JP2008305772A - Nonaqueous electrolyte solution secondary battery and nonaqueous electrolyte solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of restraining swelling at high-temperature storage while maintaining charging and discharging efficiency. <P>SOLUTION: In the nonaqueous electrolyte solution secondary battery provided with electrolyte together with a cathode and an anode, the nonaqueous electrolyte solution contains a halide of an element selected from Zr, a group consisting of the groups 5, 6 and 12 to 15 groups of the periodic table. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery having reduced expansion under a high temperature environment while maintaining good cycle characteristics.

  In recent years, many portable electronic devices such as a camera-integrated VTR, 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. As portable power sources for these electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among them, a lithium ion secondary battery that uses carbon as a negative electrode active material, a lithium-transition metal composite oxide as a positive electrode active material, and a carbonate ester mixture as an electrolyte is a lead battery that is a conventional non-aqueous electrolyte secondary battery, Since a large energy density can be obtained compared to a nickel cadmium battery, it is widely put into practical use. In addition, a laminate battery using an aluminum laminate film for the exterior can increase the amount of active material and has a high energy density because the exterior is thin and lightweight.

  On the other hand, when the battery is exposed to a high temperature environment, the carbonic acid ester in the electrolytic solution may be decomposed by reacting with the electrode to generate gas. Such a phenomenon is particularly problematic in a thin battery such as a laminate battery because it leads to battery expansion. In view of this, it has been proposed to add a fluoroethylene carbonate to the electrolytic solution to suppress a decrease in the discharge capacity retention rate during the charge / discharge cycle (Patent Document 1).

JP 2005-38722 A

  However, when fluoroethylene carbonate is used, it is still insufficient for suppressing battery expansion in a high temperature environment, and there is room for improvement. Therefore, the present invention has been made in view of such problems, and an object thereof is to provide a battery capable of suppressing expansion during high-temperature storage while maintaining charge / discharge efficiency.

In the present invention, it has been found that by containing a halide of a specific element in an electrolytic solution, expansion under a high temperature environment is reduced while maintaining good charge / discharge cycle characteristics.
That is, the present invention provides the following non-aqueous electrolyte secondary battery and non-aqueous electrolyte.
(1) A nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte together with a positive electrode and a negative electrode,
The non-aqueous electrolyte secondary contains a halide of an element selected from the group consisting of Zr, groups 5 and 6 of the periodic table, and groups 12 to 15 battery.
(2) A nonaqueous electrolytic solution comprising a halide of an element selected from the group consisting of Zr, groups 5 and 6, and groups 12 to 15 of the periodic table.

  According to the non-aqueous electrolyte and the non-aqueous electrolyte secondary battery of the present invention, a halide of a specific element contained in the electrolyte is decomposed on the electrode surface during the first charge to form a lithium halide protective film. This is considered to suppress gas generation due to the reaction between the electrolytic solution and the battery active material. Thereby, while suppressing battery expansion at the time of high temperature preservation | save, the outstanding charging / discharging efficiency can be hold | maintained.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following mode.

  FIG. 1 schematically shows a configuration of a laminated battery according to an embodiment of the present invention. This secondary battery is a so-called laminate film type, and has a wound electrode body 20 to which a positive electrode lead 21 and a negative electrode lead 22 are attached accommodated in a film-shaped exterior member 30.

  The positive electrode lead 21 and the negative electrode lead 22 are led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The positive electrode lead 21 and the negative electrode lead 22 are made of, for example, a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 30 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 30 is disposed, for example, so that the polyethylene film side and the wound electrode body 20 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive. An adhesion film 31 is inserted between the exterior member 30 and the positive electrode lead 21 and the negative electrode lead 22 to prevent intrusion of outside air. The adhesion film 31 is made of a material having adhesion to the positive electrode lead 21 and the negative electrode lead 22, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 30 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 spirally wound electrode body 20 shown in FIG. The wound electrode body 20 is obtained by laminating a positive electrode 23 and a negative electrode 24 via a separator 25 and an electrolyte layer 26 and winding them, and the outermost periphery is protected by a protective tape 27.

