JP2010140765A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery which suppresses elution of metal ions from a positive electrode and is superior in floating characteristics. <P>SOLUTION: In the nonaqueous electrolyte battery, equipped with the positive electrode 21 in which a positive electrode active material layer 21B is installed on a positive electrode current collector 21A, a negative electrode 22, and a nonaqueous electrolyte, the positive electrode active material layer contains a first polymer that serves as the main binder and a second polymer that serves as a dispersant, and the nonaqueous electrolyte contains at least one kind of sulfon compound which is expressed by formula (1) and formula (2). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte battery. More specifically, the present invention relates to a non-aqueous electrolyte battery that avoids capacity deterioration associated with battery storage and float.

  2. Description of the Related Art Conventionally, portable electronic devices represented by a camera-integrated VTR (videotape recorder), a mobile phone device or a laptop computer have been widely used, and their miniaturization, weight reduction, and energy density, that is, energy storage per unit volume. There is a strong demand for increased amounts. Along with this, development of batteries, particularly secondary batteries, as power sources has been actively promoted. Especially, a lithium ion secondary battery is anticipated as a thing which can implement | achieve a big energy density compared with the lead battery and nickel cadmium battery which are the conventional nonaqueous electrolyte secondary batteries.

  However, if a portable electronic device such as a portable personal computer is left connected to a power source, the battery in the battery pack is exposed to a charged state (flow and state). The capacity deteriorates rapidly. This is because cobalt (Co) or the like contained in the positive electrode active material is easily eluted in an oxidizing environment, the interface resistance is increased, and at the same time, the battery capacity is reduced due to the change of the layered structure. Furthermore, an increase in ambient temperature accompanying the driving of the portable electronic device is a factor that accelerates deterioration (decrease in battery capacity).

In order to improve such a decrease in battery capacity, for example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery containing a compound that forms a complex with cobalt in the electrolyte. This non-aqueous electrolyte secondary battery avoids adverse effects on the negative electrode, such as a reduction in the reaction area of the negative electrode, by stabilizing the cobalt ions eluted in the electrolyte and suppressing the deposition on the negative electrode.
JP 2002-134170 A

However, according to Patent Document 1, adverse effects on the negative electrode can be avoided, but the problem that the positive electrode resistance increases due to the structural change of the positive electrode and the capacity deteriorates is not solved. That is, a battery having high reliability cannot be obtained unless the elution of cobalt contained in the positive electrode active material itself is suppressed.
Such a phenomenon that metal ions are eluted from the positive electrode is not limited to a battery using a lithium cobalt composite oxide as an active material of the positive electrode, but as an active material of the positive electrode, nickel oxide, manganese oxide, iron olivine phosphorus oxide This also applies to batteries using the above.

  Accordingly, an object of the present invention is to provide a non-aqueous electrolyte battery that suppresses the elution of metal ions from the positive electrode and has excellent float characteristics.

In order to solve the above-mentioned problems,
This invention
A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte provided with a positive electrode active material layer on a positive electrode current collector,
A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte provided with a positive electrode active material layer on a positive electrode current collector,
The positive electrode active material layer includes a first polymer serving as a main binder and a second polymer serving as a dispersant different from the first polymer,
The nonaqueous electrolyte is a nonaqueous electrolyte battery containing at least one of sulfone compounds represented by the following formulas (1) and (2).

(In Formula (1), R1 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.)

(In Formula (2), R2 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.)

  In the present invention, the positive electrode active material layer includes a first polymer serving as a main binder and a second polymer serving as a dispersant different from the first polymer, and the nonaqueous electrolyte is represented by the formula (1). ) And at least one of the sulfone compounds represented by formula (2), a good protective film is formed on the surface of the positive electrode active material by the first charge, and the battery is subjected to a long-time charging environment. Even if exposed, elution of metal ions from the positive electrode can be suppressed.

  Thereby, it is possible to provide a non-aqueous electrolyte battery having excellent float characteristics and an improved capacity retention rate.

