JP6690381B2 - Negative electrode active material for non-aqueous electrolyte secondary battery and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an alkali metal salt-containing silicon oxycarbide suitable as a negative electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same.

  With the recent miniaturization and higher performance of portable electronic devices, there is a demand for higher capacity of lithium ion secondary batteries mounted therein. As a means for increasing the capacity of lithium-ion secondary batteries, silicon, germanium, tin and their metal oxides, alloys, and metal oxycarbides, which have higher capacities than graphite currently used as the negative electrode active material, are used as the negative electrode active material. It is being considered for use. Among them, silicon and silicon oxide (SiO) have attracted attention as a next-generation negative electrode active material because they have a high capacity. However, since silicon and silicon oxide have a high volume expansion coefficient when occluding lithium, they are greatly deteriorated by charging and discharging, and the cycle characteristics are insufficient. As described above, in the demand for an active material having both cycle characteristics and high capacity, the capacity is not higher than that of silicon or silicon oxide, but the volume expansion coefficient due to lithium occlusion is suppressed to be low and stable. Silicon oxycarbide (SiOC), which exhibits cycle characteristics, is drawing attention (Patent Document 1).

  On the other hand, silicon oxycarbide has a low initial coulombic efficiency, which is a major obstacle to its practical application. In order to improve the initial Coulombic efficiency, a technique called lithium doping in which lithium is added to the active material in advance has been studied. It is known that the initial Coulombic efficiency is improved by using this technique for silicon oxycarbide (Patent Document 2). However, in the lithium-doped silicon oxycarbide prepared by the conventional technique, highly reactive lithium remains in the substance, so that oxygen in water or air easily reacts with lithium. Therefore, it cannot be handled in the air, and since an aqueous binder that is generally used in the negative electrode manufacturing process cannot be used, there is a problem in practical use.

JP, 2006-062949, A JP, 2007-294422, A

  In view of the above circumstances, the problem to be solved by the present invention is to have a high capacity, an excellent initial Coulombic efficiency, and be suitable as an active material of a non-aqueous electrolyte secondary battery negative electrode that can be handled in the atmosphere. It is to provide a material, and further to provide a method for producing the material, a negative electrode using the active material, and a non-aqueous electrolyte secondary battery having the negative electrode.

  In order to solve the above-mentioned problems, the present inventors have made intensive studies by paying attention to the existence of an irreversible lithium storage site contained in lithium-doped silicon oxycarbide, and eliminating this irreversible lithium storage site. Thus, it is possible to provide a material for obtaining a highly practical negative electrode active material such that there is no problem in handling in the air and an aqueous binder can be adopted, and when the material is used as the negative electrode active material. In addition, they found that the same excellent initial Coulombic efficiency as that obtained by using the active material obtained by the lithium doping technique can be obtained, and completed the present invention.

  The present invention provides a negative electrode active material for a non-aqueous electrolyte secondary battery, which contains silicon oxycarbide and an alkali metal salt.

  The present invention also provides a method for producing the negative electrode active material for the non-aqueous electrolyte secondary battery.

  Further provided are a non-aqueous electrolyte secondary battery negative electrode using the negative electrode active material for the non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery having the negative electrode.

That is, the present invention relates to the following items 1 to 12.
Item 1. A negative electrode active material for a non-aqueous electrolyte secondary battery, which contains silicon oxycarbide and an alkali metal salt.
Item 2.
Item 2. The negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 1, wherein the silicon oxycarbide is represented by a composition formula of SiOyCz (0 <y <3, 0 <z <10).
Item 3.
Item 2. The negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 1, wherein the alkali metal of the alkali metal salt is lithium or sodium.
Item 4.
The content of the alkali metal salt is such that the ratio of the silicon atom (Si) in the silicon oxycarbide and the alkali metal atom (MA) in the alkali metal salt can be expressed in the range of 0 <MA / Si <10. The negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 1.
Item 5.
Item 4. A negative electrode for a non-aqueous electrolyte secondary battery, comprising the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of items 1 to 4 and a binder.
Item 6.
Item 6. A non-aqueous electrolyte secondary battery having the negative electrode for a non-aqueous electrolyte secondary battery according to Item 5.
Item 7.
A step (1) of mixing silicon oxycarbide and an alkali metal source containing at least one selected from the group consisting of alkali metals and alkali metal compounds to obtain an alkali metal-containing silicon oxycarbide;
A non-aqueous electrolyte (2) comprising a step (2) of washing the alkali metal-containing silicon oxycarbide obtained in the step (1) with at least one selected from the group consisting of alcohol, water and an acidic solution. Manufacturing method of negative electrode active material for secondary battery.
Item 8.
Item 8. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 7, wherein the alkali metal source is at least one selected from the group consisting of lithium, sodium, lithium metal compounds and sodium metal compounds. Method.
Item 9.
Item 8. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 7, wherein the alcohol is an alcohol having a boiling point of 200 ° C or lower.
Item 10.
Item 8. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 7, wherein the acidic solution is at least one kind of solution selected from the group consisting of inorganic acids, sulfonic acids and carboxylic acids.
Item 11.
A step (1) of mixing silicon oxycarbide and an alkali metal source containing at least one selected from the group consisting of alkali metals and alkali metal compounds to obtain an alkali metal-containing silicon oxycarbide;
A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, comprising a step (2) of heating the alkali metal-containing silicon oxycarbide obtained in the step (1) in an oxygen atmosphere or a nitrogen atmosphere.
Item 12.
Item 12. The negative electrode active material for a non-aqueous electrolyte secondary battery according to Item 11, wherein the alkali metal source is at least one selected from the group consisting of lithium, sodium, lithium metal compounds and sodium metal compounds. Method.

  The active material for a non-aqueous electrolyte secondary battery negative electrode containing the silicon oxycarbide and the alkali metal salt of the present invention has high safety and is easy to handle in the air, and therefore has good workability during battery production. Aqueous binders that have been improved and are commonly used in the production of negative electrodes can also be employed. Furthermore, the active material exhibits excellent battery characteristics. Specifically, it has a high capacity and excellent initial Coulombic efficiency. As described above, the present invention exerts a particularly remarkable effect capable of achieving the battery characteristics equivalent to those of the conventionally known lithium doping method while ensuring safety. Further, according to the present invention, an active material for a non-aqueous electrolyte secondary battery negative electrode containing silicon oxycarbide and an alkali metal salt having the above excellent properties can be easily produced.

