JP2013175313A - Lithium ion secondary battery, and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having a high capacity and excellent cycle characteristics, and a vehicle equipped with the lithium ion secondary battery.SOLUTION: The lithium ion secondary battery includes a positive electrode and a negative electrode. The positive electrode contains a positive electrode active material containing no Li, the negative electrode contains a negative electrode active material, and at least one of the positive electrode and the negative electrode contains a binder. The binder is a cured alkoxysilyl-containing resin with a structure represented by the formula (I): RSiO, where m represents an integer from 0 to 2, and Rrepresents an alkyl or aryl group with a carbon number of 8 or smaller.

Description

  The present invention relates to a lithium ion secondary battery and a vehicle equipped with the lithium ion secondary battery.

  As electronic devices become smaller and lighter, secondary batteries with high energy density are desired as power sources for electronic devices that are reduced in size and weight. A secondary battery having a high energy density in practical use is a lithium ion secondary battery. Among them, organic electrolyte-based lithium ion secondary batteries (hereinafter simply referred to as “lithium ion secondary batteries”) are in widespread use.

  In lithium ion secondary batteries, lithium-containing metal composite oxides such as lithium cobalt composite oxide are mainly used as the positive electrode active material, and lithium ion insertion and intercalation of lithium ions from the interlayer are used as the negative electrode active material. A carbon-based material having a multilayer structure capable of releasing is mainly used. The positive and negative electrode plates are produced as follows. An active material and a binder resin are dispersed in a solvent to form a slurry. The slurry is applied onto a metal foil as a current collector. The solvent of the slurry is removed by drying to form a mixture layer on the metal foil. The metal foil having the mixture layer formed on the surface is compression-molded with a roll press, and the binder resin is cured to produce positive and negative electrode plates.

  As a binder resin, polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) is frequently used for both electrodes. Since this PVdF is a fluorine-based resin, it is difficult for PVdF and the metal current collector to be in close contact with each other. Therefore, when PVdF is used for the binder resin, the active material may fall off from the current collector.

  In recent years, a negative electrode active material having a charge / discharge capacity that greatly exceeds the theoretical capacity of a carbon-based material has been developed as a negative electrode active material of a lithium ion secondary battery. For example, a material containing an element that can be alloyed with lithium, such as Si or Sn, is expected as a negative electrode active material. When a material containing Si or Sn is used for the negative electrode active material, the volume change of Si or Sn due to insertion / extraction of Li during charge / discharge is large. It is difficult to maintain a good binding state with the substance.

  As a result of earnest research, the inventors of the present invention have used a specific resin that has not been used as a binder resin for lithium ion secondary battery electrodes, that is, by using an alkoxysilyl group-containing resin as a binder resin for an electrode. It has been found that an electrode for a lithium ion secondary battery having excellent cycle characteristics can be provided by suppressing separation and dropping of the active material from the current collector.

  For example, as disclosed in Patent Document 1, by using an alkoxysilyl group-containing resin as an electrode binder resin, the cycle characteristics of a lithium ion secondary battery can be improved.

JP 2009-043678 A

  In recent years, with the expansion of applications of lithium ion secondary batteries, there is a demand for lithium ion secondary batteries that have a large charge / discharge capacity and are excellent in cycle characteristics. Conventionally, lithium-containing metal composite oxides such as lithium cobalt composite oxides are mainly used as positive electrode active materials. However, various positive electrode active materials have been studied for use in lithium ion secondary batteries.

  The present invention has been made in view of such circumstances, and lithium ions having a large charge / discharge capacity and excellent cycle characteristics can be obtained without using a lithium-containing metal composite oxide as a positive electrode active material. An object of the present invention is to provide a secondary battery and a vehicle equipped with the lithium ion secondary battery.

The lithium ion secondary battery of the present invention that solves the above problems is a lithium ion secondary battery having a positive electrode and a negative electrode, wherein the positive electrode has a positive electrode active material not containing Li, and the negative electrode is a negative electrode active material And at least one of the positive electrode and the negative electrode has a binder, and the binder is represented by the formula (I): R ¹ _m SiO _{(4-m) / 2} (m = integer of 0 to 2, R ¹ is carbon It is an alkoxysilyl group-containing resin cured product having a structure represented by the following formula (8).

