JP2009224282A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery capable of effectively restraining battery expansion at the time of storage at high temperature on the battery where lithium composite oxide with high nickel contents is used as a positive electrode active material. <P>SOLUTION: An electrolyte is impregnated in a separator 15. The electrolyte includes, for example, a solvent and electrolyte salt dissolved in the solvent. The solvent formed by a nonaqueous solvent contains cyclic pyrrolidone derivative such as 1-methyl-2-pyrrolidone. <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 secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator including a lithium composite oxide having a high nickel content.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Video Tape Recorder), a digital still camera, a mobile phone, a personal digital assistant, and a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for these electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted.

  Among them, for example, a lithium ion secondary battery uses a lithium-transition metal composite oxide as a positive electrode active material, a carbon material as a negative electrode active material, and a carbonate ester mixture as an electrolytic solution. Compared to lead batteries and nickel cadmium batteries, which are batteries, a large energy density can be obtained, so that they are widely put into practical use. In particular, a laminated battery using an aluminum laminated film for the exterior has a high energy density because it is lightweight. In the laminate battery, since the deformation of the laminate battery can be suppressed by swelling the electrolyte in the polymer, the laminate polymer battery is also widely used.

  In the laminate battery, there is a problem that the battery swells due to gas generated by decomposition of the electrolyte. As a method for solving this problem, there is a method using a chain carbonate having a relatively large number of carbon atoms such as diethyl carbonate as the chain carbonate, but the viscosity and conductivity are improved, and the discharge capacity is maintained during repeated charge and discharge. The rate will drop.

  In addition, there is a technique for suppressing swelling during high-temperature storage by using propylene carbonate or γ-butyrolactone having high electrical conductivity in combination with ethylene carbonate and a chain carbonate solvent. However, when a graphite-based material is used as the negative electrode active material, this method cannot be used because propylene carbonate and γ-butyrolactone react with the negative electrode.

  Furthermore, it has been reported that by adding various additives to the electrolytic solution, a decomposition film is formed on the surface of the electrode at the time of initial charge, thereby suppressing the decomposition of the electrolytic solution. For example, Patent Document 1 proposes the combined use of a sultone derivative and isocyanuric acid. For example, Patent Document 2 proposes the combined use of a sulfone, a cyclic sulfonate ester and a high carbon chain carbonate. These additives are decomposed at the time of the first charge, and an organic thin film is coated on the electrode surface, thereby suppressing swelling at a high temperature.

JP 2002-358999 A

JP2007-207483

  By the way, in the future, in order to further increase the capacity, a technique has been proposed in which a lithium composite oxide having a high nickel content, such as lithium nickelate, is used as the positive electrode active material.

  However, when a lithium composite oxide having a high nickel content, such as lithium nickelate, is used as the positive electrode active material, not only the electrolyte solution in the vicinity of the positive electrode and the negative electrode but also the nickel content when stored under high temperature conditions. There is a problem in that the carbon content of the lithium composite oxide and the moisture-derived gas are generated in a high amount, which promotes battery swelling.

  Accordingly, an object of the present invention is to provide a non-aqueous electrolyte battery that can effectively suppress battery swelling during high-temperature storage in a battery using a lithium composite oxide having a high nickel content as a positive electrode active material. .

（Ｒ１は、水素、炭素数１〜６のアルキル、炭素数６〜１２のアリール、炭素数３〜１１０のシクロアルキル、炭素数２〜６のアルケニル、炭素数２〜６のアルキニル、「−ＣＯＲ５（Ｒ５はアルキル）」で表されるアシル基、「−ＣＯＯＲ６（Ｒ６はアルキル）」で表されるエステル、または「−ＣＯ（ＯＲ７）（Ｒ７はアルキル）」で表されるカーボネートである。
Ｒ２は、Ｃ_mＨ_2m-nＸ_nである。（Ｘはハロゲンである。ｍは２以上７以下の整数であり、ｎは０以上２ｍ以下の整数である。）
Ｒ３およびＲ４は、それぞれ独立して、水素、ハロゲン、アルキルまたはハロゲン化アルキルを表す。） In order to solve the above-mentioned problems,
This invention
A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode, and an electrolyte,
The positive electrode includes a lithium composite oxide in which nickel is included in a mole fraction of 50% or more among constituent metal elements excluding lithium,
The electrolyte is a nonaqueous electrolyte battery including a cyclic pyrrolidone derivative represented by the formula (1).

