JP2002033117A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that chain carbonic ester such as dimethyl carbonate to be mainly used as a nonaqueous solvent of a nonaqueous electrolyte secondary battery is high in vapor pressure and low in firing point, thereby the battery is expanded at the time of high temperature preservation according to the height vapor pressure in a thin battery and higher safety is required in this kind of battery. SOLUTION: Mixed solvent of total three kinds of at least one selected from a group of cyclic carbonic ester such as ethylene carbonate and vinylene carbonate, one of dibutyl carbonate and dipropyl carbonate and at least one selected from a group of sulfolane, 3-methylsulfolane, 1,4-butane sulfon, ethylene glycolic mono-n-butyl ether acetate and 1, 2 diacetoxy ethane is made and the mixed solvent with dissolved supporting electrolyte is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrolytic solution for a non-aqueous electrolyte secondary battery, and more particularly to a portable information terminal, a portable electronic device, and a household device in which the storage characteristics as a battery are improved by improving the electrolytic solution. The present invention relates to a non-aqueous electrolyte secondary battery suitable for a small power storage device, a motorcycle powered by a motor, an electric vehicle, a hybrid electric vehicle, and the like.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries used as main power sources for mobile communication devices and portable electronic devices have the characteristics of high electromotive force and high energy density.

A lithium secondary battery uses, as a negative electrode material, lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium, or a metal oxide. However,
Metallic lithium and lithium alloys tend to form dendrites during charging, which may cause internal short circuits through the separator.Therefore, commercially available practical batteries include carbon materials or metal oxides capable of occluding and releasing lithium. Things are used.

On the other hand, transition metal oxides such as lithium cobalt oxide, lithium nickel oxide, and lithium manganate are often used as a positive electrode material in order to achieve a battery with high voltage and high energy density. These materials have a high potential of 4 V or more based on the potential of metallic lithium.

[0005] As a solvent of an electrolytic solution used for a non-aqueous electrolyte battery, cyclic carbonate represented by propylene carbonate (PC) and ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) Γ-butyrolactone (GBL), γ
-Cyclic carboxylic acid esters represented by valerolactone (GVL), chain ethers such as dimethoxymethane (DMM) and 1,3-dimethoxypropane (DMP), tetrahydrofuran (THF) and 1,3-dioxolane (DOL) Are widely used.

[0006] When these solvents are applied to a non-aqueous electrolyte secondary battery, those having high electric conductivity are desirable. For this purpose, a solvent having a high relative dielectric constant and a low viscosity is preferably used. However, a high relative dielectric constant is nothing less than a strong polarity, that is, a high viscosity. For this reason, in the current practical battery, among the above-mentioned electrolytes, a high dielectric constant solvent such as ethylene carbonate (dielectric constant ε = 90), dimethyl carbonate (DMC, ε = 3.1), and ethyl methyl carbonate (EMC) , Ε = 2.9) and are often used in combination with a low dielectric constant solvent.

The electrolyte used for the non-aqueous electrolyte battery is obtained by dissolving a supporting electrolyte having a concentration of about 1 mol in the above-mentioned solvent. As the supporting electrolyte, lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiB
F ₄ ), lithium salts of inorganic acids typified by lithium phosphofluoride (LiPF ₆ ), lithium trifluoromethanesulfonate (LiSO ₃ CF ₃ ), lithium bistrifluoromethanesulfonimide ((CF ₃ SO ₂ ) ₂ N
Li) and the like are used.

[0008]

However, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, which are widely used as non-aqueous electrolytes, have a high vapor pressure and a low flash point. For this reason, particularly in thin batteries such as prismatic batteries, polymer gel electrolyte batteries, and laminate pack batteries, there is a problem that the batteries swell during high-temperature storage due to high vapor pressure. In addition, a lithium ion battery with a high energy density requires higher safety, and a low flash point is a negative factor. Furthermore, even during manufacture, a low flash point is dangerous.

