JP2017117686A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower an irreversible capacity produced in the case of using, as a negative electrode active material, graphite arranged to have a small particle diameter, and to reduce a battery resistance.SOLUTION: A lithium ion secondary battery comprises: a positive electrode; a negative electrode; and an electrolyte. The negative electrode has graphite as a negative electrode active material. The graphite has an average particle diameter (d50) in a range of 0.5-10 μm. The electrolyte includes an additive agent expressed by the formula (1) or (2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion secondary battery.

  In recent years, development of lithium ion secondary batteries (Li batteries) has been actively promoted. Problems with Li batteries include reduction of battery resistance and reduction of irreversible capacity.

  In order to improve the performance of the Li battery, a technique of adding various compounds to the electrolytic solution is disclosed, and the following prior art is disclosed.

  In Patent Document 1, an attempt is made to improve high-temperature storage characteristics by adding a lactone compound and a boron compound to an electrolyte of a Li battery.

  Patent Document 2 discloses a technique for adding a boron-based compound to a Li battery and improving high-temperature storage characteristics.

JP2009-004258 JP2008-066004

  In general, in order to reduce the battery resistance, it is considered to reduce the resistance by reducing the particle size of graphite of the negative electrode active material and increasing the reaction surface area. However, when the material of Patent Document 1 is added to the reduced particle size graphite, the irreversible capacity increases and the battery resistance increases. It is estimated that the film on the negative electrode formed by a combination of lactone and boron is a factor. Moreover, when the material of patent document 2 is used, the increase in irreversible capacity will be seen and battery performance will fall.

  Therefore, in the present invention, a novel Li battery additive and its additive were used for the purpose of reducing the irreversible capacity and battery resistance, which are generated when the reduced particle size graphite is used as the negative electrode active material. An object is to provide a Li battery.

  The features of the present invention for solving the above-described problems are as follows.

  The negative electrode has graphite as a negative electrode active material, the graphite has an average particle size (d50) in the range of 0.5 to 10 μm, and the electrolytic solution has a positive electrode, a negative electrode, and an electrolytic solution. A lithium ion secondary battery having an additive represented by formula (1) or formula (2).

(In Formula 1, R ₁ , R ₂ and R ₃ are any of an alkyl group having 5 or less carbon atoms, a halogen group, a halogenated alkyl group having 5 or less carbon atoms, or hydrogen. R ₄ is an alkane group. (C _n H _{2n + 2} ), a halogenated alkane group, and R ₄ may be omitted, H may be substituted with halogen, and X is either an alkali metal or an alkaline earth metal .)

(R _{5 in} formula (2) is hydrogen, an alkali metal, an alkaline earth metal, or an alkyl group. X is an alkali metal or an alkaline earth metal.)

  According to the present invention, it is possible to provide a Li battery with low irreversible capacity and low battery resistance. Problems, configurations, and effects other than those described will be clarified by the following description of embodiments.

The figure which represents typically the internal structure of the battery which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

  FIG. 1 is a diagram schematically showing the internal structure of a battery according to an embodiment of the present invention. A battery 1 according to an embodiment of the present invention shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery container (that is, a battery can) 13, a positive electrode current collecting tab 14, a negative electrode current collecting tab 15, an inner lid 16, An internal pressure release valve 17, a gasket 18, a positive temperature coefficient (PTC) resistance element 19, a battery lid 20, and an axis 21 are included. The battery lid 20 is an integrated part composed of the inner lid 16, the internal pressure release valve 17, the gasket 18, and the PTC resistance element 19. A positive electrode 10, a separator 11, and a negative electrode 12 are wound around the shaft center 21.

  The separator 11 is inserted between the positive electrode 10 and the negative electrode 12 to produce an electrode group wound around the axis 21. As the axis 21, any known one can be used as long as it can support the positive electrode 10, the separator 11, and the negative electrode 12. In addition to the cylindrical shape shown in FIG. 1, the electrode group has various shapes such as a laminate of strip electrodes, or a positive electrode 10 and a negative electrode 12 wound in an arbitrary shape such as a flat shape. Can do. The shape of the battery case 13 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group.

