JP2001043867A - Electrolyte for battery, battery using same electrolyte, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for battery improved in ionic conductivity and in low-temperature working properties, and high in electrochemical stability, and provide a battery using the same electrolyte. SOLUTION: This electrolyte for battery is made up of one or more kinds of solvents containing cyclopentanon, one or more kinds of salts dissolved in the solvents, and one or more kinds of additive agents associated with the solvents. The battery is made up of first and second electrodes at least one of which includes an active material applied to a metallic current collector, an electrolyte containing salts dissolved in one or more kinds of solvents containing cyclopentanon, and one or more kinds of additive agents associated with the solvents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolyte for a cyclopentanone-containing battery, and more particularly to an electrolyte for a cyclopentanone-containing battery capable of improving Coulomb efficiency and widening the operating temperature range of the battery. The present invention further relates to a battery using the above electrolyte and a method for producing the same.

[0002]

2. Description of the Related Art Lithium ion secondary batteries which can be used in various fields are known. In general, lithium ion batteries are particularly preferably used compared to other rechargeable batteries such as nickel cadmium and nickel metal hydride batteries because of their excellent light weight, energy density and overall efficiency.

Further, lithium-based electrochemical cells using a low-volatile high-boiling electrolyte solvent such as propylene carbonate (PC) have been developed. Generally, dimethyl carbonate (DMC) or methyltetrahydrofuran (Me
By adding an auxiliary solvent such as -THF), the ionic conductivity and low-temperature operability of the electrolyte solution are improved.
However, the above-mentioned co-solvent improves the ionic conductivity and low-temperature operability of the electrolyte, but has the disadvantage of low electrochemical stability due to the original reactivity. Further, these auxiliary solvents tend to have substantially higher flammability than the main solvent. On the other hand, other electrolyte solvent formulations such as propylene carbonate / ethylene carbonate (PC / EC) mixtures have also been developed. But EC
These formulations have a relatively high melting point of 37-39 ° C. and thus have the disadvantage of poor low temperature operability.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolyte for a battery which has improved ionic conductivity and low temperature operability, and has high electrochemical stability.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by using cyclopentanone as an electrolyte solvent and using an electrolyte containing an additive. And completed the present invention.

The present invention has been completed based on the above findings, and a first gist of the present invention is to provide at least one solvent containing cyclopentanone and at least one salt dissolved in the solvent. , A battery electrolyte comprising the solvent and one or more additives associated therewith.

[0007] A second aspect of the present invention resides in the electrolyte according to the first aspect, wherein the solvent includes a mixture of cyclopentanone and propylene carbonate.

A third gist of the present invention is that a mixing ratio (volume) of cyclopentanone: propylene carbonate is 1: 1:
The electrolyte according to the first or second aspect, wherein the electrolyte is 99 to 99:10.

[0009] A fourth gist of the present invention is that the additive is selected from the group consisting of cis-1,2,3,6-tetrahydrophthalic anhydride (T
HPA), 1-cyclopentene-1,2-dicarboxylic anhydride, succinic anhydride (SA), and mixtures thereof.

A fifth aspect of the present invention resides in the electrolyte according to any one of the first to fourth aspects, wherein the concentration of the additive is 0.5 to 5% by weight based on the electrolyte.

According to a sixth aspect of the present invention, at least one of the first and second electrodes includes an active material coated on a metal current collector, and the electrolyte according to any one of the first to fifth aspects. Battery.

A seventh aspect of the present invention resides in the battery according to the sixth or seventh aspect, wherein the active material is selected from the group consisting of graphite, carbon black, and a mixture thereof.

According to an eighth aspect of the present invention, in a battery electrolyte prepared by dissolving a lithium salt in a solvent, the solvent contains at least one cyclic ketone solvent selected from cyclopentanones and cyclohexanones, and The electrolyte for a battery according to the present invention is characterized in that the electrolyte contains an additive having a lower reduction potential than the cyclic ketone solvent.

A ninth aspect of the present invention resides in the electrolyte for a battery according to the eighth aspect, wherein the content of the additive is 10% by weight or less based on the electrolyte.