  Hereinafter, the present invention will be described in detail.

  The present invention is a negative electrode active material for a non-aqueous electrolyte secondary battery, which contains silicon oxycarbide and an alkali metal salt.

First, technical terms used in the present invention will be described.
<Silicon oxycarbide>
Silicon oxycarbide (also referred to as SiOC) used in the present invention is obtained by thermally decomposing a silicon-containing composite resin. The silicon oxycarbide thus obtained contains silicon, carbon and oxygen in a wide range of combination ratios. The composition of silicon oxycarbide can be represented as SiOyCz, and is preferably silicon oxycarbide represented by the composition formula of SiOyCz (0 <y <3, 0 <z <10), and SiOyCz (0 <y <2 , 0 <z <10) is more preferable.

  Here, the silicon-containing composite resin is a resin containing at least one of polycarbosilane, polysilazane, polysilane, and polysiloxane segment.

  Examples of the method for producing silicon oxycarbide used in the present invention include the following methods.

  In Examples described later, a silicon-containing composite resin (A containing a silanol group and / or a hydrolyzable silyl group, a polysiloxane segment (a1), and a polymer segment (a2) other than the polysiloxane segment (a1). ) Is obtained by thermal decomposition of silicon oxycarbide. It is preferable to use one in which the polysiloxane segment (a1) is a polysiloxane segment having a structural unit represented by the following general formula (S-2) and / or the following general formula (S-3).

(In the general formulas (S-2) and (S-3), R ³ , R ⁴ and R ⁵ are each independently an alkyl group having 1 to 6 carbon atoms, and 3 to 8 carbon atoms. It represents a cycloalkyl group, an aryl group or an aralkyl group having 7 to 12 carbon atoms.)
In this case, the content of the polysiloxane segment (a1) is preferably 10 to 95 mass% with respect to the silicon-containing composite resin (A). Further, the polymer segment (a2) is preferably a vinyl polymer segment. Furthermore, it is preferable that the silicon-containing composite resin (A) is a composite resin in which a polysiloxane segment (a1) and a polymer segment (a2) are bonded in a structure represented by the following structural formula (S-5). .

(In the formula, carbon atoms are carbon atoms constituting the polymer segment (a2), and two silicon atoms are silicon atoms constituting the polysiloxane segment (a1).)

  Examples of the silicon-containing composite resin (A) used herein include, for example, a composite resin having a graft structure in which the polysiloxane segment (a1) is chemically bonded to a side chain of the polymer segment (a2), and the polymer segment. Examples thereof include a composite resin having a block structure in which the polysiloxane segment (a1) is chemically bonded to the end of (a2).

  The polysiloxane segment (a1) included in the silicon-containing composite resin (A) may have a functional group capable of reacting by heating such as a polymerizable double bond in the polysiloxane segment (a1). By heat-treating the silicon-containing composite resin (A) before thermal decomposition, the crosslinking reaction proceeds, and by making it solid, the thermal decomposition treatment can be easily performed.

  Examples of the polymerizable double bond include a vinyl group and a (meth) acryloyl group. Two or more polymerizable double bonds are preferably present in the polysiloxane segment (a1), more preferably 3 to 200, and even more preferably 3 to 50. Further, by using a composite resin having two or more polymerizable double bonds as the silicon-containing composite resin (A), the crosslinking reaction can easily proceed.

  The polysiloxane segment (a1) has a silanol group and / or a hydrolyzable silyl group. In parallel with the thermosetting reaction, a hydrolysis-condensation reaction proceeds between the hydroxyl group in the silanol group and the hydrolyzable group in the hydrolyzable silyl group to crosslink the polysiloxane structure of the obtained coating film. The reaction proceeds, and a solid silicon-containing composite resin (A) can be obtained.

  The silanol group referred to in the present invention is a silicon-containing group having a hydroxyl group directly bonded to a silicon atom. The hydrolyzable silyl group referred to in the present invention is a silicon-containing group having a hydrolyzable group directly bonded to a silicon atom, and specific examples thereof include groups represented by the following general formula.

(In the formula, R ¹ represents a monovalent organic group such as an alkyl group, an aryl group or an aralkyl group, and R ² represents a halogen atom, an alkoxy group, an acyloxy group, an aryloxy group, a mercapto group, an amino group, an amide group, an amino group. It is an oxy group, an iminooxy group or an alkenyloxy group, and b is an integer of 0 to 2.)

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 1, 1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1-ethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethyl Examples include 2-methylpropyl group and 1-ethyl-1-methylpropyl group.

  Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group and a 3-isopropylphenyl group.

  Examples of the aralkyl group include a benzyl group, a diphenylmethyl group, a naphthylmethyl group and the like.

  Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

  Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a second butoxy group, and a third butoxy group.

  Examples of the acyloxy group include formyloxy, acetoxy, propanoyloxy, butanoyloxy, pivaloyloxy, pentanoyloxy, phenylacetoxy, acetoacetoxy, benzoyloxy, naphthoyloxy and the like.

  Examples of the aryloxy group include phenyloxy and naphthyloxy.

  Examples of the alkenyloxy group include a vinyloxy group, an allyloxy group, a 1-propenyloxy group, an isopropenyloxy group, a 2-butenyloxy group, a 3-butenyloxy group, a 2-petenyloxy group, a 3-methyl-3-butenyloxy group, 2-hexenyloxy group etc. are mentioned.

  Examples of the hydrolyzable group in the hydrolyzable silyl group contained in the polysiloxane segment (a1) include, for example, a halogen atom, an alkoxy group, a substituted alkoxy group, an acyloxy group, a phenoxy group, a mercapto group, an amino group and an amide group. , An aminooxy group, an iminooxy group, an alkenyloxy group, and the like, and by hydrolyzing these groups, the hydrolyzable silyl group becomes a silanol group. Then, the hydroxyl group of this silanol group is used for dehydration condensation, and the crosslinking reaction of the polysiloxane segment (a1) portion proceeds.