  The material of the battery case 13 is selected from materials that are corrosion-resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery container 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material is not deteriorated due to corrosion of the battery container 13 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery container 13 is selected.

  The electrode group is housed in the battery container 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery container 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery lid 20. The electrolyte is injected into the battery container interior 13 before the battery is sealed. As a method for injecting the electrolyte, there are a method of adding directly to the electrode group in a state where the battery cover 20 is released, or a method of adding from an injection port installed in the battery cover 20.

  Thereafter, the battery lid 20 is brought into close contact with the battery container 13 to seal the entire battery. If there is an electrolyte inlet, seal it as well. As a method for sealing the battery, there are known techniques such as welding and caulking.

  The lithium ion battery according to an embodiment of the present invention can be manufactured, for example, by disposing the following negative electrode and positive electrode facing each other via a separator and injecting an electrolyte. The structure of the lithium ion battery according to an embodiment of the present invention is not particularly limited. Usually, the positive electrode and the negative electrode and the separator separating them are wound into a wound electrode group, or the positive electrode, the negative electrode, and the separator are combined. A stacked electrode group can be formed by stacking.

<Positive electrode>
The positive electrode 10 includes a positive electrode active material, a conductive agent, a binder, and a current collector. Illustrative examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ . In addition, LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , Li ₄ Mn ₅ O ₁₂ , LiMn _2−x MxO ₂ (where M = Co, Ni, Fe, Cr, Zn, Ti, at least 1 type, x = 0.01 to 0.2), Li ₂ Mn ₃ MO ₈ (where M = at least one selected from the group consisting of Fe, Co, Ni, Cu, Zn), Li _1-x A _x Mn ₂ O ₄ (where A = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, at least one selected from the group consisting of x, 0.01 to 0.1), LiNi _{1 -x} M _x O ₂ (however, M = Co, Fe, at least one selected from the group consisting of _{Ga, x = 0.01~0.2), LiFeO} 2, Fe 2 (SO 4) 3, LiCo 1 _-X M _x O ₂ (however, M = at least one selected from the group consisting of Ni, Fe and Mn, x = 0.01 to 0.2), LiNi _1-x M _x O ₂ (where M = Mn, Fe, Co, Al, Ga) , At least one selected from the group consisting of Ca, Mg, x = 0.01 to 0.2), Fe (MoO ₄ ) ₃ , FeF ₃ , LiFePO ₄ , LiMnPO ₄ , and the like. One or more positive electrode active materials may be mixed and used. Moreover, the positive electrode active material may be previously coated with an inorganic material or an organic material. Examples of the inorganic substance include oxides such as Al, Mg, Ti, Zr, Mo, and W. As the organic substance, an ion exchange resin having an ion exchange functional group in the molecule is preferably used. The particle size of the positive electrode active material is usually defined so as to be equal to or less than the thickness of the mixture layer formed from the positive electrode active material, the conductive agent, and the binder. When there are coarse particles having a size equal to or greater than the thickness of the mixture layer in the positive electrode active material powder, the coarse particles can be removed in advance by sieving classification or wind classification to produce particles having a thickness of the mixture layer thickness or less. preferable.

  In addition, since the positive electrode active material is generally oxide-based and has high electrical resistance, it is preferable to use a conductive agent made of carbon powder for supplementing electrical conductivity. Since both the positive electrode active material and the conductive agent are usually powders, a binder can be mixed with the powders, and the powders can be bonded together and simultaneously bonded to the current collector.

  For the current collector of the positive electrode 10, an aluminum foil having a thickness of 10 to 100 μm, an aluminum perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, or a metal foam plate is used. . In addition to aluminum, materials such as stainless steel and titanium are also applicable. In the present invention, any current collector can be used without being limited by the material, shape, manufacturing method and the like.