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

FIG. 1 shows a cross-sectional structure of a secondary battery according to an embodiment of the present invention.
This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20. FIG. 1 shows a cross-sectional structure of a battery according to the first embodiment of the present invention.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

(Positive electrode)
FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, 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, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21B includes, for example, a positive electrode material that can occlude and release lithium as an electrode reactant as a positive electrode active material.

As a positive electrode material capable of inserting and extracting lithium, for example, lithium-containing compounds such as lithium oxide, lithium sulfide, an intercalation compound containing lithium, and a phosphoric acid compound are suitable. May be used. Among them, a composite oxide containing lithium and a transition metal element, or a phosphoric acid compound containing lithium and a transition metal element is preferable. In particular, as the transition metal element, cobalt (Co), nickel, manganese (Mn), iron, aluminum , One containing at least one of vanadium (V) and titanium (Ti) is preferable. The chemical formula is represented by, for example, Li _x MIO ₂ or Li _y MIIPO ₄ . In the formula, MI and MII contain one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Specific examples of the composite oxide containing lithium and a transition metal element include a lithium cobalt composite oxide (Li _x CoO ₂ ), a lithium nickel composite oxide, and a lithium manganese composite oxide (LiMn ₂ O having a spinel structure). ₄ ). Examples of the lithium nickel composite oxide include LiNi _x Co _1-x O ₂ (O ≦ x ≦ 1), Li _x NiO ₂ , LiNixCoyO ₂ and Li _x Ni _1-z Co _z O ₂ (z <1). Is mentioned. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO ₄ ) and a lithium iron manganese phosphate compound [LiFe _1-u Mn _u PO ₄ (u <1)]. Etc.

  Examples of the positive electrode material capable of inserting and extracting lithium include other metal compounds and polymer materials. Examples of other metal compounds include oxides such as titanium oxide, vanadium oxide and manganese dioxide, or disulfides such as titanium sulfide and molybdenum sulfide. Examples of the polymer material include polyaniline and polythiophene.

  As the polymer material, as the first polymer, at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride maleic acid modified product, and polytetrafluoroethylene It is preferred to use a seed polymer.

  Moreover, polyvinyl alcohol and / or polyvinyl pyrrolidone are mentioned as a 2nd polymer used as a dispersing agent different from the said 1st polymer.

  The positive electrode active material layer 21B may contain a conductive material as necessary. Examples of the conductive material include carbon materials such as graphite, carbon black, and ketjen black, and one kind or a mixture of two or more kinds is used. In addition to the carbon material, a metal material, a conductive polymer material, or the like may be used as long as the material has conductivity.

(Negative electrode)
The negative electrode 22 has, for example, a configuration in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B preferably includes any one or more negative electrode materials capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material. Moreover, a conductive material and a binder may be included as necessary.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. These carbon materials are preferable because the change in crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good charge / discharge cycle characteristics can be obtained. The graphite may be natural graphite or artificial graphite.

As non-graphitizable carbon, the (002) plane spacing is 0.37 nm or more, the true density is less than 1.70 g / cm ³ , and in differential thermal analysis (DTA) in air Those that do not show an exothermic peak at 700 ° C. or higher are preferred.

  Examples of the negative electrode material capable of inserting and extracting lithium include a single element, alloy or compound of a metal element or a metalloid element capable of forming an alloy with lithium, even if such a material is included. good. These are preferable because a high energy density can be obtained. In particular, when used together with a carbon material, a high energy density can be obtained and excellent charge / discharge cycle characteristics can be obtained. Note that in this specification, alloys include those composed of one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them.

Examples of metal elements or metalloid elements capable of forming an alloy with lithium include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth. (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf). These alloys or compounds, such as those represented by the chemical formula Ma _s Mb _t. In this chemical formula, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents at least one of elements other than Ma. The values of s and t are s> 0 and t ≧ 0, respectively.