(Active material layer)
The positive electrode 23 has a structure in which a positive electrode active material layer 23B is provided on both surfaces of a positive electrode current collector 23A. The negative electrode 24 has a structure in which a negative electrode active material layer 24B is provided on both surfaces of a negative electrode current collector 24A, and the negative electrode active material layer 24B and the positive electrode active material layer 23B are arranged to face each other. In the non-aqueous electrolyte secondary battery of the present invention, the thickness of each of the positive electrode active material layer 23B and the negative electrode active material layer 24B per side is 40 μm or more, preferably 80 μm or less. More preferably, it is the range of 40 micrometers or more and 60 micrometers or less. By setting the thickness of the active material layer to 40 μm or more, it is possible to increase the capacity of the battery. Moreover, the discharge capacity maintenance factor when charging / discharging is repeated can be enlarged by setting it as 80 micrometers or less.

(Positive electrode)
The positive electrode current collector 23A is made of, for example, a metal material such as aluminum, nickel, or stainless steel. The positive electrode active material layer 24B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium as a positive electrode active material. It may contain a binder.

Examples of the positive electrode material capable of inserting and extracting lithium include lithium cobaltate, lithium nickelate, and solid solutions thereof (Li (NiCo _y Mn _z ) O ₂ )) (x, y, and z have values of 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.), Manganese spinel (LiMn ₂ O ₄ ) and its solid solution (Li (Mn _2−v Ni _v ) O ₄ ) (The value of v is v <2.) Lithium composite oxides and the like, and phosphate compounds having an olivine structure such as lithium iron phosphate (LiFePO ₄ ) are preferable. This is because a high energy density can be obtained. 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 iron disulfide, titanium disulfide and molybdenum sulfide, sulfur, And conductive polymers such as polyaniline and polythiophene.

(Negative electrode)
The negative electrode 24 has, for example, a structure in which a negative electrode active material layer 24B is provided on both surfaces of a negative electrode current collector 24A having a pair of opposed surfaces. The negative electrode current collector 24A is made of a metal material such as copper, nickel, and stainless steel, for example.

  The negative electrode active material layer 24B includes one or more negative electrode materials capable of occluding and releasing lithium as a negative electrode active material. In this secondary battery, the charge capacity of the negative electrode material capable of inserting and extracting lithium is larger than the charge capacity of the positive electrode 23 so that lithium metal does not deposit on the negative electrode 24 during the charge. It has become.

  Examples of the negative electrode material capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, graphite, 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 in part, it is made of non-graphitizable carbon or graphitizable carbon. Some are classified. Examples of the polymer material include polyacetylene and polypyrrole. These carbon materials are preferable because the change in crystal structure that occurs during charge and discharge is very small, a high charge and 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, those having a low charge / discharge potential, specifically, those having a charge / discharge potential close to that of lithium metal are preferable because a high energy density of the battery can be easily realized.

  Further, as the negative electrode material, in addition to the carbon material shown above, a material containing an element that forms an alloy with lithium, such as silicon, tin, and a compound thereof, magnesium, aluminum, germanium, or the like may be used. Further, a material containing an element that forms a composite oxide with lithium, such as titanium, can be considered.

(Separator)
The separator 25 separates the positive electrode 23 and the negative electrode 24 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 25 is made of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a multi-hard film made of ceramic, and a plurality of these porous films are laminated. It may be a structure. For example, the separator 25 is impregnated with an electrolytic solution that is a liquid electrolyte.

(Nonaqueous electrolyte)
In the present invention, the nonaqueous electrolytic solution (hereinafter also simply referred to as the electrolytic solution) is a halide of an element selected from the group consisting of Zr, Group 5 of the periodic table, Group 6 and Groups 12 to 15 (hereinafter referred to as the electrolyte). Simply referred to as "halide"). These halides are considered to suppress gas generation due to the reaction between the electrolytic solution and the battery active material by decomposing on the electrode surface during the first charge to form a protective film of lithium halide. Further, when these halides are dissolved in the electrolytic solution, it is considered that halide ions are not generated in the solution. If halide ions are present, they bind to lithium ions in the electrolyte solution and become insoluble lithium chloride, resulting in white turbidity. However, even if the halide used in the present invention is dissolved in the electrolyte solution, such a phenomenon is observed. Absent.

