JP6102492B2 - Non-aqueous electrolyte and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte and a lithium ion secondary battery.

  Lithium ion secondary batteries are smaller and lighter than conventional lead storage batteries and nickel metal hydride batteries, have a high single cell voltage, high energy density, low memory effect, and low self-discharge. Because of its features, it is mounted on small portable devices such as mobile phones and laptop computers, and is beginning to be used in some hybrid cars and electric vehicles.

  However, in the case of a battery, there is a problem that the electric capacity gradually decreases as charging and discharging are repeated. In particular, when these lithium ion secondary batteries are used mainly in these devices, charging and discharging tend to be repeated frequently, so that the electric capacity tends to decrease. When the discharge capacity decreases, the operation time of the device in one charge decreases, or in the case of an electric vehicle, the travel distance decreases, and the usability of the device decreases correspondingly.

  Factors that decrease the discharge capacity vary depending on the battery configuration and usage conditions. Examples include deactivation of the positive electrode and the negative electrode active material, peeling from the current collector, increase in resistance due to the formation of a film on the active material surface, deformation of the battery due to gas generation, and depletion of the electrolyte. In the case of the negative electrode, a film called SEI (surface electronic interface) is formed on the negative electrode active material, and this film is excessively generated and the resistance is increased, which tends to become a member of the capacity reduction.

  In order to improve the cycle life due to the formation of the negative electrode film, various methods have been proposed, such as Patent Documents 1 and 2. However, these methods are insufficient to meet recent battery requirements. In particular, it is still insufficient for a negative electrode containing silicon or tin, which has attracted attention in recent years due to its high capacity.

Japanese Patent No. 4288976 Japanese Patent No. 4386666

  This invention is made | formed in view of the said subject, and it aims at providing the non-aqueous electrolyte and lithium ion secondary battery which have favorable cycling characteristics.

In order to achieve the above object, a nonaqueous electrolytic solution according to the present invention includes a nonaqueous solvent, an electrolyte, a halogenated cyclic ester carbonate, and a thiol represented by the following chemical formula 1 [wherein R1, R2, R3 is hydrogen, or an alkyl group (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ ), an alkoxycarbonyl group (—COOR 4, where R 4 is —C _n H _{2n + 1} , n = 1 to 4), an alkyl group having a carboxy group (—C _n H _2n COOH, n = 1 to 4), an alkyl group having a carboxylate group (—C _n H _2n COO ⁻ , n = 1 to 4), an amino group (—NH ₂ , —NHR 5, —NR 5 R 6, R 5, R 6 is an alkyl group (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ ). A sulfanyl group. The thiol is composed of a compound having at least one of a carboxy group, the carboxylate group, and the amino group.

By using the nonaqueous electrolytic solution according to the present invention, the cycle life of the lithium ion secondary battery is improved. This is presumed to be because the thiol forms a good SEI film on the positive electrode and negative electrode surfaces, particularly on the negative electrode active material, so that capacity deterioration of the positive electrode and the negative electrode due to charging and discharging is suppressed.

The reason why a good SEI film is formed in the present invention is unknown, but is presumed as follows. The SEI film is formed by decomposing the electrolyte component, but the contents are not composed of a single compound, and various compounds exist. The reactivity of these compounds varies. On the other hand, the nonaqueous electrolytic solution according to the present invention contains a sulfanyl group, the thiol having either a carboxy group, a carboxylate group, or an amino group, and a halogenated cyclic carbonate. By reacting the thiol with the halogenated cyclic carbonate, compounds having various functional groups are synthesized on the halogenated carbonate. When this further reacts on the surface of the active material, compounds having both various functional groups and halogens of the thiol are introduced into the SEI film. Thereby, it is considered that a better SEI film can be formed on the active material, particularly the negative electrode active material.

