上の整数である。）

(M and n are integers of 1 or more.)

（Ｒ４１は炭素数２以上４以下の直鎖状あるいは分岐状のパーフルオロアルキレン基である。）

(R41 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

（ｐ、ｑおよびｒは１以上の整数である。）

(P, q and r are integers of 1 or more.)

Examples of the chain compound shown in Chemical formula 7 include bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), bis (pentafluoroethanesulfonyl) imide lithium (LiN (C ₂ F ₅ SO ₂ ) ₂ ), (trifluoromethanesulfonyl) (pentafluoroethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )), (trifluoromethanesulfonyl) (heptafluoropropanesulfonyl) imide lithium ( LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ )) or (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl) imidolithium (LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ )) Can be mentioned. Of these, bis (trifluoromethanesulfonyl) imidolithium is preferable. This is because a high effect can be obtained.

  Examples of the cyclic compound represented by Chemical Formula 8 include a series of compounds represented by Chemical Formula 10. That is, 1,2-perfluoroethanedisulfonylimide lithium of (1) shown in Chemical formula 10, 1,3-perfluoropropane disulfonylimide lithium of (2), 1,3-perfluorobutane of (3) Examples thereof include disulfonylimidolithium and (4) 1,4-perfluorobutanedisulfonylimidelithium. Among these, 1,2-perfluoroethanedisulfonylimide lithium is preferable. This is because a high effect can be obtained.

Examples of the chain compound shown in Chemical Formula 9 include lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ).

  The content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because, outside this range, the ion conductivity may be extremely lowered.

  The electrolytic solution may contain various additives along with the solvent and the electrolyte salt. This is because the chemical stability of the electrolytic solution is further improved.

  Examples of this additive include sultone (cyclic sulfonic acid ester). This sultone is, for example, propane sultone or propene sultone, among which propene sultone is preferable. These may be single and multiple types may be mixed. The content of sultone in the electrolytic solution is, for example, not less than 0.5 wt% and not more than 5 wt%.

  Moreover, as an additive, an acid anhydride is mentioned, for example. Examples of the acid anhydride include carboxylic acid anhydrides such as succinic acid anhydride, glutaric acid anhydride and maleic acid anhydride, disulfonic acid anhydrides such as ethanedisulfonic acid anhydride and propanedisulfonic acid anhydride, Examples thereof include carboxylic acid and sulfonic acid anhydrides such as benzoic acid anhydride, sulfopropionic acid anhydride and sulfobutyric acid anhydride, among which succinic acid anhydride and sulfobenzoic acid anhydride are preferable. These may be single and multiple types may be mixed. The content of the acid anhydride in the electrolytic solution is, for example, 0.5% by weight or more and 5% by weight or less.

  According to this electrolytic solution, the solvent is ethylene carbonate or the like as the first solvent, diethyl carbonate or the like as the second solvent, and 4,5-difluoro-1,3-dioxolane- as the third solvent. 2 -one and 4-fluoro-1,3-dioxolan-2-one etc. which are 4th solvents are contained, and content in a solvent is 5 to 45 weight% in a 1st solvent. , 40 wt% or more and 70 wt% or less in the second solvent, 1 wt% or more and 15 wt% or less in the third solvent, 3 wt% or more and 24 wt% or less in the fourth solvent, the third and fourth solvents Is 4 wt% or more and 25 wt% or less. In this case, since the chemical stability is improved as compared with the case where the solvent does not have the above-described composition, the state of the electrode reactant is stabilized when used in an electrochemical device such as a battery. At the same time, the decomposition reaction of the electrolytic solution is suppressed. Therefore, the electrical performance of the electrochemical device is improved and gas generation due to the decomposition reaction of the electrolytic solution is suppressed, which contributes to ensuring excellent cycle characteristics, load characteristics, swelling characteristics and safety. it can.

  In addition, the electrolyte salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate. A higher effect can be obtained if at least one member selected from the group consisting of compounds and at least one member selected from the group consisting of compounds shown in Chemical Formulas 7 to 9 are contained.

  Further, if the electrolytic solution contains sultone or acid anhydride as an additive, a higher effect can be obtained.

  Next, usage examples of the above-described electrolytic solution will be described. Here, taking a secondary battery as an example of the electrochemical device, the electrolytic solution is used in the secondary battery as follows.

(First secondary battery)
1 and 2 show a cross-sectional configuration of the first secondary battery, and FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The secondary battery described here is, for example, a lithium ion secondary battery in which the capacity of the negative electrode 22 is expressed based on insertion and extraction of lithium as an electrode reactant.

  The secondary battery mainly includes a wound electrode body 20 in which a positive electrode 21 and a negative electrode 22 are wound via a separator 23 inside a substantially hollow cylindrical battery can 11, a pair of insulating plates 12, 13 is stored. The battery structure using the cylindrical battery can 11 is called a cylindrical type.

  The battery can 11 has, for example, a hollow structure in which one end is closed and the other end is opened, and is made of a metal material such as iron, aluminum, or an alloy thereof. In addition, when the battery can 11 is comprised with iron, plating, such as nickel, may be given, for example. The pair of insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 from above and below and to extend perpendicularly to the wound peripheral surface.

  A battery lid 14 and a safety valve mechanism 15 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 provided on the inside of the battery can 11 are caulked to the open end of the battery can 11 via a gasket 17. ing. Thereby, the inside of the battery can 11 is sealed. The battery lid 14 is made of a metal material similar to that of the battery can 11, for example. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16. In the safety valve mechanism 15, when the internal pressure becomes a certain level or more due to an internal short circuit or external heating, the disk plate 15 </ b> A is reversed and the electric power between the battery lid 14 and the wound electrode body 20 is reversed. Connection is cut off. The heat-sensitive resistor element 16 is configured to prevent abnormal heat generation caused by a large current by limiting the current by increasing the resistance in response to a rise in temperature. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface thereof.

  A center pin 24 may be inserted in the center of the wound electrode body 20. In this wound electrode body 20, a positive electrode lead 25 made of a metal material such as aluminum is connected to the positive electrode 21, and a negative electrode lead 26 made of a metal material such as nickel is connected to the negative electrode 22. . The positive electrode lead 25 is welded to the safety valve mechanism 15 and electrically connected to the battery lid 14, and the negative electrode lead 26 is welded to the battery can 11 and electrically connected thereto.

  For example, the positive electrode 21 is obtained by providing a positive electrode active material layer 21B on both surfaces of a positive electrode current collector 21A having a pair of surfaces. However, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.

  The positive electrode current collector 21A is made of a metal material such as aluminum, nickel, or stainless steel, for example.

  The positive electrode active material layer 21B includes one or more positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a binder, a conductive agent, and the like as necessary. Other materials may be included.

As a positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide containing lithium and a transition metal element, and a phosphate compound containing lithium and a transition metal element. Especially, what contains at least 1 sort (s) of the group which consists of cobalt, nickel, manganese, and iron as a transition metal element is preferable. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x M1O ₂ or Li _y M2PO ₄ . In the formula, M1 and M2 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni). _1-z Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _(1-vw) Co _v Mn _w O ₂ (v + w <1)), or lithium having a spinel structure Manganese composite oxide (LiMn ₂ O ₄ ) and the like can be mentioned. Among these, a complex oxide containing cobalt is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can be obtained. Examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (u <1)). Is mentioned.

  In addition, examples of the positive electrode material capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium disulfide and molybdenum sulfide, and niobium selenide. And chalcogenides such as sulfur, polyaniline and polythiophene, and other conductive polymers.

  Of course, the positive electrode material capable of inserting and extracting lithium may be other than the above. Further, two or more kinds of the series of positive electrode materials described above may be mixed in any combination.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, acetylene black, and ketjen black. These may be single and multiple types may be mixed. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed.

  In the negative electrode 22, for example, a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of surfaces. However, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A.

  The anode current collector 22A is made of, for example, a metal material such as copper, nickel, or stainless steel. The surface of the anode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion between the negative electrode current collector 22A and the negative electrode active material layer 22B. In this case, the surface of the negative electrode current collector 22A only needs to be roughened at least in a region facing the negative electrode active material layer 22B. Examples of the roughening method include a method of forming fine particles by electrolytic treatment. This electrolytic treatment is a method of forming irregularities by forming fine particles on the surface of the anode current collector 22A by an electrolytic method in an electrolytic bath. The copper foil subjected to this electrolytic treatment is generally called “electrolytic copper foil”.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as a negative electrode active material, and a binder, a conductive agent, and the like as necessary. Other materials may be included. Note that details regarding the binder and the conductive agent are the same as those described for the positive electrode 21, for example.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and having at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained. Such a negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, and may have one or two or more phases thereof at least in part. The “alloy” in the present invention includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Further, the “alloy” may contain a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a material in which two or more of them coexist.

  Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon, germanium (Ge), tin, lead (Pb), bismuth (Bi), cadmium (Cd) Silver (Ag), zinc, hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), platinum (Pt), and the like. Among these, at least one of silicon and tin is preferable. This is because a high energy density can be obtained because the ability to occlude and release lithium is large.

  Examples of the negative electrode material having at least one of silicon and tin include at least a part of a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or one or two or more phases thereof. The material which has in is mentioned.

Examples of the silicon alloy include, as the second constituent element other than silicon, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium. Those having at least one of the groups are mentioned. Examples of the silicon compound include those having oxygen or carbon (C), and may contain the second constituent element described above in addition to silicon. Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi. ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), SnO _w (0 <w ≦ 2) or LiSiO etc. are mentioned.