(R1 is hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, cycloalkyl having 3 to 110 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, “—COR 5 (R5 is alkyl) ", an ester represented by" -COOR6 (R6 is alkyl) ", or a carbonate represented by" -CO (OR7) (R7 is alkyl) ".
R2 is a _{C m H 2m-n X n} . (X is halogen. M is an integer of 2 to 7, and n is an integer of 0 to 2 m.)
R3 and R4 each independently represents hydrogen, halogen, alkyl or halogenated alkyl. )

  In this invention, since the electrolyte contains a cyclic pyrrolidone derivative represented by the formula (1), a lithium composite oxide containing nickel in a molar fraction of 50% or more among constituent metal elements excluding lithium in the positive electrode is used. In such a battery, gas generation caused by decomposition of the electrolyte during high-temperature storage can be reduced, and battery swelling can be suppressed.

  According to the present invention, in a battery including a lithium composite oxide in which nickel is contained in a mole fraction of 50% or more among constituent metal elements excluding lithium in the positive electrode, battery swelling during high-temperature storage can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. In this nonaqueous electrolyte secondary battery, the wound electrode body 10 to which the positive electrode lead 11 and the negative electrode lead 12 are attached is housed in a film-shaped exterior member 21.

  Each of the positive electrode lead 11 and the negative electrode lead 12 is led out from the inside of the exterior member 21 to the outside, for example, in the same direction. The positive electrode lead 11 and the negative electrode lead 12 are made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel, respectively, and have a thin plate shape or a mesh shape, respectively.

  The exterior member 21 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 21 is disposed, for example, so that the polyethylene film side and the electrode winding body 10 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive.

  An adhesion film 22 is inserted between the exterior member 21 and the positive electrode lead 11 and between the exterior member 21 and the negative electrode lead 12 to prevent intrusion of outside air. The adhesion film 22 is made of a material having adhesion to the positive electrode lead 11 and the negative electrode lead 12, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 21 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 2 shows a cross-sectional structure taken along line II of the electrode winding body 10 shown in FIG. The electrode winding body 10 is obtained by laminating a positive electrode 13 and a negative electrode 14 with a separator 15 interposed between them, and the outermost peripheral portion is protected by a protective tape 16.

  The positive electrode 13 includes, for example, a positive electrode current collector 13A and a positive electrode active material layer 13B provided on the positive electrode current collector 13A. The positive electrode current collector 13A is made of, for example, aluminum, nickel, stainless steel, or the like.

  The positive electrode active material layer 13B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive agent such as a carbon material and the like as necessary. A binder such as polyvinylidene fluoride may be included.

  The positive electrode active material layer 13B includes a lithium composite oxide in which nickel is included in a mole fraction of 50% or more among constituent metal elements excluding lithium, and a conductive agent such as a carbon material and polyvinylidene fluoride as required. The binder may be included.

Specific examples of the lithium composite oxide containing 50% or more of nickel by mole in the constituent metal elements excluding lithium include, for example, a lithium composite oxide whose average composition is represented by the chemical formula (1). .
(Chemical formula 1)
_{Li x Co y Ni z M 1} -yz O ba X a
(In the formula, M represents boron (B), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), manganese (Mn ), Iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), yttrium (Y), zirconium (Zr), molybdenum (Mo), silver (Ag), barium (Ba) ), Tungsten (W), indium (In), tin (Sn), lead (Pb), and antimony (Sb), X is a halogen element, x, y, z , A and b are 0.8 <x ≦ 1.2, 0 ≦ y ≦ 0.5, 0.5 ≦ z ≦ 1.0, 1.8 ≦ b ≦ 2.2, and 0 ≦ a ≦ 1. (The value is in the range of 0.)

  The negative electrode 14 includes, for example, a negative electrode current collector 14A and a negative electrode active material layer 14B provided on the negative electrode current collector 14A.

  The negative electrode active material layer 14B includes one or more negative electrode materials capable of occluding and releasing lithium as the negative electrode active material, and the positive electrode active material layer 13B as necessary. It is comprised including the binder similar to.

  Examples of negative electrode materials capable of inserting and extracting lithium include graphite, non-graphitizable carbon, graphitizable carbon, pyrolytic carbons, cokes, glassy carbons, and fired organic polymer compounds And carbon materials such as carbon fiber or activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body refers to a carbonized material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: Examples of the polymer material include polyacetylene and polypyrrole. These carbon materials are preferable because the change in the crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent characteristics can be obtained. Furthermore, a battery having a low charge / discharge potential, specifically, a battery having a charge / discharge potential close to that of lithium metal is preferable because a high energy density of the battery can be easily realized.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and containing 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 by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. The negative electrode material may be a single element, alloy, or compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. In the present invention, the alloy 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. Moreover, the nonmetallic element may be included. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a mixture of two or more of them.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), and germanium (Ge). ), Tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) ) Or platinum (Pt). These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon (Si) and tin (Sn) is particularly preferable. It is included as an element. This is because silicon (Si) and tin (Sn) have a large ability to occlude and release lithium (Li), and a high energy density can be obtained.