According to a tenth aspect of the present invention, in a battery electrolyte obtained by dissolving a lithium salt in a solvent, the solvent contains at least one cyclic ketone solvent selected from cyclopentanones and cyclohexanones, and The electrolyte comprises at least one additive selected from acid anhydrides, carbonates, esters, ethers, ketones (excluding cyclopentanones and cyclohexanones), sulfur-containing compounds, and nitrogen-containing compounds. 1 for
0% by weight or less of the electrolyte for a battery.

An eleventh aspect of the present invention resides in the electrolyte for a battery according to the tenth aspect, wherein the additive contains an additive having a lower reduction potential than the cyclic ketone solvent.

A twelfth aspect of the present invention resides in the electrolyte for a battery according to any one of the eighth to eleventh aspects, wherein the additive contains an acid anhydride.

The thirteenth aspect of the present invention is that the content of the cyclic ketone solvent is from 8 to 12 in which the content of the cyclic ketone solvent is 30% by weight or more of the whole solvent.
The present invention resides in the electrolyte for a battery according to any one of the above items.

A fourteenth aspect of the present invention resides in the battery electrolyte according to any one of the eighth to thirteenth aspects, wherein the solvent further contains propylene carbonate.

A fifteenth aspect of the present invention resides in a battery having a first electrode, a second electrode, and the electrolyte according to any one of the eighth to fourteenth aspects.

According to a sixteenth aspect of the present invention, at least one of the first and second electrodes is a negative electrode containing a carbon material.
The battery according to the fifth aspect is provided.

[0022]

Since a solvent such as cyclopentanone has a relatively low melting point and a high boiling point, the operating temperature range of the battery can be extended. On the other hand, these cyclic ketone-based solvents tend to have high reactivity and relatively low reduction potential, so that an electrolyte using them is decomposed and deteriorated when used as a battery, and is particularly easily reduced. Disassembled with
Easily degraded. In the present invention, it is considered that the decomposition and deterioration of the solvent are suppressed by the action of the additive. Although the mechanism is not clear, the electrode active material, particularly the SEI layer formed on the carbon surface, has excellent characteristics due to the combined use of the additives, and as a result, it is related that excellent battery performance is provided. Seems to be.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Since the present invention is capable of various embodiments, the present invention is not limited to the following embodiments and descriptions.

FIG. 1 shows a schematic view of the battery of the present invention. The battery 10 of the present invention includes a first electrode 12, a second electrode 14, and an electrolyte 16. The first electrode 12 includes an aluminum current collector 18 and an electrode active material layer 20. The electrode active material layer 20 is made of LiNi held by a conventional binder.
Contains metal components such as O ₂ , LiCoO ₂ and / or LiMn ₂ O ₄ .

The second electrode 14 comprises a copper current collector 22 and an electrode active material layer 24. The electrode active material layer 24 is made of a carbonaceous material such as graphite or carbon black.

The electrolyte 16 is composed of LiP dissolved in a solvent 26.
Conventional salts such as F ₆ , LiAsF ₆ and / or LiBF ₄ are included. The solvent 26 constituting the electrolyte 16 of the present invention contains cyclopentanone (CP) represented by the following chemical structural formula.

[0027]

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[0028] Solvent 26 can optionally include an auxiliary solvent such as propylene carbonate. Cyclopentanone can easily dissolve conventional electrolyte salts such as LiPF ₆ , LiAsF ₆ and / or LiBF ₄ . As will be described in detail below, by using cyclopentanone as an electrolyte solvent, a battery having a substantially wide operating temperature range can be manufactured. Since the melting point of cyclopentanone is relatively low at −51 ° C., the lower limit operating temperature of the battery is widened. In addition, cyclopentanone is 130 to 13
Since it has a relatively high boiling point of 1 ° C., the upper limit operating temperature of the battery becomes extremely high.

As will be described below, the use of cyclopentanone as the electrolyte solvent substantially prevents the solvent from deteriorating and / or decomposing during the battery cycling process and storage by using additive 28. There is a need.
As the additive 28, acid anhydrides, carbonates, esters and the like can be used as long as they are compatible with cyclopentanone itself and can passivate the electrode / electrolyte interface to substantially prevent deterioration of battery components. Any additives such as ethers, cyclic or chain ketones, sulfur-containing compounds, and nitrogen-containing compounds may be used. Preferably, those having a lower reduction potential than cyclopentanones and cyclohexanones used as solvents are used. As a result, the effect of the present invention becomes more remarkable.