  The thiol contained in the non-aqueous electrolyte according to the present invention is a thiol having one or more carboxy groups or carboxylate groups and one or more amino groups, and three different functional groups. Therefore, the SEI film can be formed more easily and the cycle characteristics are further improved.

  It is preferable that the thiol contained in the non-aqueous electrolyte according to the present invention is penicillamine and derivatives thereof because cycle characteristics are further improved.

  It is preferable that the halogenated cyclic carbonate contained in the non-aqueous electrolyte according to the present invention is fluoroethylene carbonate because cycle characteristics are further improved.

  It is preferable that the content of the thiol contained in the non-aqueous electrolyte according to the present invention in the electrolyte is 0.01 to 3% by mass because cycle characteristics are further improved.

  The content of the halogenated cyclic carbonate contained in the nonaqueous electrolytic solution according to the present invention in the electrolytic solution is preferably 0.1 to 5% by mass because cycle characteristics are further improved.

  The lithium ion secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte, and the negative electrode contains silicon to improve energy density and cycle characteristics of the battery. preferable.

According to the present invention, it is possible to provide a non-aqueous electrolyte and a lithium ion secondary battery having good cycle characteristics.

It is a schematic cross section of a lithium ion secondary battery.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In addition, the dimensional ratio of drawing is not restricted to the ratio of illustration.

First, the non-aqueous electrolyte used for the lithium ion secondary battery according to this embodiment will be described.

(Nonaqueous electrolyte)
The non-aqueous electrolyte according to the present embodiment includes a non-aqueous solvent, various electrolytes to be a supporting salt, a halogenated cyclic carbonate, and a thiol represented by Chemical Formula 1 [wherein R1, R2, and R3 are hydrogens. Or an alkyl group (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ ), an alkoxycarbonyl group (—COOR 4, where R 4 is —C _n H _{2n + 1} , n = 1 to 4), an alkyl group having a carboxy group (—C _n H _2n COOH, n = 1 to 4), an alkyl group having a carboxylate group (—C _n H _2n COO ⁻ , n = 1 to 4), An amino group (—NH ₂ , —NHR 5, —NR 5 R 6, R 5, R 6 are an alkyl group (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ )), It is a fanyl group. The thiol is composed of a compound having at least one of a carboxy group, the carboxylate group, or the amino group.

  Examples of the thiol represented by Chemical Formula 1 include penicillamine, penicillamine methyl, penicillamine ethyl, β-homopenicillamine, N-methylpenicillamine, 3-methyl-3-sulfanylbutanoic acid, 2-amino-1,1-dimethylethane. Examples include thiol.

  The thiol represented by Chemical Formula 1 is preferably added in an amount of 0.01 to 3.0% by weight based on the total amount of the non-aqueous electrolyte from the viewpoint of the cycle life improving effect. If the content of the thiol represented by Chemical Formula 1 is less than the lower limit, the cycle life improving effect may be insufficient. On the other hand, when the amount is larger than the above upper limit value, the cycle life tends to decrease. By adjusting the content of the thiol represented by Chemical Formula 1 within the above numerical value, the effect of the present invention can be obtained more reliably. If it is 0.05 weight%-1.0 weight%, it is still more preferable.

  Examples of the halogenated cyclic carbonate include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, bromoethylene carbonate, and fluorochloroethylene carbonate.

  The halogenated cyclic carbonate is preferably added in an amount of 0.1 to 5% by weight based on the total amount of the non-aqueous electrolyte from the viewpoint of the cycle life improving effect. If the content of the halogenated cyclic carbonate is less than the lower limit, the cycle life improving effect may be insufficient. On the other hand, when the amount is higher than the above upper limit value, there is a tendency that gas generation increases when stored at a high temperature. By adjusting the content of the halogenated cyclic carbonate within the above numerical value, the effect of the present invention can be obtained more reliably. 1.0 to 3.0% by weight is more preferable.