  The polysiloxane segment (a1) is preferably a polysiloxane segment having a structural unit represented by the following general formula (S-2) and / or the following general formula (S-3). The polysiloxane segment having the structural unit represented by the following general formula (S-2) and / or the following general formula (S-3) has a three-dimensional network polysiloxane structure. Therefore, it becomes possible to obtain silicon oxycarbide by thermally decomposing the silicon-containing composite resin (A) having such a polysiloxane segment as the composite resin.

(In the general formulas (S-2) and (S-3), R ³ , R ⁴ and R ⁵ are each independently an alkyl group having 1 to 6 carbon atoms, and 3 to 8 carbon atoms. It represents a cycloalkyl group, an aryl group or an aralkyl group having 7 to 12 carbon atoms.)

Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert- butyl group, a pentyl group, an isopentyl group, Neopentyl group, tert-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1-ethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2 -Trimethylpropyl group, 1-ethyl-2-methylpropyl group, 1-ethyl-1-methylpropyl group and the like can be mentioned.

  Examples of the cycloalkyl group having 3 to 8 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group and the like.

  Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group and a 3-isopropylphenyl group.

  Examples of the aralkyl group having 7 to 12 carbon atoms include benzyl group, diphenylmethyl group and naphthylmethyl group.

  Examples of the polysiloxane segment having a structural unit represented by the general formula (S-2) and / or the following general formula (S-3) include those having the following structures.

  Examples of the polymer segment (a2) other than the polysiloxane segment (a1) included in the silicon-containing composite resin (A) include an acrylic polymer, a fluoroolefin polymer, a vinyl ester polymer, an aromatic vinyl polymer, Examples thereof include vinyl polymer segments such as polyolefin polymers, and polymer segments such as polyurethane polymer segments, polyester polymer segments and polyether polymer segments. Of these, vinyl polymer segments are preferred.

  The polymer segment (a2) may have various functional groups as needed, as long as the effects of the present invention are not impaired. Examples of such functional groups include carboxyl groups, blocked carboxyl groups, carboxylic acid anhydride groups, tertiary amino groups, hydroxyl groups, blocked hydroxyl groups, cyclocarbonate groups, epoxy groups, carbonyl groups, primary amide groups, and secondary amide groups. An amide, a carbamate group, a functional group represented by the following structural formula (S-4), and the like can be used.

  Further, the polymer segment (a2) may have a polymerizable double bond such as a vinyl group or a (meth) acryloyl group.

  The silicon-containing composite resin (A) used in the present invention is a composite resin in which a polysiloxane segment (a1) and a polymer segment (a2) are bonded in a structure represented by the following structural formula (S-5) or the following structure Examples thereof include a composite resin bonded with the structure represented by the formula (S-6).

  In the structural formula (S-5), carbon atoms are carbon atoms constituting the polymer segment (a2), and two silicon atoms are silicon atoms constituting the polysiloxane segment (a1).)

  In the structural formula (S-6), the carbon atom is a carbon atom forming the polymer segment (a2), and the silicon atom is a silicon atom forming the polysiloxane segment (a1).

  The silicon-containing composite resin (A) used in the present invention can be manufactured by a known method, but it is preferable to manufacture it by the methods shown in the following (1) to (3). However, it is not limited to these.

  (1) As a raw material for the polymer segment (a2), a polymer segment (a2-1) containing a silanol group and / or a hydrolyzable silyl group is prepared in advance, and the polymer segment (a2-1) is prepared. ) And a silane compound containing a silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond, and performing a hydrolytic condensation reaction.

  (2) As a raw material of the polymer segment (a2), a polymer segment (a2-1) containing a silanol group and / or a hydrolyzable silyl group is prepared in advance. Further, a polysilane (a1-1) is prepared in advance by subjecting a silane compound containing a silane compound having a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond to hydrolysis and condensation reaction. Then, the polymer segment (a2-1) and the polysiloxane (a1-1) are mixed, and a hydrolysis condensation reaction is performed.

  (3) A silane compound containing the polymer segment (a2-1), a silane compound having a silanol group and / or a hydrolyzable silyl group, and a polymerizable double bond, and a polysiloxane (a1-1). A method of mixing with and performing a hydrolysis condensation reaction.

  The silicon oxycarbide may further include graphitic particles. The graphite particles (graphitic substance) are roughly classified into artificial graphite and natural graphite, but from the viewpoint of battery capacity and purity, artificial graphite is preferable.

  The silicon oxycarbide may further contain silicon particles. As the silicon, any of relatively low-purity silicon commercially available for industrial use to high-purity silicon used as a material for electronic parts can be used. The volume average particle diameter of the silicon particles is preferably 0.01 μm to 20 μm, more preferably 0.05 μm to 10 μm, further preferably 0.1 μm to 5 μm, and particularly preferably 0.1 μm to 1 μm. is there. When the volume average particle diameter of the silicon particles is in the range of 0.01 μm to 20 μm, it can be used as a negative electrode material for a lithium ion secondary battery exhibiting high initial charge / discharge efficiency and excellent cycle characteristics. When the volume average particle diameter is 0.01 μm or more, the productivity and handleability of silicon particles are improved.

  The thermal decomposition can be carried out by a known and commonly used method, and there is no particular limitation. For example, the temperature can be raised at 5 ° C. per minute in an inert gas atmosphere and the thermal decomposition can be carried out at the following temperature. it can.

  The temperature of the thermal decomposition is not limited, but preferably 500 to 1500 ° C., more preferably 600 to 1500 ° C., and particularly preferably 600 to 1300 ° C.

  Examples of the inert gas include nitrogen, helium, argon and the like. The inert gas may include a reducing gas such as hydrogen gas.