  A positive electrode slurry in which a positive electrode active material, a conductive agent, a binder, and an organic solvent are mixed is attached to a current collector by a doctor blade method, a dipping method, or a spray method, and then the organic solvent is dried and applied by a roll press. The positive electrode 10 can be produced by pressure forming. In addition, a plurality of mixture layers can be laminated on the current collector by performing a plurality of times from application to drying.

<Negative electrode>
The negative electrode has a structure in which a negative electrode mixture and a negative electrode mixture are applied to a current collector. The negative electrode mixture has at least a negative electrode active material, and a conductive agent, a binder, and other additives are added as necessary.

  A material having graphite can be used as the negative electrode active material. Graphite has an average (002) plane spacing of 0.3400 nm or less as measured by X-ray diffraction. The particle diameter (d50) of graphite is preferably 0.5 to 10 μm in consideration of the relationship with the additives represented by the formulas (1) and (2). The effect of the present application is manifested when the additive is adsorbed on graphite and then reduced. The mechanism of the reduction reaction varies depending on the structure of the additive and the particle size of graphite as an electrode. Therefore, the combination of the additive and the particle size of graphite is important in obtaining the effects of the present application. The additive of the present application is highly reducible as compared with vinylene carbonate (VC) that has been widely used in lithium ion batteries. Therefore, when the graphite particle size is 0.5 μm or less, the specific surface area increases, and the additive of the present application reacts excessively. Therefore, since the film which exists on graphite produces | generates excessively, the effect of this application falls. On the other hand, when the particle size of graphite is 10 μm or more, it becomes difficult for the additive to be adsorbed on the graphite, and the additive of the present application is difficult to reduce. As a result, film formation does not proceed smoothly, and the effect of the present application is reduced. From the above, the graphite used in the present application preferably has a particle diameter (d50) of 0.5 to 10 μm. Here, the average particle diameter (d50) is a value measured by a laser diffraction particle size distribution measuring apparatus, and is a value defined by the particle diameter when the cumulative particle amount is 50%.

  By using the graphite described above as the physical properties of graphite, the resistance to electrolytic solution reduction of the film formed by the reaction of the additive of the present invention is improved, the irreversible capacity is reduced, and the ion conductivity of the formed film is reduced. It is considered that the resistance of the Li battery is also reduced because of its high performance.

  As the negative electrode active material, in addition to graphite, a metal alloying with lithium or a material having a metal supported on the surface of carbon particles can be used. For example, a metal or alloy selected from lithium, silver, aluminum, tin, silicon, indium, gallium, and magnesium. Further, the metal or an oxide of the metal can be used as a negative electrode active material. Furthermore, lithium titanate can also be used.

<Electrolyte>
The electrolytic solution is composed of, for example, a solvent, an electrolyte salt, and an additive. Non-aqueous solvents that can be used in the electrolyte include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphoric acid triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2-oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane , Chloroethylene carbonate, or chloropropylene carbonate. In obtaining the effects of the present application, the selection of the electrolyte component is important. As the solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. As the cyclic carbonate, ethylene carbonate is preferably used. As the chain carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferably used.

  Further, chain carbonates may be used in combination. By adjusting the volume ratio of the cyclic carbonate and the chain carbonate, a synergistic effect with the additive described later is exhibited, and as a result, the effect of the present application can be enhanced. The volume ratio (a / (a + b)) between the cyclic carbonate (a) and the chain carbonate (b) is 0 ≦ a / (a + b) ≦ 0.9, preferably 0.01 ≦ a / (a + b) ≦. 0.50, particularly preferably 0.1 ≦ a / (a + b) ≦ 0.30. The solvent component undergoes a decomposition reaction at the electrode during the initial charge, and a decomposition product is generated on the electrode surface. The decomposition product is a factor that determines the resistance of the battery.