[0009]

The present invention provides a non-aqueous electrolyte,
In a non-aqueous electrolyte secondary battery including a separator, and a positive electrode and a negative electrode capable of inserting and extracting lithium, the non-aqueous electrolyte is formed of ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valero. At least one selected from the group of lactones and dibutyl carbonate, at least one of dipropyl carbonate and sulfolane, 3-methylsulfolane, 1,4-butanesultone,
Ethylene glycol mono-n-butyl ether acetate, a mixed solvent with at least one selected from the group of 1,2-diacetoxyethane, at least one of which is a solvent having a melting point of -20 ° C. or less, a solvent comprising a compound, A solution in which a supporting electrolyte having lithium as a cation is dissolved is used.

The mixed solvent used here does not wet a polyolefin separator such as polyethylene and polypropylene or a composite thereof, and makes it difficult to charge and discharge a large current. Therefore, a surfactant is added for improvement. is there. When the thus obtained electrolytic solution is used, a novel non-aqueous electrolyte secondary battery having excellent high-rate charge / discharge characteristics can be provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A positive electrode and a negative electrode used in the present invention are a mixture layer containing a conductive agent, a binder and the like in a positive electrode active material or a negative electrode material capable of electrochemically and reversibly absorbing and releasing lithium ions. Is applied to the surface of the current collector.

The invention according to claims 1 to 4 of the present invention comprises a plurality of cyclic compounds using a carbon material capable of occluding and releasing lithium for a negative electrode and a transition metal oxide containing lithium as a positive electrode. By using a solvent in which a supporting electrolyte having lithium as a cation is dissolved as a non-aqueous electrolyte, it can be used in a wide temperature range, has a high energy density, has a small decrease in discharge capacity due to repeated use of a battery, and has a high efficiency. A novel non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics is achieved.

The non-aqueous electrolyte used in the present invention comprises at least one selected from the group consisting of ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone and γ-valerolactone, and sulfolane, 3-methylsulfolane, A mixed solvent of at least one selected from the group consisting of 4-butane sultone, ethylene glycol mono-n-butyl ether acetate, and 1,2-diacetoxyethane, and at least one of dibutyl carbonate and dipropyl carbonate, wherein at least one of them has a melting point But-
A solution obtained by dissolving a supporting electrolyte having lithium as a cation in a solvent composed of a compound having a temperature of 20 ° C. or lower was used.

Among the above-mentioned compounds, compounds having a high melting point such as ethylene carbonate or vinylene carbonate are included, and these high-melting compounds are mixed with a low-melting cyclic compound having a melting point of −20 ° C. or less. It can be used without problems even at a low temperature of 0 ° C. or lower. From this point, dibutyl carbonate and dipropyl carbonate have a volume fraction of 0.1 in the mixed solvent.
Preferably it is 5 to 75%.

Examples of lithium salts dissolved in these solvents include LiClO ₄ , LiBF ₄ , LiPF ₆ and Li
AlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ S
O ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAs
F ₆ , LiB ₁₀ Cl ₁₀ , lithium lower aliphatic carboxylate, LiCl, LiBr, LiI, lithium chloroborane, bis (1,2-benzenediolate (2-) — O,
O ') lithium borate, bis (2,3-naphthalenedioleate (2-)-O, O') lithium borate, bis (2,2'-biphenyldiolate (2-)-O,
O ') lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid -O, O') borate borate salts such as lithium, bis trifluoromethane sulfonic acid imide lithium _{((CF 3 SO 2) 2NLi} ) , Lithium tetrafluoromethanesulfonate nonafluorobutanesulfonate imide (LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO
₂ )) and imide salts such as lithium bispentafluoroethanesulfonimide ((C ₂ F ₅ SO ₂ ) 2NLi), etc., and these may be used alone or in combination of two or more with an electrolytic solution or the like using them. Can be used. Further, among these, the organic acid anion-based lithium salt has excellent thermal stability as compared with the inorganic acid anion-based lithium salt represented by lithium perchlorate and lithium phosphofluoride. During storage at high temperatures, these supporting electrolytes do not thermally decompose and do not degrade the battery characteristics, and are more preferably used.