  The positive electrode active material not containing Li means that, for example, a lithium-containing metal composite oxide generally used as a positive electrode active material is not used.

  The positive electrode active material not containing Li preferably contains at least one selected from simple sulfur, a composite of sulfur and carbon, manganese dioxide, and vanadium oxide.

Alkoxy having a structure in which the binder is represented by the formula (I): R ¹ _m SiO _{(4-m) / 2} (m = 0 to 2 integer, R ¹ represents an alkyl group or aryl group having 8 or less carbon atoms) By being a silyl group-containing resin cured product, the adhesion between the current collector or active material, which is an inorganic base material, and the binder is improved.

  As an alkoxysilyl group-containing resin cured product, an alkoxy group-containing silane-modified bisphenol A type epoxy resin cured product, an alkoxy group-containing silane-modified novolac-type epoxy resin cured product, an alkoxy group-containing silane-modified acrylic resin cured product, an alkoxy group-containing silane-modified phenol Cured resin, alkoxy group-containing silane-modified polyimide resin cured product, alkoxy group-containing silane-modified soluble polyimide resin cured product, alkoxy group-containing silane-modified polyurethane resin cured product, and alkoxy group-containing silane-modified polyamideimide resin cured product One can be used.

  By using the alkoxysilyl group-containing resin cured product for the binder, the binder has good adhesion to the current collector and the active material and is excellent in heat resistance.

  The binder is preferably obtained by curing an alkoxysilyl group-containing resin having a structure represented by the formula (II).

（Ｒ_１は、炭素数１〜８のアルキル基、Ｒ_２は、炭素数１〜８のアルキル基、又はアルコキシ基、ｑは１〜１００の整数）

(R ₁ is an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 1 to 8 carbon atoms or an alkoxy group, and q is an integer of 1 to 100)

  As alkoxysilyl group-containing resins, alkoxy group-containing silane-modified bisphenol A type epoxy resins, alkoxy group-containing silane-modified novolac type epoxy resins, alkoxy group-containing silane-modified acrylic resins, alkoxy group-containing silane-modified phenol resins, alkoxy group-containing silane-modified polyamics Any one selected from an acid resin, an alkoxy group-containing silane-modified soluble polyimide resin, an alkoxy group-containing silane-modified polyurethane resin, and an alkoxy group-containing silane-modified polyamideimide resin can be used.

  In particular, the alkoxysilyl group-containing resin is more preferably an alkoxy group-containing silane-modified polyamic acid resin or an alkoxy group-containing silane-modified polyamideimide resin. The alkoxy group-containing silane-modified polyamic acid resin and the alkoxy group-containing silane-modified polyamideimide resin have good workability and are easy to handle.

  The negative electrode active material preferably contains at least one of a carbon-based material, an element that can be alloyed with lithium, and an element compound that has an element that can be alloyed with lithium.

  The element that can be alloyed with lithium preferably contains Si and / or Sn.

  A vehicle according to the present invention includes the lithium ion secondary battery.

  The lithium ion secondary battery of the present invention has a large charge / discharge capacity and excellent cycle characteristics.

  Since the vehicle of the present invention is equipped with the lithium ion secondary battery, it can be equipped with a battery having excellent cycle characteristics and can be a high-performance vehicle.

The graph which compares the cycle characteristics of Test Examples 1-4 is shown. The graph which compares the charging / discharging curve of the 1st cycle test of the test example 1 and the test example 4 is shown.

(Lithium ion secondary battery)
The lithium ion secondary battery of the present invention has a positive electrode having a positive electrode active material not containing Li, and a negative electrode having a negative electrode active material.

  As the positive electrode active material not containing Li, it is preferable to use a material that can react with lithium (Li) and has a high potential during the reaction with lithium. As the positive electrode active material not containing Li, a metal compound or a polymer material can be used. Examples of the metal compound that can be used include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium sulfide and molybdenum sulfide, sulfur alone, and a composite of sulfur and carbon.