  In the present invention, the battery to which the formula (1) or the formula (2) is added reacts with the electrode to form a film, and the reaction occurs in concert with the decomposition of the electrolytic solution. The coating is formed in concert by the decomposition of the additive and solvent.

<Additives>
An additive represented by the formula (1) or the formula (2) is added to the electrolytic solution.

(In Formula 1, R ₁ , R ₂ and R ₃ are any of an alkyl group having 5 or less carbon atoms, a halogen group, a halogenated alkyl group having 5 or less carbon atoms, or hydrogen. R ₄ is an alkane group. (C _n H _{2n + 2} ), a halogenated alkane group, and R ₄ may be omitted, H may be substituted with halogen, and X is either an alkali metal or an alkaline earth metal .)
In Formula 1, R ₁ to R ₃ are preferably those having 5 or less carbon atoms. Of these, a methyl group, an ethyl group, and a propyl group are preferably used. In the case of a halogen group, fluorine and chlorine are preferably used.

X is preferably an alkali metal, particularly Li, Na, or K. Adjusting X affects the structure of the film formed by the additive, so the effect of the present application is considered to be enhanced. When R ₄ is present, those having 5 or less carbon atoms are preferably used. By adjusting the number of carbon atoms, the solubility in the electrolytic solution can be improved, so that a uniform film can be formed. When R ₄ is not present, B and the vinyl group are directly connected.

(R _{5 in} formula (2) is hydrogen, an alkali metal, an alkaline earth metal, or an alkyl group. X is an alkali metal or an alkaline earth metal.)
As R _{5 in the} formula (2), an alkyl group is preferably used. By using an alkyl group, an excessive decomposition reaction due to R ₅ can be suppressed, so that irreversible capacity can be reduced. X in the formula (2) is an alkali metal or an alkaline earth metal. X is preferably an alkali metal, particularly Li, Na, or K.

  The addition amount (Y / wt%) of the formula (1) or the formula (2) with respect to the electrolytic solution is 0 <Y ≦ 5, preferably 0.01 ≦ Y ≦ 3, particularly preferably with respect to the electrolytic solution. Is 0.01 ≦ Y <0.1. If the amount added is large, the irreversible capacity increases and the battery capacity decreases. Moreover, since the density | concentration of the component derived from the additive which exists in an electrode interface will fall when there is little addition amount, the effect of this invention falls.

  Formula (1) and Formula (2) react when charged and discharged in a battery to form a film on the electrode. In the case of Formula (1) as one form of the structure of the film, Formula (3) is used, and in the case of Formula (2), Formula (4) is used.

(In Formula 1, R ₁ , R ₂ and R ₃ are any of an alkyl group having 5 or less carbon atoms, a halogen group, a halogenated alkyl group having 5 or less carbon atoms, or hydrogen. R ₄ is an alkane group. (C _n H _{2n + 2} ), a halogenated alkane group, and R ₄ may be omitted, H may be substituted with halogen, and X is either an alkali metal or an alkaline earth metal N is the number of polymerizations.)

(R _{5 in} formula (2) is hydrogen, an alkali metal, an alkaline earth metal, or an alkyl group. X is an alkali metal or an alkaline earth metal.)
Note that R ₁ to R ₅ and X in Formula (3) and Formula (4) correspond to Formula (1) and Formula (2).

  It is also possible to prepare Equation (3) and Equation (4) in advance, cover the negative electrode active material, and produce a battery using the active material. As the active material to be coated, either a positive electrode active material or a negative electrode active material can be used. In order to reduce battery resistance, it is particularly effective to coat the negative electrode active material. By covering the negative electrode active material, the properties of the film formed on the surface of the negative electrode active material are affected, and as a result, a battery having low battery resistance can be manufactured.

  Moreover, in this application, an active material may be disperse | distributed to a solvent, Formula (1) and a polymerization initiator may be added there, and it heat-polymerizes, and then an active material may be taken out and a negative electrode active material may be coat | covered.