As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing which has at least 1 sort (s) of these is mentioned. Examples of the tin compound include those having oxygen or carbon, and may contain the above-described second constituent element in addition to tin. Examples of tin alloys or compounds include SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.

  In particular, as the negative electrode material having at least one of silicon and tin, for example, a material having tin and the second constituent element in addition to tin as the first constituent element is preferable. The second constituent elements are cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum, silver, indium, cerium (Ce), It is at least one selected from the group consisting of hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). This is because having the second and third constituent elements improves the cycle characteristics.

  Among them, tin, cobalt and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is 30. An SnCoC-containing material having a mass% of 70% by mass or less is preferable. This is because a high energy density can be obtained in such a composition range.

  This SnCoC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like are preferable, and two or more of them may be included. . This is because a higher effect can be obtained.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase is preferably a low crystalline or amorphous phase. This phase is a reaction phase capable of reacting with lithium, whereby excellent cycle characteristics can be obtained. The half-value width of the diffraction peak obtained by X-ray diffraction of this phase is 1.0 ° or more at a diffraction angle 2θ when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min. Is preferred. This is because lithium is occluded and released more smoothly and the reactivity with the electrolyte is reduced.

  Whether or not the diffraction peak obtained by X-ray diffraction corresponds to a reaction phase capable of reacting with lithium can be easily determined by comparing X-ray diffraction charts before and after electrochemical reaction with lithium. can do. For example, if the position of the diffraction peak changes before and after the electrochemical reaction with lithium, it corresponds to a reaction phase capable of reacting with lithium. In this case, for example, a diffraction peak of a low crystalline or amorphous reaction phase is observed between 2θ = 20 ° and 50 °. This low crystalline or amorphous reaction phase contains, for example, each of the above-described constituent elements, and is considered to be mainly low-crystallized or amorphous due to carbon.

  Note that the SnCoC-containing material may have a phase containing a simple substance or a part of each constituent element in addition to a low crystalline or amorphous phase.

  In particular, in the SnCoC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a metalloid element as another constituent element. This is because aggregation or crystallization of tin or the like is suppressed.

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. This XPS irradiates the sample surface with soft X-rays (Al-Kα ray or Mg-Kα ray is used in a commercial apparatus), and measures the kinetic energy of photoelectrons jumping out of the sample surface. To elemental composition in the region of several nanometers and the bonding state of the elements.

  The binding energy of the core orbital electrons of the element changes in a first approximation in correlation with the charge density on the element. For example, when the charge density of the carbon element decreases due to an interaction with an element present in the vicinity, the outer electrons such as 2p electrons decrease, so the 1s electron of the carbon element exerts a strong binding force from the shell. Will receive. That is, the binding energy increases as the charge density of the element decreases. In XPS, when the binding energy increases, the peak shifts to a high energy region.

  In XPS, if the peak of carbon 1s orbital (C1s) is graphite, it appears at 284.5 eV in an energy calibrated apparatus so that the peak of 4f orbital (Au4f) of gold atom is obtained at 84.0 eV. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when it is bonded to an element more positive than carbon, the C1s peak appears in a region lower than 284.5 eV. That is, when at least a part of the carbon contained in the SnCoC-containing material is bonded to another constituent element such as a metal element or a metalloid element, the peak of the synthetic wave of C1s obtained for the SnCoC-containing material is 284. Appears in the region lower than 5 eV.

  When performing XPS measurement, it is preferable that the surface is lightly sputtered with an argon ion gun attached to the XPS apparatus when the surface is covered with surface-contaminated carbon. When the SnCoC-containing material to be measured is present in the negative electrode 22, the secondary battery is disassembled and the negative electrode 22 is taken out and then washed with a volatile solvent such as dimethyl carbonate. This is to remove the low-volatile solvent and the electrolyte salt present on the surface of the negative electrode 22. These samplings are desirably performed in an inert atmosphere.

  In XPS measurement, for example, the peak of C1s is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface of the substance, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In XPS measurement, the waveform of the peak of C1s is obtained as a form including the surface contamination carbon peak and the carbon peak in the SnCoC-containing material. For example, by analyzing using commercially available software, The surface contamination carbon peak is separated from the carbon peak in the SnCoC-containing material. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  This SnCoC-containing material can be formed, for example, by melting a mixture of raw materials of each constituent element in an electric furnace, a high-frequency induction furnace, an arc melting furnace or the like and then solidifying the mixture. Also, various atomizing methods such as gas atomization or water atomization, methods using various mechanochemical reactions such as various roll methods, mechanical alloying methods, and mechanical milling methods may be used. Among these, a method using a mechanochemical reaction is preferable. This is because the SnCoC-containing material has a low crystalline or amorphous structure. In the method using the mechanochemical reaction, for example, a manufacturing apparatus such as a planetary ball mill apparatus or an attritor can be used.

  The raw material may be a mixture of individual constituent elements, but it is preferable to use an alloy for some of the constituent elements other than carbon. This is because, by adding carbon to such an alloy and synthesizing it by a method using the mechanical alloying method, a low crystallization or amorphous structure can be obtained, and the reaction time can be shortened. The raw material may be in the form of powder or a block.

  In addition to this SnCoC-containing material, an SnCoFeC-containing material having tin, cobalt, iron and carbon as constituent elements is also preferable. The composition of the SnCoFeC-containing material can be arbitrarily set. For example, as a composition when the iron content is set to be small, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the iron content is 0.3 mass% or more and 5.9 mass% %, And the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is preferably 30% by mass or more and 70% by mass or less. In addition, for example, as a composition when the content of iron is set to be large, the content of carbon is 11.9 mass% or more and 29.7 mass% or less, and cobalt and iron with respect to the total of tin, cobalt, and iron The total ratio of (Co + Fe) / (Sn + Co + Fe)) is 26.4 mass% to 48.5 mass%, and the ratio of cobalt to the total of cobalt and iron (Co / (Co + Fe)) is 9.9 mass% It is preferable that it is 79.5 mass% or more. This is because a high energy density can be obtained in such a composition range. The crystallinity of the SnCoFeC-containing material, the method for measuring the bonding state of elements, the formation method, and the like are the same as those of the above-described SnCoC-containing material.

  In addition to the above, examples of the anode material capable of inserting and extracting lithium include a carbon material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less. It is. More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks. Of these, the cokes include pitch coke, needle coke, petroleum coke, and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. The carbon material is preferable because the change in crystal structure associated with insertion and extraction of lithium is very small, so that a high energy density can be obtained, and excellent cycle characteristics can be obtained. The shape of the carbon material may be any of fibrous, spherical, granular or scale-like.

  Further, examples of the negative electrode material capable of inserting and extracting lithium include metal oxides and polymer compounds capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Of course, the negative electrode material capable of inserting and extracting lithium may be other than the above. Further, two or more kinds of the series of negative electrode materials described above may be mixed in any combination.

  The negative electrode active material made of the negative electrode material described above has a plurality of particles. That is, the negative electrode active material layer 22B has a plurality of negative electrode active material particles, and the negative electrode active material particles are formed by, for example, the above-described vapor phase method. However, the negative electrode active material particles may be formed by a method other than the gas phase method.

  When the negative electrode active material particles are formed by a deposition method such as a vapor phase method, the negative electrode active material particles may have a single layer structure formed through a single deposition step, or may be a plurality of times. It may have a multilayer structure formed through the deposition process. However, when the negative electrode active material particles are formed by a vapor deposition method that involves high heat during deposition, the negative electrode active material particles preferably have a multilayer structure. By performing the deposition process of the negative electrode material in a plurality of times (the negative electrode material is sequentially formed and deposited thinly), the negative electrode current collector 22A has a higher heat than when the deposition process is performed once. This is because the exposure time is shortened and it is difficult to receive thermal damage.

  The negative electrode active material particles grow, for example, from the surface of the negative electrode current collector 22A in the thickness direction of the negative electrode active material layer 22B, and are connected to the negative electrode current collector 22A at the root. In this case, the negative electrode active material particles are formed by a vapor phase method, and as described above, it is preferable that the negative electrode active material particles are alloyed at least at a part of the interface with the negative electrode current collector 22A. Specifically, the constituent element of the negative electrode current collector 22A may be diffused into the negative electrode active material particles at the interface between them, or the constituent element of the negative electrode active material particles may be diffused into the negative electrode current collector 22A. Alternatively, both constituent elements may be diffused.

  In particular, the negative electrode active material layer 22B preferably has an oxide-containing film that covers the surface of the negative electrode active material particles (a region in contact with the electrolytic solution) as necessary. This is because the oxide-containing film functions as a protective film against the electrolytic solution, and even when charging and discharging are repeated, the decomposition reaction of the electrolytic solution is suppressed, so that the cycle characteristics are improved. This oxide-containing film may cover a part of the surface of the negative electrode active material particles, or may cover the whole.

  This oxide-containing film contains, for example, at least one oxide selected from the group consisting of silicon, germanium, and tin, and among these, it is preferable to contain an oxide of silicon. This is because the entire surface of the negative electrode active material particles can be easily covered and an excellent protective action can be obtained. Of course, the oxide-containing film may contain an oxide other than the above. The oxide-containing film is formed by, for example, a gas phase method or a liquid phase method, and among them, a liquid phase method such as a liquid phase deposition method, a sol-gel method, a coating method, or a dip coating method is preferable. More preferred. This is because the surface of the negative electrode active material particles can be easily covered over a wide range.

  In addition, the negative electrode active material layer 22B preferably includes a metal material that does not alloy with the electrode reactant in the gaps between the particles of the negative electrode active material particles or the gaps in the particles as necessary. Since a plurality of negative electrode active material particles are bound via a metal material, and the expansion and contraction of the negative electrode active material layer 22B are suppressed due to the presence of the metal material in the gap, the cycle characteristics are improved. It is.