In the case of a lithium secondary battery, a lithium salt is used as the electrolyte. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN _{(CF 3 CF 2 SO 2)} 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiN (SO 2 F) 2, LiN (CF 3 CF 2 CO) 2 , and the like. In addition, these salts may be used individually by 1 type, and may use 2 or more types together. As the electrolyte, LiPF ₆ , LiBF ₄ , and LiN (SO ₂ F) ₂ are preferable from the viewpoint of cycle characteristics and storage characteristics, and LiPF ₆ is more preferable. The concentration of the electrolyte is preferably 0.8 to 1.5 M regardless of whether it is one type or two or more types.

As the non-aqueous solvent, a solvent used in a known electrochemical device can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxylene, 4-methyl-1,3 -Dixylene, methyl formate, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, sulfolane, 2-methyl sulfolane, dimethyl sulfoxide, N, N-dimethylformamide, N-methyloxazolidinone, etc. . These solvents can be used alone or in combination. Cyclic carbonates and chain carbonates are preferable from the viewpoint of cycle characteristics and storage characteristics, and ethylene carbonate and diethyl carbonate are more preferable.

Moreover, you may add a well-known additive as an additive. For example, 0.01 to 5% by weight of vinylene carbonate, 1,3-propane sultone, 1,3,2-dioxathiolane-2,2-dioxide, ethylene sulfite, or the like may be added.
[Lithium ion secondary battery]

    Next, the electrode and the lithium ion secondary battery according to this embodiment will be briefly described with reference to FIG. The lithium ion secondary battery 100 mainly includes a laminate 30, a case 50 that accommodates the laminate 30 in a sealed state, and a pair of leads 60 and 62 connected to the laminate 30.

The laminated body 30 is configured such that a pair of the positive electrode 10 and the negative electrode 20 are opposed to each other with the separator 18 interposed therebetween. The positive electrode 10 is obtained by providing a positive electrode active material layer 14 on a plate-like (film-like) positive electrode current collector 12. The negative electrode 20 is obtained by providing a negative electrode active material layer 24 on a plate-like (film-like) negative electrode current collector 22. The positive electrode active material layer 14 and the negative electrode active material layer 24 are in contact with both sides of the separator 18. Leads 60 and 62 are connected to the end portions of the positive electrode current collector 12 and the negative electrode current collector 22, respectively, and the end portions of the leads 60 and 62 extend to the outside of the case 50.

  Hereinafter, the positive electrode 10 and the negative electrode 20 are collectively referred to as electrodes 10 and 20, and the positive electrode current collector 12 and the negative electrode current collector 22 are collectively referred to as current collectors 12 and 22, and the positive electrode active material layer 14 and the negative electrode The active material layers 24 are collectively referred to as active material layers 14 and 24.

[electrode]
The electrodes 10 and 20 will be specifically described. The electrodes 10 and 20 include current collectors 12 and 22 and active material layers 14 and 24 including active materials and binders formed on the surfaces of the current collectors 12 and 22.

(Positive electrode 10)
The positive electrode current collector 12 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.

  The positive electrode active material layer 14 includes the active material according to the present embodiment, a binder, and a conductive material in an amount necessary.

The positive electrode active material may be any compound that contains lithium ions and can occlude and release lithium ions. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li (Co _x Ni _y Mn _z ) O ₂ Li-containing metal oxides such as Li (Ni _x Co _y Al _z ) O ₂ , Li ( _M n _x Al _y ) ₂ O ₄ , Li [Li _w Mn _x Ni _y Co _z ] O ₂ , LiVOPO ₄ , LiFePO ₄ Is mentioned. The binder bonds the active materials to each other and bonds the active material to the positive electrode current collector 12.

The binder bonds the active materials to each other and bonds the active material to the positive electrode current collector 12.
The material of the binder is not particularly limited as long as the above-described bonding is possible. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride ( Fluorine resin such as PVF).