It is preferable to add an electrolyte salt to the electrolytic solution. Examples of the electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, variety There is a lithium salt. An electrolytic solution obtained by dissolving these salts in the above solvent can be used as an electrolytic solution for a battery. In the present application, selection of the electrolyte salt is important for enhancing the effect of the present application. As the electrolyte salt, LiPF ₆ , LiBF ₄ , and LiClO ₄ are preferable, LiPF ₆ and LiBF ₄ are more preferable, and LiPF ₆ is particularly preferable. When LiPF ₆ is used, it is considered that the effect of the present application is enhanced because the component of the film formed by the formula (1) is affected, and as a result, a low-resistance film is formed.

<Second additive>
As an additive to be added to the electrolytic solution, a second additive can be added in addition to the formula (1) or the formula (2).

  Examples of the second additive include vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfate, or a derivative thereof. Among these, vinylene carbonate, fluoroethylene carbonate, 1,3-propene sultone, or a mixture thereof is particularly preferable. By adding the second additive, a film of Formula (1) or Formula (2) and the second additive can be formed on the surface of the active material, and a stronger film can be formed. As a 2nd additive, you may use individually and may use multiple.

  The addition amount (Z / wt%) of the second additive is preferably added in the range of 0 <Z ≦ 10 with respect to the electrolytic solution. More preferably, 0.01 ≦ Z ≦ 2. By adding the second additive, the effect of adding the formula (1) is further enhanced. It is considered that the resistance is further lowered because the ionic conductivity of the film produced by the combination of the formula (1) and the second additive is high. In the case where the second additive contains a double bond functional group, the one containing a structure in which the double bond part of the formula (1) and the double bond part of the second additive are connected is the coating component. It may exist as one form.

  When a solid polymer electrolyte (polymer electrolyte) is used, an ion conductive polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used for the electrolyte. When these solid polymer electrolytes are used, there is an advantage that the separator 11 can be omitted.

Furthermore, an ionic liquid can be used. For example, 1-ethyl-3-methylimidazole tetrafluoroborate (EMI-BF4), a lithium salt LiN (SO ₂ CF ₃ ) ₂ (LiTFSI), a mixed complex of triglyme and tetraglyme, a cyclic quaternary ammonium cation (N-methyl) -N-propylpyrrolidinium is exemplified) and an imide-based anion (example is bis (fluorosulfonyl) imide), a combination that does not decompose at the positive electrode 10 and the negative electrode 12 is selected, and this embodiment is concerned. Can be used for batteries.

<Separator>
The separator 11 is inserted between the positive electrode 10 and the negative electrode 12 produced by the above method to prevent a short circuit between the positive electrode 10 and the negative electrode 12. The separator 11 can be a polyolefin polymer sheet made of polyethylene, polypropylene, or the like, or a two-layer structure in which a polyolefin polymer and a fluorine polymer sheet typified by tetrafluoropolyethylene are welded. It is. A mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator 11 so that the separator 11 does not shrink when the battery temperature increases. Since these separators 11 need to allow lithium ions to permeate during charging and discharging of the battery, they can be used for lithium ion batteries as long as the pore diameter is generally 0.01 to 10 μm and the porosity is 20 to 90%. .

<Copper foil>
The thickness of the copper foil is preferably 5 to 30 μm, particularly preferably 7 to 21 μm. This reacts with graphite when the additive reacts with the negative electrode, but also with copper foil. It is assumed that the current density with respect to the copper foil at that time influences the reaction of the additive.

<Battery system>
A Li battery using Formula (1) or Formula (2) as an electrolyte has an excellent property of low resistance. Therefore, heat generation due to the internal resistance of the battery can be suppressed when the battery is used. Therefore, since the battery cooling mechanism can be simplified, it is useful not only for small batteries for portable devices but also for large batteries for in-vehicle use.