  When the final temperature reaches 1500 ° C. or higher, the growth of silicon carbide is promoted, which is not preferable. On the other hand, when the final temperature reached is lower than the lower limit of the above range, carbonization of the organic component becomes insufficient. The thermal decomposition step may be performed in two or more steps. That is, in the first stage, thermal decomposition can be performed at a temperature lower than the final reached temperature for a certain period of time and then again heated to perform thermal decomposition.

  The heat treatment can be performed in a fixed-bed or fluidized-bed carbonization furnace, and the heating system and type of the carbonization furnace are not particularly limited as long as the furnace has a function of raising the temperature to a predetermined temperature. Examples of the carbonization furnace include a lead hammer furnace, a tunnel furnace, and a single furnace.

  Specific examples of the alkali metal salt contained in the negative electrode active material of the present invention include silicates, carbonates, hydroxides, halides, sulfates, nitrates, phosphates, sulfonates, carboxylates and alkoxides. And so on. Specific examples of the silicate include lithium orthosilicate, lithium metasilicate, sodium orthosilicate, sodium metasilicate, potassium orthosilicate, potassium metasilicate and the like. Specific examples of the carbonate include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate and the like. Specific examples of the hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide and cesium hydroxide. Specific examples of the halide, lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, lithium bromide, sodium bromide, Examples thereof include potassium bromide, rubidium bromide, cesium bromide, lithium iodide, sodium iodide, potassium iodide, rubidium iodide and cesium iodide. Specific examples of the sulfate include lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, and cesium sulfate. Specific examples of the nitrate include lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate and the like. Specific examples of the phosphate include lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate and the like. Specific examples of the sulfonate include lithium methanesulfonate, sodium methanesulfonate, lithium benzenesulfonate, sodium benzenesulfonate, lithium p-toluenesulfonate, sodium p-toluenesulfonate, potassium p-toluenesulfonate, and the like. Can be mentioned. Specific examples of the carboxylate, lithium formate, sodium formate, potassium formate, lithium acetate, sodium acetate, potassium acetate, lithium propionate, sodium propionate, potassium propionate, lithium benzoate, sodium benzoate, potassium benzoate, Examples thereof include lithium oxalate, sodium oxalate, potassium oxalate, lithium citrate, sodium citrate, potassium citrate, lithium tartrate, sodium tartrate and potassium tartrate.

  The alkali metal salt contained may be a single kind or two or more kinds of alkali metal salts.

The content of the alkali metal salt contained in the negative electrode active material of the present invention is such that the ratio of the silicon atom (Si) in silicon oxycarbide to the alkali metal atom (MA) in the alkali metal salt is 0 <MA / Si <10. It is preferable to contain it in the range of 0, and it is more preferable to contain it in the range of 0 <MA / Si <2.
<Lithium dope>
In the present invention, lithium dope is expressed by various words such as metallic lithium and / or a lithium compound, which occludes lithium in the active material (lithiatenization, intercalation, dope, insertion, occlusion, loading, alloying, etc. However, these are collectively referred to as “dope” in the present invention, and will be described).
<Deactivation>
The term "deactivated" used in the manufacturing process of the present invention means that the alkali metal doped in the active material is oxidized to become an alkali metal ion. Alkali metal ions are in a salt state, and are present as silicates, carbonates, hydroxides, halides, sulfates, nitrates, phosphates, sulfonates, carboxylates, alkoxides and the like. In order to confirm whether or not the alkali metal in the silicon oxycarbide is deactivated, it can be confirmed by adding water to the silicon oxycarbide and not generating hydrogen. When the alkali metal remains, the alkali metal reacts with water to form hydrogen and a hydroxide of the alkali metal.

  An example of the method for producing the negative electrode active material containing the silicon oxycarbide and the alkali metal salt of the present invention will be described below, but the present invention is not limited thereto.

Silicon oxycarbide is reacted with an alkali metal source containing at least one selected from the group consisting of alkali metals and alkali metal compounds to obtain a reaction product (step 1), and the obtained reaction product is alcohol, water. And at least one selected from the group consisting of acidic solutions (step 2).
<Step 1>
In the manufacturing method of the present invention, <Step 1> will be described below. In this step, silicon oxycarbide is reacted with an alkali metal and / or an alkali metal compound in an inert gas to obtain a reaction product obtained by doping silicon oxycarbide with an alkali metal. An organic solvent can be used during this reaction.

  The method of reacting silicon oxycarbide with an alkali metal is not particularly limited, for example, a method of reacting silicon oxycarbide with lithium naphthalenide in an tetrahydrofuran atmosphere in tetrahydrofuran, or a method of reacting silicon oxycarbide with lithium metal in an argon atmosphere. It can be carried out by a method of mixing and reacting with a device such as a ball mill that applies high shear stress.

The form of silicon oxycarbide is not particularly limited, but it is appropriately selected from spherical particles, amorphous particles, fibrous forms, etc., and can be used for electrode production without a step such as pulverization. It is preferably determined in consideration of the thickness, density (porosity) of the electrode, the input / output characteristics of the intended electricity storage device, reliability, safety, and the like. For example, the spherical particles, the average particle size in the case of irregular particles, or the average fiber length of the fibrous material is preferably usually 50 μm or less, more preferably 30 μm or less, further preferably 10 μm or less, The lower limit is practically 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.5 μm or more.

  Examples of the alkali metal source used here include lithium, sodium, lithium metal compounds, and sodium metal compounds. Examples of lithium metal compounds include lithium naphthalenide, lithium biphenylide, lithium hydride, butyllithium, phenyllithium and the like. Examples of sodium metal compounds include sodium naphthalenide, sodium biphenylide, sodium hydride and the like. These may be used alone or in a suitable combination of two or more.

  The inert gas used here may be a mixed gas of one or more selected from the group consisting of argon, nitrogen, neon, helium and krypton.

  The organic solvent is one kind or a mixture of two or more kinds selected from carbonates, lactones, sulfones, ethers, esters and hydrocarbons, and preferably carbonates, lactones, sulfones and ethers. It is one kind or a mixture of two or more kinds selected. Specifically, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, carbonates such as methyl ethyl carbonate, tetrahydrofuran, dimethoxyethane, diethylene glycol dimethyl ether, ethers such as dioxane, lactones such as γ-butyrolactone, sulfolane, diether An organic solvent composed of one or more sulfones such as propyl sulfone can be used. It is also possible to use hydrocarbons such as hexane, dodecane, decalin, etc., esters such as methyl acetate, methyl formate, etc.