  As an alloy of tin (Sn), for example, as a second constituent element other than tin (Sn), silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr) The thing containing at least 1 sort is mentioned. As an alloy of silicon (Si), for example, as a second constituent element other than silicon (Si), tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned.

  Examples of the tin (Sn) compound or silicon (Si) compound include those containing oxygen (O) or carbon (C), and in addition to tin (Sn) or silicon (Si), Two constituent elements may be included.

Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Examples of other metal compounds include oxides such as MnO ₂ , V ₂ O ₅ , and V ₆ O ₁₃ , sulfides such as NiS and MoS, and lithium nitrides such as LiN ₃ , and polymer materials include polyacetylene. , Polyaniline or polypyrrole.

  The separator 15 separates the positive electrode 13 and the negative electrode 14 and allows lithium ions to pass while preventing a short circuit of current due to contact between both electrodes. For example, a polyolefin-based material such as polyethylene (PE) or polypropylene (PP) is used. It is composed of a porous film made of a material. The separator 15 may have a structure in which two or more porous films are stacked. The separator 15 may be a porous film made of a polyolefin-based material and a porous resin layer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) formed thereon.

  The separator 15 is impregnated with an electrolytic solution. The electrolytic solution contains, for example, a solvent and an electrolyte salt dissolved in the solvent, and may contain an additive as necessary.

  The solvent is composed of a non-aqueous solvent and includes a cyclic pyrrolidone derivative represented by the formula (1).

（Ｒ１は、水素、炭素数１〜６のアルキル、炭素数６〜１２のアリール、炭素数３〜１１０のシクロアルキル、炭素数２〜６のアルケニル、炭素数２〜６のアルキニル、「−ＣＯＲ５（Ｒ５はアルキル）」で表されるアシル基、「−ＣＯＯＲ６（Ｒ６はアルキル）」で表されるエステル、または「−ＣＯ（ＯＲ７）（Ｒ７はアルキル）」で表されるカーボネートである。
Ｒ２は、Ｃ_mＨ_2m-nＸ_n（Ｘはハロゲンである。ｍは２以上７以下の整数であり、ｎは０以上２ｍ以下の整数である。）である。
Ｒ３およびＲ４は、それぞれ独立して、水素、ハロゲン、アルキルまたはハロゲン化アルキルを表す。）

(R1 is hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, cycloalkyl having 3 to 110 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, “—COR 5 (R5 is alkyl) ", an ester represented by" -COOR6 (R6 is alkyl) ", or a carbonate represented by" -CO (OR7) (R7 is alkyl) ".
R2 _{is, C m H 2m-n X} n ( the X .m is halogen is 2 or more and 7 or less an integer, n represents an integer less than or equal to 0 or 2m.) Is.
R3 and R4 each independently represents hydrogen, halogen, alkyl or halogenated alkyl. )

  Examples of the cyclic pyrrolidone derivative represented by the formula (1) include a cyclic pyrrolidone derivative represented by the formula (2).

（Ｒ１は、水素、炭素数１〜６のアルキル、炭素数６〜１２のアリール、炭素数３〜１１０のシクロアルキル、炭素数２〜６のアルケニル、炭素数２〜６のアルキニル、「−ＣＯＲ５（Ｒ５はアルキル）」で表されるアシル基、「−ＣＯＯＲ６（Ｒ６はアルキル）」で表されるエステル、または「−ＣＯ（ＯＲ７）（Ｒ７はアルキル）」で表されるカーボネートである。）

(R1 is hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, cycloalkyl having 3 to 110 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, “—COR 5 (R5 is alkyl) ”, an ester represented by“ —COOR6 (R6 is alkyl) ”, or a carbonate represented by“ —CO (OR7) (R7 is alkyl) ”.

  Examples of the cyclic pyrrolidone derivative represented by the formula (2) include 1-methyl-2-pyrrolidone represented by the formula (3), 1-ethyl-2-pyrrolidone represented by the formula (4), and the formula ( Examples thereof include 1-phenylpyrrolidone represented by 5), 1-vinyl-2-pyrrolidone represented by formula (6), and 1-acetyl-2-pyrrolidone represented by (7).

