JP6984349B2 - Crosslinked polymer - Google Patents

Description

The present invention relates to crosslinked polymers.

Secondary batteries typified by lithium-ion secondary batteries are currently mainly used as power sources for portable electronic devices, and are also put into practical use as power sources for electric vehicles. With the diversification of usage modes, it is required to increase the capacity of the secondary battery. Therefore, studies are being conducted to increase the capacity of the secondary battery by driving it at a high voltage. However, when the secondary battery is driven at a high voltage, there is a problem that oxidative decomposition of the electrolytic solution occurs due to contact with the positive electrode active material in an oxidized state.

Therefore, as a technique for reducing the direct contact between the positive electrode active material and the electrolytic solution, a technique for forming a protective layer on the surface of the positive electrode active material layer containing the positive electrode active material has been proposed.

For example, Patent Document 1 discloses a technique for providing a coat layer that covers the surface of a positive electrode active material. Specifically, a technique is disclosed in which a positive electrode composed of a current collector and a positive electrode active material layer is immersed in a polyethyleneimine solution and a polyethylene glycol solution, and the positive electrode is coated with a polymer.

Patent Document 2 also discloses a technique for providing a coat layer that covers the surface of a positive electrode active material. Specifically, a technique of immersing a positive electrode composed of a current collector and a positive electrode active material layer in a polyethylene glycol solution and coating the positive electrode with a polymer is disclosed.

Further, a technique of coating the surface of the negative electrode active material layer containing the negative electrode active material with the polymer-containing layer has also been proposed.

Patent Document 3 describes a negative electrode having a conductive polymer layer on the surface of the negative electrode active material layer, and as the polymer of the conductive polymer layer, polypyrrole, polythiophene, polyisotianaften, polyaniline, polyphenylene vinylene, polyethylene di Oxythiophene is specifically described.

Patent Document 4 specifically describes a negative electrode in which the surface of the negative electrode active material layer is coated with polyacrylic acid, and a negative electrode in which the surface of the negative electrode active material layer is coated with polyacrylic acid and polyamine.

In Patent Document 5, the negative electrode is immersed in a solution containing polyvinyl alcohol, phosphoric acid, hydrofluoric acid, etc., and the V-C-O-PF layer or C-O- is formed on the surface of the negative electrode active material layer. A technique for providing the PF layer is described.

Japanese Unexamined Patent Publication No. 2013-243105 Japanese Unexamined Patent Publication No. 2014-96343 Japanese Unexamined Patent Publication No. 2013-16364 Japanese Unexamined Patent Publication No. 2016-9670 Japanese Unexamined Patent Publication No. 2016-81706

In recent years, the industrial world has demanded a secondary battery having excellent characteristics, and a new technology for realizing the demand has been demanded.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a new polymer that can serve as a protective film for an electrode.

By the way, the polymer is originally a resistance factor to the movement of charge carriers such as lithium ions. Therefore, the polymer used for the protective film of the electrode in the power storage device such as a secondary battery is required to have ionic conductivity. It is considered that a polymer having excellent ionic conductivity needs a moving space surrounded by polar groups so that ions, which are charge carriers, can move smoothly. Therefore, the present inventor has conceived to use an ate complex-like polymer containing a charge carrier M. However, the electrode coated with an ate complex-like polymer was not satisfactory in its performance.

As a result of further studies by the present inventor, it has been found that a crosslinked polymer obtained by cross-linking an ate complex-like polymer with a polyamine is suitable as a coating material for an electrode. Based on such findings, the present inventor has completed the present invention.