The supporting electrolytes having lithium as a cation include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), trifluorofluoride Lithium methanesulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethanesulfonate imide ((CF ₃ SO ₂ ) 2NLi),
Bispentafluoroethanesulfonyl imide lithium _{((C 2 F 5 SO 2} ) 2NLi), bis (1,2-benzene diolate (2 -) - O, O ') lithium borate, bis (2,3 naphthalenedioate Rate (2-)-O,
O ') lithium borate, bis (2,2'-biphenyldiolate (2-)-O, O') lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ') It is at least one compound selected from the group consisting of lithium borate.

The lithium bis (trifluoromethanesulfonate) ((CF ₃ ) having the following structural formula (Formula 3)
For SO ₂ ) 2NLi), the withstand voltage for reduction and decomposition on the platinum electrode is 0 V with respect to the lithium reference electrode, and the withstand voltage for oxidative decomposition is 4.7 V.

[0018]

Embedded image

Further, lithium bispentafluoroethanesulfonimide ((C ₂
For F ₅ SO ₂ ) 2NLi), the breakdown voltage on the platinum electrode is 0 V and the oxidation breakdown voltage is 4.7 V.

[0020]

Embedded image

Further, lithium bis (5-fluoro-2-olate-1-benzenesulfonate-O, O ') borate has a breakdown voltage of 0 V on a platinum electrode and a breakdown voltage of 4.5 V on a platinum electrode. Lithium bis (2,2'-biphenyldiolate (2-)-O, O ') borate has a withstand voltage of 0 V and a withstand voltage of 4.1 V or more on a platinum electrode. . Therefore, these organic acid anion lithium salts are lithium cobaltate, lithium nickelate,
4 with respect to lithium reference electrode such as lithium manganate
Application to an active material that generates a high voltage of V or more is preferable in terms of increasing the energy density of a lithium secondary battery.
In particular, lithium salts having the structural formulas represented by Chemical Formulas 3 and 4 are preferably used in combination with one of LiPF ₆ and LiBF ₄ from the viewpoint of improving storage characteristics.

On the other hand, lithium bis (1,2-benzenediolate (2-)-O, O ') borate has a reduction decomposition withstand voltage on a platinum electrode of 0 V with respect to a lithium reference electrode, and has the same oxidation withstand voltage. Lithium bis (2,3-naphthalenediolate (2-)-O, O ') borate has a breakdown voltage of 0 V on a platinum electrode and a breakdown voltage of 3.8 V on an platinum electrode. is there. Applying an electrolytic solution in which these supporting electrolytes are dissolved to an active material that generates a high voltage of 4 V or more with respect to a lithium reference electrode such as lithium cobaltate, lithium nickelate, and lithium manganate involves decomposition of the supporting electrolyte. However, lithium titanium disulfide (L
iTiS ₂ ) and lithium molybdenum sulfide (LiMo)
A transition metal sulfide having an electromotive force of about 3 V with respect to the lithium reference electrode such as S ₂ ) can be used in this potential region.

In the present invention, the amount of the electrolyte to be added to the battery is not particularly limited, but the required amount can be used depending on the amounts of the positive electrode material and the negative electrode material and the size of the battery. The amount of the supporting electrolyte dissolved in the nonaqueous solvent is not particularly limited, but is preferably 0.2 to 2 mol / l. In particular, 0.5
More preferably, it is set to と す る 1.5 mol / l.