  The composite of sulfur and carbon refers to a composite in which sulfur is disposed in the pores of carbon and sulfur and carbon are combined, and acetylene black or mesoporous carbon can be used as the carbon. As the polymer material, for example, a conductive polymer such as polyaniline or polythiophene can be used.

  The positive electrode active material not containing Li preferably contains at least one selected from simple sulfur, a composite of sulfur and carbon, manganese dioxide, and vanadium oxide. By using these positive electrode active materials for the positive electrode, a lithium ion secondary battery having a large battery capacity can be obtained. For example, the charge / discharge capacity of a lithium ion secondary battery using sulfur alone as a positive electrode active material is about 6 times the charge / discharge capacity of a lithium ion secondary battery using lithium cobaltate, which is a common positive electrode material. .

  As the negative electrode active material, a carbon-based material that can occlude and release lithium, an element that can be alloyed with lithium, an elemental compound that has an element that can be alloyed with lithium, or a polymer material can be used.

  Examples of the carbon-based material include non-graphitizable carbon, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.

  Elements that can be alloyed with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge, Sn. , Pb, Sb, Bi may be included. Among them, the element capable of alloying lithium is preferably silicon (Si) or tin (Sn).

Examples of elemental compounds having elements that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO can be used. The elemental compound having an element capable of alloying with lithium is preferably a silicon compound or a tin compound. The silicon compound is preferably SiO _x (0.5 ≦ x ≦ 1.5). As the tin compound, for example, a tin alloy (Cu-Sn alloy, Co-Sn alloy, or the like) can be used.

Among these, the negative electrode active material may have silicon (Si), and may further have SiO _x (0.5 ≦ x ≦ 1.5). Silicon has a large theoretical capacity, but has a large volume change at the time of charge / discharge. Therefore, the volume change can be reduced by using SiO _x .

  As the polymer material, polyacetylene, polypyrrole, or the like can be used.

  In the lithium ion secondary battery of the present invention, a positive electrode active material is a combination of a material capable of reacting with lithium (Li) and having a high potential during reaction as a positive electrode active material, and a material having a low potential during reaction as a negative electrode active material. And a negative electrode active material are preferably used.

  Since the positive electrode active material does not contain Li, it is necessary to supply Li to the negative electrode active material from the outside. When a negative electrode active material that does not contain Li, for example, a carbon-based material, an element that can be alloyed with lithium, an elemental compound that has an element that can be alloyed with lithium, or a polymer material is used as the negative electrode active material, It is necessary to dope (insert) Li.

  As a method of doping Li into the negative electrode active material, a method of inserting Li into the negative electrode active material in advance (pre-doping) may be used, or Li may be inserted into the negative electrode active material when used as a battery. A method may be used.

  For example, as a method of pre-doping Li into the negative electrode active material, a half-cell is assembled using metallic lithium as the counter electrode, and Li is inserted by electrolytic doping method in which Li is electrochemically doped; a metallic lithium foil is attached to the electrode After that, there is a method in which Li is inserted by a pasting pre-doping method in which it is left in an electrolytic solution and doped using diffusion of lithium to the electrode. After inserting Li in advance by such a method, the battery may be configured in combination with the counter electrode.

  As a method for inserting Li into the negative electrode active material when used as a battery, there is a method in which a negative electrode is formed by previously integrating a Li source (for example, metal Li) on the surface and / or inside of the negative electrode. Can be used.

  The amount of Li pre-doped into the negative electrode active material or the amount of Li integrated into the negative electrode varies depending on the use conditions of the battery such as the positive electrode active material, the negative electrode active material, the electrolytic solution, and the like, and the voltage. . For this reason, the amount of Li may be obtained by actual measurement or calculation according to the configuration of the battery to be manufactured.