  Since the electrolytic solution contains the cyclic pyrrolidone derivative represented by the formula (1), swelling during high-temperature storage can be suppressed. In a non-aqueous electrolyte battery using a lithium composite oxide in which nickel is included in a mole fraction of 50% or more among constituent metal elements excluding lithium, the electrolyte solution is decomposed in the vicinity of the positive electrode and the negative electrode by storage under high temperature conditions. In addition, a large amount of gas derived from carbonic acid and moisture is generated, which causes a problem of promoting battery swelling. Therefore, a nonaqueous electrolyte battery using a lithium composite oxide in which nickel is included in a molar fraction of 50% or more among constituent metal elements excluding lithium includes a cyclic pyrrolidone derivative represented by the formula (1). It is particularly effective from the viewpoint of suppressing swelling during high temperature storage.

  The content of the cyclic pyrrolidone derivative represented by the formula (1) is preferably in the range of 0.01% by weight to 10% by weight with respect to the electrolytic solution.

  In addition to the cyclic pyrrolidone derivative represented by the formula (1), the solvent preferably further contains a cyclic carbonate derivative represented by the formula (8). When the amount of the cyclic pyrrolidone derivative represented by the formula (1) is increased, the cycle characteristics deteriorate. Therefore, by including the cyclic carbonate derivative represented by the formula (8), the cycle characteristics are deteriorated. Can be suppressed. By using the cyclic pyrrolidone derivative represented by the formula (1) and the cyclic carbonate derivative represented by the formula (8) in combination, excellent swelling characteristics and cycle characteristics can be obtained.

（Ｒ１〜Ｒ４は、それぞれ独立して、水素、ハロゲン、アルキルまたはハロゲン化アルキルを表す。Ｒ１〜Ｒ４のうちの少なくとも一つはハロゲンを構成元素として有する。）

(R1 to R4 each independently represent hydrogen, halogen, alkyl, or alkyl halide. At least one of R1 to R4 has halogen as a constituent element.)

  More specifically, examples of the compound represented by the formula (8) include, for example, 4-fluoro-1,3-dioxolan-2-one (FEC) represented by the formula (9) and the formula (10). 4-chloro-1,3-dioxolan-2-one represented by formula (4), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) represented by formula (11), formula (12) Tetrafluoro-1,3-dioxolan-2-one represented by formula 4,4,5-trifluoro-5-chloro-1,3-dioxolan-2-one represented by formula (13), 14) 4,5-dichloro-1,3-dioxolan-2-one represented by formula (15), tetrachloro-1,3-dioxolan-2-one represented by formula (15), represented by formula (16) 4,5-bistrifluoromethyl-1,3-dioxolan-2-one 4-trifluoromethyl-1,3-dioxolane-2-one represented by formula (17), 4,5-difluoro-4,5-dimethyl-1,3-dioxolane- represented by formula (18) 2-one, 4-methyl-4,5,5-trifluoro-1,3-dioxolan-2-one represented by formula (19), 4-ethyl-5,5 represented by formula (20) -Difluoro-1,3-dioxolan-2-one etc. are mentioned.

  Further, 4-methyl-5-fluoro-1,3-dioxolan-2-one represented by the formula (21), 4-trifluoromethyl-5-methyl-1,3- represented by the formula (22) Dioxolan-2-one, 4-fluoro-4,5-dimethyl-1,3-dioxolan-2-one represented by formula (23), 4,4-difluoro-5-form represented by formula (24) (1,1-difluoroethyl) -1,3-dioxolan-2-one, 4,5-dichloro-4,5-dimethyl-1,3-dioxolan-2-one represented by formula (25), 4-ethyl-5-fluoro-1,3-dioxolane-2-one represented by (26), 4-ethyl-4,5-difluoro-1,3-dioxolane-2 represented by formula (27) -On, 4-ethyl-4,5,5-trifluoro represented by the formula (28) 1,3-dioxolan-2-one, 4-fluoro-4-trifluoromethyl-1,3-dioxolan-2-one represented by the formula (29) below.

  These may be used alone or in combination of two or more. Among them, the cyclic carbonate having halogen as a constituent element is preferably 4-fluoro-1,3-dioxolan-2-one (FEC) represented by the formula (9), and 4,4 represented by the formula (11) 5-Difluoro-1,3-dioxolan-2-one (DFEC) is more preferred. This is because they are easily available and higher effects can be obtained. In particular, as 4,5-difluoro-1,3-dioxolan-2-one (DFEC), a trans isomer is preferable to a cis isomer in order to obtain a higher effect.