  Among these, a simple substance, alloy or compound of a group 14 metal element or metalloid element in the long-period periodic table is preferable, and silicon or tin, or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

Specific examples of such alloys or compounds include LiAl, AlSb, CuMgSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, 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), SnSiO ₃ , LiSiO, and LiSnO.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber and ethylene propylene diene rubber, or polymer materials such as polyvinylidene fluoride, and one or more kinds are used in combination. It is done.

  It allows lithium ions to pass through. The separator 23 is made of, for example, a porous film made of synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous film made of ceramic, and these two or more kinds of porous films are laminated. It may be a structure. Among these, a porous film made of polyolefin is preferable because it is excellent in the effect of preventing short circuit and can improve the safety of the battery due to the shutdown effect. In particular, polyethylene is preferable as a material constituting the separator 23 because a shutdown effect can be obtained within a range of 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable. In addition, any resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

(Nonaqueous electrolyte)
The separator 23 is impregnated with a nonaqueous electrolyte solution. The electrolytic solution includes, for example, a solvent and an electrolyte salt.
Examples of the solvent include 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, and γ-valerolactone. 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, ethyl propionate, acetonitrile, glutaronitrile, adiponitrile, Methoxyacetonitrile, 3-methoxypropyronitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, trimethyl phosphate, lithium Room temperature molten salts such as triethyl phosphate, ethylene sulfite, and bistrifluoromethylsulfonylimide trimethylhexylammonium. Among them, at least one of the group consisting of 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and ethylene sulfite is used as a mixture. It is preferable because excellent charge / discharge capacity characteristics and charge / discharge cycle characteristics can be obtained.

The electrolyte salt may contain one kind or a mixture of two or more kinds of materials. Examples of the electrolyte salt include lithium hexafluorophosphate (LiPF ₆ ), bis (pentafluoroethanesulfonyl) imide lithium (Li (C ₂ F ₅ SO ₂ ) ₂ N), lithium perchlorate (LiClO ₄ ), Lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiSO ₃ CF ₃ ), lithium bis (trifluoromethanesulfonyl) imide (Li (CF ₃ SO ₂ ) ₂ N), tris (trifluoromethanesulfonyl) methyllithium (LiC (SO ₂ CF ₃ ) ₃ ), lithium chloride (LiCl) and lithium bromide (LiBr).

  The nonaqueous electrolyte contains at least one of sulfone compounds represented by the following formulas (1) and (2) as an additive.

(In Formula (1), R1 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.)

(In Formula (2), R2 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.)

The hydrogen atoms of R1 and R2 may be substituted with a halogen atom such as a fluorine atom. Moreover, when R1 and R2 have an alkyl group as a substituent, it is preferably a methyl group.
Specific examples of the sulfone compound are shown below.

  Among these, those having the following structure are particularly preferable. This is because the most favorable film that suppresses cobalt elution from the positive electrode can be formed.

  The content of the sulfone compound in the electrolyte is preferably in the range of 0.01% by weight to 1.0% by weight. This is because if it exceeds 1.0% by weight, the positive electrode film becomes thick and the film resistance becomes too large.

(Battery manufacturing method)
This non-aqueous electrolyte battery can be manufactured, for example, as follows.

  First, for the positive electrode, for example, polyvinylidene fluoride is dispersed in a solvent such as N-methyl-2-pyrrolidone. Next, a positive electrode active material containing cobalt, a conductive agent, and polyvinyl pyrrolidone are mixed with this mixed liquid to prepare a positive electrode mixture coating liquid that is a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture coating liquid is applied to the positive electrode current collector 21A, and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is manufactured. Further, the positive electrode active material layer 21B may be formed by attaching a positive electrode mixture to the positive electrode current collector 21A.

  Also, for example, a carbon material that is a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A negative electrode mixture slurry is prepared. Subsequently, the negative electrode mixture coating liquid is applied to the negative electrode current collector 22A and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured. The negative electrode active material layer 22B may be formed by sticking a negative electrode mixture to the negative electrode current collector 22A.

  Next, 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. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, an electrolytic solution containing a sulfone compound is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution. In addition, when discharging is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution.

  Further, specific embodiments of the present invention will be described in detail.

(Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-6)
The cylindrical secondary battery shown in FIGS.
As the positive electrode active material, lithium cobaltate (LiCoO ₂ ) having a cumulative 50% particle diameter (median particle diameter) of 12 μm obtained by a laser diffraction method was used. Subsequently, the positive electrode was prepared by mixing 94% by mass of lithium cobaltate powder and Ketjen as a conductive material in a mixed liquid in which 3.0% by mass of polyvinylidene fluoride as a first polymer was well dispersed in N-methyl-2-pyrrolidone. In Example 1-1 to 1-3 and Comparative Examples 1-1 to 1-2, 3% by weight of black was mixed, and polyvinyl pyrrolidone (PVP) was added as a second polymer dispersant. -4 and Comparative Example 1-3, polyvinyl alcohol (PVA) was added as a dispersant that was the second polymer to prepare a positive electrode mixture, which was used as a positive electrode mixture coating liquid.

  Next, this positive electrode mixture coating solution is uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression-molded to form a positive electrode active material layer 21B to produce the positive electrode 21. did. At that time, the thickness of one surface of the positive electrode active material layer 21B was 80 μm. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

Further, as a negative electrode active material, 95% by mass of granular graphite powder composed of mesophase spherules having a lattice plane distance d ₀₀₂ in the C-axis direction of 0.336 nm and a median particle diameter of 15.6 μm in X-ray diffraction, and polyfluoride as a binder Vinylidene (5.0% by mass) was mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a negative electrode mixture coating solution.

Next, this negative electrode mixture coating solution was uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm, dried, and compression-molded to form a negative electrode active material layer 22B to produce a negative electrode 22. . At that time, the thickness of one surface of the negative electrode active material layer 22B is 52 μm. It was. Subsequently, nickel negative electrode leads 26 were attached to one end of the negative electrode current collector 22A at three locations.

  After preparing the positive electrode 21 and the negative electrode 22, the positive electrode 21 and the negative electrode 22 are laminated in the order of the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 through a separator 23 made of a microporous polyethylene stretched film having a thickness of 18 μm. The jelly roll type wound electrode body 20 was produced by winding a large number of turns. Next, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. 11 was stored inside. Subsequently, an electrolytic solution was injected into the battery can 11, and the battery lid 14 was caulked to the battery can 11 through the gasket 17 to produce a cylindrical secondary battery.

  In the electrolyte, lithium hexafluorophosphate as an electrolyte salt was added to a solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and propylene carbonate (PC) were mixed at a ratio of 20/70/10. What was dissolved at a rate of 1.28 mol / kg was used. At that time, any of the sulfone compounds of Compounds 1 to 4 shown below was added as an additive. In Examples 1-1 to 1-4, the sulfone compound was changed. Moreover, Comparative Example 1-1 to 1-3 did not add the sulfone compound of the present invention, and Comparative Example 1-4 added the sulfone compound of the present invention, but did not add a dispersant. In Comparative Example 1-5, a chain sulfone compound of Compound 5 shown below was added. Or Comparative Example 1-6 added the cyclic | annular anhydrous compound of the compound 6 shown below.

(Compound 5)
CH ₃ SO ₃ C ₄ H ₉ : butyl methanesulfonate

(Measurement of capacity maintenance rate)
The manufactured lithium batteries of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-6 were subjected to a 55 ° C. float test, and the capacity retention rate after 2000 hours was examined. First, the battery was charged with a constant current of 1 C until the battery voltage reached 4.2 V, and then switched to a constant voltage charge of 4.2 V to be in a float state. As for the capacity maintenance rate, the batteries after 1 hour and 2000 hours were discharged at a constant current of 1 C, and when the battery voltage reached 3.0 V, the discharge was terminated and the discharge capacity was measured. From {(battery capacity after 2000 hours) / (battery capacity after 1 hour)} × 100, the capacity retention rate after 2000 hours was determined. The results are shown in Table 1.