  The element selected from the group consisting of Zr, Group 5 and Group 6 and Group 12 to 15 of the periodic table is zirconium, Group 5 vanadium, niobium, tantalum, Group 6 molybdenum, tungsten, Examples include Group 12 zinc, Group 13 aluminum, gallium, indium, Group 14 silicon, germanium, tin, Group 15 phosphorus and antimony. Among these, from the viewpoint of easily forming an oxide film, an element selected from Group 6 or Group 13 is preferable, and molybdenum is most preferable.

  Of the halides, chloride is considered effective. This is because, compared with chloride, fluoride has a high ionicity and thus has a low solubility in an organic electrolyte solution, and bromide has a high solubility in lithium bromide to be formed, so that it is difficult to form a protective film.

  The concentration of the halide in the non-aqueous electrolyte is preferably 0.02 to 0.50 mass%, more preferably 0.05 to 0.2 mass%. A concentration in the range of 0.02 to 0.50 mass% is preferable because a sufficient film is formed and the resistance is small.

  These halides are effective when combined with carbonates. These carbonic acid esters are thought to suppress gas generation by forming a protective film by another mechanism. As the carbonate, cyclic carbonates such as vinylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, and vinyl ethylene carbonate, halogenated carbonates in which a part thereof is substituted with halogen, and the like are preferable. The content of carbonate is preferably 0.1 to 2% by mass. By setting it within this range, a sufficient film is formed and the resistance is reduced.

  The nonaqueous electrolytic solution in the present invention further contains a solvent and an electrolyte salt dissolved in the solvent. The solvent used for the electrolytic solution is preferably a high dielectric constant solvent having a relative dielectric constant of 30 or more. This is because the number of lithium ions can be increased. The content of the high dielectric constant solvent in the electrolytic solution is preferably in the range of 15 to 50% by mass. It is because higher charging / discharging efficiency is obtained by setting it within this range.

  Examples of the high dielectric constant solvent include cyclic carbonates such as vinylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate and vinyl ethylene carbonate, lactones such as γ-butyrolactone and γ-valerolactone, and N-methyl-2-pyrrolidone. And lactams such as N-methyl-2-oxazolidinone, and sulfone compounds such as tetramethylene sulfone. Cyclic carbonates are particularly preferable, and ethylene carbonate and vinylene carbonate having a carbon-carbon double bond are more preferable. Moreover, the said high dielectric constant solvent may be used individually by 1 type, and may mix and use multiple types.

  The solvent used for the electrolytic solution is preferably used by mixing a low-viscosity solvent having a viscosity of 1 mPa · s or less with the high dielectric constant solvent. This is because high ion conductivity can be obtained. The ratio (mass ratio) of the low-viscosity solvent to the high-dielectric-constant solvent is preferably in the range of high-dielectric-constant solvent: low-viscosity solvent = 2: 8 to 5: 5. It is because a higher effect can be obtained by setting it within this range.

  Examples of the low viscosity solvent include chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and trimethyl. Chain carboxylic acid esters such as methyl acetate and ethyl trimethylacetate, chain amides such as N, N-dimethylacetamide, chain carbamic acid esters such as methyl N, N-diethylcarbamate and ethyl N, N-diethylcarbamate And ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran and 1,3-dioxolane. These low-viscosity solvents may be used alone or in combination of two or more.

As the electrolyte salt, e.g., lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ , Inorganic lithium salts such as lithium perchlorate (LiClO ₄ ) and lithium tetrachloroaluminate (LiAlCl ₄ ), and lithium trifluoromethanesulfonate (CF ₃ SO ₃ Li), lithium bis (trifluoromethanesulfone) imide [(CF ₃ SO ₂ ) ₂ NLi], lithium bis (pentafluoroethanesulfone) imide [(C ₂ F ₅ SO ₂ ) ₂ NLi] and lithium tris (trifluoromethanesulfone) methide [(CF ₃ SO ₂ ) ₃ CLi] Of perfluoroalkanesulfonic acid derivatives Lithium salts. One electrolyte salt may be used alone, or a plurality of electrolyte salts may be mixed and used. The content of the electrolyte salt in the electrolytic solution is preferably 6 to 25% by weight.