Specific examples of the acid anhydride include succinic anhydride (SA), cis-1,2,3,6-tetrahydrophthalic anhydride (THPA) and 1-cyclopentene-1,2.
-Dicarboxylic anhydride CAS # 3205-94-5 (C
Many compounds such as PDA) can be exemplified.

Examples of the carbonates include vinylene carbonate, trifluoropropylene carbonate, and catechol carbonate. Examples of the esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate. Examples of the ethers include 12-crown-4-ether. Examples of the sulfur-containing compound include sultones such as 1,3-propane sultone and 1,4-butane sultone, and thiocarbonates. Examples of the nitrogen-containing compound include imides such as succinimide, and pyridine and pyrrole. Among them, acid anhydrides and esters, particularly acid anhydrides are preferable. The molecular weight of these additives is usually 10
00 or less, preferably 500 or less, more preferably 3 or less.
00 or less. If the molecular weight is too large, the influence of the inhibiting factor on charge / discharge increases, and ion conduction may be inhibited, resulting in an adverse effect.

Other suitable additives include, for example, 1,6-dioxaspiro [4,4] nonane-2,7-dione and 1,4-diamine described in US Pat. No. 5,853,917.
Spiro ketones such as dioxaspiro [4,5] decan-2-one, and those shown below as described in US Pat. No. 6,045,937, both of which are incorporated herein by reference in their entirety. And various additives.

[0033]

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The above description is merely illustrative, and the present invention
Various modifications and changes can be made without departing from the gist of the invention. Hereinafter, as an example of the above change, a configuration of a lithium ion battery preferably used as a battery will be described.

A lithium ion battery usually includes first and second electrodes corresponding to a positive electrode and a negative electrode, and an electrolyte layer interposed therebetween. The first electrode and the second electrode are generally formed by binding an active material on a current collector substrate.

Current collector substrate: The material of the current collector substrate is as follows.
In addition to the above-described copper and aluminum, various metals such as nickel and stainless steel and alloys thereof can be exemplified. Preferably, aluminum is used as the current collector substrate of the positive electrode, and copper is used as the current collector substrate of the negative electrode.

The thickness of the current collector is appropriately selected, but is preferably 1 to 30 μm, and more preferably 1 to 20 μm. If it is too thin, the mechanical strength tends to be weak, which is a problem in production. If it is too thick, the capacity of the battery as a whole decreases.

It is preferable that the surface of the current collector is previously subjected to a surface roughening treatment, since the adhesive strength of the electrode material is increased. Examples of the surface roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. Examples of the mechanical polishing method include a method of polishing the surface of the current collector with a polishing cloth paper having abrasive particles fixed thereon, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like. Further, an intermediate layer may be formed on the surface of the current collector to increase the adhesive strength and the conductivity.

The shape of the current collector may be a plate shape other than the metal mesh.

Active material: The active material used for the first electrode or the second electrode may be appropriately selected according to the type and characteristics of the battery to be manufactured. In the present invention, as described above, it is preferable to use a carbonaceous material such as carbon black or graphite as the active material of the first or second electrode, because the effects of the present invention are remarkable.

In the case of a lithium secondary battery, an inorganic compound or an organic compound can be used as a positive electrode active material as long as lithium ions can be inserted and extracted. Examples of the inorganic compound include a transition metal oxide, a composite oxide of lithium and a transition metal, and a chalcogen compound such as a transition metal sulfide. Here, Fe, Co, Ni, Mn, or the like is used as the transition metal. Specifically, MnO, V ₂ O ₅ , V
Transition metal oxides such as ₆ O ₁₃ and TiO ₂ ; composite oxides of lithium and transition metals such as lithium nickelate, lithium cobaltate and lithium manganate; TiS ₂ , FeS;
Transition metal sulfides such as MoS ₂ are exemplified. These compounds may be partially substituted with elements in order to improve their properties. Examples of the organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, and polysulfide-based compounds. These inorganic compounds and organic compounds may be mixed and used as a positive electrode material. Preferably, it is a composite oxide of lithium and at least one transition metal selected from the group consisting of cobalt, nickel and manganese.