The surfactant used in the present invention includes:
Anionic surfactants such as carboxylate, sulfonate, sulfate ester salt and phosphate ester salt, aliphatic amine salts and their quaternary ammonium salts, aromatic quaternary ammonium salts, heterocyclic quaternary ammonium salts, etc. Cationic surfactants, carboxybetaines, sulfobetaines, aminocarboxylates, amphoteric surfactants such as imidazoline derivatives,
Nonionic surfactants such as polyoxyethylene ether, sugar ester and glycerin ester, and fluorine surfactants such as perfluoroalkyl sulfonate can be used. Especially high chemical and thermal stability,
Fluorosurfactants which hardly affect the electrode reaction and which are effective with a small amount of addition are preferably used. Examples of the fluorinated surfactant include perfluoroalkyl (C2-C20) carboxylic acid, disodium N-perfluorooctanesulfonylglutamate, 3- [fluoroalkyl (C6-C11) oxy] -1-alkyl (C3-C4) Sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino]
-1-sodium propanesulfonate, N- [3- (perfluorooctanesulfonamido) propyl] -N,
N-dimethyl-N-carboxymethylene ammonium betaine, perfluoroalkyl carboxylic acid (C7-C1
3), perfluorooctanesulfonic acid diethanolamide, perfluoroalkyl (C4-C12) sulfonate (Li, Na, K), N-propyl-N- (2-hydroxyethyl) perfluorooctanesulfonamide, perfluoro Alkyl (C6-C10) sulfonamidopropyl trimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt (K), bis (N-perfluorooctylsulfonyl-N-ethylaminoethyl) phosphate, Monoperfluoroalkyl (C6 to C16) ethyl phosphate may be mentioned.

In the present invention, the amount of the fluorinated surfactant added to the electrolyte is preferably 0.00001 to 1 wt%. In order to further reduce the influence on the electrode reaction of the battery, it is more preferable to add 0.00001 to 0.3 wt%.

The negative electrode conductive agent used in the present invention may be any material as long as it is an electron conductive material. For example, graphite such as natural graphite (flaky graphite, etc.), artificial graphite, etc., carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black, conductive fibers such as carbon fiber and metal fiber. Fibers, metal powders such as carbon fluoride, copper and nickel, and organic conductive materials such as polyphenylene derivatives may be included alone or as a mixture thereof. Among these conductive agents, artificial graphite, acetylene black and carbon fiber are particularly preferred. The amount of the conductive agent is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 1 to 30% by weight. In addition, since the negative electrode material of the present invention itself has electronic conductivity, it is possible to function as a battery without adding a conductive agent.

The binder for the negative electrode used in the present invention may be either a thermoplastic resin or a thermosetting resin. Preferred binders in the present invention include, for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene Ethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), poly Chlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer ( CTFE), vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethyl vinyl ether - tetrafluoroethylene copolymer, ethylene - acrylic acid copolymer or (Na ⁺⁾ ions Crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl methacrylate copolymer Alternatively, (Na ⁺ ) ion crosslinked products of the above materials can be mentioned, and these materials can be used alone or as a mixture. Among these materials, more preferable materials are styrene-butadiene rubber, polyvinylidene fluoride, ethylene-acrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the above-mentioned material, ethylene-methacrylic acid copolymer or the above-mentioned material. (Na ⁺ ) ion crosslinked product, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl methacrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material .

As the current collector for the negative electrode used in the present invention, any collector may be used as long as it does not cause a chemical change in the constructed battery. For example, in addition to stainless steel, nickel, copper, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of copper or stainless steel with carbon, nickel, or titanium is used. Particularly, copper or a copper alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. As the shape, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used. The thickness is not particularly limited, but 1 to
Those having a size of 500 μm are used.

As the positive electrode material used in the present invention, a compound containing or not containing lithium can be used. For example, LixCoO ₂ , LixNiO ₂ , LixMn
O ₂ , LixCoyNi _1-y O ₂ , LixCoyM _1-y O
z, LixNi _1-y MyOz, LixMn ₂ O ₄ , Lix
Mn _2-y MyO ₄ (M = Na, Mg, Sc, Y, Mn, F
e, Co, Ni, Cu, Zn, Al, Cr, Pb, S
b, at least one of B), (where x = 0 to 1.
2, y = 0 to 0.9, z = 2.0 to 2.3). Here, the above x value is a value before the start of charging and discharging,
It increases or decreases due to charge and discharge. However, it is also possible to use other positive electrode active materials such as transition metal chalcogenides, vanadium oxides and lithium compounds thereof, niobium oxides and lithium compounds thereof, conjugated polymers using organic conductive substances, and Chevrel phase compounds. is there. It is also possible to use a mixture of a plurality of different positive electrode active materials. Although the average particle diameter of the positive electrode active material particles is not particularly limited,
It is preferably from 30 to 30 μm.