  This metal material has, for example, a metal element that does not alloy with lithium as a constituent element. Examples of such a metal element include at least one selected from the group consisting of iron, cobalt, nickel, zinc, and copper, and among these, cobalt is preferable. This is because the metal material can easily enter the gap, and an excellent binding action can be obtained. Of course, the metal material may have a metal element other than the above. However, the “metal material” mentioned here is not limited to a simple substance, but is a broad concept that includes alloys and metal compounds. This metal material is formed by, for example, a gas phase method or a liquid phase method, and among them, a liquid phase method such as an electrolytic plating method or an electroless plating method is preferable, and an electrolytic plating method is more preferable. This is because the metal material can easily enter the gap and the formation time can be shortened.

  Note that the negative electrode active material layer 22B may include only one of the oxide-containing film or the metal material described above, or may include both. However, in order to further improve the cycle characteristics, it is preferable to include both.

  Here, the detailed configuration of the negative electrode 22 will be described with reference to FIGS.

  First, the case where the negative electrode active material layer 22B has an oxide-containing film together with a plurality of negative electrode active material particles will be described. FIG. 3 schematically shows a cross-sectional structure of the negative electrode 22 of the present invention, and FIG. 4 schematically shows a cross-sectional structure of the negative electrode of the reference example. 3 and 4 show a case where the negative electrode active material particles have a single layer structure.

  In the negative electrode of the present invention, as shown in FIG. 3, for example, when a negative electrode material is deposited on the negative electrode current collector 22A by a vapor phase method such as a vapor deposition method, a plurality of negative electrodes are formed on the negative electrode current collector 22A. Active material particles 221 are formed. In this case, when the surface of the negative electrode current collector 22A is roughened and a plurality of protrusions (for example, fine particles formed by electrolytic treatment) exist on the surface, the negative electrode active material particles 221 have the protrusions described above. Each of the negative electrode active material particles 221 is arranged on the negative electrode current collector 22A and connected to the surface of the negative electrode current collector 22A at the root. After that, for example, when the oxide-containing film 222 is formed on the surface of the negative electrode active material particle 221 by a liquid phase method such as a liquid phase precipitation method, the oxide-containing film 222 substantially covers the surface of the negative electrode active material particle 221. The entire surface is covered, and in particular, a wide range from the top of the negative electrode active material particle 221 to the root is covered. This wide covering state by the oxide-containing film 222 is a characteristic obtained when the oxide-containing film 222 is formed by a liquid phase method. That is, when the oxide-containing film 222 is formed by the liquid phase method, the covering action extends not only to the top of the negative electrode active material particles 221 but also to the root, so that the base is covered with the oxide-containing film 222.

  On the other hand, in the negative electrode of the reference example, as shown in FIG. 4, for example, after the plurality of negative electrode active material particles 221 are formed by the vapor phase method, the oxide-containing film 223 is similarly formed by the vapor phase method. When formed, the oxide-containing film 223 covers only the tops of the negative electrode active material particles 221. This narrow-range covering state by the oxide-containing film 223 is a characteristic obtained when the oxide-containing film 223 is formed by a vapor phase method. That is, when the oxide-containing film 223 is formed by a vapor phase method, the covering action does not reach the root of the negative electrode active material particle 221, and thus the base is not covered by the oxide-containing film 223.

  Note that although FIG. 3 illustrates the case where the negative electrode active material layer 22B is formed by a vapor phase method, a plurality of negative electrode active materials are similarly formed when the negative electrode active material layer 22B is formed by a sintering method or the like. An oxide-containing film is formed so as to cover the entire surface of the particles.

  Next, the case where the negative electrode active material layer 22B includes a metal material that does not alloy with the electrode reactant together with the plurality of negative electrode active material particles will be described. FIG. 5 shows an enlarged cross-sectional structure of the negative electrode 22, (A) is a scanning electron microscope (SEM) photograph (secondary electron image), and (B) is an SEM shown in (A). It is a schematic picture of the statue. FIG. 5 shows a case where a plurality of negative electrode active material particles 221 have a multilayer structure in the particles.

  When the negative electrode active material particles 221 have a multilayer structure, a plurality of gaps 224 are generated in the negative electrode active material layer 22B due to the arrangement structure, multilayer structure, and surface structure of the plurality of negative electrode active material particles 221. Yes. The gap 224 mainly includes two types of gaps 224A and 224B classified according to the cause of occurrence. The gap 224 </ b> A is generated between adjacent negative electrode active material particles 221, and the gap 224 </ b> B is generated between layers in the negative electrode active material particles 221.

  Note that a void 225 may be formed on the exposed surface (outermost surface) of the negative electrode active material particles 221. The void 225 is generated between the protrusions as a whisker-like fine protrusion (not shown) is formed on the surface of the negative electrode active material particle 221. The void 225 may be generated over the entire exposed surface of the negative electrode active material particles 221 or may be generated only in part. However, since the above-described whisker-like protrusions are generated on the surface every time the negative electrode active material particles 221 are formed, the void 225 is generated not only on the exposed surface of the negative electrode active material particles 221 but also between the layers. There is.

  FIG. 6 shows another cross-sectional structure of the negative electrode 22 and corresponds to FIG. The negative electrode active material layer 22B has a metal material 226 that does not alloy with the electrode reactant in the gaps 224A and 224B. In this case, only one of the gaps 224A and 224B may have the metal material 226, but it is preferable that both have the metal material 226. This is because a higher effect can be obtained.

  The metal material 226 enters the gap 224A between the adjacent negative electrode active material particles 221. Specifically, when the negative electrode active material particles 221 are formed by a vapor phase method or the like, as described above, the negative electrode active material particles 221 grow for each protrusion existing on the surface of the negative electrode current collector 22A. A gap 224 </ b> A is generated between the adjacent negative electrode active material particles 221. Since the gap 224A causes a decrease in the binding property of the negative electrode active material layer 22B, the above-described gap 224A is filled with the metal material 226 in order to improve the binding property. In this case, it is sufficient that a part of the gap 224A is filled, but a larger filling amount is preferable. This is because the binding property of the negative electrode active material layer 22B is further improved. The filling amount of the metal material 226 is preferably 20% or more, more preferably 40% or more, and further preferably 80% or more.

  In addition, the metal material 226 enters the gap 224 </ b> B in the negative electrode active material particles 221. Specifically, when the negative electrode active material particles 221 have a multilayer structure, a gap 224B is generated between the layers. The gap 224B, like the gap 224A, causes a decrease in the binding property of the negative electrode active material layer 22B. Therefore, in order to increase the binding property, the gap 224B is filled with the metal material 226. ing. In this case, it is sufficient that a part of the gap 224B is filled, but a larger filling amount is preferable. This is because the binding property of the negative electrode active material layer 22B is further improved.

  Note that the negative electrode active material layer 22B is provided in order to prevent negative whisker-like protrusions (not shown) generated on the exposed surface of the uppermost negative electrode active material particles 221 from adversely affecting the performance of the secondary battery. A metal material 226 may be provided in the gap 225. Specifically, when the negative electrode active material particles 221 are formed by a vapor phase method or the like, fine whisker-like protrusions are formed on the surface thereof, and thus voids 225 are generated between the protrusions. This void 225 causes an increase in the surface area of the negative electrode active material particles 221 and also increases the amount of irreversible film formed on the surface, which causes a reduction in the degree of progress of the electrode reaction (charge / discharge reaction). there is a possibility. Therefore, the metal material 226 is embedded in the above-described gap 225 in order to suppress a decrease in the progress of the electrode reaction. In this case, it is sufficient that a part of the gap 225 is embedded, but it is preferable that the amount to be embedded is larger. This is because a decrease in the degree of progress of the electrode reaction is further suppressed. In FIG. 6, the fact that the metal material 226 is scattered on the surface of the uppermost negative electrode active material particle 221 indicates that the above-described fine protrusions are present at the spot. Of course, the metal material 226 does not necessarily have to be scattered on the surface of the negative electrode active material particle 221, and may cover the entire surface.

  In particular, the metal material 226 that has entered the gap 224B also functions to fill the gap 225 in each layer. Specifically, when the negative electrode material is deposited a plurality of times, the fine protrusions described above are generated on the surface of the negative electrode active material particles 221 every time the negative electrode material is deposited. From this, the metal material 226 not only fills the gap 224B in each layer, but also fills the gap 225 in each layer.

  5 and 6, the negative electrode active material particles 221 have a multilayer structure, and the case where both the gaps 224A and 224B exist in the negative electrode active material layer 22B has been described. 22B has a metal material 226 in the gaps 224A and 224B. On the other hand, when the negative electrode active material particle 221 has a single layer structure and only the gap 224A exists in the negative electrode active material layer 22B, the negative electrode active material layer 22B has the metal material 226 only in the gap 224A. It will have. Of course, since the gap 225 is generated in both cases, the gap 225 has the metal material 226 in either case.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and these two or more kinds of porous films are laminated. It may be what was done.

  The separator 23 is impregnated with the above-described electrolytic solution as a liquid electrolyte. This is because excellent cycle characteristics, load characteristics, swell characteristics and safety can be obtained. In addition, the influence which the 1st-4th solvent in electrolyte solution has on each above-mentioned characteristic is as follows.

  The first solvent, such as ethylene carbonate, mainly affects battery capacity, cycle characteristics, and swelling characteristics. When the content of the first solvent is small, the battery capacity and cycle characteristics are improved, but the swelling characteristics are lowered. On the other hand, when the content of the first solvent is large, the swelling characteristic is improved, but the battery capacity and the cycle characteristic are lowered. For these reasons, when the content of the first solvent is within an appropriate range of 5% by weight or more and 45% by weight or less, the battery capacity, the cycle characteristics, and the swelling characteristics are improved.