  Other solvents include, for example, cyclic carbonates such as ethylene carbonate and propylene carbonate, lactones such as γ-butyrolactone and γ-valerolactone, cyclic carbamates such as N-methyloxazolidinone, sulfone compounds such as tetramethylene sulfone, and the like. Viscous solvents such as chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl acetate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate Chain carboxylic acid esters such as ethyl trimethylacetate, chain amides such as N, N-dimethylacetamide, methyl N, N-diethylcarbamate, N, N-diethylcarbamate One or two or more kinds selected from chain carbamates such as ethyl minate, ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane and the like are appropriately added and used.

As the electrolyte salt, lithium tetrafluoroborate (LiBF ₄ ) is preferably used. This is because the resistance of the film having a high resistance derived from the cyclic pyrrolidone represented by the formula (1) can be relaxed, and the cycle characteristics can be further improved. Electrolyte salts include inorganic lithium salts such as lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium perchlorate, and lithium tetrachloride aluminum lithium, lithium trifluoromethanesulfonate 1 type or 2 types or more of lithium salts of perfluoroalkanesulfonic acid derivatives such as lithium bis (trifluoromethanesulfone) imide, lithium bis (pentafluoroethanesulfone) methide, lithium tris (trifluoromethanesulfone) methide May be used.

  The electrolytic solution may be used as it is, or may be retained in a polymer compound to form a so-called gel electrolyte. In that case, the electrolyte may be impregnated in the separator 15, or may exist in a layer form between the separator 15 and the positive electrode 13 or the negative electrode 14.

  Any high molecular compound may be used as long as it absorbs the solvent and gels. Specifically, for example, polyvinyl formal represented by the formula (30), polyacrylic acid ester represented by the formula (31), polyvinylidene fluoride represented by the formula (32), and the like can be used. A high molecular compound may be used individually by 1 type, and 2 or more types may be mixed and used for it.

（ＲはＣ_nＨ_2n-1Ｏ_mである。但し、ｎは１≦ｎ≦８である。ｍは０≦ｍ≦４である。）

(R is C _n H _2n-1 O _m , where n is 1 ≦ n ≦ 8 and m is 0 ≦ m ≦ 4.)

  The nonaqueous electrolyte secondary battery described above can be manufactured, for example, as described below. First, for example, a positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to both surfaces, dried and compression molded to form the positive electrode active material layer 13B, and the positive electrode 13 is produced. Next, for example, the positive electrode lead 11 is joined to the positive electrode current collector 13A by, for example, ultrasonic welding or spot welding.

  Further, for example, a negative electrode material and a binder are mixed to prepare a negative electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 14A, dried, and compression molded to form the negative electrode active material layer 14B, whereby the negative electrode 14 is produced. Next, for example, the negative electrode lead 12 is joined to the negative electrode current collector 14A by, for example, ultrasonic welding or spot welding.

  Subsequently, the positive electrode 13 and the negative electrode 14 are wound through the separator 15 and sandwiched in the exterior member 21, and then an electrolyte is injected into the exterior member 21 to seal the exterior member 21. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  When the electrolytic solution is held in the polymer compound, the polymerizable compound is injected into the exterior member 21 together with the electrolytic solution, and the polymerizable compound is polymerized in the exterior member 21 so as to be gelled. It may be. Alternatively, before the positive electrode 13 and the negative electrode 14 are wound through the separator 15, an electrolyte in which an electrolytic solution is held in a polymer compound may be formed on the positive electrode 13 or the negative electrode 14.

  Specific examples of the present invention will be described below. However, the present invention is not limited to these examples.

<Example 1-1>
First, 94 parts by weight of lithium nickel composite oxide (LiNiO ₂ ) as a positive electrode active material, 3 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder were mixed homogeneously. -Methylpyrrolidone was added to obtain a positive electrode mixture slurry.

  Next, this positive electrode mixture slurry is uniformly coated on both sides of an aluminum foil having a thickness of 10 μm, dried and compression-molded, and a positive electrode active material layer having a thickness of 30 μm per side (volume density of the active material layer) : 3.40 g / cc). This was cut into a shape having a width of 50 mm and a length of 300 mm to obtain a positive electrode.

  Further, 97 parts by weight of MCMB (mesocarbon microbeads) graphite as a negative electrode active material and 3 parts by weight of PVdF as a binder were mixed homogeneously, and N-methylpyrrolidone was added to obtain a negative electrode mixture slurry.

  Next, this negative electrode mixture slurry was uniformly applied on both sides of a 10 μm thick copper foil serving as a negative electrode current collector, dried and pressed at 200 MPa to form a negative electrode active material layer having a thickness of 30 μm per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to obtain a negative electrode (volume density of the mixture: 1.80 g / cc).