The conductive agent for the positive electrode used in the present invention may be any electronic conductive material which does not cause a chemical change at the charge / discharge potential of the positive electrode material used. For example, graphites such as natural graphite (flaky graphite, etc.), artificial graphite, acetylene black, Ketjen black, channel black, furnace black, lamp black,
Carbon blacks such as thermal black, carbon fiber,
Conductive fibers such as metal fibers, metal powders such as carbon fluoride, copper, nickel, aluminum and silver, zinc oxide,
A conductive whisker such as potassium titanate, a conductive metal oxide such as titanium oxide, an organic conductive material such as a polyphenylene derivative, or the like can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite, acetylene black and nickel powder are particularly preferred. The amount of the conductive agent is not particularly limited,
It is preferably from 1 to 50% by weight, particularly preferably from 1 to 30% by weight. For carbon and graphite, 2 to 15% by weight is particularly preferred.

The binder for the positive electrode used in the present invention may be either a thermoplastic resin or a thermosetting resin. Preferred binders in the present invention are, for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene Copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentane Fluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl Vinyl ether-
A tetrafluoroethylene copolymer, an ethylene-acrylic acid copolymer or a (Na ⁺ ) ion cross-linked product of the above material,
Ethylene-methacrylic acid copolymer or (N
a ⁺ ) ion crosslinked product, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above-mentioned material, ethylene-methyl methacrylate copolymer or (N
a ⁺ ) ion-crosslinked product. In particular, the most preferred of these is polyvinylidene fluoride (PVD).
F), polytetrafluoroethylene (PTFE).

The current collector for the positive electrode used in the present invention may be any electronic conductor that does not cause a chemical change in the charge / discharge potential of the positive electrode material used. For example, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of aluminum or stainless steel with carbon or titanium is used. Particularly, aluminum or an aluminum alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. As the shape, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foamed body, a fiber group, a molded body of a nonwoven fabric body, or the like is used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used.

In the electrode mixture, a filler, a dispersant, an ion conductor and other various additives can be used in addition to a conductive agent and a binder. As the filler, any fibrous material that does not cause a chemical change in the configured battery can be used. Usually, fibers such as olefin-based polymers such as polypropylene and polyethylene, glass, and carbon are used. The amount of the filler added is not particularly limited, but is preferably 0 to 30% by weight.

The structure of the negative electrode plate and the positive electrode plate in the present invention is as follows.
It is preferable that the negative electrode mixture surface exists at least on the surface opposite to the positive electrode mixture surface.

As the separator used in the present invention,
A microporous thin film having high ion permeability, predetermined mechanical strength and insulating properties is used. Further, it is preferable to use a material having a shutdown function for closing the hole at a certain temperature or higher and increasing the resistance. Sheets, nonwoven fabrics or woven fabrics made from olefin polymers such as polypropylene and polyethylene alone or in combination or glass fibers are used because of their organic solvent resistance and hydrophobicity. The pore diameter of the separator is the positive and negative electrode material detached from the electrode sheet, the binder,
It is desirable that the conductive agent does not pass through, for example, 0.01 to 1 μm. Generally, the thickness of the separator is 10 to 300 μm. The porosity is determined according to the electron and ion permeability, the material, and the film pressure, but is generally preferably 30 to 80%.

A mixture of a polymer material and an organic electrolyte composed of a solvent and a lithium salt dissolved in the solvent is absorbed and held in the positive electrode mixture and the negative electrode mixture. It is also possible to configure a battery in which a porous separator made of a retained polymer is integrated with a positive electrode and a negative electrode. As the polymer material, any material can be used as long as it can absorb and hold an organic electrolytic solution, and a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.

The shape of the battery can be any of a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, and a large type used for electric vehicles.

Further, the non-aqueous electrolyte secondary battery of the present invention includes a portable information terminal, a portable electronic device, a small household power storage device,
The present invention can be used for a motorcycle, an electric vehicle, a hybrid electric vehicle, and the like, but is not particularly limited thereto.

[0039]

The present invention will be described in more detail with reference to the following examples.