The amount of alkali metal doped into silicon oxycarbide is preferably in the range of 0.1 to 10 in terms of element ratio (MA / Si) of alkali metal (MA) and silicon (Si) in silicon oxycarbide. More preferably, it is in the range of -8. With such a range, productivity is improved.
<Step 2>
In the production method of the present invention, the “washing treatment” means that the reaction product obtained in step 1 is washed with a solution that reacts with an alkali metal to deactivate the alkali metal in the reaction product, and an alkali metal salt-containing silicon oxyde. This is the process of obtaining carbide. The solution used for washing the reaction product may be at least one selected from the group consisting of alcohol, water and an acidic solution.

  As the alcohol used here, an alcohol having a boiling point of 200 ° C. or lower can be preferably used. Specific examples of alcohols include methanol, ethanol, n-propanol, iso-propanol, 1-butanol, 2-butanol, tert-butanol, iso-butanol, ethylene glycol and the like.

  As the acidic solution used here, a solution of an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be preferably used.

  Specific examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and the like.

Specific examples of the carboxylic acid include formic acid, acetic acid, propionic acid, benzoic acid, oxalic acid, citric acid and tartaric acid. Specific examples of the sulfonic acid include methane sulfonic acid, ethane sulfonic acid, benzene sulfonic acid, p-toluene sulfonic acid, and the like. These may be used alone, or two or more may be appropriately selected and used. Good.

  Specifically, ethanol is added to lithium-doped silicon oxycarbide in an inert gas to deactivate the doped lithium. Then, the reaction product is filtered and washed with ethanol and water.

The washing method is not particularly limited, and for example, it can be performed by adding ethanol to the reaction product, filtering it, and washing the filter cake with ethanol and 1N hydrochloric acid in this order.
<Step 2B>
As another aspect of the production method of the present invention, after the step 1, a step of heating the reaction product obtained in the step 1 in an oxygen atmosphere or a nitrogen atmosphere can be included. The lithium in the reaction product obtained in step 1 can be deactivated by reacting with nitrogen and oxygen. The heating temperature varies depending on the atmosphere, and in the oxygen atmosphere, the range of 200 ° C to 500 ° C is preferable, and the range of 200 ° C to 300 ° C is more preferable. If it exceeds 500 ° C, carbon in silicon oxycarbide is decomposed, which is not preferable. In the nitrogen atmosphere, the range of 200 ° C to 1000 ° C is preferable, and the range of 300 ° C to 700 ° C is more preferable.

  The heating method is not particularly limited, but a reaction apparatus having a heating mechanism may be used, and a continuous method or a batch method can be used. Specifically, a fluidized bed reactor, a rotary furnace, or a vertical moving bed reactor. A tunnel furnace, a batch furnace, a rotary kiln, or the like can be appropriately selected according to the purpose.

In the negative electrode active material of the present invention obtained by the above-mentioned production method, the alkali metal and / or the alkali metal compound in silicon oxycarbide is deactivated and exists as an alkali metal salt.
<Preparation of non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery negative electrode is constituted by using the non-aqueous electrolyte secondary battery negative electrode active material of the present invention and a binder as essential components, and optionally containing other components such as a conductive auxiliary agent. Since the negative electrode thus obtained contains the non-aqueous electrolyte secondary battery negative electrode active material of the present invention as an active material, it is easy to handle in the air, has a high capacity and excellent cycle characteristics, and is excellent. It also serves as a negative electrode for a non-aqueous electrolyte secondary battery that also has initial coulombic efficiency. The negative electrode is prepared by, for example, kneading the negative electrode active material for a non-aqueous electrolyte secondary battery described above and a binder which is an organic binder together with a solvent by a dispersing device such as a stirrer, a ball mill, a super sand mill, a pressure kneader or the like. Then, a negative electrode material slurry is prepared and applied to a current collector to form a negative electrode layer. It can also be obtained by forming a paste-like negative electrode material slurry into a sheet shape, a pellet shape, or the like, and integrating this with a current collector.

  The organic binder (also referred to as “binder” in the present specification) is not particularly limited, and examples thereof include styrene-butadiene copolymer; ethylenically unsaturated carboxylic acid ester (eg, methyl (meth) acrylate, ethyl). (Meth) acrylate, butyl (meth) acrylate, (meth) acrylonitrile, and hydroxyethyl (meth) acrylate), and ethylenically unsaturated carboxylic acid (for example, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid) (Meth) acrylic copolymers composed of poly (vinylidene fluoride), polyethylene oxide, polyepiclohydrin, polyphosphazene, polyacrylonitrile, polyimide, polyamide imide, carboxymethyl cellulose and the like.

  These organic binders may be dispersed or dissolved in water or dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP) depending on their physical properties. The content ratio of the organic binder in the negative electrode layer of the negative electrode of the lithium ion secondary battery is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and 3 to 15% by mass. Is more preferable.

  When the content ratio of the organic binder is 1% by mass or more, the adhesion is good, and the negative electrode is prevented from being broken by the expansion / contraction during charging / discharging. On the other hand, when the content is 30% by mass or less, increase in electrode resistance can be suppressed.

  At this time, in the present invention, an aqueous binder can also be employed, which is superior to the conventional lithium doping technique in terms of practical use.

  Moreover, you may mix a conductive auxiliary material with the said negative electrode material slurry as needed. Examples of the conductive aid include carbon black, graphite, acetylene black, and oxides and nitrides having conductivity. The amount of the conductive additive used may be about 1 to 15 mass% with respect to the lithium ion secondary battery negative electrode material of the present invention.

  Further, the material and shape of the current collector are not particularly limited, and for example, aluminum, copper, nickel, titanium, stainless steel or the like may be used in the form of a foil, a perforated foil, a mesh or the like. Good. Further, a porous material such as porous metal (foamed metal) or carbon paper can also be used.