As shown in Table 1, in Examples 1-1 to 1-4, the capacity retention rate was significantly improved as compared with Comparative Example 1-1 in which no sulfone compound was added. Moreover, it turned out that the structure of the compound 1 can express an effect especially.
From Comparative Examples 1-1 to 1-3, when polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) is added, unstable film formation on the surface of the positive electrode active material is suppressed by improving the potential imbalance in the electrode, and polyvinylpyrrolidone. (PVP) and polyvinyl alcohol (PVA) itself can improve the capacity retention rate by forming a good quality film, but the addition of polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) completely suppresses deterioration. Not done.
Further, according to Comparative Example 1-4, when a sulfone compound is added, a relatively stable film is formed on the surface of the active material, and the secondary elution is essentially suppressed and cobalt elution itself is suppressed from the active material, Although the capacity retention rate is improved, cobalt elution cannot be completely prevented. A sulfone compound in the electrolytic solution and polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) in the electrode can form a good quality film for all positive electrode active materials for the first time without any disparity, thereby suppressing deterioration.
Moreover, in Comparative Example 1-5 to which a chain sulfone compound was added, it was found that the effect of improving the capacity retention rate was not obtained, and excellent characteristics were obtained by using a cyclic structure.
In Comparative Example 1-6 in which a compound having a carboxylic acid structure is added even with a cyclic anhydride, the effect of improving the capacity retention rate cannot be obtained, and excellent characteristics can be obtained by using the cyclic sulfonic acid anhydride structure. I understood.

(Examples 2-1 to 2-6)
In Examples 2-1 to 2-6, cylindrical secondary batteries were produced in the same manner as in Example 1-1 except that the addition amount of the sulfone compound 1 was changed. The capacity retention ratios of the produced Examples 2-1 to 2-6 were determined. The results are shown in Table 2.

  In Examples 2-1 to 2-6, it was confirmed that the capacity retention rate was improved by the addition of the sulfone compound 1. If the amount added is small, the effect of forming a sufficient film on the surface of the positive electrode is small. If the amount added is large, the film on the surface of the positive electrode becomes too thick. The effect of a decrease in capacity maintenance rate increases. From this, it was found that the optimum addition amount was in the range of 0.01 wt% to 1.0 wt%.

(Examples 3-1 to 3-5, Comparative examples 3-1 to 3-5)
In Examples 3-1 to 3-5, cylindrical secondary batteries were produced in the same manner as in Example 1-1 except that the type of the positive electrode active material was changed. In Comparative Examples 3-1 to 3-5, cylindrical secondary batteries were produced in the same manner as Comparative Example 1-1 except that the type of the positive electrode active material was changed. The capacity retention rates of the produced Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-5 were determined. The results are shown in Table 3.

  From the results shown in Table 3, it was found that the battery having the positive electrode active material changed also had the effect of adding the sulfone compound. This is considered to be an effect of suppressing the elution of each metal.

(Examples 4-1 to 4-2, Comparative examples 4-1 to 4-2)
In Examples 4-1 to 4-2, cylindrical secondary batteries were produced in the same manner as in Example 1-1 except that the type of the electrolyte solvent was changed. In Comparative Examples 4-1 to 4-2, cylindrical secondary batteries were produced in the same manner as Comparative Example 1-1 except that the type of the electrolyte solvent was changed. The capacity retention rates of the produced Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-2 were determined. The results are shown in Table 4.

  From the results in Table 4, it was confirmed that the capacity retention rate was improved by adding the sulfone compound, regardless of which electrolyte was used.