The particle size of the positive electrode active material may be appropriately selected depending on the balance with other components of the battery.
The thickness is preferably from 30 to 30 μm, particularly from 1 to 10 μm, since battery characteristics such as initial efficiency and cycle characteristics are improved.

As the negative electrode active material capable of inserting and extracting lithium ions that can be used for the negative electrode, the above-mentioned carbonaceous particles are usually mentioned. Such a carbon-based material can also be used in the form of a mixture or coating with a metal, metal salt, oxide, or the like. Further, as the negative electrode active material, silicon,
Oxides and sulfates of tin, zinc, manganese, iron, nickel, etc., metallic lithium, Li-Al, Li-Bi-Cd, L
A lithium alloy such as i-Sn-Cd, a lithium transition metal nitride, silicon and the like can also be used. The average particle size of the negative electrode active material is generally 12 μm or less, preferably 1 μm or less, from the viewpoint of improving battery characteristics such as initial efficiency, late characteristics, and cycle characteristics.
0 μm or less. If the particle size is too large, the electron conductivity deteriorates. Further, it is usually at least 0.5 μm, preferably at least 7 μm.

Other structure of electrode: It is preferable to use a binder in order to bind the active material on the current collector. As the binder, inorganic compounds such as silicate and glass, and various resins mainly composed of polymers can be used.

Examples of the resin include alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N -Polymers having a ring such as vinylpyrrolidone; acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid and polyacrylamide Fluorinated resins such as polyvinyl fluoride, polyvinylidene fluoride and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl acetate, polyvinyl alcohol, etc. Polyvinyl chloride, halogen-containing polymers such as polyvinylidene chloride; a conductive polymer such as polyaniline can be used polyvinyl alcohol-based polymer. Further, a mixture of the above-mentioned polymers and the like, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer and the like can also be used.

The amount of the binder is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of the active material. If the amount of the resin is too small, the strength of the electrode may decrease. If the amount of the resin is too large, the capacity may decrease, or the late characteristics may decrease.

The electrode may contain additives, such as conductive materials and reinforcing materials, which exhibit various functions, powders, fillers, and the like, if necessary. The conductive material is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with the active material, but usually, acetylene black, carbon black, carbon powder such as graphite, and various metal fibers,
Foil and the like. As additives, trifluoropropylene carbonate, vinylene carbonate, 1,6-
Dioxaspiro [4,4] nonane-2,7
-Dione, 12-crown-4-ether and the like can be used to increase the stability and life of the battery. As the reinforcing material, various inorganic or organic spherical or fibrous fillers can be used.

As a method of forming an electrode on a current collector,
For example, a method in which a powdery active material is mixed with a solvent together with a binder, and if necessary, a ball mill, a sand mill, a twin-screw kneader or the like is used to form a dispersion paint, and then applied on a current collector and dried. Done. In this case, the type of the solvent used is not particularly limited as long as it is inert to the electrode material and can dissolve the binder. For example, any of commonly used inorganic and organic solvents such as N-methylpyrrolidone can be used. Can also be used.

Further, the electrode material layer may be formed by a method of pressing or spraying the active material on a current collector in a state of being softened by mixing and heating the active material with a binder. Furthermore, it can be formed by firing the active material alone on the current collector.

The thickness of the active material layer is usually at least 1 μm, preferably at least 10 μm. In addition, usually 200
μm or less, preferably 150 μm or less. If it is too thin, it becomes difficult to ensure uniformity of the active material layer, and the capacity tends to decrease. On the other hand, if the thickness is too large, the rate characteristics tend to decrease.

A primer layer can be provided between the current collecting substrate and the active material layer. As a result, the adhesiveness between the current collecting substrate and the active material layer can be further improved. The primer layer is a paint containing a conductive material, a binder and a solvent,
It can be formed by drying after coating on the current collecting substrate.