In the lithium ion secondary battery of the present invention, at least one of the positive electrode and the negative electrode has a binder. The binder has a structure represented by the formula (I): R ¹ _m SiO _{(4-m) / 2} (m = 0 to 2 and R ¹ represents an alkyl group or aryl group having 8 or less carbon atoms). It is an alkoxysilyl group-containing resin cured product.

The structure represented by the formula (I) is a gelled fine silica site structure (high-order network structure of siloxane bonds). This structure is a structure of an organosilicon polymer composed of a siloxane bond, and is a structure obtained by polycondensation of silanol of the following formula (A).
_{nR m Si (OH) 4-} m → (R m SiO (4-m) / 2) n ···· formula (A)
(R: organic group, m = 1 to 3, n> 1)
The alkoxysilyl group-containing resin cured product includes an alkoxy group-containing silane-modified bisphenol A-type epoxy resin cured product, an alkoxy group-containing silane-modified novolak-type epoxy resin cured product, an alkoxy group-containing silane-modified acrylic resin cured product, and an alkoxy group-containing silane-modified phenol. Any one selected from a cured resin, an alkoxy group-containing silane-modified polyimide resin cured product, an alkoxy group-containing silane-modified polyurethane resin cured product, and an alkoxy group-containing silane-modified polyamideimide resin cured product can be used.

  The binder is preferably obtained by curing an alkoxysilyl group-containing resin having a structure represented by the formula (II).

（Ｒ_１は、炭素数１〜８のアルキル基、Ｒ_２は、炭素数１〜８のアルキル基、又はアルコキシ基、ｑは１〜１００の整数）

(R ₁ is an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 1 to 8 carbon atoms or an alkoxy group, and q is an integer of 1 to 100)

  The structure represented by the formula (II) includes a sol-gel reaction site structure, and the alkoxysilyl group-containing resin is a hybrid of a resin that is an organic material and silica that is an inorganic material. Since the alkoxysilyl group-containing resin is a hybrid of resin and silica, it has good adhesion to any of the current collector, active material, and conductive additive, which are inorganic components. Can be held firmly.

The sol-gel reaction site structure is a structure that contributes to a reaction when performing the sol-gel method. In the sol-gel method, a solution of an inorganic or organometallic salt is used as a starting solution, this solution is converted into a colloidal solution (Sol) by hydrolysis and condensation polymerization reaction, and a solid (Gel) that loses fluidity by further promoting the reaction is obtained. It is a method of forming. In general, the sol-gel method uses a metal alkoxide (a compound represented by M (OR) _x , M is a metal, and R is an alkyl group) as a raw material. The compound represented by M (OR) _x reacts as shown in the following formula (B) by hydrolysis.

nM (OR) _x + nH ₂ O → nM (OH) (OR) _x−1 + nROH (B)
When the reaction shown here is further promoted, it finally becomes M (OH) _x , and when a polycondensation reaction occurs between the two molecules of hydroxide generated here, it reacts as shown in the following formula (C).

M (OH) _x + M (OH) _x → (OH) _x-1 M-OM (OH) _x-1 + H ₂ O (C)
At this time, all the OH groups can be polycondensed, and a dehydration condensation polymerization reaction with an organic polymer having an OH group at the terminal is also possible.

  Therefore, a sol-gel reaction also occurs when the binder resin is cured. The sol-gel reaction reacts between sol-gel reaction sites, and the sol-gel reaction site also reacts with the OH group of the resin. It is also conceivable that the sol-gel reaction site reacts with the current collector surface. Therefore, the alkoxysilyl group-containing resin can be strongly bound to the current collector and the active material.

  At this time, bisphenol A type epoxy resin, novolac type epoxy resin, acrylic resin, phenol resin, polyamic acid resin, soluble polyimide resin, polyurethane resin, and polyamideimide resin can be used as the resin that is an organic material. These resins and silica can be made into a hybrid having a structure represented by the formula (II) by a sol-gel method, and each alkoxy group-containing silane-modified bisphenol A type epoxy resin, alkoxy group-containing silane-modified novolak type epoxy resin, Alkoxy group-containing silane-modified acrylic resin, alkoxy group-containing silane-modified phenol resin, alkoxy group-containing silane-modified polyamic acid resin, alkoxy group-containing silane-modified soluble polyimide resin, alkoxy group-containing silane-modified polyurethane resin or alkoxy group-containing silane-modified polyamideimide resin It becomes.