  As the separator, a 7 μm-thick microporous polyethylene film coated with 2 μm each of polyvinylidene fluoride was used.

As an electrolytic solution, a mixture of ethylene carbonate (EC), diethyl carbonate (DEC) and 4-fluoro-1,3-dioxolan-2-one (FEC) represented by the formula (9) as a solvent A solution containing a solvent, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt, and 1-methyl-2-pyrrolidone represented by formula (3) as a cyclic pyrrolidone derivative represented by formula (1) Using.

The composition of the mixed solvent is EC: DEC = 40: 60 (weight ratio) to which 4-fluoro-1,3-dioxolan-2-one (FEC) is added at 1% by weight, and the concentration of LiPF ₆ in the electrolytic solution Was 1 mol / kg. Further, the content of 1-methyl-2-pyrrolidone represented by the formula (3) in the electrolytic solution was set to 0.1% by weight. “Wt%” is a value when the solvent is 100% by weight. (The same applies to the following explanation)

  Example 1 After winding a positive electrode and a negative electrode through a separator and putting them in a bag-shaped exterior member made of an aluminum laminate film, 2 g of an electrolyte solution was injected, and then the bag was heat-sealed. A laminate film type battery was prepared. The capacity of this laminated film type battery was 850 mAh.

<Example 1-2>
A battery of Example 1-2 was made in the same manner as Example 1-1 except that the content of 1-methyl-2-pyrrolidone represented by Formula (3) was 1% by weight.

<Example 1-3>
A battery of Example 1-3 was made in the same manner as Example 1-1 except that the content of 1-methyl-2-pyrrolidone represented by Formula (3) was 3% by weight.

<Example 1-4>
A battery of Example 1-4 was made in the same manner as Example 1-1 except that the content of 1-methyl-2-pyrrolidone represented by Formula (3) was 5% by weight.

<Example 1-5>
A battery of Example 1-5 was made in the same manner as Example 1-2, except that the content of 4-fluoro-1,3-dioxolan-2-one (FEC) was 2% by weight.

<Example 1-6>
A battery of Example 1-6 was made in the same manner as Example 1-2, except that the content of 4-fluoro-1,3-dioxolan-2-one (FEC) was 5% by weight.

<Example 1-7>
A battery of Example 1-7 was made in the same manner as Example 1-2, except that the content of 4-fluoro-1,3-dioxolan-2-one (FEC) was 10% by weight.

<Example 1-8>
A battery of Example 1-8 was fabricated in the same manner as Example 1-2, except that 1% by weight of LiBF ₄ was further added as the electrolyte salt.

<Example 1-9>
A battery of Example 1-9 was made in the same manner as Example 1-2, except that 3% by weight of LiBF ₄ was further added as the electrolyte salt.

<Example 1-10>
A battery of Example 1-10 was made in the same manner as Example 1-2, except that 5% by weight of LiBF ₄ was further added as the electrolyte salt.

<Example 1-11>
A battery of Example 1-11 was made in the same manner as Example 1-2 except that 4-fluoro-1,3-dioxolan-2-one (FEC) was not added.

<Comparative Example 1-1>
Except that 4-fluoro-1,3-dioxolan-2-one (FEC) and 1-methyl-2-pyrrolidone represented by the formula (3) were not added, the same as in Example 1-2, A battery of Comparative Example 1-1 was produced.

<Comparative Example 1-2>
A battery of Comparative Example 1-2 was produced in the same manner as Example 1-2 except that 1-methyl-2-pyrrolidone represented by Formula (3) was not added.

<Comparative Example 1-3>
A battery of Comparative Example 1-3 was produced in the same manner as Comparative Example 1-1 except that 1 wt% LiBF ₄ was further added as the electrolyte salt.

<Example 2-1>
Example 1-8 was performed except that 1-ethyl-2-pyrrolidone represented by formula (4) was used instead of 1-methyl-2-pyrrolidone represented by formula (3). A battery of Example 2-1 was produced.

<Example 2-2>
Example 1 was carried out in the same manner as in Example 1-8 except that 1-phenylpyrrolidone represented by formula (5) was used instead of 1-methyl-2-pyrrolidone represented by formula (3). A battery 2-2 was prepared.

<Example 2-3>
Example 1-8 was performed except that 1-vinyl-2-pyrrolidone represented by formula (6) was used instead of 1-methyl-2-pyrrolidone represented by formula (3). A battery of Example 2-3 was produced.

<Example 2-4>
Example 1-8 was performed except that 1-acetyl-2-pyrrolidone represented by formula (7) was used instead of 1-methyl-2-pyrrolidone represented by formula (3). A battery of Example 2-4 was produced.