Example 1 Manufacturing Method of Evaluation Battery FIG. 1 is a longitudinal sectional view of a cylindrical battery according to the present invention. The positive electrode plate 5 and the negative electrode plate 6 are spirally wound a plurality of times via a separator 7 and housed in the battery case 1. Then, a positive electrode lead 5 a is pulled out from the positive electrode plate 5 and connected to the sealing plate 2, and a negative electrode lead 6 a is connected from the negative electrode plate 6.
Is pulled out and connected to the bottom of the battery case 1.
The battery case and the lead plate can be made of a metal or an alloy having an organic electrolyte resistance and electron conductivity. For example, iron,
Metals such as nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used. In particular, the battery case is preferably formed by processing a stainless steel plate or an Al-Mn alloy plate, the positive electrode lead is most preferably aluminum, and the negative electrode lead is most preferably nickel. For the battery case, various types of engineering plastics and a combination thereof with a metal can be used to reduce the weight. Reference numeral 8 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively. Then, an electrolytic solution is injected, and a battery can is formed using the sealing plate. At this time, the safety valve can be used as a sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided. For example, a fuse, a bimetal, a PTC element, or the like is used as the overcurrent prevention element. In addition to the safety valve, as a countermeasure against an increase in the internal pressure of the battery case, a method of making a cut in the battery case, a gasket cracking method, a sealing plate cracking method, or a cutting method with a lead plate can be used. Also, the charger may be provided with a protection circuit incorporating measures for overcharging and overdischarging, or may be connected independently. As a measure against overcharging, a method of interrupting the current by increasing the internal pressure of the battery can be provided. At this time, a compound for increasing the internal pressure can be contained in the mixture or the electrolyte. Compounds that increase the internal pressure include Li ₂ CO ₃ and Li
HCO ₃ , Na ₂ CO ₃ , NaHCO ₃ , CaCO ₃ , Mg
Carbonates such as CO ₃ . As a welding method of the cap, the battery case, the sheet, and the lead plate, for example, DC or AC electric welding, laser welding, or ultrasonic welding can be used. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for closing.

The negative electrode plate 6 was prepared by mixing 20% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder with respect to 75% by weight of artificial graphite powder, and dehydrated them.
-Dispersed in methylpyrrolidinone to make a slurry,
It was applied on a negative electrode current collector made of copper foil, dried, and then rolled.

On the other hand, the positive electrode plate 5 was prepared by mixing 10% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder with respect to 85% by weight of lithium cobalt oxide powder, and dehydrated N-methyl. A slurry is prepared by dispersing in pyrrolidinone and applied on a positive electrode current collector made of aluminum foil,
After drying, it was produced by rolling.

The electrode group produced as described above was loaded into a battery case, and non-aqueous electrolysis based on combinations of various mixed solvents, electrolyte salts and surfactants as shown in Table 1 was performed. The solution was injected to produce a battery. The manufactured battery was a laminate pack type having a design capacity of 750 mAh.

These batteries were charged at a constant current of 100 mA until they reached 4.1 V, and then charged at a constant current of 100 mA.
The charge / discharge cycle of discharging the battery to 2.0 V at mA was repeated. The charge / discharge was repeated up to 200 cycles, and the initial discharge capacity and the discharge capacity at the 200th cycle are shown in (Table 2). Further, (Table 2) shows that the same configuration was used at a constant current of 100 mA until the voltage reached 4.1 V, the battery was once discharged until the voltage reached 2.0 V, the initial battery capacity was checked, and then the same voltage was applied again. When the battery charged to 4.1 V under the conditions was stored at 60 ° C. for 20 days, the discharge capacity after storage and the thickness of the battery after storage were measured, and the results were shown as swollen amount.

[0045]

[Table 1]

[0046]

[Table 2]

According to the present invention, as shown in (Table 2), it is clear that a highly reliable lithium secondary battery that generates very little gas, has excellent cycle life, and has excellent high-temperature storage characteristics can be obtained. Was.