(Polymer compound)
The battery of the present invention may be in the form of a gel by containing a polymer compound that swells with the electrolyte and serves as a holding body that holds the electrolyte. It is because high ion conductivity can be obtained by including a polymer compound that swells with the electrolytic solution, excellent charge / discharge efficiency can be obtained, and battery leakage can be prevented. When a polymer compound is added to the electrolytic solution and used, the content of the polymer compound in the electrolytic solution is preferably in the range of 0.1% by mass to 2.0% by mass. Further, when a polymer compound such as polyvinylidene fluoride is applied on both sides of the separator, the mass ratio of the electrolytic solution to the polymer compound is preferably in the range of 50: 1 to 10: 1. It is because higher charging / discharging efficiency is obtained by setting it within this range.

  Examples of the polymer compound include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide and polyethylene oxide represented by the following formula (1), and ester-based polymers such as polymethacrylate represented by the following formula (2). Examples thereof include a polymer of vinylidene fluoride such as a molecular compound, an acrylate polymer compound, and polyvinylidene fluoride represented by the following formula (3), and a copolymer of vinylidene fluoride and hexafluoropropylene. A high molecular compound may be used individually by 1 type, and multiple types may be mixed and used for it. In particular, from the viewpoint of the effect of preventing swelling during high temperature storage, it is desirable to use a fluorine-based polymer compound such as polyvinylidene fluoride.

In the formulas (1) to (3), s, t and u are each an integer of 100 to 10000, R is C _x H _2x-1 O _y (x is 1 to 8, y is 0 to 4) Indicated.

(Production method)
For example, the secondary battery can be manufactured as follows.

  The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture. A slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 23A and the solvent is dried. Then, the positive electrode active material layer 23B is formed by compression molding using a roll press or the like, and the positive electrode 23 is manufactured. At this time, the thickness of the positive electrode active material layer 23B is set to 40 μm or more.

  Moreover, a negative electrode can be produced by the following method, for example. First, after preparing a negative electrode mixture by mixing a negative electrode active material containing at least one of silicon and tin as constituent elements, a conductive agent, and a binder, the negative electrode mixture was mixed with N-methyl-2. -Disperse in a solvent such as pyrrolidone to obtain a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 24A, dried, and compression-molded to form a negative electrode active material layer 24B containing negative electrode active material particles made of the negative electrode active material described above. Get. At this time, the thickness of the negative electrode active material layer 24B is set to 40 μm or more.

  Next, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 23 and the negative electrode 24, and the mixed solvent is volatilized to form the electrolyte layer 26. Next, the positive electrode lead 21 is attached to the positive electrode current collector 23A, and the negative electrode lead 22 is attached to the negative electrode current collector 24A. Subsequently, the positive electrode 23 and the negative electrode 24 on which the electrolyte layer 26 is formed are laminated through a separator 25 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and the protective tape 27 is attached to the outermost peripheral portion. The wound electrode body 20 is formed by bonding. After that, for example, the wound electrode body 20 is sandwiched between the exterior members 30, and the outer edges of the exterior members 30 are brought into close contact by thermal fusion or the like and sealed. At that time, an adhesion film 31 is inserted between the positive electrode lead 21 and the negative electrode lead 22 and the exterior member 30. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 23 and the negative electrode 24 are prepared as described above, and after the positive electrode lead 21 and the negative electrode lead 22 are attached to the positive electrode 23 and the negative electrode 24, the positive electrode 23 and the negative electrode 24 are stacked and wound via the separator 25. Rotate and adhere the protective tape 27 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 20. Next, the wound body is sandwiched between the exterior members 30, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 30. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, and other materials such as a polymerization initiator or a polymerization inhibitor as necessary is prepared, and the interior of the exterior member 30 is prepared. After the injection, the opening of the exterior member 30 is heat-sealed and sealed. After that, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 26 and assembling the secondary battery shown in FIGS.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 23 and inserted in the negative electrode 24 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are extracted from the negative electrode 24 and inserted into the positive electrode 24 through the electrolytic solution.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment, and various modifications can be made. For example, in the above embodiment and the case where an electrolytic solution is used as the electrolyte, and the case where a gel electrolyte in which the electrolytic solution is held in a polymer compound is also described, other electrolytes are used. It may be. Other electrolytes include, for example, a mixture of an ion conductive ceramic 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.