  In addition to the above, as binders, for example, polyethylene, polypropylene, polyethylene terephthalate, polyamide (PA), polyimide (PI), polyamideimide (PAI), aromatic polyamide, cellulose, styrene-butadiene rubber, isoprene rubber, butadiene Rubber, ethylene / propylene rubber, polyacrylic acid and its salt, alginic acid and its salt and the like may be used. Also, thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers, and hydrogenated products thereof. May be used. Further, syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer may be used.

  Alternatively, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material. Examples of the ion conductive conductive polymer include those obtained by combining a polymer compound such as polyethylene oxide and polypropylene oxide with a lithium salt or an alkali metal salt mainly composed of lithium.

  Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. It is done.

(Negative electrode 20)
The negative electrode current collector 22 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.

The negative electrode active material may be any compound that can occlude and release lithium ions, and known negative electrode active materials for batteries can be used. Examples of the negative electrode active material include carbon materials such as graphite (natural graphite, artificial graphite) capable of occluding and releasing lithium ions, carbon nanotubes, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, aluminum, silicon And particles containing a metal that can be combined with lithium such as tin, an amorphous compound mainly composed of an oxide such as silicon dioxide and tin dioxide, and lithium titanate (Li ₄ Ti ₅ O ₁₂ ). . It is preferable to use silicon having a high capacity per unit weight.

  As the binder and the conductive material, the same materials as those for the positive electrode can be used.

(Method for manufacturing electrodes 10 and 20)
Next, a method for manufacturing the electrodes 10 and 20 according to this embodiment will be described.

The active material, binder and solvent are mixed. A conductive material may be further added as necessary. As the solvent, for example, water, N-methyl-2-pyrrolidone or the like can be used. The mixing method of the components constituting the paint is not particularly limited, and the mixing order is not particularly limited.
The paint is applied to the current collectors 12 and 22. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used.

  Subsequently, the solvent in the paint applied on the current collectors 12 and 22 is removed. The removal method is not particularly limited, and the current collectors 12 and 22 to which the paint is applied may be dried, for example, in an atmosphere of 80 ° C. to 150 ° C.

  Then, the electrode on which the active material layers 14 and 24 are formed in this way is subjected to a press treatment by a roll press device or the like as necessary. The linear pressure of the roll press can be, for example, 10 to 50 kgf / cm.

  Through the above steps, the electrode active material layers 14 and 24 are formed on the current collectors 12 and 22.

  The separator 18 is an electrically insulating porous body, for example, a single layer of a film made of polyolefin, a stretched film of a laminate or a mixture of the above resins, or at least selected from the group consisting of cellulose, polyester and polypropylene. Examples thereof include a fiber nonwoven fabric made of one kind of constituent material.

  The case 50 seals the laminated body 30 and the electrolytic solution therein. The case 50 is not particularly limited as long as it can prevent leakage of the electrolytic solution to the outside and entry of moisture and the like into the electrochemical device 100 from the outside. For example, as the case 50, as shown in FIG. 1, a metal laminate film in which a metal foil 52 is coated with a polymer film 54 from both sides can be used. For example, an aluminum foil can be used as the metal foil 52 and a film such as polypropylene can be used as the polymer film 54. For example, the material of the outer polymer film 54 is preferably a polymer having a high melting point such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film 54 is polyethylene (PE) or polypropylene (PP). preferable.

  The leads 60 and 62 are made of a conductive material such as aluminum.

Then, the leads 60 and 62 are welded to the positive electrode current collector 12 and the negative electrode current collector 22 by a known method, respectively, and a separator is provided between the positive electrode active material layer 14 of the positive electrode 10 and the negative electrode active material layer 24 of the negative electrode 20. 18 may be inserted into the case 50 together with the electrolytic solution with the 18 interposed therebetween, and the entrance of the case 50 may be sealed.
As mentioned above, although non-aqueous electrolyte of this invention, an electrode, a lithium ion secondary battery provided with the said electrolyte and electrode, and suitable one Embodiment of those manufacturing methods were demonstrated in detail, this invention is the said embodiment. It is not limited to.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
[Preparation of electrolyte]
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. To the solution in which the electrolyte was dissolved, D-(−)-penicillamine was added at 0.1% by weight with respect to the solution amount, and fluoroethylene carbonate was added at 3.0% by weight with respect to the solution amount, and dissolved. In this way, a non-aqueous electrolyte was produced.