  Each of the binder resins can be synthesized by a known technique. For example, when the binder resin is an alkoxy group-containing silane-modified polyamic acid resin, it can be formed by reacting a polyamic acid composed of a carboxylic acid anhydride component and a diamine component as a precursor with an alkoxysilane partial condensate. . The alkoxysilane partial condensate is obtained by partially condensing a hydrolyzable alkoxysilane monomer in the presence of an acid or base catalyst and water. At this time, the alkoxysilane partial condensate may be reacted with an epoxy compound in advance to form an epoxy group-containing alkoxysilane partial condensate and then reacted with a polyamic acid to form an alkoxy group-containing silane-modified polyamic acid resin.

  Moreover, a commercial item can be used suitably for said binder resin. For example, the trade name “COMPOCERAN E” (manufactured by Arakawa Chemical Industries), which is an alkoxy group-containing silane-modified bisphenol A type epoxy resin or an alkoxy group-containing silane-modified novolak type epoxy resin, and the trade name “COMPOCELAN”, which is an alkoxy group-containing silane-modified acrylic resin. AC ”(manufactured by Arakawa Chemical Industries Co., Ltd.), trade name“ Composeran P ”(manufactured by Arakawa Chemical Industries Co., Ltd.) which is an alkoxy group-containing silane-modified phenolic resin, and trade name“ Composeran H800 ”which is an alkoxy group-containing silane-modified polyamic acid resin ( Arakawa Chemical Industries, Ltd.), trade name “Composeran H700” (made by Arakawa Chemical Industries) which is an alkoxy group-containing silane-modified soluble polyimide resin, and trade name “Yuliano U” (Arakawa Chemical Industries, which is an alkoxy group-containing silane-modified polyurethane resin). Or alkoxy group A chromatic silane-modified polyamideimide resin has the trade name "Compoceran H900" (manufactured by Arakawa Chemical Industries, Ltd.) and the like various commercial products.

  The above-mentioned product name “COMPOCERAN E” (manufactured by Arakawa Chemical Industry Co., Ltd.), the product name “COMPOCELAN AC” (manufactured by Arakawa Chemical Industry Co., Ltd.), the product name “COMPOCERAN P” (manufactured by Arakawa Chemical Industries Ltd.), the product name “COMPOCERAN H800” ( The chemical formula of the basic skeleton of Arakawa Chemical Industries, Ltd.) or the trade name “COMPOCERAN H900” (Arakawa Chemical Industries, Ltd.) is shown below.

(Bisphenol A epoxy type trade name "Composeran E")

(Product name of phenol novolac epoxy type “COMPOCERAN E”)

(Product name “Composeran AC”)

(Product name “Composeran P”)

(Product name “Composeran H800”)

(Product name “Composeran H900”)

  At least one of the positive electrode and the negative electrode of these lithium ion secondary batteries can be produced by the following method. The manufacturing method of an electrode has an application | coating process and a hardening process. The coating process is a process of coating the binder resin and the active material described above on the surface of the current collector. Moreover, you may apply | coat a conductive support agent together in an application | coating process. The curing step is a step of curing the binder resin and binding the active material to the current collector surface.

  A current collector is a chemically inert electronic high conductor that keeps current flowing through an electrode during discharging or charging. The current collector can adopt a shape such as a foil or a plate, but is not particularly limited as long as it has a shape according to the purpose. As the current collector, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless steel foil can be suitably used.

  What is necessary is that the binder resin and the active material can be placed on the current collector. As a coating method, a coating method generally used for producing electrodes such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method can be used.