  The second solvent, such as diethyl carbonate, mainly affects battery capacity, cycle characteristics, and swelling characteristics. When the content of the second solvent is small, the cycle characteristics are improved, but the battery capacity and the swelling characteristics are lowered. On the other hand, when the content of the second solvent is large, the battery capacity and the swelling characteristics are improved, but the cycle characteristics are lowered. For these reasons, when the content of the second solvent is within an appropriate range of 40% by weight or more and 70% by weight or less, the battery capacity, the cycle characteristics, and the swelling characteristics are improved.

  The third solvent, 4,5-difluoro-1,3-dioxolan-2-one, mainly affects cycle characteristics, load characteristics, blister characteristics and safety. When the content of the third solvent is small, the swelling characteristic is improved, but the cycle characteristic, the load characteristic and the safety are lowered. On the other hand, when the content of the third solvent is large, cycle characteristics, load characteristics and safety are improved, but swelling characteristics are lowered. For these reasons, when the content of the third solvent is in the range of 1% by weight or more and 15% by weight or less, cycle characteristics, load characteristics, swell characteristics, and safety are improved.

  The fourth solvent, 4-fluoro-1,3-dioxolan-2-one, etc. mainly affects the cycle characteristics and the swelling characteristics. When the content of the fourth solvent is small, the swelling characteristic is improved, but the cycle characteristic is lowered. On the other hand, when the content of the fourth solvent is large, the cycle characteristics are improved, but the swelling characteristics are lowered. For these reasons, when the content of the fourth solvent is within an appropriate range of 3% by weight or more and 24% by weight or less, the cycle characteristics and the swollenness characteristics are improved.

  As described above, the third and fourth solvents affect many characteristics such as cycle characteristics, load characteristics, blister characteristics, and safety. In particular, the third solvent has a great influence on the blister characteristics. give. From these facts, when the total content of the third and fourth solvents is within an appropriate range of 4 wt% or more and 25 wt% or less, the swelling characteristics are maintained while the cycle characteristics, load characteristics and safety are ensured. Can be prevented from decreasing.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution impregnated in the separator 23.

  This secondary battery is manufactured as follows, for example.

  First, the positive electrode 21 is manufactured by forming the positive electrode active material layer 21B on both surfaces of the positive electrode current collector 21A. In this case, for example, a positive electrode mixture in which a positive electrode active material, a conductive agent, and a binder are mixed is dispersed in a solvent to form a paste-like positive electrode mixture slurry, and the positive electrode mixture slurry is used as a positive electrode current collector. After applying and drying on both surfaces of the body 21A, the positive electrode active material layer 21B is formed by compression molding with a roll press. For example, the negative electrode 22 is manufactured by forming the negative electrode active material layer 22B on both surfaces of the negative electrode current collector 22A by the same manufacturing procedure as that of the positive electrode 21.

  Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. Subsequently, after the positive electrode 21 and the negative electrode 22 are laminated via the separator 23 and wound to form the wound electrode body 20, the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15 and the negative electrode lead 26 is welded to the battery can 11. Subsequently, the wound electrode body 20 is housed inside the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13 from above and below. Subsequently, after preparing the above electrolytic solution, it is injected into the battery can 11 and impregnated in the separator 23. Finally, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are caulked and fixed to the opening end of the battery can 11 via the gasket 17. As a result, the secondary battery shown in FIG. 2 is completed.

  According to this cylindrical secondary battery, when the capacity of the negative electrode 22 is expressed based on insertion and extraction of lithium, the above-described electrolytic solution is provided, so that the state of lithium is stabilized during charging and discharging. In addition, the decomposition reaction of the electrolytic solution is suppressed. Therefore, excellent cycle characteristics, load characteristics, swelling characteristics and safety can be obtained.

  In this case, in particular, if the negative electrode active material of the negative electrode 22 is capable of inserting and extracting lithium and includes a negative electrode material having at least one of a metal element and a metalloid element, charge / discharge is performed. Sometimes the electrolytic solution is more easily decomposed, but a higher effect can be obtained because the decomposition reaction of the electrolytic solution is more effectively suppressed than when a carbon material is included.

  Other effects relating to the secondary battery are the same as those described for the above-described electrolytic solution.

  Next, the second and third secondary batteries will be described. At this time, the same reference numerals are assigned to the same components as those of the first secondary battery, and the description thereof is omitted.

(Secondary secondary battery)
The second secondary battery has the same configuration, operation, and effect as the first secondary battery except that the configuration of the negative electrode 22 is different, and is manufactured by the same procedure.

  The negative electrode 22 is provided with a negative electrode active material layer 22B on both surfaces of a negative electrode current collector 22A, as in the first secondary battery. The negative electrode active material layer 22B includes, for example, a material having silicon or tin as a constituent element as a negative electrode active material. Specifically, for example, a simple substance, an alloy or a compound of silicon, or a simple substance, an alloy or a compound of tin is included, and two or more kinds thereof may be included.

  The negative electrode active material layer 22B is formed by using a vapor phase method, a liquid phase method, a thermal spraying method, a firing method, or two or more of these methods. The negative electrode active material layer 22B and the negative electrode current collector It is preferable that 22A is alloyed in at least a part of the interface. Specifically, at the interface, the constituent elements of the negative electrode current collector 22A may diffuse into the negative electrode active material layer 22B, or the constituent elements of the negative electrode active material layer 22B diffuse into the negative electrode current collector 22A. Alternatively, the constituent elements of both may diffuse to each other. This is because, during charging / discharging, breakage due to expansion and contraction of the negative electrode active material layer 22B is suppressed, and electronic conductivity between the negative electrode active material layer 22B and the negative electrode current collector 22A is improved.

  As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, vacuum deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD) Or plasma chemical vapor deposition. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder, dispersed in a solvent, applied, and then heat-treated at a temperature higher than the melting point of the binder. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

(Third secondary battery)
The third secondary battery is a lithium metal secondary battery in which the capacity of the negative electrode 22 is expressed based on precipitation and dissolution of lithium. This secondary battery has the same configuration as the first secondary battery except that the negative electrode active material layer 22B is made of lithium metal, and is manufactured by the same procedure.

  This secondary battery uses lithium metal as a negative electrode active material, and can thereby obtain a high energy density. The negative electrode active material layer 22B may already exist from the time of assembly, but may not be present at the time of assembly, and may be configured by lithium metal deposited during charging. Further, the negative electrode current collector 22A may be omitted by using the negative electrode active material layer 22B as a current collector.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and deposited as lithium metal on the surface of the negative electrode current collector 22A through the electrolytic solution impregnated in the separator 23. On the other hand, when discharging is performed, for example, lithium metal is eluted from the negative electrode active material layer 22 </ b> B as lithium ions and inserted into the positive electrode 21 through the electrolytic solution impregnated in the separator 23.

  According to this cylindrical secondary battery, when the capacity of the negative electrode 22 is expressed based on the precipitation and dissolution of lithium, the above-described electrolytic solution is provided, so that excellent cycle characteristics, load characteristics, and swelling characteristics are provided. And you can get safety. Other effects relating to the secondary battery are the same as those of the first secondary battery described above.

(Fourth secondary battery)
FIG. 7 shows an exploded perspective configuration of the fourth secondary battery, and FIG. 8 shows an enlarged cross section taken along line VIII-VIII of the spirally wound electrode body 30 shown in FIG.

  The secondary battery is, for example, a lithium ion secondary battery, similar to the first secondary battery described above, and the positive electrode lead 31 and the negative electrode lead 32 are mainly attached to the inside of the film-shaped exterior member 40. The wound electrode body 30 is accommodated. The battery structure using the film-shaped exterior member 40 is called a laminate film type.

  For example, the positive electrode lead 31 and the negative electrode lead 32 are led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 is made of, for example, a metal material such as aluminum, and the negative electrode lead 32 is made of, for example, a metal material such as copper, nickel, or stainless steel. These metal materials are, for example, in a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, an aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 40 has a structure in which, for example, outer edges of two rectangular aluminum laminate films are bonded to each other by fusion or an adhesive so that the polyethylene film faces the wound electrode body 30. ing.

  An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. Examples of such a material include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

  In addition, the exterior member 40 may be constituted by a laminate film having another laminated structure instead of the above-described aluminum laminate film, or may be constituted by a polymer film such as polypropylene or a metal film.

  The electrode winding body 30 is wound after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35 and the electrolyte 36, and the outermost periphery thereof is protected by a protective tape 37.

  In the positive electrode 33, for example, a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A. The negative electrode 34 is, for example, provided with a negative electrode active material layer 34B on both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B is disposed so as to face the positive electrode active material layer 33B. The configuration of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 is the same as that of the positive electrode current collector 21A and the positive electrode active material layer in the first secondary battery described above. The configurations of 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23 are the same.

  The electrolyte 36 is a so-called gel electrolyte that includes the above-described electrolytic solution and a polymer compound that holds the electrolytic solution. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and liquid leakage is prevented.

  Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropyrene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, poly Examples thereof include siloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, and polycarbonate. These may be single and multiple types may be mixed. Among these, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene or polyethylene oxide is preferable. This is because it is electrochemically stable.

  In the electrolyte 36 which is a gel electrolyte, the solvent of the electrolytic solution is a wide concept including not only a liquid solvent but also an ion conductive substance capable of dissociating the electrolyte salt. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

  Instead of the gel electrolyte 36 in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the separator 35 is impregnated with the electrolytic solution.