  In the above embodiment, a battery using lithium as an electrode reactant has been described. However, another alkali metal such as sodium (Na) or potassium (K), or an alkaline earth metal such as magnesium or calcium (Ca). The present invention can also be applied to the case of using other light metals such as aluminum.

  Further, in the above embodiment, the capacity of the negative electrode is a so-called lithium ion secondary battery represented by a capacity component due to insertion and extraction of lithium, or lithium metal is used for the negative electrode active material, and the capacity of the negative electrode is Although a so-called lithium metal secondary battery represented by a capacity component due to precipitation and dissolution has been described, the present invention makes the charge capacity of the negative electrode material capable of occluding and releasing lithium smaller than the charge capacity of the positive electrode. Thus, the present invention can be similarly applied to a secondary battery in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof. .

  Furthermore, in the above embodiment, the laminate type secondary battery has been specifically described, but it goes without saying that the present invention is not limited to the above shape. That is, the present invention can be applied to a cylindrical battery, a square battery, and the like. Further, the present invention is not limited to the secondary battery but can be similarly applied to other batteries such as a primary battery.

<Examples 1-1 to 1-13>
(Example 1-1)
First, 94 parts by weight of lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 3 parts by weight of graphite as a conductive material, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder are homogeneous. After mixing, N-methylpyrrolidone was added to obtain a positive electrode mixture coating solution. Next, the obtained positive electrode mixture coating solution was uniformly applied on both surfaces of an aluminum foil having a thickness of 20 μm and dried to form a positive electrode mixture layer of 40 mg / cm ² per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to produce a positive electrode.
Next, 97 parts by weight of graphite as a negative electrode active material and 3 parts by weight of PVdF as a binder were homogeneously mixed, and N-methylpyrrolidone was added to obtain a negative electrode mixture coating solution. Next, the obtained negative electrode mixture coating liquid was uniformly applied on both sides of a 15 μm thick copper foil serving as a negative electrode current collector and dried to form a negative electrode mixture layer of 20 mg / cm ² per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to prepare a negative electrode.
The electrolyte was mixed at a ratio (mass ratio) of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / lithium hexafluorophosphate / molybdenum chloride (V) = 34/51 / 14.9 / 0.1. Created. Molybdenum chloride (V) was obtained from Sigma-Aldrich Japan (the same applies to halides described below).

  The positive electrode and the negative electrode were laminated and wound up via a separator made of a microporous polyethylene film having a thickness of 9 μm, and placed in a bag made of an aluminum laminate film. After 2 g of electrolyte solution was poured into this bag, the bag was heat-sealed to produce a laminate type battery. The capacity of this battery was 700 mAh.

  Table 1 shows the change in battery thickness as a percentage of expansion when the battery was charged at 700 mA at 23 ° C and 4.2 V as the upper limit for 3 hours and then stored at 90 ° C for 4 hours. The expansion coefficient is a value calculated using the battery thickness before storage as the denominator and the thickness increased during storage as the numerator. In addition, Table 1 shows discharge capacity retention rates when charging at 700 mA and upper limit of 4.2 V for 3 hours in a 23 ° C. environment and then repeating discharge at 700 mA and lower limit of 3.0 V for 300 times.

(Examples 1-2 and 1-3)
A laminated battery was prepared in the same manner as in Example 1-1 except that the concentration of molybdenum chloride (V) was 0.02% by mass and 0.50% by mass, respectively, and lithium hexafluorophosphate was increased or decreased accordingly. . Table 1 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 1-4 to 1-13)
A laminated battery was prepared in the same manner as in Example 1-1 except that each halide shown in Table 1 was blended instead of molybdenum chloride (V). Table 1 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Comparative Example 1-1)
A laminated battery was prepared in the same manner as in Example 1-1 except that molybdenum chloride (V) was not blended and the amount of lithium hexafluorophosphate was increased accordingly. Table 1 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

  As shown in Table 1, in Example 1-1 containing molybdenum chloride in the electrolytic solution, the expansion coefficient of the battery decreased by 20% compared to Comparative Example 1-1 not containing, and the discharge capacity after 300 cycles. Maintenance rate improved. That is, it was found that by adding a halide unique to the present application to the electrolytic solution, expansion of the battery during high-temperature storage is suppressed and cycle characteristics are improved.