  A conductive additive can be applied to the surface of the current collector together with the active material. The conductive assistant is added to increase the conductivity of the electrode. Carbon black, graphite, acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (VGCF), etc., which are carbonaceous fine particles, are used alone or in combination as a conductive additive. Can be added. The amount of the conductive auxiliary agent used is not particularly limited, but can be, for example, about 20 to 100 parts by mass with respect to 100 parts by mass of the active material.

  The binder resin is used as a binder when these active materials and conductive assistants are applied to the current collector. The binder resin is required to bind the active material and the conductive assistant in as small an amount as possible, and the amount is desirably 0.5% by mass to 50% by mass of the total of the active material, the conductive auxiliary and the binder resin.

  In the coating step, the binder resin and the active material are mixed in advance, and a solvent or the like is added to form a slurry, which is then applied to the current collector. The conductive auxiliary agent may also be applied as a slurry. The coating thickness is preferably 10 μm to 300 μm. In addition, the mixing ratio of the binder resin and the active material is preferably by weight, and the active material: binder resin = 99: 1 to 70:30. The mixing ratio in the case of containing a conductive auxiliary agent is preferably active material: conductive auxiliary agent: binder resin = 98: 1: 1 to 60:20:20.

  The curing step is a step of curing the binder resin. The active material is bound to the current collector surface by curing the binder resin. When the conductive assistant is included, the conductive assistant is also bound in the same manner. What is necessary is just to harden | cure binder resin according to the hardening conditions of binder resin to be used. Further, when the binder resin is cured, a sol-gel curing reaction is also caused by the structure represented by the formula (II) of the binder resin. Since the alkoxysilyl group-containing resin in which the sol-gel curing reaction has occurred has a fine gelled silica site structure (high-order network structure of siloxane bonds), it has good adhesion to the active material, the conductive auxiliary agent and the current collector.

  The lithium ion secondary battery of the present invention uses a separator and an electrolyte in addition to the above-described positive electrode and negative electrode as battery components.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. As the separator, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramics can be used.

  As the electrolytic solution, an electrolytic solution that can be used for a lithium ion secondary battery can be used. The electrolytic solution includes a solvent and an electrolyte dissolved in the solvent.

  For example, cyclic esters, chain esters, and ethers can be used as the solvent. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers that can be used include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, and the like.

As the electrolyte dissolved in the electrolytic solution, for example, a lithium salt such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ can be used.

For example, as an electrolytic solution, 0.5 mol / l to 1.7 mol / l of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 in} a solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and dimethyl carbonate. A solution dissolved at a certain concentration can be used.

(vehicle)
The vehicle of the present invention is equipped with the lithium ion secondary battery. The vehicle of the present invention can be equipped with a lithium ion secondary battery having excellent cycle characteristics and can be a high-performance vehicle. The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, a forklift, an electric wheelchair, an electric assist. Bicycles and electric motorcycles are examples.

  As mentioned above, although the lithium ion secondary battery of this invention and embodiment of the vehicle were demonstrated, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to examples. The lithium ion secondary battery of this invention was produced as follows, and the charge / discharge cycle test was done using the model battery for evaluation. In the test, a negative electrode of a lithium ion secondary battery was used as an evaluation electrode, and a coin-type lithium ion secondary battery was used.
<Production of electrode for evaluation>
(Negative electrode 1, negative electrode 2, negative electrode 3, and negative electrode 4)
Si powder was used as the negative electrode active material. Si particles (manufactured by High-Purity Chemical) having a particle diameter of 4 μm or less were prepared as Si powder. To 85 parts by weight of Si powder, 10 parts by weight of a paste in which a binder resin was dissolved in N-methylpyrrolidone (NMP) and 5 parts by weight of ketjen black (KB) were added and mixed to prepare a slurry.

  The negative electrode 1 has an alkoxy group-containing silane-modified polyamideimide resin (trade name Composeran, product number H901-2, solvent composition: NMP / xylene (Xyl), curing residue 30%, viscosity 8000 mPas as a binder resin. -S, silica in the cured residue, 2 wt%, and the cured residue means a resin-cured solid content excluding volatile components). The alkoxy group-containing silane-modified polyamideimide resin used in the negative electrode 1 is one of the above-mentioned trade name Composeran H900 series and has the structure shown in [Chemical Formula 7].