As the conductive material used for the primer layer, various materials such as carbonaceous particles such as carbon black and graphite, metal powder, and conductive polymers can be used. The same binder and solvent as those used for the active material layer can be used for the primer layer. The thickness of the primer layer is usually 0.05 μm or more, preferably 0.1 μm or more, and usually 20 μm or less, preferably 10 μm or less. If it is too thin, it tends to be difficult to ensure uniformity of the primer layer. If the thickness is too large, the capacity rate characteristics of the battery tend to decrease.

Electrolyte: The electrolyte interacts with the first and second electrodes and participates in ion transfer between the electrodes. The electrolyte usually exists as an electrolyte layer between the electrodes and also exists in the active material layer, and comes into contact with at least a part of the surface of the active material. The electrolyte can be related to the electrode or the electrode active material by being brought into contact with the first electrode or the second electrode by a method such as coating.

The electrolyte generally includes various electrolytes such as an electrolyte having fluidity and a non-fluid electrolyte such as a gel electrolyte and a completely solid electrolyte. An electrolyte or a gel electrolyte is preferable in terms of battery characteristics, and a non-fluid electrolyte is preferable in terms of safety. In particular, when a non-fluid electrolyte is used, liquid leakage can be more effectively prevented for a battery using a conventional electrolyte.

The electrolytic solution used as the electrolyte is usually obtained by dissolving a supporting electrolyte in a non-aqueous solvent.

As the supporting electrolyte, any non-aqueous substance which is stable to the positive electrode and the negative electrode as an electrolyte, and which can transfer lithium ions to perform an electrochemical reaction with the positive electrode active material or the negative electrode active material can be used. Can also be used. Specifically, LiPF ₆ , Li
AsF ₆ , LiSbF ₆ , LiBF ₄ , LiClO ₄ , Li
I, LiBr, LiCl, LiAlCl, LiHF ₂ ,
Lithium salts such as LiSCN and LiSO ₃ CF ₂ are exemplified. Among them, LiPF ₆ and LiClO ₄ are particularly preferable.

When these supporting electrolytes are used in the state of being dissolved in a non-aqueous solvent, the concentration is usually 0.5 to 3 mol / mol.
L, preferably 0.5 to 2.5 mol / L.

One of the features of the present invention resides in the use of cyclopentanones and cyclohexanone (hereinafter sometimes collectively referred to as "cyclic ketone solvent") as a solvent. Examples of cyclopentanones and cyclohexanones include those represented by the following general formula (1).

[0059]

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Here, R ¹ and R ² are each independently:
A hydrocarbon group having 1 to 4 carbon atoms, preferably a hydrocarbon group having 1 to 2 carbon atoms. m is a natural number of 0 to 4, preferably 0
Represents a natural number of ~ 3. n represents a natural number of 0 to 5, preferably 0 to 3. When a plurality of R ¹ or R ² are present, they may be the same or different.

These cyclopentanones and cyclohexanones have a relatively low melting point and a high boiling point, and enable battery operation in a wide temperature range. Specific examples of the cyclic ketone solvent include cyclopentanone, cyclohexanone, methylcyclopentanone, methylcyclohexanone, dimethylcyclopentanone, dimethylcyclohexanone, trimethylcyclopentanone, trimethylcyclohexanone, ethylcyclopentanone, ethylcyclohexanone, and diethylcyclohexanone. Examples include pentanone, diethylcyclohexanone, triethylcyclopentanone, and triethylcyclohexanone. The most preferred solvent is cyclopentanone. A plurality of these cyclic ketone solvents can be used in combination.

The solvent for the electrolyte may be the above-mentioned cyclic ketone solvent alone, or may be used in combination with another solvent. However, if the content of the cyclic ketone solvent is too small, the effect of the present invention will not be remarkable. As another solvent that can be used in combination, a solvent having a relatively high dielectric constant is suitably used. Specifically, ethylene carbonate, cyclic carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate, acyclic carbonates such as ethyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, glymes such as dimethoxyethane, γ-butyrolactone and the like Lactones,
Examples thereof include sulfur compounds such as sulfolane and nitriles such as acetonitrile. Also, one or a mixture of two or more of these can be used. Among these, one or more solvents selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and acyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly suitable. In addition, those in which a part of hydrogen atoms in these molecules are substituted with halogen or the like can also be used. Other preferred solvents include cyclic carbonates, especially propylene carbonate. When propylene carbonate is used, the volume mixing ratio of cyclic ketone solvent: propylene carbonate is usually 1:99 to 90: 1.
It is about 0, preferably about 10:90 to 80:20.