[Production of negative electrode]
As the negative electrode active material, a material obtained by mixing silicon and silicon oxide at silicon / silicon oxide = 1/2 (weight ratio) and pulverizing and mixing using a planetary ball mill was used. The planetary ball mill media used alumina beads with a diameter of 3 mm, the rotation speed was 500 rpm, and the pulverization and mixing time was 60 min.
A negative electrode mixture was prepared by mixing 87 parts by mass of the mixture of silicon and silicon oxide as a negative electrode active material, 3 parts by mass of acetylene black as a conductive additive, and 10 parts by mass of polyamideimide as a binder. The negative electrode mixture was mixed with N-methyl-2-pyrrolidone as a solvent to prepare a paint. This paint was applied to a copper foil (thickness 15 μm) as a current collector by a doctor blade method, dried at 80 ° C., and then rolled to form a negative electrode active material layer on the surface of the copper foil. The copper foil was provided with a portion to which no paint was applied in order to connect the external lead terminal. This was dried in vacuum at 350 ° C. for 3 hours. As the external lead terminal, a nickel foil wound with polypropylene grafted with maleic anhydride was prepared for the purpose of improving the sealing performance with the exterior body. The nickel foil and the copper foil after the coating material was applied and dried were ultrasonically welded.

[Production of positive electrode]
Li (Ni _0.85 Co _0.10 Al _0.05 ) O ₂ as a positive electrode active material, polyvinylidene fluoride as a binder, carbon black and graphite as a conductive assistant, and N-methyl-2-pyrrolidone as a solvent A paint was prepared. This paint was applied to an aluminum foil (thickness 20 μm) as a current collector by a doctor blade method, dried at 100 ° C., and then rolled to form a positive electrode active material layer on the surface of the aluminum foil. The aluminum foil was provided with a portion to which no paint was applied in order to connect the external lead terminal. As an external lead terminal, for the purpose of improving the sealing property with the exterior body, an aluminum foil wrapped with polypropylene grafted with maleic anhydride was prepared. This aluminum foil and the aluminum foil after the coating material was applied and dried were ultrasonically welded.

[Production of lithium ion secondary battery cells]
The positive electrode, negative electrode, and polyolefin separator produced as described above were cut into predetermined dimensions. The cut positive electrode, negative electrode, and separator were laminated in the order of the negative electrode, separator, positive electrode, separator, and negative electrode to produce a full cell laminate. The laminate was placed in the outer package, an appropriate amount of the electrolyte prepared as described above was added, and the outer package was vacuum-sealed to produce a lithium ion secondary battery cell (hereinafter referred to as a cell).

[Initial charge / discharge]
The cell produced as described above was charged for 3 hours with a charge / discharge tester at a current value at which the current density with respect to the positive electrode active material was 10 mA / g. Then, after removing the gas generated inside the cell, it is charged again using a charge / discharge tester until the cell potential becomes 4.2 V at a current value of 19 mA / g for the positive electrode active material, Thereafter, discharging was performed until the cell potential became 2.5 V at a current value corresponding to a current density of 19 mA / g with respect to the positive electrode active material.

[Measurement of discharge capacity]
The cell produced as described above was charged and discharged with a charge / discharge tester, the charge / discharge rate was 0.5 C (the current value at which discharge was completed in 2 hours when constant current discharge was performed at 25 ° C.), and the cell voltage was 4. The discharge capacity (unit: mAh) was measured when the cell voltage was 2.5 V after being charged to 2 V. Table 1 shows the change in discharge capacity when this is repeated 400 times.