  The negative electrode 2 has an alkoxy-containing silane-modified polyamic acid resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name Composeran, product number H850D, solvent composition: N, N-dimethylacetamide (DMAc), 15% cure residue, viscosity 5000 mPa as binder resin. S, silica in the cured residue, 2 wt%). The alkoxy-containing silane-modified polyamic acid resin used in the negative electrode 2 is one of the above-mentioned trade name Composeran H800 series and has the structure shown in [Chemical Formula 6].

  The negative electrode 3 used PVdF (made by Kureha) as a binder resin. The negative electrode 4 used polyamideimide resin (made by Arakawa Chemical Industries) as binder resin.

After the slurry was adjusted, the slurry was placed on an electrolytic copper foil having a thickness of 20 μm, and a film was formed on the copper foil using a doctor blade. After the obtained sheet was dried at 80 ° C. for 20 minutes to volatilize and remove NMP, the current collector made of electrolytic copper foil and the negative electrode layer made of the above composite powder were firmly adhered and bonded by a roll press machine. I let you. This was extracted with a 1 cm ² circular punch, the negative electrode 1 and the negative electrode 2 were vacuum dried at 200 ° C. for 3 hours, the negative electrode 3 was 140 ° C. for 3 hours, and the negative electrode 4 was vacuum dried at 200 ° C. for 3 hours. It was.

<Production of coin-type battery>
(Test Example 1, Test Example 2, Test Example 3, Test Example 4)
The above-described electrodes (negative electrode 1, negative electrode 2, negative electrode 3 and negative electrode 4) were used as negative electrodes, lithium metal was used as a counter electrode, and 1 mol of LiPF ₆ / ethylene carbonate (EC) + diethyl carbonate (DEC) ( A coin-type model battery (CR2032 type) was produced in a dry room using an EC: DEC = 1: 1 (volume ratio) solution as an electrolyte. A coin-type model battery is a model of Test Example 1 to Test Example 4 in which a spacer, a Li foil with a thickness of 500 μm as a counter electrode, a separator (trade name Celgard # 2400 manufactured by Celgard), and each negative electrode are sequentially stacked and caulked. A battery was produced.

Example 1
A half cell was assembled using the negative electrode 2 and a metal lithium foil, and a negative electrode 21 in which Li was inserted by pre-doping at a temperature of 25 ° C., a rate of 1/100 C, and a cutoff of 0 CV to 0.01 V was prepared.

A 20 μm aluminum foil is prepared as a current collector, vanadium oxide (V ₂ O ₅ ) is prepared as a positive electrode active material, polyvinylidene fluoride (PVDF) is prepared as a binder resin, and the positive electrode 1 is prepared in the same manner as the negative electrode. Produced. A model battery of Example 1 was produced in the same manner as in Test Example 1 except that the negative electrode 21 and the positive electrode 1 were used.
<Coin-type battery evaluation>
This model battery was evaluated by the following method. First, the model battery was discharged at a constant current of 0.2 mA until reaching 0 V, and after resting for 5 minutes, it was charged until it reached 2.0 V at a constant current of 0.2 mA. This was made into 1 cycle, charging / discharging was performed repeatedly and the discharge capacity was investigated.

  About the model battery of Test Examples 1-4, the graph which shows the cycle number and discharge capacity is shown in FIG. As can be seen from FIG. 1, the model batteries of Test Example 1 and Test Example 2 have a smaller decrease in initial discharge capacity than the model batteries of Test Example 3 and Test Example 4.

  The model battery of Test Example 3 using PVdF, which is a conventional binder resin, as the binder resin for the negative electrode shows a sudden drop in discharge capacity to about 10% in one cycle test, whereas Test Model 1 and Test In the model battery of Example 2, the discharge capacity was maintained by about 70 to 80%. Moreover, the discharge capacity after 20 cycles of the model batteries of Test Example 3 and Test Example 4 is 0, whereas the discharge capacity after 20 cycles of the model battery of Test Example 2 is maintained at 10% or more. It was.