The gel electrolyte that can be used as the electrolyte is
Usually, the above electrolyte is held by a polymer. In other words, the gel electrolyte is one in which the electrolyte is usually held in a polymer network and the fluidity as a whole is significantly reduced. Such a gel electrolyte exhibits properties such as ionic conductivity that are close to those of a normal electrolyte solution, but fluidity, volatility and the like are significantly suppressed, and safety is enhanced. The ratio of the polymer in the gel electrolyte is preferably 1 to
50% by weight. If the temperature is too low, the electrolyte cannot be held, and a liquid leak may occur. If it is too high, the ionic conductivity tends to decrease and battery characteristics tend to deteriorate.

As the polymer used for the gel electrolyte,
There is no particular limitation as long as it is a polymer that can form a gel together with the electrolytic solution, and polyester, polyamide, polycarbonate, those produced by polycondensation such as polyimide,
Polyurethane, polyurea, etc. produced by polyaddition, acrylic derivative polymers such as polymethyl methacrylate, and polyadditions produced by polyvinyl polymerization such as polyvinyl acetate, polyvinyl chloride, polyvinylidene fluoride, etc. and so on. Preferred polymers include polyacrylonitrile and polyvinylidene fluoride. Here, the polyvinylidene fluoride includes not only a homopolymer of vinylidene fluoride but also a copolymer with another monomer component such as hexafluoropropylene. Also, acrylic acid, methyl acrylate,
Ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate,
Ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, N-vinylpyrrolidone, diethylene glycol di Acrylic derivative obtained by polymerizing monomers such as acrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate. system Rimmer can also be preferably used.

The weight average molecular weight of the above polymer is usually 10
000 to 5,000,000. If the molecular weight is low, it is difficult to form a gel. If the molecular weight is high, the viscosity becomes too high and handling becomes difficult. The concentration of the polymer in the electrolytic solution may be appropriately selected according to the molecular weight, but is preferably from 0.1% by weight to 30% by weight. If the concentration is too low, it is difficult to form a gel, the retention of the electrolytic solution is reduced, and problems of flow and liquid leakage may occur. If the concentration is too high, the viscosity becomes too high, which causes difficulties in the process, and the proportion of the electrolytic solution is reduced, the ionic conductivity is reduced, and the battery characteristics such as rate characteristics may be reduced.

A completely solid electrolyte can be used as the electrolyte. As such a solid electrolyte, various solid electrolytes known so far can be used. For example, it can be formed by mixing the polymer used in the gel electrolyte and the supporting electrolyte salt at an appropriate ratio. In this case, in order to increase the conductivity, it is preferable to use a polymer having a high polarity and to have a skeleton having many side chains.

The surfactant comprises a first material containing a carbonaceous material.
Alternatively, it can be present in the second electrode, but is usually present in the electrolyte.

Solid electrolyte interface (SEI) layer: If necessary, a solid electrolyte interface layer can be formed on the carbonaceous surface that can be used as an active material. The solid electrolyte interface layer is formed on at least a part of the surface of the active material particles, and contributes to improving the characteristics of the battery. The SEI layer is usually formed by the action of a supporting electrolyte or a non-aqueous solvent, which is a component of the electrolyte at the time of initial charging, and the above-described additive present in the electrolyte. In the present invention, it is considered that an SEI layer having excellent characteristics can be formed by a chemical reaction including the cyclic ketone solvent and the additive.

If the amount of the additive used is too large or too small, the battery characteristics may be deteriorated. Is 2% by weight or less, and usually 0.01% by weight or more, preferably 0.1% by weight.
It is more preferably 0.5% by weight or more.

[0070]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Each experimental example was performed in the following procedure.

Examples 1 to 8: First, a 1 mol LiAsF containing a graphite base material coated on a copper current collector, a lithium metal cathode, a lithium metal reference electrode, additives and an electrolyte solvent shown in Table 1 below. _A battery comprising ₆ electrolyte solutions was manufactured.