(Example)
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples. The results of this example are summarized in Table 1.

<Method for producing positive electrode>
85: 7.5: 7.5 wt% ratio of positive electrode active material (LiMn _1/3 Co _1/3 Ni _1/3 O ₂ ), conductive agent (SP270: graphite manufactured by Nippon Graphite Co., Ltd.), and polyvinylidene fluoride binder And mixed with N-methyl-2-pyrrolidone to prepare a slurry solution. The slurry was applied to a 20 μm thick aluminum foil by a doctor blade method and dried. The mixture was pressed to a bulk density of 2.8 g / cm ³ to produce a positive electrode.

<Method for producing negative electrode>
Graphite was used as the negative electrode active material. Polyvinylidene fluoride was mixed with graphite at a ratio of 95: 5% by weight, and further mixed with N-methyl-2-pyrrolidone to prepare a slurry solution. The slurry was applied to a copper foil having a thickness of 10 μm by a doctor blade method and dried. The mixture was pressed so that the bulk density was 1.5 g / cm ³ to prepare a negative electrode. The graphite particle size (d50) was 3 μm.

<Battery preparation method and evaluation method>
A separator was inserted between the positive electrode and the negative electrode and laminated. Thereafter, the laminate was inserted into an aluminum laminate to form a battery. In the charging / discharging of the battery, the upper limit voltage of the battery was 4.2 V, and the lower limit voltage was 3.0 V. In addition, charging was performed with a constant current of 30 mA, and after reaching 4.2 V, charging was performed with a constant potential until the current value reached 3 mA. The discharge was up to 3.0 V at 30 mA. The battery capacity was defined by the capacity when a battery charged to 4.2V was discharged to 3.0V. In addition, after charging the battery to 4.2 V, the DCR was set to discharge currents of 30 mA, 60 mA, and 90 mA, and after discharging for 10 seconds, the amount of voltage drop was measured. Also, the relationship between the measured voltage drop and the discharge current was plotted, and DCR was obtained from the slope.

Example 1
The electrolytic solution used was LiPF ₆ as the electrolyte salt and EC / EMC / DMC = 1/2/2 (volume ratio) as the solvent. The electrolyte salt concentration was 1.0 mol / L. Additive A (formula (5)) was added to the electrolytic solution as a first additive (additive corresponding to formula (1) or formula (2)) to 0.95 wt%. Then, the battery was produced and battery evaluation was carried out. The battery capacity was 30.0 mAh and the DCR was 0.45 mΩ.

(Example 2)
In Example 1, it carried out similarly to Example 1 except having made the density | concentration of the additive A other than 0.045 wt%. As a result of battery evaluation, the battery capacity was 29.8 mAh and the DCR was 0.46 mΩ.

(Example 3)
In Example 1, it carried out similarly to Example 1 except adding 1.0 wt% of vinylene carbonate (VC) as a 2nd additive. As a result of battery evaluation, the battery capacity was 30.2 mAh and the DCR was 0.40 mΩ.

Example 4
In Example 1, it examined like Example 1 except having added 1, 3- propensultone to the electrolyte solution so that a density | concentration might be 1.0 wt% as a 2nd additive. As a result of battery evaluation, the battery capacity was 30.2 mAh and the DCR was 0.45 mΩ.

(Example 5)
In Example 1, it evaluated similarly to Example 1 except using the additive B (Formula (6)) instead of the additive A as a 1st additive. As a result of battery evaluation, the battery capacity was 29.5 mAh and the DCR was 0.48 mΩ.

(Example 6)
In Example 1, it evaluated similarly to Example 1 except using the additive C (Formula (7)) instead of the additive A. FIG. As a result of battery evaluation, the battery capacity was 30.1 mAh and the DCR was 0.47 mΩ.

(Example 7)
In Example 1, it evaluated similarly to Example 1 except using the additive D (Formula (8)) instead of the additive A. FIG. As a result of battery evaluation, the battery capacity was 29.5 mAh, and the DCR was 0.49 mΩ.