  When the active material is Si particles, the initial discharge capacity exceeds 3000 mAh / g. When graphite is used as the active material, the initial discharge capacity is usually 400 mAh / g or less. In the model battery of Test Example 2, the discharge capacity after 20 cycles is about 375 mAh / g. This discharge capacity value is not much different from the initial discharge capacity of a battery using graphite as an active material.

  The binder resin of the negative electrode 1 in the model battery of Test Example 1 is an alkoxy group-containing silane-modified polyamideimide resin, and the polyamideimide resin contains 2% of silica, whereas the negative electrode in the model battery of Test Example 4 The binder resin 4 is a polyamide-imide resin and does not contain silica. As shown in FIG. 1, it was found that the discharge characteristics of the model battery of Test Example 1 were superior to the discharge characteristics of the model battery of Test Example 4. A comparison of the charge / discharge curves of the first cycle test of the model battery of Test Example 1 and the model battery of Test Example 4 is shown in FIG. As can be seen from FIG. 2, the discharge characteristics at the first cycle of the model battery of Test Example 1 were almost twice as good as the model battery of Test Example 4. The model battery of Example 1 using vanadium oxide as the positive electrode active material is considered to have the same effect as the model battery of Test Example 2.

Claims (8)

A lithium ion secondary battery having a positive electrode and a negative electrode,
The positive electrode has a positive electrode active material containing no Li,
The negative electrode has a negative electrode active material,
At least one of the positive electrode and the negative electrode has a binder,
The binder has a structure represented by the formula (I): R ¹ _m SiO _{(4-m) / 2} (m = 0 to 2 and R ¹ represents an alkyl group or aryl group having 8 or less carbon atoms). A lithium ion secondary battery, which is an alkoxysilyl group-containing resin cured product.   2. The lithium ion secondary battery according to claim 1, wherein the positive electrode active material includes at least one selected from simple sulfur, a composite of sulfur and carbon, manganese dioxide, and vanadium oxide.   The alkoxysilyl group-containing resin cured product is an alkoxy group-containing silane-modified bisphenol A type epoxy resin cured product, an alkoxy group-containing silane-modified novolak type epoxy resin cured product, an alkoxy group-containing silane-modified acrylic resin cured product, or an alkoxy group-containing silane-modified product. Any one selected from a cured phenol resin, a cured silane-modified polyimide resin containing an alkoxy group, a cured silane-modified soluble polyimide resin containing an alkoxy group, a cured silane-modified polyurethane resin containing an alkoxy group, and a cured silane-modified polyamideimide resin containing an alkoxy group The lithium ion secondary battery according to claim 1 or 2, wherein the number is one. The lithium ion secondary battery according to claim 1, wherein the binder is obtained by curing an alkoxysilyl group-containing resin having a structure represented by the formula (II).

(R ₁ is an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 1 to 8 carbon atoms or an alkoxy group, and q is an integer of 1 to 100)   The alkoxysilyl group-containing resin includes an alkoxy group-containing silane-modified bisphenol A type epoxy resin, an alkoxy group-containing silane-modified novolac type epoxy resin, an alkoxy group-containing silane-modified acrylic resin, an alkoxy group-containing silane-modified phenol resin, and an alkoxy group-containing silane-modified resin. 5. The lithium ion secondary battery according to claim 4, which is any one selected from a polyamic acid resin, an alkoxy group-containing silane-modified soluble polyimide resin, an alkoxy group-containing silane-modified polyurethane resin, and an alkoxy group-containing silane-modified polyamideimide resin.   The lithium ion according to claim 1, wherein the negative electrode active material includes at least one of a carbon-based material, an element that can be alloyed with lithium, and an elemental compound that has an element that can be alloyed with lithium. Secondary battery.   The lithium ion secondary battery according to claim 6, wherein the element that can be alloyed with lithium includes Si and / or Sn.   A vehicle equipped with the lithium ion secondary battery according to claim 1.

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