  The method of applying the negative electrode material slurry to the current collector is not particularly limited, and examples thereof include metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, and gravure coating. Known methods such as a method and a screen printing method can be used. After coating, it is preferable to perform a rolling treatment using a flat plate press, a calender roll or the like, if necessary.

  The negative electrode material slurry formed into a sheet shape, a pellet shape, or the like and the current collector can be integrated by a known method such as roll, press, or a combination thereof.

  The negative electrode layer formed on the current collector and the negative electrode layer integrated with the current collector are preferably heat-treated depending on the organic binder used. For example, when an organic binder having polyimide or polyamideimide as a main skeleton is used, it is preferable to perform heat treatment at 150 to 450 ° C.

  By this heat treatment, the solvent is removed and the binder is cured to increase the strength, and the adhesion between the particles and between the particles and the current collector can be improved. Note that these heat treatments are preferably performed in an inert atmosphere of helium, argon, nitrogen or the like, or in a vacuum atmosphere in order to prevent oxidation of the current collector during the treatment.

Further, it is preferable to press (pressurize) the negative electrode before heat treatment. The negative electrode material for non-aqueous electrolyte secondary battery of the present invention, it is preferable that the electrode density of 1.1~1.7g / cm ^3, more preferably 1.2~1.7g / cm ^3, More preferably, it is 1.3 to 1.7 g / cm ³ . Regarding the electrode density, the higher the electrode density, the more the adhesion tends to improve, and the cycle property tends to improve.

  The non-aqueous electrolyte secondary battery of the present invention is characterized by using the above-mentioned negative electrode of the present invention. For example, the positive electrode and the negative electrode of the present invention may be arranged so as to face each other with a separator interposed therebetween, and the electrolytic solution may be injected.

  The positive electrode can be obtained by forming a positive electrode layer on the surface of the current collector in the same manner as the negative electrode. In this case, the current collector may be a belt-shaped collector made of a metal or alloy such as aluminum, titanium or stainless steel into a foil shape, a perforated foil shape, a mesh shape or the like.

The positive electrode material used for the positive electrode layer is not particularly limited. Among non-aqueous electrolyte secondary batteries, in the case of producing a lithium ion secondary battery, for example, a metal compound capable of doping or intercalating lithium ions, a metal oxide, a metal sulfide, or a conductive polymer material. May be used and is not particularly limited. For example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and their complex oxides (LiCoxNiyMnzO ₂ , x + y + z = 1), lithium manganese spinel (LiMn ₂ O ₄ ). , lithium vanadium _{compounds, V 2 O 5, V 6} O 13, VO 2, MnO 2, TiO 2, MoV 2 O 8, TiS 2, V 2 S 5, VS 2, MoS 2, MoS 3, Cr 3 O 8 , Cr ₂ O ₅ , olivine-type LiMPO ₄ (M: Co, Ni, Mn, Fe), conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, etc., alone or in mixture, and used. be able to.

  As the separator, for example, a non-woven fabric containing a polyolefin such as polyethylene or polypropylene as a main component, a cloth, a microporous film, or a combination thereof can be used. If the positive electrode and the negative electrode of the non-aqueous electrolyte secondary battery to be produced are not in direct contact with each other, it is not necessary to use a separator.

Examples of the electrolytic solution include lithium salts such as LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ , and LiSO ₃ CF ₃ , ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, cyclopentanone, Sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3-methyl-1,3-oxazolidin-2-one, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, Ethyl propyl carbonate, butyl ethyl carbonate, dipropyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1 It is possible to use a so-called organic electrolytic solution which is dissolved in a non-aqueous solvent of a single substance such as 3,3-dioxolane, methyl acetate or ethyl acetate or a mixture of two or more components.

  The structure of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but usually, a positive electrode and a negative electrode, and a separator provided as necessary are wound in a flat spiral shape to form a wound electrode plate group. Generally, these are laminated in the form of a flat plate to form a laminated electrode plate group, and the electrode plate group is generally enclosed in an exterior body.

  The non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but is used as a paper type battery, a button type battery, a coin type battery, a laminated type battery, a cylindrical type battery, a square type battery and the like.

  The above-described silicon oxycarbide of the present invention can be applied to all electrochemical devices having a charge / discharge mechanism for inserting and releasing lithium ions, for example, a hybrid capacitor.

  Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Unless otherwise specified, "part" and "%" are based on mass.

First, the means for evaluating and confirming the object of the present invention will be shown below.
<Elemental analysis>
The content of each element of the present invention was evaluated by the following analysis.
C analysis: Analysis was performed by the high frequency combustion-infrared absorption method.
Apparatus: LECO CS 844 type O analysis: Analysis was performed by an inert gas melting-infrared absorption method.
Apparatus: LECO TCH600 type Si, Li analysis: The sample was dissolved and decomposed with sodium hydroxide and sodium peroxide, and the melt was dissolved with hydrochloric acid, and then ICP detection was performed.
Device: Shimadzu ICPE-9820 type <Means for confirming that lithium is deactivated (present as lithium salt) in the negative electrode active material of the present invention>
Regarding the deactivation of lithium in silicon oxycarbide, the deactivation of lithium was confirmed because hydrogen was not generated by adding water to the lithium salt-containing silicon oxycarbide.

  Whether or not hydrogen was generated was confirmed by the following method. 1 g of lithium-containing silicon oxycarbide was added to the Schlenk tube, the inside of the tube was replaced with an argon atmosphere, and then 10 ml of water was added and stirred for 1 hour. Gas was collected from the Schlenk tube after stirring using a lock type syringe, and the collected gas was analyzed using a gas chromatograph (Model GC-2014 manufactured by Shimadzu Corporation) to confirm the presence or absence of hydrogen generation.

<Evaluation of battery characteristics>
The battery characteristics of the lithium salt-containing silicon oxycarbide particles of the present invention were measured as follows.
The current value set at the time of measurement was set such that the theoretical capacity per lithium salt-containing silicon oxycarbide particle was 700 mAh (1.0 C) and 70 mA (0.1 C) per lithium salt-containing silicon oxycarbide particle weight. .