  Further, in Example 1-2 in which the amount of molybdenum chloride blended is smaller than that in Example 1-1, the expansion coefficient was higher than in Example 1-1, but Comparative Example 1-1 in which no molybdenum chloride was blended was used. Compared to 10%. On the other hand, in Example 1-3 in which the amount of molybdenum chloride blended was larger than that in Example 1-1, the expansion coefficient could be further reduced. Further, the discharge capacity retention ratio after 300 cycles was improved to the same level as in Example 1-1 in both Examples 1-2 and 1-3. That is, the optimum content of halide was found to be 0.02 to 0.50 mass%.

  In each of Examples 1-4 to 1-13 in which the halide was changed, the expansion rate of the battery could be reduced to the 10% range, and the discharge capacity retention rate after 300 cycles was improved. In particular, Example 1-10 blended with gallium chloride (III) was one-fifth of the blend amount of Example 1-3 blended with 0.5% by mass of molybdenum chloride (V). The same expansion reduction effect as that of -1 was obtained. That is, other than molybdenum chloride, Zr, a chloride of an element selected from the group consisting of Groups 5 and 6, and Groups 12 to 15 of the periodic table may be blended in the electrolyte solution at high temperature storage. It was found that the expansion of the battery was suppressed and the cycle characteristics were improved.

<Examples 2-1 to 2-18>
(Example 2-1)
A laminate type battery was prepared in the same manner as in Example 1-1 except that 1% by mass of fluoroethylene carbonate (FEC) was blended in the electrolytic solution and the amount of ethylene carbonate (EC) was reduced accordingly. Table 2 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Example 2-2, 2-3)
A laminated battery was prepared in the same manner as in Example 2-2, except that the concentration of molybdenum chloride (V) was 0.02 mass% and 0.50 mass%, respectively, and lithium hexafluorophosphate was increased or decreased accordingly. . Table 2 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Example 2-4)
A laminate type battery was prepared in the same manner as in Example 1-1 except that 1% by mass of vinylene carbonate (VC) was blended in the electrolytic solution and the amount of ethylene carbonate (EC) was reduced accordingly. Table 2 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 2-5 to 2-18)
A laminated battery was prepared in the same manner as in Example 2-2 except that each halide shown in Table 2 was blended instead of molybdenum chloride (V). Table 2 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Comparative Example 2-1)
A laminate type battery was prepared in the same manner as in Example 2-2 except that molybdenum chloride (V) was not blended and the amount of lithium hexafluorophosphate was increased accordingly. Table 2 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

  As shown in Table 2, Example 2-1 containing molybdenum chloride and FEC in the electrolytic solution had a battery expansion rate of 20% compared to Comparative Example 2-1 containing FEC but no molybdenum chloride. As a result, the discharge capacity retention rate after 300 cycles was improved. That is, it was found that when FEC and a halide are used in combination rather than FEC alone, the battery expansion suppressing effect and the discharge capacity retention rate are more excellent.

  In addition, Example 1-1 containing only molybdenum chloride gave better results in both expansion coefficient and discharge capacity maintenance rate than Comparative Example 2-1 containing only FEC. That is, it was found that the halide was superior in the battery expansion suppressing effect and the discharge capacity retention rate than the FEC.

  Further, in Example 2-2 in which the amount of molybdenum chloride blended is smaller than that in Example 2-1, the expansion coefficient was higher than that in Example 2-1, but Comparative Example 2-1 without blending molybdenum chloride and Compared to 10%. On the other hand, in Example 2-3 in which the amount of molybdenum chloride blended was larger than that in Example 2-1, the expansion rate was similar. That is, it was found that the optimum content of halide when used in combination with FEC was 0.02 to 0.50 mass%.

  Example 2-4 using VC instead of FEC showed a slightly lower expansion rate than Example 2-1, but the discharge capacity retention rate after 300 cycles was improved over Example 2-1. .