  This secondary battery is manufactured by the following three types of manufacturing methods, for example.

  In the first manufacturing method, first, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A, for example, by the same procedure as the positive electrode 21 and the negative electrode 22 in the first secondary battery described above. Thus, the negative electrode 34 is manufactured by forming the negative electrode active material layer 34B on both surfaces of the negative electrode current collector 34A. Then, after preparing the precursor solution containing electrolyte solution, a high molecular compound, and a solvent and apply | coating to the positive electrode 33 and the negative electrode 34, the solvent is volatilized and the gel electrolyte 36 is formed. Subsequently, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are stacked via the separator 35 and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion thereof to produce the wound electrode body 30. To do. Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded to each other by heat fusion or the like, so that the wound electrode body 30 is Encapsulate. At this time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 7 and 8 is completed.

  In the second manufacturing method, first, after attaching the positive electrode lead 31 to the positive electrode 33 and the negative electrode lead 32 to the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35. Then, a protective tape 37 is adhered to the outermost peripheral portion to produce a wound body that is a precursor of the wound electrode body 30. Subsequently, after sandwiching the wound body between the two film-shaped exterior members 40, the remaining outer peripheral edge except for the outer peripheral edge on one side is adhered by heat fusion or the like, thereby forming a bag-shaped exterior The wound body is accommodated in the member 40. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared to form a bag-shaped exterior member. After injecting into the inside of 40, the opening part of the exterior member 40 is sealed by heat sealing or the like. Finally, the gel electrolyte 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, the secondary battery is completed.

  In the third manufacturing method, a wound body is formed by forming a wound body in the same manner as in the second manufacturing method described above except that the separator 35 coated with the polymer compound on both sides is used first. 40 is housed inside. Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component. Subsequently, after the electrolytic solution is prepared and injected into the exterior member 40, the opening of the exterior member 40 is sealed by heat fusion or the like. Finally, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36. Thus, the secondary battery is completed.

  In the third manufacturing method, the swollenness of the secondary battery is suppressed as compared with the first manufacturing method. Further, in the third manufacturing method, compared with the second manufacturing method, there are hardly any monomers or solvents that are raw materials for the polymer compound remaining in the electrolyte 36, and the formation process of the polymer compound is well controlled. Therefore, sufficient adhesion is obtained between the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte 36.

  According to this laminated film type secondary battery, when the capacity of the negative electrode 34 is expressed based on insertion and extraction of lithium, the above-described electrolytic solution is provided, so that the same as the first secondary battery. Excellent cycle characteristics, load characteristics, swell characteristics and safety can be obtained. The effects of the secondary battery other than those described above are the same as those of the first secondary battery.

  Of course, the laminated film type secondary battery is not limited to the same configuration as the first secondary battery, and may have the same configuration as the second or third secondary battery.

  Examples of the present invention will be described in detail.

(Example 1-1)
The laminate film type secondary battery shown in FIGS. 7 and 8 was produced by the following procedure. At this time, a lithium ion secondary battery in which the capacity of the negative electrode 34 is expressed based on insertion and extraction of lithium was made.

First, the positive electrode 33 was produced. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of 0.5: 1, and then calcined in air at 900 ° C. for 5 hours to form a lithium cobalt composite. An oxide (LiCoO ₂ ) was obtained. Subsequently, 91 parts by mass of lithium cobalt composite oxide as a positive electrode active material, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to form a positive electrode mixture. Dispersed in methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 33A made of a strip-shaped aluminum foil (thickness = 12 μm) by a bar coater, dried, and then compression-molded by a roll press to perform positive electrode activation. A material layer 33B was formed.

  Next, after preparing a negative electrode current collector 34A (thickness = 15 μm) made of an electrolytic copper foil, silicon is deposited as a negative electrode active material on both surfaces of the negative electrode current collector 34A by an electron beam evaporation method to form a plurality of negative electrode active materials. The negative electrode 34 was produced by forming the material particles and forming the negative electrode active material layer 34B. When forming this negative electrode active material layer 34B, the negative electrode active material particles were formed in a single deposition step so that the negative electrode active material particles had a single layer structure. The thickness of one side of the negative electrode current collector 34A was set to 10 μm.

Next, as a solvent, propylene carbonate (PC) as a first solvent (solvent 1), diethyl carbonate (DEC) as a second solvent (solvent 2), and a third solvent (solvent 3). Trans-4,5-difluoro-1,3-dioxolan-2-one (t-DFEC) and 4-fluoro-1,3-dioxolan-2-one (FEC) as the fourth solvent (solvent 4) Then, lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte salt to prepare an electrolytic solution. At this time, the composition of the solvent (PC: DEC: t-DFEC: FEC) was 44: 50: 1: 5 by weight, and the concentration of lithium hexafluorophosphate in the electrolyte was 1 mol / kg.

  Finally, a secondary battery was assembled using the electrolytic solution together with the positive electrode 33 and the negative electrode 34. First, the positive electrode lead 31 made of aluminum was welded to one end of the positive electrode current collector 33A, and the negative electrode lead 32 made of nickel was welded to one end of the negative electrode current collector 34A. Subsequently, the positive electrode 33, the separator 35 (thickness = 25 μm) made of a microporous polypropylene film, and the negative electrode 34 are laminated in this order and then wound in the longitudinal direction, and then a protective tape 37 made of an adhesive tape. Then, the winding end portion was fixed to form a wound body that is a precursor of the wound electrode body 30. Subsequently, a laminate film (total thickness) in which a nylon film (thickness = 30 μm), an aluminum foil (thickness = 40 μm), and an unstretched polypropylene film (thickness = 30 μm) are laminated from the outside. = 100 μm), the wound body was sandwiched between the exterior members 40, and the outer edges except for one side were heat-sealed to accommodate the wound body inside the bag-shaped exterior member 40. Subsequently, an electrolytic solution was injected from the opening of the exterior member 40 and impregnated in the separator 35 to produce a wound electrode body 30. Finally, the laminated film type secondary battery was completed by thermally sealing and sealing the opening of the exterior member 40 in a vacuum atmosphere. For this secondary battery, by adjusting the thickness of the positive electrode active material layer 33 </ b> B so that the charge / discharge capacity of the negative electrode 34 is larger than the charge / discharge capacity of the positive electrode 33, lithium metal is present on the negative electrode 34 during full charge. It was made not to precipitate.

(Examples 1-2 to 1-14)
The composition of the solvent (PC: DEC: t-DFEC: FEC) was 40: 50: 5: 5 (Example 1-2), 35: 50: 10: 5 (Example 1-3), 30:50:15 : 5 (Example 1-4), 30: 50: 10: 10 (Example 1-5), 25: 50: 10: 15 (Example 1-6), 36: 60: 1: 3 (Example) 1-7), 39: 50: 1: 10 (Example 1-8), 25: 50: 1: 24 (Example 1-9), 25: 50: 5: 20 (Example 1-10), 45: 40: 10: 5 (Example 1-11), 40: 45: 10: 5 (Example 1-12), 15: 70: 10: 5 (Example 1-13), or 5:70: The procedure was the same as that of Example 1-1 except that the ratio was changed to 10:15 (Example 1-14).

(Example 1-15)
A procedure similar to that of Example 1-3 was performed except that cis-4,5-difluoro-1,3-dioxolan-2-one (c-DFEC) was used as the solvent 3 instead of t-DFEC.

(Examples 1-16 and 1-17)
Dimethyl carbonate (DMC: Example 1-16) or ethyl methyl carbonate (EMC: Example 1-17) was added as solvent 2, and the composition of solvent 2 (DEC: DMC or DEC: EMC) was 45: Except for the change to 5, the same procedure as in Example 1-3 was performed.

(Examples 1-18 to 1-20)
Instead of FEC as solvent 4, fluoromethyl methyl carbonate (FDMC: Example 1-18), bis (fluoromethyl) carbonate (DFDMC: Example 1-19), or vinylene carbonate (VC) (Example 1-20) A procedure similar to that of Example 1-3 was performed except that was used.

(Examples 1-21 to 1-25)
Instead of PC as solvent 1, ethylene carbonate (EC: Example 1-21), butylene carbonate (BC: Example 1-22), γ-butyllactone (GBL: Example 1-23), γ-valerolactone ( GVL: Example 1-24), or procedure similar to Example 1-3, except that 4-trifluoromethyl-1,3-dioxolan-2-one (TFPC: Example 1-25) was used It went through.

(Comparative Example 1-1)
A procedure similar to that of Example 1-1 was performed, except that the solvents 3 and 4 (t-DFEC and FEC) were not used and the composition of the solvent (PC: DEC) was changed to 30:70 by weight ratio.

(Comparative Example 1-2)
The same procedure as in Example 1-1 was performed except that the solvent composition (PC: DEC: t-DFEC) was changed to 35:50:15 by weight ratio without using the solvent 4 (FEC).

(Comparative Example 1-3)
The same procedure as in Example 1-1 was performed, except that the solvent 3 (t-DFEC) was not used and the composition of the solvent (PC: DEC: FEC) was changed to 25:50:25 by weight ratio.

(Comparative Examples 1-4 to 1-10)
The composition of the solvent (PC: DEC: t-DFEC: FEC) was 10: 75: 10: 5 (Comparative Example 1-4), 50: 35: 10: 5 (Comparative Example 1-5), 10:50:10 : 30 (Comparative Example 1-6), 25: 50: 20: 5 (Comparative Example 1-7), 34: 50: 15: 1 (Comparative Example 1-8), 24.5: 50: 0.5: The procedure was the same as that of Example 1-1 except that it was changed to 25 (Comparative Example 1-9) or 35: 63: 1: 1 (Comparative Example 1-10).