Battery characteristics were measured using a secondary battery charge / discharge tester (Hokuto Denko), charging was performed at a current value of 0.1 C until the battery voltage reached 0.005 V, and after reaching 0.005 V, the cell The current was reduced so that the voltage was maintained at 0.005V. Then, the charging was terminated when the current value fell below one-tenth the current value. The capacity at this time was defined as the charging capacity. The discharge was performed at a current value of 0.1 C, and was terminated when the voltage exceeded 1.5V. The capacity at this time was defined as the discharge capacity. At the time of switching during each charging / discharging, it was left in an open circuit for 30 minutes. Coulombic efficiency was calculated as follows.
Coulombic efficiency (%) = discharge capacity (mAh / g) / charge capacity (mAh / g)

<Synthesis of Silicon-Containing Composite Resin (A)>
[Synthesis example 1]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, a condenser and a nitrogen gas inlet was charged with 164 g of phenyltrimethoxysilane (PTMS) and heated to 120 ° C. Then, a mixture of 226 g of methyl methacrylate (MMA), 14 g of 3-methacryloyloxypropyltrimethoxysilane (MPTS) and 24 g of tert-butylperoxy-2-ethylhexanoate was dropped into the reaction vessel in 4 hours. . Then, the mixture was stirred at the same temperature for 16 hours to prepare a vinyl polymer having a trimethoxysilyl group.

  Then, the temperature of the reaction vessel was adjusted to 80 ° C., 113 g of methyltrimethoxysilane (MTMS), 194 g of 3-acryloyloxypropyltrimethoxysilane (APTS), and 99 g of dimethyldimethoxysilane (DMDMS) were introduced into the reaction vessel. Was added. After that, a mixture of 5.4 g of Phoslex A-3 [manufactured by Sakai Chemical Industry Co., Ltd., isopropyl acid phosphate] and 83 g of deionized water was added dropwise over 5 minutes, and the mixture was stirred at the same temperature for 2 hours for hydrolysis. A condensation reaction was performed to obtain a reaction product. When the reaction product was analyzed by 1H-NMR, almost 100% of the trimethoxysilyl group in the vinyl polymer was hydrolyzed. Thereafter, the reaction product is distilled under reduced pressure of 10 to 300 mmHg at 40 to 60 ° C. for 2 hours to remove the produced methanol and water, and then 400 g of butyl acetate (BuAc) is added. Thus, 1000 g of a solution of the silicon-containing composite resin (A-1) containing the polysiloxane segment having a nonvolatile content of 59.8 mass% and the vinyl polymer segment was obtained.

[Synthesis example 2]
191 g of PTMS was charged in the same reaction vessel as in Synthesis Example 1 and heated to 120 ° C. Then, a mixture of 169 g of MMA, 11 g of MPTS, and 18 g of TBPEH was dropped into the reaction vessel over 4 hours. Then, by stirring at the same temperature for 16 hours, a vinyl polymer having a trimethoxysilyl group was prepared.

  Then, the temperature of the reaction vessel was adjusted to 80 ° C., and 454 g of MTMS and 116 g of DMDMS were added. Then, a mixture of 8.4 g of Phoslex A-3 and 134 g of deionized water was added dropwise over 5 minutes, and the mixture was stirred at the same temperature for 2 hours to cause a hydrolytic condensation reaction to obtain a reaction product. When the reaction product was analyzed by 1H-NMR, almost 100% of the trimethoxysilyl group in the vinyl polymer was hydrolyzed. After that, the reaction product is distilled under reduced pressure of 10 to 300 mmHg under the condition of 40 to 60 ° C. for 2 hours to remove the produced methanol and water, and then 400 g of BuAc is added to the nonvolatile product. 1000 g of a solution containing 60.1% of a silicon-containing composite resin (A-2) consisting of a polysiloxane segment having no polymerizable double bond and a vinyl polymer segment was obtained.

[Example 1]
200 g of the solution of the silicon-containing composite resin (A-1) obtained in Synthesis Example 1 was dried under reduced pressure at 100 ° C. for 12 hours. The dried product was heated in a nitrogen atmosphere at 1000 ° C. for 3 hours to obtain a black silicon oxycarbide solid product. The obtained solid was pulverized with a paint conditioner to obtain silicon oxycarbide particles having an average particle size of 10 μm. The composition formula of the silicon oxycarbide particles was (Si: 1.00, O (y): 1.53, C (z): 1.54) when expressed as SiOyCz.
1.5 g of the obtained silicon oxycarbide particles, 0.58 g of lithium, 11 g of naphthalene, and 50 ml of tetrahydrofuran (THF) were mixed in argon and stirred for 3 hours. Then, 20 ml of isopropanol was gradually added to the obtained reaction liquid, and then 20 ml of water was gradually added. The reaction solution was filtered, and the black filter cake was washed with water and hydrochloric acid. The washed filter cake was dried under reduced pressure for 12 hours to obtain lithium salt-containing silicon oxycarbide particles. When 10 ml of water was added to 1 g of the obtained lithium salt-containing silicon oxycarbide particles and stirred, generation of hydrogen was not confirmed. The amount of lithium salt (Li / Si value) contained in the lithium salt-containing silicon oxycarbide particles was 0.64.

[Example 2]
200 g of a solution of the silicon-containing composite resin (A-2) obtained in Synthesis Example 2 was dried under reduced pressure at 100 ° C for 12 hours. The dried product was heated in a nitrogen atmosphere at 1000 ° C. for 3 hours to obtain a black silicon oxycarbide solid product. The obtained solid was pulverized with a paint conditioner to obtain silicon oxycarbide particles having an average particle size of 10 μm. The composition formula of the silicon oxycarbide particles was (Si: 1.00, O (y): 1.47, C (z): 1.47) when expressed as SiOyCz.
1.5 g of the obtained silicon oxycarbide particles, 0.58 g of lithium, 11 g of naphthalene, and 50 ml of tetrahydrofuran (THF) were mixed in argon and stirred for 3 hours. Then, 20 ml of isopropanol was gradually added to the obtained reaction liquid, and then 20 ml of water was gradually added. The reaction solution was filtered, and the black filter cake was washed with water and hydrochloric acid. The washed filter cake was dried under reduced pressure for 12 hours to obtain lithium salt-containing silicon oxycarbide particles. When 10 ml of water was added to 1 g of the obtained lithium salt-containing silicon oxycarbide particles and stirred, generation of hydrogen was not confirmed. The amount of lithium salt (Li / Si value) contained in the lithium salt-containing silicon oxycarbide particles was 0.58.