(Example 8)
In Example 1, it evaluated similarly to Example 1 except using the additive E (Formula (9)) instead of the additive A. FIG. As a result of battery evaluation, the battery capacity was 29.6 mAh and the DCR was 0.48 mΩ.

Example 9
In Example 1, it carried out similarly to Example 1 except adding 0.9 wt% of vinylene carbonate (VC) as a 2nd additive. As a result of battery evaluation, the battery capacity was 30.0 mAh and the DCR was 0.41 mΩ.

(Example 10)
In Example 1, it carried out similarly to Example 1 except adding 1.0 wt% of vinylene carbonate (VC) as a 2nd additive. As a result of battery evaluation, the battery capacity was 30.5 mAh and the DCR was 0.39 mΩ.

(Example 11)
In Example 1, it carried out similarly to Example 1 except adding 1.5 wt% of vinylene carbonate (VC) as an additive (2). As a result of battery evaluation, the battery capacity was 30.2 mAh and the DCR was 0.41 mΩ.

(Example 12)
In Example 1, it was carried out similarly to Example 1 except adding 2.0 wt% of vinylene carbonate (VC) as an additive (2). As a result of battery evaluation, the battery capacity was 29.5 mAh and the DCR was 0.45 mΩ.

(Example 13)
In Example 1, it was carried out similarly to Example 1 except adding 2.5 wt% of vinylene carbonate (VC) as an additive (2). As a result of battery evaluation, the battery capacity was 29.2 mAh and the DCR was 0.49 mΩ.

(Example 14)
In Example 1, it was carried out similarly to Example 1 except adding 3.0 wt% of vinylene carbonate (VC) as an additive (2). As a result of battery evaluation, the battery capacity was 27.2 mAh and the DCR was 0.60 mΩ.

(Example 15)
Example 2 was the same as Example 2 except that a copper foil having a thickness of 35 μm was used. As a result, the battery capacity was 29.1 mAh and the DCR was 0.55 mΩ.

(Comparative Example 1)
In Example 1, it evaluated similarly to Example 1 except not adding the additive A. As a result, the battery capacity was 28.5 mAh and the DCR was 0.55 mΩ.

(Comparative Example 2)
In Example 1, it evaluated similarly to Example 4 except not adding the additive A. As a result, the battery capacity was 27.5 mAh and the DCR was 0.65 mΩ.

(Comparative Example 3)
In Example 3, it evaluated similarly to Example 3 except not adding the additive A. As a result, the battery capacity was 28.0 mAh and the DCR was 0.55 mΩ.

(Comparative Example 4)
In Example 3, evaluation was performed in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 0.9 wt%. As a result, the battery capacity was 28.2 mAh and the DCR was 0.58 mΩ.

(Comparative Example 5)
In Example 3, evaluation was made in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 1.0 wt%. As a result, the battery capacity was 27.0 mAh and the DCR was 0.68 mΩ.

(Comparative Example 6)
In Example 3, evaluation was made in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 1.5 wt%. As a result, the battery capacity was 25.2 mAh and the DCR was 0.71 mΩ.

(Comparative Example 7)
In Example 3, evaluation was made in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 2.0 wt%. As a result, the battery capacity was 24.8 mAh and the DCR was 0.79 mΩ.

(Comparative Example 8)
In Example 3, evaluation was made in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 2.5 wt%. As a result, the battery capacity was 24.8 mAh and the DCR was 0.98 mΩ.

(Comparative Example 9)
In Example 3, evaluation was performed in the same manner as in Example 3 except that additive A was not added and the amount of vinylene carbonate added was 3.0 wt%. As a result, the battery capacity was 20.2 mAh and the DCR was 1.20 mΩ.

(Comparative Example 10)
Example 2 was the same as Example 2 except that graphite having a particle size of 15 μm was used. As a result, the battery capacity was 27.1 mAh and the DCR was 0.80 mΩ.