  Any of Examples 2-4 to 2-18 in which the halide was changed can reduce the expansion coefficient of the battery as compared with Comparative Example 2-1 containing no halide, and the discharge capacity retention rate after 300 cycles. Improved. That is, other than molybdenum chloride, Zr, a chloride of an element selected from the group consisting of Groups 5 and 6, and Groups 12 to 15 of the periodic table may be blended in the electrolyte solution at high temperature storage. It was found that the expansion of the battery was suppressed and the cycle characteristics were improved.

<Examples 3-1 to 3-13>
(Example 3-1)
A laminate type battery was produced in the same manner as in Example 1-1, except that a separator having a thickness of 7 μm and a separator coated with 2 μm of polyvinylidene fluoride on both sides was used. At this time, the mass ratio of the electrolytic solution to polyvinylidene fluoride was 20: 1. Table 3 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 3-2 and 3-3)
A laminate type battery was prepared in the same manner as in Example 3-1, except that the concentration of molybdenum chloride (V) was 0.05 mass% and 0.50 mass%, respectively, and lithium hexafluorophosphate was increased or decreased accordingly. . Table 3 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 3-4 to 3-13)
A laminated battery was prepared in the same manner as in Example 3-1, except that each halide shown in Table 3 was blended instead of molybdenum chloride (V). Table 3 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Comparative Example 3-1)
A laminated battery was prepared in the same manner as in Example 3-1, except that molybdenum chloride (V) was not blended and the amount of lithium hexafluorophosphate was increased accordingly. Table 3 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

  As shown in Table 3, in Example 3-1, which contains molybdenum chloride in the electrolytic solution, the expansion coefficient of the battery is reduced compared to Comparative Example 3-1, which does not contain, and the discharge capacity maintenance rate after 300 cycles is reduced. Improved. Moreover, the expansion | swelling suppression effect improved further compared with Example 1-1 which does not contain a polyvinylidene fluoride. From this, it was found that, in addition to containing molybdenum chloride in the electrolytic solution, the effect of suppressing the expansion of the battery can be further improved by using polyvinylidene fluoride as the polymer compound.

  Further, in Example 3-2 in which the amount of molybdenum chloride blended is smaller than that in Example 3-1, the expansion coefficient was higher than that in Example 3-1, but Comparative Example 3-1 without blending molybdenum chloride and It was able to decrease compared with. On the other hand, in Example 3-3 in which the amount of molybdenum chloride blended was larger than that in Example 3-1, the expansion coefficient could be further reduced. Further, the discharge capacity retention ratio after 300 cycles was improved to the same level as in Example 3-1 in both Examples 3-2 and 3-3.

  Each of Examples 3-4 to 3-13 in which the halide was changed can reduce the expansion coefficient of the battery as compared with Comparative Example 3-1 in which no halide is blended, and the discharge capacity retention rate after 300 cycles. Improved. In particular, Example 3-10 in which gallium (III) chloride was blended was one-fifth of the amount of Example 3-3 in which 0.5 mass% of molybdenum chloride (V) was blended. The expansion reduction effect comparable to -3 was obtained.

<Examples 4-1 to 4-18>
(Example 4-1)
A laminate type battery was prepared in the same manner as in Example 1-1 except that 1% by mass of fluoroethylene carbonate (FEC) was blended in the electrolytic solution and the amount of ethylene carbonate (EC) was reduced accordingly. Table 4 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 4-2 and 4-3)
A laminate type battery was prepared in the same manner as in Example 4-2 except that the concentration of molybdenum chloride (V) was 0.05 mass% and 0.50 mass%, respectively, and lithium hexafluorophosphate was increased or decreased accordingly. . Table 4 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Example 4-4)
A laminate type battery was prepared in the same manner as in Example 1-1 except that 1% by mass of vinylene carbonate (VC) was blended in the electrolytic solution and the amount of ethylene carbonate (EC) was reduced accordingly. Table 4 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Examples 4-5 to 4-18)
A laminated battery was prepared in the same manner as in Example 4-2 except that each halide shown in Table 4 was blended instead of molybdenum chloride (V). Table 4 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

(Comparative Example 4-1)
A laminate type battery was prepared in the same manner as in Example 4-2 except that molybdenum chloride (V) was not blended and the amount of lithium hexafluorophosphate was increased accordingly. Table 4 shows the expansion rate (%) of the change in battery thickness and the discharge capacity retention rate when the discharge was repeated 300 times.