  The cycle characteristics, load characteristics, swelling characteristics and safety of the secondary batteries of Examples 1-1 to 1-25 and Comparative Examples 1-1 to 1-10 were examined. The results are shown in Tables 1 to 4. Results were obtained.

  When examining the cycle characteristics, charging and discharging was performed for 2 cycles in an atmosphere at 23 ° C., and the discharge capacity was measured. Subsequently, charging and discharging were performed in the same atmosphere until the total number of cycles reached 100 cycles, and the discharge capacity was measured. After that, the discharge capacity retention ratio (%) = (discharge capacity at the 100th cycle / discharge capacity at the second cycle) × 100 was calculated. In this case, charge / discharge conditions for one cycle are as follows: constant current constant voltage charging to a maximum voltage of 4.2 V at a constant current of 0.2 C, then constant current to a final voltage of 2.5 V at a constant current of 0.2 C. Discharged. This “0.2 C” is a current value at which the theoretical capacity can be discharged in 5 hours.

  When investigating the load characteristics, in a 23 ° C atmosphere, charge at a constant current of 1C to a constant voltage and constant voltage up to an upper limit voltage of 4.2V, then discharge at a constant current of 1C to a final voltage of 2.5V. The charge / discharge process was repeated 2 cycles, and the discharge capacity (1C discharge capacity: mAh) of the second cycle was measured. This “1C” is a current value at which the theoretical capacity can be discharged in one hour.

  When investigating the swelling characteristics, charge and discharge for 2 cycles in an atmosphere of 23 ° C., then charge again to measure the thickness, and then continue to be stored in an 85 ° C. constant temperature bath for 12 hours in the charged state. After measuring the thickness, the swelling (mm) = (thickness after storage−thickness before storage) was calculated. At this time, the charge / discharge conditions for one cycle were the same as those for examining the cycle characteristics.

  When investigating safety, an internal short-circuit test (nail penetration test) was performed according to the following procedure, and the upper limit value of the voltage at which no malfunction (gas ejection) occurred was determined. In the internal short-circuit test, first, in a 23 ° C. atmosphere, a constant current is charged at a constant current of 200 mA until the battery voltage reaches 4.2 V, and then a constant voltage until the current reaches 5 mA at a constant voltage of 4.2 V. After charging, the battery was discharged at a constant current of 200 mA until the battery voltage reached 3.0V. Subsequently, after charging the four types of secondary batteries at a constant current of 200 mA until the battery voltages reach 4.10V, 4.20V, 4.25V, and 4.32V, 100 mm / second is charged at the center thereof. A nail (diameter = 2.5 mm) was pierced and penetrated at a speed. Finally, the case where gas ejection did not occur was judged good, and the case where it occurred was judged bad, and the upper limit value of the voltage at which good results were obtained was taken as the upper limit voltage.

  As shown in Tables 1 to 4, the discharge capacity retention ratio, 1C discharge capacity, swelling and upper limit voltage varied depending on the composition of the solvent. In this case, the solvent is PC 1 or the like as the solvent 1 (content = 5 wt% or more and 45 wt% or less), DEC or the like as the solvent 2 (content = 40 wt% or more and 70 wt% or less), T-DFEC or the like that is solvent 3 (content = 1 wt% or more and 15 wt% or less) and FEC that is solvent 4 (content = 3 wt% or more and 24 wt% or less); In Examples 1-1 to 1-25 containing a total amount of 4% by weight or more and 25% by weight or less), unlike Comparative Examples 1-1 to 1-10 that do not satisfy these composition conditions, the amount is high. A discharge capacity retention ratio, 1C discharge capacity and upper limit voltage were obtained, and swelling was suppressed to a small level. Specifically, in Examples 1-1 to 1-25, a discharge capacity maintenance ratio of 40% or more, a 1C discharge capacity of 800 mAh or more, a swelling of 2 mm or less, and an upper limit voltage of 4.20 V or more are obtained. It was.

  Here, as a combination for each of the solvents 1 to 4, only the result when two or more types of solvents 2 are combined is shown, and the result when two or more types of solvents 1, 3, and 4 are combined is not shown. However, as is apparent from the results in Table 1, all of the PCs and the like as the solvent 1 perform the same function, and the same applies to the solvents 3 and 4. It is clear that the same result can be obtained when combining more than one type.

  For these reasons, in the secondary battery of the present invention, the solvent of the electrolytic solution is PC or the like as the solvent 1, DEC or the like as the solvent 2, and DFEC (t-DFEC or c-DFEC) as the solvent 3. FEC that is solvent 4 and the like, and the content in the solvent is 5 wt% to 45 wt% in solvent 1, 40 wt% to 70 wt% in solvent 2, and 1 wt% in solvent 3 15% by weight or less, 3% by weight or more and 24% by weight or less in the solvent 4 and 4% by weight or more and 25% by weight or less in the total of the solvents 3 and 4 It was confirmed that

(Examples 2-1 to 2-4)
Lithium tetrafluoroborate (LiBF ₄ ) is added as an electrolyte salt, and sulfobenzoic anhydride (SBAH: Example 2-1) and sulfopropionic anhydride (SPAH: Example 2-2), which are acid anhydrides, are added. ), Propanedisulfonic anhydride (PSAH: Example 2-3), or ethanedisulfonic anhydride (ESAH: Example 2-4) was added, and the same procedure as in Example 1-4 was performed. . At this time, the concentration of LiBF ₄ in the electrolytic solution was 0.05 mol / kg, and the content of SBAH and the like in the electrolytic solution was 1% by weight. The term “1% by weight” means that SBAH or the like is added by an amount corresponding to 1% by weight when the entire solvent is 100% by weight.

(Example 2-5)
A procedure similar to that in Example 1-4 was performed except that LiBF ₄ was added as an electrolyte salt and propene sultone (PRS), which is a sultone, was added. At this time, the concentration of LiBF ₄ in the electrolytic solution was 0.05 mol / kg, and the content of PRS in the electrolytic solution was 1% by weight.

(Examples 2-6 and 2-7)
As an electrolyte salt, lithium tetrafluoroborate (LiBF ₄ ) and a compound shown in Chemical Formula ₄ (6) (Example 2-6) or a compound shown in Chemical Formula 7 is bis. The same procedure as in Example 1-4 was performed, except that (trifluoromethanesulfonyl) imidolithium (LiTFSI: Example 2-7) was added. At this time, the concentration of LiBF ₄ in the electrolytic solution was set to 0.05 mol / kg, and the content of the compound shown in Chemical Formula 4 (6) in the electrolytic solution was set to 0.1 mol / kg wt%.

(Comparative Example 2-1)
A procedure similar to that of Comparative Example 1-1 was performed except that SBAH, which is an acid anhydride, was added. At this time, the content of SBAH in the electrolytic solution was 1% by weight.

(Comparative Examples 2-2 to 2-4)
A procedure similar to those of Comparative Examples 1-1, 1-6, and 1-7 was performed, except that LiBF ₄ and acid anhydride SBAH were added as electrolyte salts. At this time, the concentration of LiBF ₄ in the electrolytic solution was 0.05 mol / kg, and the content of SBAH in the electrolytic solution was 1% by weight.

  When the cycle characteristics, load characteristics and swelling characteristics of the secondary batteries of Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-4 were examined, the results shown in Table 5 and Table 6 were obtained. It was.

As shown in Tables 5 and 6, even in the case where the electrolyte contains LiBF _{4 as} another electrolyte salt, SBAH as an acid anhydride, or PRS as sultone, Results similar to those in Table 4 were obtained. That is, in Examples 2-1 to 2-7 in which the solvent of the electrolytic solution contains the solvents 1 to 4 within the predetermined range described above, unlike Comparative Example 2-1 that does not satisfy these composition conditions, % Of the discharge capacity retention rate of 1% or more and 1C discharge capacity of 800 mAh or more were obtained, and the swelling was suppressed to 2 mm or less. Moreover, in Example 2-1 in which the solvent of the electrolytic solution contains the solvents 1 to 4 within the above-described predetermined range, as compared with Comparative Examples 2-2 to 2-4 that do not satisfy the composition conditions, The discharge capacity retention ratio or 1C discharge capacity increased, or the swelling decreased.

In this case, in Examples 2-1 to 2-7 in which LiBF ₄ or the like, SBAH or the like or PRS was contained in the electrolytic solution, the discharge capacity retention ratio and 1C discharge were higher than those in Examples 1-4 that did not contain them. Capacity increased and swelling decreased.

  Here, only the results in the case of using lithium hexafluorophosphate, lithium tetrafluoroborate, or the compound shown in Chemical Formula 1 or Chemical Formula 7 as other electrolyte salts are shown, and lithium perchlorate is shown. Or the result at the time of using the compound shown to lithium hexafluoro arsenate or Chemical formula 2, Chemical formula 3, Chemical formula 8 or Chemical formula 9 is not shown. However, since lithium perchlorate and the like perform the same function as lithium hexafluorophosphate and the like, it is clear that the same result can be obtained when the former is used as when the latter is used.

  For these reasons, in the secondary battery of the present invention, the solvent of the electrolytic solution contains the solvents 1 to 4 within the above-described predetermined range, thereby changing the type of the electrolyte salt or adding an additive to the electrolytic solution. Even when added, it was confirmed that excellent cycle characteristics, load characteristics, and swelling characteristics can be obtained.