(Comparative Example 11)
Example 2 was the same as Example 2 except that graphite having a particle size of 20 μm was used. As a result, the battery capacity was 26.5 mAh and the DCR was 0.89 mΩ.

  Examples 1 to 15 indicate that the resistance of the lithium ion secondary battery can be reduced by adding the additive represented by formula (1) or formula (2) to the electrolytic solution. The effect of the additive A used in is great. Furthermore, it turns out that resistance is further reduced by adding a 2nd additive. This is because a concerted film is formed by the additive represented by the formula (1) or the formula (2) and the second additive, so that a stronger and lower resistance film can be formed. It is believed that there is.

Battery 1
Positive electrode 10,
Separator 11,
Negative electrode 12,
Battery container (ie, battery can) 13,
Positive electrode current collecting tab 14;
Negative electrode current collecting tab 15,
Inner lid 16,
Internal pressure release valve 17,
Gasket 18,
Positive temperature coefficient (PTC) resistance element 19,
Battery lid 20,
Axis 21

Claims (7)

Having a positive electrode, a negative electrode and an electrolyte,
The negative electrode has graphite as a negative electrode active material,
The average particle diameter (d50) of the graphite is in the range of 0.5 to 10 μm,
The electrolytic solution is a lithium ion secondary battery having an additive represented by formula (1) or formula (2).

(In Formula 1, R ₁ , R ₂ and R ₃ are any of an alkyl group having 5 or less carbon atoms, a halogen group, a halogenated alkyl group having 5 or less carbon atoms, or hydrogen. R ₄ is an alkane group. (C _n H _{2n + 2} ), a halogenated alkane group, and R ₄ may be omitted, H may be substituted with halogen, and X is either an alkali metal or an alkaline earth metal .)

(R _{5 in} formula (2) is hydrogen, an alkali metal, an alkaline earth metal, or an alkyl group. X is an alkali metal or an alkaline earth metal.) In claim 1,
The additive amount (Y / wt%) of the additive with respect to the electrolytic solution is a lithium ion secondary battery in a range of 0 <Y ≦ 5 with respect to the electrolytic solution. In claim 2,
The additive represented by the formula (1) is any one of the formula (5), the formula (7), the formula (8), and the formula (9).
The additive represented by said Formula (2) is a lithium ion secondary battery which is Formula (6).

In claim 3,
The electrolytic solution has a second additive,
The lithium ion secondary battery, wherein the second additive is at least one of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, and ethylene sulfate. In claim 4,
The addition amount (Z / wt%) of the second additive is a lithium ion secondary battery in a range of 0 <Z ≦ 10 with respect to the electrolytic solution. In any one of Claims 1 thru | or 5,
The negative electrode is formed by applying the negative electrode mixture to a negative electrode current collector,
The negative electrode current collector has copper,
A thickness of the current collector is a lithium ion secondary battery in a range of 5 to 30 μm. Having a positive electrode, a negative electrode and an electrolyte,
The negative electrode has graphite as a negative electrode active material,
The average particle diameter (d50) of the graphite is in the range of 0.5 to 10 μm,
The graphite is a lithium ion secondary battery having a coating represented by Formula (3) or Formula (4) on the surface.

(In Formula 1, R ₁ , R ₂ and R ₃ are any of an alkyl group having 5 or less carbon atoms, a halogen group, a halogenated alkyl group having 5 or less carbon atoms, or hydrogen. R ₄ is an alkane group. (C _n H _{2n + 2} ), a halogenated alkane group, and R ₄ may be omitted, H may be substituted with halogen, and X is either an alkali metal or an alkaline earth metal N is the number of polymerizations.)

(R _{5 in} formula (2) is hydrogen, an alkali metal, an alkaline earth metal, or an alkyl group. X is an alkali metal or an alkaline earth metal.)

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