  As shown in Table 4, Example 4-1 containing molybdenum chloride and FEC in the electrolytic solution had a battery expansion rate of 15% compared to Comparative Example 4-1 containing FEC but not containing molybdenum chloride. The discharge capacity retention rate after 300 cycles was improved. That is, it was found that when FEC and a halide are used in combination rather than FEC alone, the battery expansion suppressing effect and the discharge capacity retention rate are more excellent.

  In addition, Example 3-1 containing only molybdenum chloride gave better results in both expansion coefficient and discharge capacity maintenance rate than Comparative Example 4-1 containing only FEC. That is, it was found that the halide was superior in the battery expansion suppressing effect and the discharge capacity retention rate than the FEC.

  Moreover, in Example 4-2 in which the amount of molybdenum chloride is less than that of Example 4-1, the expansion coefficient was higher than that of Example 4-1, but Comparative Example 4-1 without molybdenum chloride and It was able to decrease compared with. On the other hand, in Example 4-3 in which the amount of molybdenum chloride blended was larger than that in Example 4-1, the expansion rate was similar. That is, it was found that the optimum content of halide when used in combination with FEC was 0.02 to 0.50 mass%.

  Example 4-4 using VC instead of FEC showed the same expansion coefficient as that of Example 4-1, and the discharge capacity retention rate after 300 cycles was higher than that of Example 4-1.

  Any of Examples 4-4 to 4-18 in which the halide was changed can reduce the expansion coefficient of the battery as compared with Comparative Example 4-1 not containing a halide, and the discharge capacity retention rate after 300 cycles. Improved. That is, other than molybdenum chloride, Zr, a chloride of an element selected from the group consisting of Groups 5 and 6, and Groups 12 to 15 of the periodic table may be blended in the electrolyte solution at high temperature storage. It was found that the expansion of the battery was suppressed and the cycle characteristics were improved.

It is a disassembled perspective view showing the structure of the nonaqueous electrolyte secondary battery which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Winding electrode body, 23 ... Positive electrode, 23A ... Positive electrode collector, 23B ... Positive electrode active material layer, 24 ... Negative electrode, 24A ... Negative electrode collector, 24B ... Negative electrode active material layer, 25 ... Separator, 21 ... Positive electrode Lead, 22 ... negative electrode lead, 26 ... electrolyte layer, 27 ... protective tape, 30 ... exterior member, 31 ... adhesion film.

Claims (15)

A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte together with a positive electrode and a negative electrode,
The non-aqueous electrolyte secondary contains a halide of an element selected from the group consisting of Zr, groups 5 and 6 of the periodic table, and groups 12 to 15 battery.   2. The non-aqueous electrolyte secondary battery according to claim 1, wherein a concentration of the halide in the non-aqueous electrolyte is 0.02 to 0.50 mass%.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the halogen is chlorine.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the element is selected from Group 6 or Group 13 of the Periodic Table.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the element is molybdenum.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte further contains a carbonate.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode body and the non-aqueous electrolyte are accommodated in an exterior member made of a laminate film.   The non-aqueous electrolyte secondary battery according to claim 1, comprising a polymer compound that swells with the non-aqueous electrolyte.   The non-aqueous electrolyte secondary battery according to claim 8, wherein the polymer compound is polyvinylidene fluoride.   A nonaqueous electrolytic solution comprising a halide of an element selected from the group consisting of Zr, groups 5 and 6 of the periodic table, and groups 12 to 15.   The non-aqueous electrolyte according to claim 10, wherein a concentration of the halide is 0.02 to 0.50 mass%.   The non-aqueous electrolyte according to claim 10, wherein the halogen is chlorine.   The non-aqueous electrolyte according to claim 10, wherein the element is selected from Group 6 or Group 13 of the Periodic Table.   The non-aqueous electrolyte according to claim 10, wherein the element is molybdenum.   The nonaqueous electrolytic solution according to claim 10, further comprising a carbonate ester.

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