  In this case, in the electrolyte solution, as other electrolyte salts, lithium tetrafluoroborate, lithium perchlorate or lithium hexafluoroarsenate, the compounds shown in Chemical Formula 1 to Chemical Formula 3 or Chemical Formula 7 to Chemical Formula 9 It was also confirmed that when the acid anhydride or sultone was added, the cycle characteristics, load characteristics and swelling characteristics were further improved.

(Examples 3-1 and 3-2)
When forming the negative electrode active material layer 34B, after forming a plurality of negative electrode active material particles, a silicon oxide (SiO ₂ ) is deposited as an oxide-containing film on the surface of the negative electrode active material particles by a liquid phase deposition method. The same procedure as in Examples 1-3 and 1-5 was performed. In the case of forming this oxide-containing film, the negative electrode current collector 34A in which the negative electrode active material particles are formed is immersed for 3 hours in a solution in which boron is dissolved as an anion scavenger in hydrofluoric acid, After depositing silicon oxide on the surface of the negative electrode active material particles, it was washed with water and dried under reduced pressure.

(Comparative Example 3-1)
Procedures similar to those in Examples 3-1 and 3-2 except that the solvents 3 and 4 (t-DFEC and FEC) were not used and the composition of the solvent (PC: DEC) was changed to 30:70 by weight ratio. It went through.

(Comparative Example 3-2)
The same procedure as in Examples 3-1 and 3-2 except that the solvent 4 (FEC) was not used and the composition of the solvent (PC: DEC: t-DFEC) was changed to 40:50:10 by weight ratio. It went through.

(Comparative Example 3-3)
The same procedure as in Examples 3-1 and 3-2, except that the solvent 3 (t-DFEC) was not used and the composition of the solvent (PC: DEC: FEC) was changed to 40:50:10 by weight ratio. It went through.

  When the cycle characteristics, the load characteristics, and the swollenness characteristics of the secondary batteries of Examples 3-1 and 3-2 and Comparative examples 3-1 to 3-3 were examined, the results shown in Table 7 were obtained.

  As shown in Table 7, when the oxide-containing film was formed, the same results as those in Tables 1 to 4 were obtained. That is, in Examples 3-1 and 3-2 in which the solvent of the electrolytic solution contains the solvents 1 to 4 within the predetermined range described above, Comparative Examples 3-1 to 3-3 not satisfying the composition conditions In comparison, the 1C discharge capacity was secured and the discharge capacity retention rate was increased while suppressing swelling. Moreover, in Examples 3-1 and 3-2 in which the oxide-containing film was formed, the discharge capacity retention ratio and 1C discharge capacity were higher than in Examples 1-3 and 1-5 in which the oxide-containing film was not formed, The blister has become smaller.

  Therefore, in the secondary battery of the present invention, excellent cycle characteristics can be obtained even when an oxide-containing film is formed when the solvent of the electrolytic solution contains the solvents 1 to 4 within the predetermined range described above. It was confirmed that load characteristics and swelling characteristics can be obtained. It was also confirmed that if an oxide-containing film is formed, cycle characteristics, load characteristics, and swelling characteristics are further improved.

(Examples 4-1 and 4-2)
In the case of forming the negative electrode active material layer 34B, Example 1-3, except that after forming a plurality of negative electrode active material particles, a plating film of cobalt (Co) was grown as a metal material by an electrolytic plating method. The same procedure as in 1-5 was performed. In the case of forming this metal material, current was supplied while supplying air to the plating bath, and cobalt was deposited on both surfaces of the negative electrode current collector 34A. At this time, a cobalt plating solution manufactured by Japan High Purity Chemical Co., Ltd. was used as the plating solution, the current density was 2 A / dm ^{2 to} 5 A / dm ² , and the plating rate was 10 nm / second.

(Comparative Example 4-1)
Procedures similar to those of Examples 4-1 and 4-2, except that the solvents 3 and 4 (t-DFEC and FEC) were not used and the composition of the solvent (PC: DEC) was changed to 30:70 by weight. It went through.

(Comparative Example 4-2)
The same procedure as in Examples 4-1 and 4-2, except that the solvent 4 (FEC) was not used and the composition of the solvent (PC: DEC: t-DFEC) was changed to 40:50:10 by weight ratio. It went through.

(Comparative Example 4-3)
The same procedure as in Examples 4-1 and 4-2, except that the solvent 3 (t-DFEC) was not used and the composition of the solvent (PC: DEC: FEC) was changed to 40:50:10 by weight ratio. It went through.

  When the cycle characteristics, the load characteristics, and the swelling characteristics of the secondary batteries of Examples 4-1 and 4-2 and Comparative examples 4-1 to 4-3 were examined, the results shown in Table 8 were obtained.

  As shown in Table 8, even when the metal material was formed, results similar to those in Tables 1 to 4 were obtained. That is, in Examples 4-1 and 4-2 in which the solvent of the electrolytic solution contains the solvents 1 to 4 within the predetermined range described above, Comparative Examples 4-1 to 4-3 that do not satisfy the composition conditions In comparison, the 1C discharge capacity was secured and the discharge capacity retention rate was increased while suppressing swelling. Moreover, in Examples 4-1 and 4-2 in which the metal material was formed, the discharge capacity retention ratio and the 1C discharge capacity were higher than those in Examples 1-3 and 1-5 in which the metal material was not formed, and swelling was caused. It has become smaller.

  From these facts, in the secondary battery of the present invention, even when the solvent of the electrolytic solution contains the solvents 1 to 4 within the predetermined range described above, even when a metal material is formed, excellent cycle characteristics and load It was confirmed that characteristics and swollenness characteristics were obtained. It was also confirmed that if a metal material is formed, the cycle characteristics, load characteristics, and swelling characteristics are further improved.

  As is clear from the results of Tables 1 to 8 above, in the secondary battery of the present invention, the solvent of the electrolytic solution is propylene carbonate or the like as the first solvent and diethyl carbonate or the like as the second solvent. A fourth solvent, 4,5-difluoro-1,3-dioxolan-2-one, a fourth solvent, 4-fluoro-1,3-dioxolan-2-one, and the like, The content in the first solvent is 5% by weight to 45% by weight, the second solvent is 40% by weight to 70% by weight, the third solvent is 1% by weight to 15% by weight, 3 wt% or more and 24 wt% or less in the solvent, and 4 wt% or more and 25 wt% or less in the total of the third and fourth solvents, without depending on the type of electrolyte salt or the presence or absence of additives. Excellent cycle characteristics, load characteristics, swelling characteristics And that safety is obtained was confirmed.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments described in the above embodiments and examples, and various modifications can be made. For example, the usage of the electrolytic solution of the present invention is not necessarily limited to a battery, and may be an electrochemical device other than a battery. Other applications include, for example, capacitors.

  In the above-described embodiments and examples, the types of secondary batteries include lithium ion secondary batteries in which the negative electrode capacity is expressed based on insertion and extraction of lithium, and the negative electrode capacity is lithium deposition and dissolution. Although the lithium metal secondary battery expressed based on the above has been described, the present invention is not necessarily limited thereto. In the battery of the present invention, when the negative electrode includes a negative electrode material capable of occluding and releasing lithium, the negative electrode material has a smaller capacity than the positive electrode, thereby reducing the capacity of the negative electrode. In addition, the present invention can be similarly applied to a secondary battery including a capacity associated with release and a capacity associated with precipitation and dissolution of lithium, and represented by a sum of these capacities.

  In the above-described embodiments and examples, the case where the electrolytic solution or the gel electrolyte in which the electrolytic solution is held in the polymer compound is used as the electrolyte of the battery of the present invention has been described. However, other types of electrolytes are used. May be used. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolyte, or a mixture of another inorganic compound and an electrolyte. Or a mixture of these inorganic compounds and a gel electrolyte.

  Further, in the above-described embodiments and examples, the case where the battery structure is a cylindrical type and a laminate film type, and the case where the battery element has a winding structure have been described as examples, but the battery of the present invention is The present invention can be similarly applied to a case where other battery structures such as a square shape, a coin shape, and a button shape are provided, and a case where the battery element has another structure such as a laminated structure.

  In the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements such as sodium (Na) or potassium (K), magnesium (Mg) or calcium ( Group 2 elements such as Ca) or other light metals such as aluminum may be used. Also in these cases, the negative electrode material described in the above embodiment can be used as the negative electrode active material.

  In the above-described embodiments and examples, regarding the electrolytic solution or the secondary battery of the present invention, the appropriate ranges derived from the results of the examples for the contents of the first to fourth solvents in the solvent are described. However, the explanation does not completely deny the possibility that the content will be outside the above range. In other words, the appropriate range described above is a particularly preferable range for obtaining the effect of the present invention, and the content may be slightly deviated from the above range as long as the effect of the present invention is obtained.

It is sectional drawing showing the structure of the 1st secondary battery provided with the electrolyte solution which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. FIG. 3 is an enlarged cross-sectional view illustrating a configuration of a negative electrode illustrated in FIG. 2. It is sectional drawing showing the structure of the negative electrode of a reference example. FIG. 3 is an SEM photograph showing a cross-sectional structure of the negative electrode shown in FIG. 2 and a schematic diagram thereof. FIG. 3 is an SEM photograph showing another cross-sectional structure of the negative electrode shown in FIG. 2 and a schematic diagram thereof. It is sectional drawing showing the structure of the 4th secondary battery provided with the electrolyte solution which concerns on one embodiment of this invention. It is sectional drawing along the VIII-VIII line of the wound electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator 24, center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte, 37 ... protective tape, 40 ... exterior member, 41 ... adhesion film.