Example 2 LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding 0.1% by weight of D-(-)-penicillamine to this solution and dissolving 5.0% by weight of fluoroethylene carbonate with respect to the solution amount. Used as. The rest is the same as in the first embodiment.

(Example 3)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding 0.1% by weight of D-(−)-penicillamine and 1.0% by weight of fluoroethylene carbonate to the solution and dissolving the solution. Used as. The rest is the same as in the first embodiment.

Example 4
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte is obtained by adding 0.1 wt% of D-(−)-penicillamine and 0.1 wt% of fluoroethylene carbonate to the solution and dissolving the solution. Used as. The rest is the same as in the first embodiment.

(Example 5)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding D-(-)-penicillamine to this solution in an amount of 0.3% by weight with respect to the solution amount and 3.0% by weight of fluoroethylene carbonate with respect to the solution amount. Used as. The rest is the same as in the first embodiment.

(Example 6)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding D-(-)-penicillamine to this solution in an amount of 0.5% by weight with respect to the solution amount and 3.0% by weight of fluoroethylene carbonate with respect to the solution amount. Used as. The rest is the same as in the first embodiment.

(Example 7)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding 1.0% by weight of D-(-)-penicillamine to this solution and dissolving 3.0% by weight of fluoroethylene carbonate with respect to the amount of solution. Used as. The rest is the same as in the first embodiment.

(Example 8)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding 3.0% by weight of D-(−)-penicillamine to this solution and dissolving 3.0% by weight of fluoroethylene carbonate with respect to the solution amount. Used as. The rest is the same as in the first embodiment.

Example 9
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding D-(−)-penicillamine to this solution in an amount of 0.01% by weight with respect to the amount of the solution and 3.0% by weight of fluoroethylene carbonate relative to the amount of the solution. Used as. The rest is the same as in the first embodiment.

(Example 10)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol%. A non-aqueous electrolyte was prepared by adding 0.05 wt% of D-(−)-penicillamine to this solution and dissolving 3.0 wt% of fluoroethylene carbonate with respect to the solution amount. Used as. The rest is the same as in the first embodiment.

(Example 11)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol%, propylene carbonate at 30 vol%, and diethyl carbonate at a ratio of 40 vol%. A non-aqueous electrolyte was prepared by adding 0.1% by weight of D-(-)-penicillamine to this solution and dissolving 3.0% by weight of fluoroethylene carbonate with respect to the amount of solution. Used as. The rest is the same as in the first embodiment.

(Example 12)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 40 vol%, diethyl carbonate at 50 vol%, and ethyl methyl carbonate at a ratio of 10 vol%. A non-aqueous electrolyte was prepared by adding 0.1% by weight of D-(-)-penicillamine to this solution and dissolving 3.0% by weight of fluoroethylene carbonate with respect to the amount of solution. Used as. The rest is the same as in the first embodiment.

(Example 13)
Instead of D-(−)-penicillamine, 0.1 wt% of penicillamine ethyl was added and dissolved as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Example 14)
Instead of D-(−)-penicillamine, 0.1% by weight of β-homopenicillamine was added and dissolved as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Example 15)
Instead of D-(−)-penicillamine, 0.1% by weight of N-methylpenicillamine was added and dissolved as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Example 16)
Instead of D-(−)-penicillamine, 0.1% by weight of 3-methyl-3-sulfanylbutanoic acid was added to dissolve the solution, and the non-aqueous electrolyte was used. The rest is the same as in the first embodiment.

(Example 17)
Instead of D-(−)-penicillamine, a solution prepared by adding 2-amino-1,1-dimethylethanethiol by 0.1% by weight with respect to the amount of solution and dissolving it was used as the non-aqueous electrolyte. The rest is the same as in the first embodiment.