Although the positive electrode material used in this embodiment has been described with reference to lithium cobaltate, other transition metal oxides such as lithium nickelate and lithium manganate, and transition metal sulfides such as titanium disulfide and molybdenum disulfide. It is apparent that the same effect can be obtained even when a material is used, and the present invention is not limited to this embodiment. Also,
Although the present embodiment has been described using artificial graphite as the negative electrode material, lithium metal, a lithium alloy and a compound negative electrode,
It is clear that similar effects can be obtained without changing the essence of the present invention even when using a carbon material other than artificial graphite capable of inserting and extracting lithium, and the present invention is not limited to this example.

Further, the method of manufacturing the electrode does not change the essence of the present invention and is not limited to the present embodiment.

Further, the combination of the electrolytes, the mixing ratio, and the amount of the supporting electrolyte used in the present embodiment are not uniquely determined, but can be set to any combination, mixing ratio, and addition amount. In that case, a similar effect was obtained. Therefore, the electrolytic solution is not limited to the combinations, mixing ratios, and addition amounts described in this example. However, the type of the supporting electrolyte needs to be selected depending on the positive electrode material to be used in view of the oxidation resistance voltage.

[0051]

As described above, according to the present invention, the transesterification reaction is extremely unlikely to occur, that is, almost no alkoxide group which is a strong nucleophilic reagent is generated, and the chemical stability of the non-aqueous electrolyte is enhanced. As a result, based on the finding that gas generation during charging and high-temperature storage and the effect of suppressing characteristic degradation due to metal elution of the active material, particularly the positive electrode material, it can be used in a wide temperature range, and has a high energy density and high battery density. There is little decrease in discharge capacity due to repeated use,
A new non-aqueous electrolyte secondary battery having excellent high-rate charge / discharge characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a cylindrical battery according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive electrode plate 5a Positive electrode lead 6 Negative electrode plate 6a Negative electrode lead 7 Separator 8 Insulating ring

Continued on the front page F term (reference) 5H029 AJ02 AJ05 AJ12 AK02 AK03 AK05 AK16 AK18 AL06 AL07 AM02 AM03 AM04 AM05 AM07 BJ02 BJ14 DJ08 DJ09 EJ11 HJ02 HJ14

Claims (5)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte, a separator and a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the non-aqueous electrolyte is ethylene carbonate, vinylene carbonate, propylene carbonate, carbonate Butylene, γ-butyrolactone, at least one selected from the group of γ-valerolactone, and either dibutyl carbonate or dipropyl carbonate, sulfolane, 3-methylsulfolane, 1,4-butanesultone,
A non-aqueous electrolyte secondary battery in which a supporting electrolyte having lithium as a cation is dissolved in a mixed solvent with at least one selected from the group consisting of ethylene glycol mono-n-butyl ether acetate and 1,2-diacetoxyethane. 2. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte, a separator and a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the non-aqueous electrolyte is ethylene carbonate, vinylene carbonate, propylene carbonate, carbonate Butylene, γ-butyrolactone and γ
-At least one selected from the group of valerolactone;
Mixed solvent of at least one selected from sulfolane, 3-methylsulfolane, 1,4-butanesultone, ethylene glycol mono-n-butyl ether acetate, and 1,2-diacetoxyethane, and either dibutyl carbonate or dipropyl carbonate A non-aqueous electrolyte secondary battery obtained by dissolving a supporting electrolyte having lithium as a cation and further adding a surfactant. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the surfactant is a fluorine-based surfactant. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least one of the plurality of compounds that is a solvent of the non-aqueous electrolyte has a melting point of −20 ° C. or less. 5. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte, a separator, and a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein a supporting electrolyte having lithium as a cation dissolved in a solvent of the non-aqueous electrolyte. Represents lithium hexafluorophosphate (LiPF ₆ ) or lithium tetrafluoroborate (LiBF ₄ ) and lithium bistrifluoromethanesulfonimide (CF ₃ SO ₂ ) ₂ NLi having a structural formula represented by the following chemical formula (1). Or a non-aqueous electrolyte secondary battery in which lithium bispentafluoroethanesulfonimide (C ₂ F ₅ SO ₂ ) 2NLi having a structural formula represented by (Chemical Formula ₂ ) is used in combination. Embedded image Embedded image