<Comparative Example 3-1>
A battery of Comparative Example 3-1 was produced in the same manner as Example 1-2 except that 1-methyl-2-pyrrolidone represented by Formula (3) was not added.

<Comparative Example 3-2>
A battery of Comparative Example 3-2 was produced in the same manner as Comparative Example 3-1, except that lithium cobalt composite oxide (LiCoO ₂ ) was used instead of lithium nickel composite oxide (LiNiO ₂ ).

<Comparative Example 3-3>
A battery of Comparative Example 3-3 was produced in the same manner as Example 1-2, except that lithium cobalt composite oxide (LiCoO ₂ ) was used instead of lithium nickel composite oxide (LiNiO ₂ ).

<Comparative Example 3-4>
A battery of Comparative Example 3-4 was produced in the same manner as Example 1-3 except that lithium cobalt composite oxide (LiCoO ₂ ) was used instead of lithium nickel composite oxide (LiNiO ₂ ).

(Evaluation)
For Example 1-1 to Example 2-4 and Comparative Example 1-1 to Comparative Example 3-4, the measurement of the discharge capacity retention rate and the swelling during high temperature storage were measured.

(Measurement of discharge capacity maintenance rate)
After charging each battery for 3 hours under an environment of 23 ° C. at 900 mA and 4.2 V as the upper limit, the discharge rate up to 2.5 V at 900 mA was repeated 300 times, and the maintenance rate relative to the initial discharge capacity was obtained as the discharge capacity maintenance rate. It was.

(Measures swelling when stored at high temperature)
Each battery was stored at 85 ° C. for 96 hours in a charged state of 4.2 V, and the difference between the battery thickness after storage and the battery thickness before storage was determined as the swelling during high temperature storage. The charge state of 4.2 V is the charge state at the time of the first charge, and the charge condition is the same as the measurement of the discharge capacity maintenance rate.

  Table 1 shows the evaluation results of Example 1-1 to Example 1-11 and Comparative Example 1-1 to Comparative Example 1-3. Table 2 shows the evaluation results of Example 1-8, Example 1-11, Example 2-1 to Example 2-4, and Comparative Example 1-1 to Comparative Example 1-2. Table 3 shows the evaluation results of Example 1-2 to Example 1-3 and Comparative Example 3-1 to Comparative Example 3-4. In Table 3, the swelling suppression rate of Example 1-2 and Example 1-3 and the swelling after storage of Comparative Example 3-2 obtained by setting the swelling after storage of Comparative Example 3-1 as 1 are 1 The swelling suppression rate of Comparative Example 3-3 and Comparative Example 3-4 obtained as follows is shown.

As shown in Table 1, by using an electrolytic solution containing 1-methyl-2-pyrrolidone represented by the formula (3) and 4-fluoro-1,3-dioxolan-2-one (FEC), the positive electrode is used. Even when lithium nickel composite oxide (LiNiO ₂ ) was used, it was found that sufficient characteristics were obtained in the discharge capacity retention rate after 300 cycles while acting on swelling suppression during high temperature storage.

Further, from Example 1-11, by using an electrolytic solution containing 1-methyl-2-pyrrolidone represented by Formula (3), even when lithium nickel composite oxide (LiNiO ₂ ) was used for the positive electrode, It was found that swelling during high temperature storage can be effectively suppressed.

As shown in Table 2, even in the cyclic pyrrolidone derivative in which the 1-position is substituted with various substituents, lithium nickel is added to the positive electrode by using 4-fluoro-1,3-dioxolan-2-one (FEC) in combination. Even when the composite oxide (LiNiO ₂ ) is used, it has been found that sufficient characteristics can be obtained in the discharge capacity maintenance ratio after 300 cycles while acting on swelling suppression during high temperature storage.

As shown in Table 3, when lithium cobalt composite oxide (LiCoO ₂ ) is used for the positive electrode, the swelling suppression effect of 1-methyl-2-pyrrolidone represented by the formula (3) is observed, but LiNiO Compared to ₂ , the swelling suppression effect was less. That is, when using a battery containing lithium nickel (LiNiO ₂ ) for the positive electrode, using an electrolytic solution containing 1-methyl-2-pyrrolidone represented by the formula (3) from the viewpoint of suppressing battery swelling. It was found to be particularly effective.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, in the above-described embodiments and examples, the secondary battery having a winding structure has been described as a specific example, but the present invention includes a battery element in which a positive electrode and a negative electrode are stacked and folded in a zigzag manner, or The present invention can be similarly applied to a secondary battery having another stacked structure in which a positive electrode and a negative electrode are stacked.