(Examples 5-1 to 5-2, Comparative examples 5-1 to 5-2)
The type of negative electrode active material was changed. In Example 5-1 and Comparative Example 5-1, a negative electrode active material containing tin as the first constituent element was synthesized using a mechanochemical reaction. The composition analysis was performed about the obtained negative electrode active material powder. The carbon content was measured by a carbon / sulfur analyzer, and the content of other elements was measured by ICP (Inductively Coupled Plasma) emission analysis. The obtained results are shown in parentheses in the negative electrode active material column of the table. Note that the numbers shown in parentheses separated by slashes indicate the content (mass%) of the elements described above in order. Next, 80 parts by mass of the obtained negative electrode active material powder, 11 parts by mass of graphite (KS-15 manufactured by Lonza) and 1 part by mass of acetylene black as a conductive material, and 8 parts by mass of polyvinylidene fluoride as a binder were mixed. The negative electrode mixture slurry was dispersed in N-methyl-2-pyrrolidone as a solvent. Subsequently, the negative electrode mixture slurry is uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 10 μm, dried, and compression-molded at a constant pressure to form a negative electrode active material layer 22B. Was made. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A.
In Example 5-2 and Comparative Example 5-2, the negative electrode active material layer 22B made of silicon was formed on the negative electrode current collector 22A by electron beam evaporation, and then the negative electrode 22 was fabricated by heat treatment. A cylindrical secondary battery was produced in the same manner as in Example 1-1 and Comparative Example 1-1 except that the type of the negative electrode active material was changed. The capacity retention rates of the produced Examples 5-1 to 5-2 and Comparative Examples 5-1 to 5-2 were determined. The results are shown in Table 5.

  From the results of Table 5, no matter which negative electrode was used, it was confirmed that the capacity retention rate was improved by adding the sulfone compound.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment and the examples, and various modifications can be made. Any structure including an iron phosphate compound in the positive electrode active material and a sulfone compound in the electrolytic solution is applicable.

  In the embodiments and examples described above, the cylindrical secondary battery having a winding structure has been specifically described, but the present invention is not limited to an elliptical or polygonal secondary battery having a winding structure. The present invention can be similarly applied to a battery, or a secondary battery having another shape in which a positive electrode and a negative electrode are folded or a plurality of layers are stacked. In addition, the present invention can be similarly applied to secondary batteries having other shapes such as a coin shape, a button shape, a square shape, or a laminate film shape.

  Furthermore, in the embodiments and examples described above, the case where a liquid electrolytic solution is used as the electrolyte has been described. However, a gel electrolyte in which the electrolytic solution is held by a holding body such as a polymer compound may be used. Good. Examples of such a polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, and polyphosphazene. , Polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene and polycarbonate. In particular, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene and polyethylene oxide are preferable from the viewpoint of electrochemical stability. Although the ratio of the polymer compound to the electrolytic solution varies depending on the compatibility thereof, it is usually preferable to add a polymer compound corresponding to 5% by mass or more and 50% by mass or less in the electrolytic solution.

It is sectional drawing showing the structure of the 1st secondary battery which concerns on embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery 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 ... Winding electrode body, 21 ... Positive electrode, 21A DESCRIPTION OF SYMBOLS ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode collector, 22B ... Negative electrode active material layer, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead.

Claims (5)

A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte provided with a positive electrode active material layer on a positive electrode current collector,
The positive electrode active material layer includes a first polymer serving as a main binder and a second polymer serving as a dispersant different from the first polymer,
The nonaqueous electrolyte is a nonaqueous electrolyte battery containing at least one of sulfone compounds represented by the following formulas (1) and (2).

(In Formula (1), R1 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.)

(In Formula (2), R2 has a C2-C4 alkylene group which may have a substituent, a C2-C4 alkenylene group which may have a substituent, and a substituent. An aromatic ring or a bridged ring optionally having a substituent, wherein the substituent represents a halogen atom or an alkyl group.) The nonaqueous electrolyte battery according to claim 1, wherein the sulfone compound represented by the formula (1) is a compound represented by the following formula (3).

  The nonaqueous electrolyte battery according to claim 1, wherein the content of the sulfone compound in the nonaqueous electrolyte is in the range of 0.01 wt% to 1.0 wt%.   The first polymer is at least one polymer selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, modified polyvinylidene fluoride maleic acid, and polytetrafluoroethylene. The nonaqueous electrolyte battery according to claim 1.   The nonaqueous electrolyte battery according to claim 1, wherein the second polymer is polyvinyl alcohol and / or polyvinyl pyrrolidone.

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