[0072]

[Table 1]

After the battery was manufactured, the battery was subjected to a cycle step of gradually reducing the voltage from 3.0 volts to 0.0 volts, and the Coulomb efficiency was determined. The results of the voltammetry are shown in Table 2 below.

[0074]

[Table 2]

As is evident from Examples 1 to 6, cells using the additive and cyclopentanone or a mixture of cyclopentanone / propylene carbonate exhibited high first cycle coulombic efficiency. Furthermore, as is clear from Comparative Examples 1 and 2, batteries without the use of any additives were inoperable. Although not quantitatively confirmed, the batteries prepared according to the invention described above could operate over a very wide temperature range due to the large differences in the melting and boiling points of cyclopentanone.

[0076]

Industrial Applicability The battery electrolyte of the present invention is an electrolyte for a battery that improves the ionic conductivity and low-temperature operability of the electrolyte and has high electrochemical stability, and the industrial value of the present invention is high.

[Brief description of the drawings]

FIG. 1 is a schematic view of a battery of the present invention.

[Description of Signs] 10: Battery of the present invention 12: First electrode 14: Second electrode 16: Electrolyte 18: Aluminum current collector 20: Electrode active material layer 22: Copper current collector 24: Electrode active material layer 26: Solvent 28: Additive

Claims (16)

[Claims] 1. A battery electrolyte comprising one or more solvents containing cyclopentanone, one or more salts dissolved in the solvents, and one or more additives associated with the solvents. 2. The electrolyte of claim 1, wherein said solvent comprises a mixture of cyclopentanone and propylene carbonate. 3. The electrolyte according to claim 1, wherein the mixing ratio (volume) of cyclopentanone: propylene carbonate is 1:99 to 99:10. 4. The method according to claim 1, wherein the additive is cis-1,2,3,6-
The method according to any one of claims 1 to 3, which is selected from the group consisting of tetrahydrophthalic anhydride (THPA), 1-cyclopentene-1,2-dicarboxylic anhydride, succinic anhydride (SA), and a mixture thereof. Electrolytes. 5. The method according to claim 1, wherein said additive has a concentration of 0.5 to the electrolyte.
The electrolyte according to any one of claims 1 to 4, wherein the content is 5 to 5% by weight. 6. A first electrode and a second electrode at least one of which includes an active material applied to a metal current collector, and
5. A battery comprising the electrolyte according to any one of 5. 7. The battery according to claim 6, wherein the active material is selected from the group consisting of graphite, carbon black, and a mixture thereof. 8. A battery electrolyte obtained by dissolving a lithium salt in a solvent, wherein the solvent contains at least one cyclic ketone solvent selected from cyclopentanones and cyclohexanones, and the electrolyte is the cyclic ketone solvent. An electrolyte for batteries, comprising an additive having a lower reduction potential than that of a battery. 9. The content of the additive is 10 to the electrolyte.
9. The electrolyte for a battery according to claim 8, wherein the content is not more than weight%. 10. A battery electrolyte obtained by dissolving a lithium salt in a solvent, wherein the solvent contains at least one cyclic ketone solvent selected from cyclopentanones and cyclohexanones, and the electrolyte is an acid anhydride. And at least one additive selected from carbonates, esters, ethers, ketones (excluding cyclopentanones and cyclohexanones), sulfur-containing compounds, and nitrogen-containing compounds in an amount of 10% by weight or less based on the electrolyte. An electrolyte for a battery, comprising: 11. The method according to claim 1, wherein the additive contains an additive having a lower reduction potential than the cyclic ketone solvent.
The electrolyte for a battery according to 0. 12. The method according to claim 8, wherein the additive contains an acid anhydride.
12. The electrolyte for a battery according to any one of items 11 to 11. 13. The battery electrolyte according to claim 8, wherein the content of the cyclic ketone solvent is 30% by weight or more of the whole solvent. 14. The battery electrolyte according to claim 8, wherein the solvent further contains propylene carbonate. 15. A first electrode and a second electrode;
15. A battery comprising the electrolyte according to any one of 14. 16. The battery according to claim 15, wherein at least one of the first and second electrodes is a negative electrode containing a carbon material.