Claims (21)

A first solvent comprising at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and 4-trifluoromethyl-1,3-dioxolan-2-one;
A second solvent comprising at least one member selected from the group consisting of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate;
A third solvent consisting of 4,5-difluoro-1,3-dioxolan-2-one;
And a fourth solvent consisting of at least one member selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and vinylene carbonate. ,
The content of the first solvent in the solvent is 5 wt% or more and 45 wt% or less,
The content of the second solvent in the solvent is 40 wt% or more and 70 wt% or less,
The content of the third solvent in the solvent is 1 wt% or more and 15 wt% or less,
The content of the fourth solvent in the solvent is 3 wt% or more and 24 wt% or less,
The total content of said 3rd and 4th solvent is 4 to 25 weight%. Electrolyte characterized by the above-mentioned.   The electrolytic solution according to claim 1, comprising sultone.   The electrolytic solution according to claim 1, comprising an acid anhydride. At least one selected from the group consisting of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), and lithium hexafluoroarsenate (LiAsF ₆ ) The electrolyte solution according to claim 1, comprising an electrolyte salt containing 2. The electrolytic solution according to claim 1, wherein the electrolytic solution contains an electrolyte salt containing at least one selected from the group consisting of compounds represented by Chemical Formulas 1 to 3. 3.

(X11 is a group 1 element or group 2 element in the long-period periodic table, or aluminum. M11 is a transition metal, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R11 is Y11 is —OC—R12—CO—, —OC—C (R13) ₂ — or —OC—CO—, wherein R12 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated group. R13 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, wherein a1 is an integer of 1 to 4, b1 is an integer of 0, 2 or 4, and c1 , D1, m1 and n1 are integers of 1 to 3.)

(X21 is a group 1 element or group 2 element in the long-period periodic table. M21 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Y21 is -OC-. _{(C (R21) 2) b2} -CO -, - (R23) 2 C- (C (R22) 2) c2 -CO -, - (R23) 2 C- (C (R22) 2) c2 -C (R23 ) ₂ -,-(R23) ₂ C- (C (R22) ₂ ) _c2 -SO _2- , -O ₂ S- (C (R22) ₂ ) _d2 -SO ₂ -or -OC- (C (R22) ₂ ) _d2 —SO ₂ —, wherein R21 and R23 are a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, and at least one of each is a halogen group or a halogenated alkyl group. R22 is hydrogen group, alkyl group, halogen Or a halogenated alkyl group, wherein a2, e2 and n2 are integers of 1 or 2, b2 and d2 are integers of 1 to 4, c2 is an integer of 0 to 4, and f2 and m2 are It is an integer from 1 to 3.)

(X31 is a group 1 element or group 2 element in the long-period periodic table. M31 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Rf is a fluorinated alkyl. Or a fluorinated aryl group, each having 1 to 10 carbon atoms, Y31 is —OC— (C (R31) ₂ ) _d3 —CO—, — (R32) ₂ C— (C (R31) _{2 D3} —CO—, — (R32) ₂ C— (C (R31) ₂ ) _d3 —C (R32) ₂ —, — (R32) ₂ C— (C (R31) ₂ ) _d3 —SO ₂ —, — O ₂ S— (C (R 31) ₂ ) e ₃ —SO ₂ — or —OC— (C (R 31) ₂ ) e ₃ —SO ₂ —, wherein R 31 is a hydrogen group, an alkyl group, a halogen group or a halogenated group. R32 represents a hydrogen group, an alkyl group, or a halogen. Or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a3, f3 and n3 are integers of 1 or 2, and b3, c3 and e3 are 1 to 4; (It is an integer, d3 is an integer of 0 to 4, and g3 and m3 are integers of 1 to 3.) The compounds shown in the chemical formula 1 are compounds represented by chemical formulas (1) to (6), and the compounds shown in the chemical formula 2 are represented by chemical formulas (1) to (8). The electrolytic solution according to claim 5, wherein the electrolyte is a compound represented by the chemical formula 3:

2. The electrolytic solution according to claim 1, wherein the electrolytic solution contains an electrolyte salt containing at least one selected from the group consisting of compounds represented by chemical formulas (7) to (9).

(M and n are integers of 1 or more.)

(R41 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

(P, q and r are integers of 1 or more.) A secondary battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The electrolyte is
A first solvent comprising at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and 4-trifluoromethyl-1,3-dioxolan-2-one;
A second solvent comprising at least one member selected from the group consisting of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate;
A third solvent consisting of 4,5-difluoro-1,3-dioxolan-2-one;
And a fourth solvent consisting of at least one member selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and vinylene carbonate. ,
The content of the first solvent in the solvent is 5 wt% or more and 45 wt% or less,
The content of the second solvent in the solvent is 40 wt% or more and 70 wt% or less,
The content of the third solvent in the solvent is 1 wt% or more and 15 wt% or less,
The content of the fourth solvent in the solvent is 3 wt% or more and 24 wt% or less,
The total content of the said 3rd and 4th solvent is 4 weight% or more and 25 weight% or less. The secondary battery characterized by the above-mentioned.   The secondary battery according to claim 8, wherein the electrolytic solution contains sultone.   The secondary battery according to claim 8, wherein the electrolytic solution contains an acid anhydride.   The electrolytic solution includes an electrolyte salt containing at least one member selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate. The secondary battery according to claim 8. The secondary battery according to claim 8, wherein the electrolytic solution includes an electrolyte salt containing at least one selected from the group consisting of compounds represented by chemical formulas 10 to 12.

(X11 is a group 1 element or group 2 element in the long-period periodic table, or aluminum. M11 is a transition metal, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R11 is Y11 is —OC—R12—CO—, —OC—C (R13) ₂ — or —OC—CO—, wherein R12 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated group. R13 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, wherein a1 is an integer of 1 to 4, b1 is an integer of 0, 2 or 4, and c1 , D1, m1 and n1 are integers of 1 to 3.)

(X21 is a group 1 element or group 2 element in the long-period periodic table. M21 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Y21 is -OC-. _{(C (R21) 2) b2} -CO -, - (R23) 2 C- (C (R22) 2) c2 -CO -, - (R23) 2 C- (C (R22) 2) c2 -C (R23 ) ₂ -,-(R23) ₂ C- (C (R22) ₂ ) _c2 -SO _2- , -O ₂ S- (C (R22) ₂ ) _d2 -SO ₂ -or -OC- (C (R22) ₂ ) _d2 —SO ₂ —, wherein R21 and R23 are a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, and at least one of each is a halogen group or a halogenated alkyl group. R22 is hydrogen group, alkyl group, halogen Or a halogenated alkyl group, wherein a2, e2 and n2 are integers of 1 or 2, b2 and d2 are integers of 1 to 4, c2 is an integer of 0 to 4, and f2 and m2 are It is an integer from 1 to 3.)

(X31 is a group 1 element or group 2 element in the long-period periodic table. M31 is a transition metal, or a group 13, element or group 15 element in the long-period periodic table. Rf is a fluorinated alkyl. Or a fluorinated aryl group, each having 1 to 10 carbon atoms, Y31 is —OC— (C (R31) ₂ ) _d3 —CO—, — (R32) ₂ C— (C (R31) _{2 D3} —CO—, — (R32) ₂ C— (C (R31) ₂ ) _d3 —C (R32) ₂ —, — (R32) ₂ C— (C (R31) ₂ ) _d3 —SO ₂ —, — O ₂ S— (C (R 31) ₂ ) e ₃ —SO ₂ — or —OC— (C (R 31) ₂ ) e ₃ —SO ₂ —, wherein R 31 is a hydrogen group, an alkyl group, a halogen group or a halogenated group. R32 represents a hydrogen group, an alkyl group, or a halogen. Or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a3, f3 and n3 are integers of 1 or 2, and b3, c3 and e3 are 1 to 4; (It is an integer, d3 is an integer of 0 to 4, and g3 and m3 are integers of 1 to 3.) The compounds shown in Chemical formula 10 are the compounds represented by Chemical formulas (1) to (6), and the compounds shown in Chemical formula 11 are represented by Chemical formulas (1) to (8). The secondary battery according to claim 12, wherein the compound is a compound represented by the chemical formula 12:

9. The secondary battery according to claim 8, wherein the electrolytic solution contains an electrolyte salt containing at least one selected from the group consisting of compounds represented by chemical formulas 16 to 18.

(M and n are integers of 1 or more.)

(R41 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

(P, q and r are integers of 1 or more.)   The negative electrode includes a negative electrode active material containing at least one selected from the group consisting of a simple substance, an alloy and a compound of silicon (Si), and a simple substance, an alloy and a compound of tin (Sn). 8. The secondary battery according to 8.   The negative electrode has a negative electrode active material layer on a negative electrode current collector, and the negative electrode active material layer is formed by at least one method selected from the group consisting of a vapor phase method, a liquid phase method, and a firing method. The secondary battery according to claim 8, wherein: The negative electrode has a negative electrode active material layer on a negative electrode current collector,
The secondary battery according to claim 8, wherein the negative electrode active material layer includes a plurality of negative electrode active material particles and an oxide-containing film that covers a surface of the negative electrode active material particles.   The secondary battery according to claim 17, wherein the oxide-containing film contains at least one oxide of silicon, germanium (Ge), and tin. The negative electrode has a negative electrode active material layer on a negative electrode current collector,
The secondary battery according to claim 8, wherein the negative electrode active material layer includes a plurality of negative electrode active material particles and a metal material that does not alloy with the electrode reactant in a gap between the negative electrode active material particles. .   The secondary electrode according to claim 19, wherein the negative electrode active material particles have a multilayer structure in the particles, and the negative electrode active material layer has the metal material in a gap in the negative electrode active material particles. battery.   The secondary battery according to claim 19, wherein the metal material is at least one of iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and copper (Cu). .

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