[Test Example 1]
To 80 parts of the lithium salt-containing silicon oxycarbide particles obtained in Example 1, 10 parts of acetylene black, 2.5 parts of sodium carboxymethyl cellulose, 7.5 parts of styrene-butadiene rubber, and 150 parts of water were added to prepare a slurry. did. Next, the slurry was applied to a copper foil having a thickness of 18 μm, dried at 120 ° C. for 1 hour, pressure-molded with an electrode, and finally punched out to 1.54 cm ² to obtain a negative electrode. A non-aqueous electrolyte obtained by using lithium foil for the obtained negative electrode and a counter electrode, and dissolving lithium phosphorus hexafluoride as a non-aqueous electrolyte in a 1/1 (volume ratio) mixed solution of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / L. Using the solution, a lithium ion secondary battery half cell for evaluation using a polyethylene microporous film having a thickness of 30 μm as a separator was prepared.

  After leaving the obtained half cell for 12 hours at room temperature, the initial charge / discharge capacity and the initial Coulombic efficiency were evaluated using a secondary battery charge / discharge tester (Hokuto Denko). The results are shown in Table 3.

[Test Example 2]
A battery was prepared and battery characteristics were evaluated in the same manner as in Test Example 1 except that the lithium salt-containing silicon oxycarbide particles obtained in Example 2 were used. The results are shown in Table 3.

<Comparative example>
Comparative Example
200 g of the solution of the silicon-containing composite resin obtained in Synthesis Example 1 was dried under reduced pressure at 100 ° C. for 12 hours. The dried product was heated in a nitrogen atmosphere at 1000 ° C. for 3 hours to obtain a black silicon oxycarbide solid product. The obtained solid was pulverized with a paint conditioner to obtain silicon oxycarbide particles having an average particle size of 10 μm. To 1.5 g of the obtained silicon oxycarbide particles, 0.1 g of lithium powder was added in an argon atmosphere and mixed with stirring in a mortar to obtain lithium-doped silicon oxycarbide particles. When 1 ml of the obtained lithium-doped silicon oxycarbide particles was added with 10 ml of water, generation of hydrogen was confirmed.

[Comparative Test Example 1]
A slurry was prepared by adding 10 parts of acetylene black, 10 parts of polyvinylidene fluoride and 150 parts of NMP to 80 parts of the lithium-containing silicon oxycarbide particles obtained in the comparative example. Then, the slurry was applied to a copper foil having a thickness of 18 μm to prepare a negative electrode containing lithium-containing silicon oxycarbide, and the lithium foil was used as a counter electrode with the obtained lithium-containing silicon oxycarbide negative electrode. A nonaqueous electrolyte solution prepared by dissolving lithium phosphorus oxide in a 1/1 (volume ratio) mixture of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / L was used as a separator, and a microporous polyethylene film having a thickness of 30 μm was used as a separator. A lithium-ion secondary battery half cell for evaluation was prepared.

  After leaving the obtained half cell for 12 hours at room temperature, the initial charge / discharge capacity and the initial Coulombic efficiency were evaluated using a secondary battery charge / discharge tester (Hokuto Denko). The results are shown in Table 3.

It was confirmed that the irreversible capacity was reduced and the initial coulombic efficiency was improved as compared with the comparative test example.
Furthermore, since the negative electrode active material of the present invention does not contain metallic lithium and has the above-described excellent initial charge / discharge capacity and initial Coulombic efficiency, work safety while satisfying the characteristics required in practical situations It can be seen that this is an excellent active material that is improved and can be used with an aqueous binder.

Claims (12)

A negative electrode active material for a non-aqueous electrolyte secondary battery, which contains silicon oxycarbide and an alkali metal salt. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the silicon oxycarbide is represented by a composition formula of SiOyCz (0 <y <3, 0 <z <10). The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the alkali metal of the alkali metal salt is lithium or sodium. The content of the alkali metal salt is such that the ratio of the silicon atom (Si) in the silicon oxycarbide and the alkali metal atom (MA) in the alkali metal salt can be expressed in the range of 0 <MA / Si <10. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1. A negative electrode for a non-aqueous electrolyte secondary battery, comprising the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4 and a binder. A non-aqueous electrolyte secondary battery comprising the negative electrode for a non-aqueous electrolyte secondary battery according to claim 5. A step (1) of reacting silicon oxycarbide with an alkali metal source containing at least one selected from the group consisting of alkali metals and alkali metal compounds to obtain alkali metal-containing silicon oxycarbide;
A non-aqueous electrolyte (2) comprising a step (2) of washing the alkali metal-containing silicon oxycarbide obtained in the step (1) with at least one selected from the group consisting of alcohol, water and an acidic solution. Manufacturing method of negative electrode active material for secondary battery. 8. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the alkali metal source is at least one selected from the group consisting of lithium, sodium, lithium metal compounds and sodium metal compounds. Production method. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the alcohol has an boiling point of 200 ° C. or lower. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the acidic solution is at least one solution selected from the group consisting of inorganic acids, sulfonic acids and carboxylic acids. A step (1) of reacting silicon oxycarbide with an alkali metal source containing at least one selected from the group consisting of alkali metals and alkali metal compounds to obtain alkali metal-containing silicon oxycarbide;
A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, comprising a step (2) of heating the alkali metal-containing silicon oxycarbide obtained in the step (1) in an oxygen atmosphere or a nitrogen atmosphere. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 11, wherein the alkali metal source is at least one selected from the group consisting of lithium, sodium, a lithium metal compound and a sodium metal compound. Production method.