  Moreover, although the above-mentioned embodiment and Example demonstrated the case where a film-shaped exterior member was used, you may use the exterior member of a can. In that case, the shape may be a cylindrical shape, a square shape, a coin shape or a button shape.

  Furthermore, in the above-described embodiments and examples, the case where lithium is used for the electrode reaction has been described. However, other alkali metals such as sodium (Na) or potassium (K), or alkaline earth such as magnesium or calcium (Ca). The present invention can also be applied to the case where other light metals such as a similar metal or aluminum are used, and the same effect can be obtained. Further, lithium metal may be used as the negative electrode active material.

It is a disassembled perspective view which shows the structure of the secondary battery by one Embodiment of this invention. It is sectional drawing which shows the structure along the II line | wire of the battery element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Exterior member 10 ... Electrode winding body 11 ... Positive electrode lead 12 ... Negative electrode lead 13 ... Positive electrode 13A ... Positive electrode collector 13B ... Positive electrode active material layer 14 ... -Negative electrode 14A ... Negative electrode current collector 14B ... Negative electrode active material layer 15 ... Separator 16 ... Protective tape 22 ... Adhesive film

Claims (9)

A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode, and an electrolyte,
The negative electrode includes a lithium composite oxide in which nickel is contained in a mole fraction of 50% or more among constituent metal elements excluding lithium,
The non-aqueous electrolyte battery, wherein the electrolyte includes a cyclic pyrrolidone derivative represented by the formula (1).

(R1 is hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, cycloalkyl having 3 to 110 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, “—COR 5 (R5 is alkyl) ", an ester represented by" -COOR6 (R6 is alkyl) ", or a carbonate represented by" -CO (OR7) (R7 is alkyl) ".
R2 is a _{C m H 2m-n X n} . (X is halogen. M is an integer of 2 to 7, and n is an integer of 0 to 2 m.)
R3 and R4 each independently represents hydrogen, halogen, alkyl or halogenated alkyl. ) The non-aqueous electrolyte battery according to claim 1, wherein the lithium composite oxide is represented by Chemical Formula 1.
(Chemical formula 1)
_{Li x Co y Ni z M 1} -yz O ba X a
(In the formula, M represents boron (B), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), manganese (Mn ), Iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), yttrium (Y), zirconium (Zr), molybdenum (Mo), silver (Ag), barium (Ba) ), Tungsten (W), indium (In), tin (Sn), lead (Pb), and antimony (Sb), X is a halogen element, x, y, z , A and b are 0.8 <x ≦ 1.2, 0 ≦ y ≦ 0.5, 0.5 ≦ z ≦ 1.0, 1.8 ≦ b ≦ 2.2, and 0 ≦ a ≦ 1. (The value is in the range of 0.) The nonaqueous electrolyte battery according to claim 1, further comprising a film-shaped exterior member. The non-aqueous electrolyte battery according to claim 1, wherein the cyclic pyrrolidone derivative represented by the formula (1) is a cyclic pyrrolidone carbonate derivative represented by the formula (2).

(R1 is hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, cycloalkyl having 3 to 110 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, “—COR 5 (R5 is alkyl) ”, an ester represented by“ —COOR6 (R6 is alkyl) ”, or a carbonate represented by“ —CO (OR7) (R7 is alkyl) ”. The cyclic pyrrolidone derivative includes 1-methyl-2-pyrrolidone represented by formula (3), 1-ethyl-2-pyrrolidone represented by formula (4), and 1-phenylpyrrolidone represented by formula (5). And at least one selected from the group consisting of 1-vinyl-2-pyrrolidone represented by formula (6) and 1-acetyl-2-pyrrolidone represented by formula (7). Item 2. A nonaqueous electrolyte battery according to item 1.

The non-aqueous electrolyte battery according to claim 1, wherein the content of the cyclic pyrrolidone derivative is in the range of 0.01 wt% to 10 wt%. The non-aqueous electrolyte battery according to claim 1, wherein the electrolyte further contains a cyclic carbonate derivative represented by the formula (8).

(R1 to R4 each independently represent hydrogen, halogen, alkyl, or alkyl halide. At least one of R1 to R4 has halogen as a constituent element.)   The cyclic carbonate is at least one of 4-fluoro-1,3-dioxolan-2-one and 4,5-difluoro-1,3-dioxolan-2-one. The nonaqueous electrolyte battery according to 1. The non-aqueous electrolyte battery according to claim 7, wherein the electrolyte contains LiBF ₄ as an electrolyte salt.

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