( Reference Example 18)
Instead of D-(−)-penicillamine, a solution prepared by adding 0.1% by weight of 3-amino-2,2-dimethylpropanoic acid to the solution and dissolving it was used as the non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Comparative Example 1)
A solution obtained by dissolving LiPF ₆ at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol% was used as a non-aqueous electrolyte as it was. The rest is the same as in the first embodiment.

(Comparative Example 2)
Instead of D-(-)-penicillamine, a solution prepared by adding butanoic acid having only a carboxy group to 0.1% by weight with respect to the amount of solution was used as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Comparative Example 3)
Instead of D-(-)-penicillamine, a solution prepared by adding 0.1% by weight of butylamine having only an amino group to the solution amount and dissolving it was used as the non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Comparative Example 4)
Instead of D-(−)-penicillamine, 1-butanethiol having only a sulfanyl group was added and dissolved in an amount of 0.1% by weight based on the amount of the solution, and used as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

(Comparative Example 5)
LiPF ₆ was dissolved at a concentration of 1 M in a solution in which ethylene carbonate was mixed at a ratio of 40 vol%, diethyl carbonate at 50 vol%, and ethyl methyl carbonate at a ratio of 10 vol%. A solution obtained by adding 3.0% by weight of fluoroethylene carbonate to this solution and dissolving it was used as a non-aqueous electrolyte. The rest is the same as in the first embodiment.

Table 1 shows the results of the cycle tests of the examples of the present invention and the comparative examples. In addition, with reference to 7.5 of JIS C 8711, a capacity maintenance rate of 60% in 400 cycles was used as a criterion for pass / fail as a criterion.
As shown in Table 1, in the examples, the capacity retention rate after 400 cycles was improved as compared with the comparative example, and all passed.

  As described above, according to the present invention, a lithium ion secondary battery with good cycle characteristics can be manufactured.

  DESCRIPTION OF SYMBOLS 10 ... Positive electrode, 20 ... Negative electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 22 ... Negative electrode collector, 24 ... Negative electrode active material layer, 30 ... Laminate body, 50 ... Case, 52 ... Metal foil, 54 ... Polymer film, 60, 62 ... Lead, 100 ... Lithium ion secondary battery.

Claims (5)

Nonaqueous solvent, electrolyte, halogenated cyclic carbonate, and thiol represented by the following chemical formula 1 [wherein R1, R2, R3 are hydrogen or alkyl groups (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ ), an alkoxycarbonyl group (—COOR 4, where R 4 is —C _n H _{2n + 1} , n = 1 to 4), an alkyl group having a carboxy group (—C _{n H 2n COOH, n = 1~4} ), an alkyl group having carboxylate group ^{_{(-C n H 2n COO -,}} n = 1~4), amino group _{(-NH 2, -NHR5, -NR5R6,} R5, R6 is an alkyl group (—C _n H _{2n + 1} , n = 1 to 4), a carboxy group, a carboxylate group (—COO ⁻ ), or a sulfanyl group. And the thiol is a non-aqueous electrolyte composed of a compound having at least one of a carboxy group, the carboxylate group, and the amino group , and the content of the thiol in the electrolyte is 0.00. A non-aqueous electrolytic solution having a content of 0.1 to 5% by mass, and the content of the halogenated cyclic carbonate in the electrolytic solution is 0.1 to 5% by mass .

The non-aqueous electrolyte according to claim 1, wherein the thiol is a compound having at least one carboxy group or at least one carboxylate group and at least one amino group. The non-aqueous electrolyte according to claim 1, wherein the thiol is penicillamine and derivatives thereof. The nonaqueous electrolytic solution according to claim 1, wherein the halogenated cyclic carbonate is fluoroethylene carbonate. A lithium ion secondary battery comprising: a positive electrode; a negative electrode; a separator; and the nonaqueous electrolytic solution according to any one of claims 1 to 4 , wherein the negative electrode contains silicon.

Images