The crosslinked polymer of the present invention is
General formula (1): ^{First monomer unit represented by M +} [((CH _2- CR ^1-1 ) COR ^1-2 O) _4-n Al (L ¹ ) _n ] ⁻ (general formula (1)) In, M is an alkali metal. R ^1-1 is an H or an alkyl group. R ^1-2 is absent or OR ^1-2-1 , SR ^1-2-1 , NR ^{1-2. -2} R ^{1-2-1 is} selected. R ^1-2-1 is a divalent hydrocarbon group that may be substituted with a substituent. R ^1-2-2 is an H or an alkyl group. L ¹ is OH or OR ^1-3 , and R ^1-3 is a hydrocarbon group that may be substituted with a substituent. N is an integer of 0 to 3). (2): (CH _2- CR ^2-1 ) ^{Second monomer unit represented by COL 2} (in the general formula (2), R ^2-1 is an H or an alkyl group. L ² is OH, halogen or OR ^2-2 , where R ^2-2 is a hydrocarbon group which may be substituted with a substituent), and a polymer containing.
It is characterized by being crosslinked with a polyamine.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a new polymer that can be a protective film for an electrode.

c) It is a reaction formula showing an example of a step.

Hereinafter, embodiments for carrying out the present invention will be described. Unless otherwise specified, the numerical range "a to b" described in the present specification includes the lower limit a and the upper limit b in the range. Then, a numerical range can be configured by arbitrarily combining these upper limit values and lower limit values, as well as the numerical values listed in the examples. Further, a numerical value arbitrarily selected from these numerical values can be used as a new upper limit or lower limit numerical value.

The crosslinked polymer of the present invention is characterized in that a polymer containing a first monomer unit and a second monomer unit is crosslinked with a polyamine.
In addition, in this specification, the description of "+" and "-" charges in an ate complex or an ate complex-like chemical structure may be omitted. In addition, the description of [] or charge may be omitted for art complexes or art complex-like chemical structures that do not customarily specify [] or charge.

The first monomer unit has the general formula _{^{(1): M + [(}} (CH 2 -CR 1-1) COR 1-2 O) 4-n Al (L 1) n] - in are those represented, ( The _{ethylene moiety represented by CH 2-} CR ^1-1 ) constitutes the main chain of the polymer chain.
In the general formula (1), M is an alkali metal, and Li, Na, and K can be exemplified as M. When the crosslinked polymer of the present invention is used as a component of the power storage device, it is preferable that M is the same as the charge carrier of the power storage device.

In the general formula (1), R ^1-1 is an H or an alkyl group. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms.

In the general formula (1), R ^1-2 does not exist or is selected from ^{OR 1-2-1} , SR ^1-2-1 , and NR ^1-2-2 R ^{1-2-1. R1-2-1} is a divalent hydrocarbon group which may be substituted with a substituent. Divalent hydrocarbon groups have 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, and 1 to 1 carbon atoms. 2 can be exemplified.
Specific examples of the divalent hydrocarbon group include an alkylene group and an aromatic group such as a benzene ring and a naphthalene ring. Further, the divalent hydrocarbon group may be a combination of an alkylene group and an aromatic group.
R ^1-2-2 is an H or an alkyl group. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms.

The phrase "may be substituted with a substituent" in the present specification will be described. For example, in the case of "hydrocarbon group which may be substituted with a substituent", the hydrocarbon group has one or more of hydrogens of the hydrocarbon group substituted with the substituent, or has a special substituent. Means no hydrocarbon group.

The substituents in the phrase "may be substituted with a substituent" include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen and an OH. , SH, CN, SCN, OCN, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, Acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphate amide group, sulfo group, carboxyl group, Examples thereof include a hydroxamic acid group, a sulfino group, a hydradino group, an imino group, a silyl group and the like. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different.

As ^R1-2-1 , a divalent hydrocarbon group having no particular substituent or a divalent hydrocarbon group having an alkoxy group or fluorine as a substituent is preferable. Examples of the number of carbon atoms of the alkoxy group include 1 to 6, 1 to 4, and 1 to 2.

In the general formula (1), L ¹ is OH or OR ^1-3 , and R ^1-3 is a hydrocarbon group which may be substituted with a substituent. Hydrocarbon groups have 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, and 1 to 2 carbon atoms. Can be exemplified. Specific examples of the hydrocarbon group include an alkyl group and an aromatic group such as a benzene ring and a naphthalene ring.
Further, as the substituent, an alkoxy group or fluorine is preferable. Examples of the number of carbon atoms of the alkoxy group include 1 to 6, 1 to 4, and 1 to 2.

In the general formula (1), n is an integer of 0 to 3. When n = 3, Al is bound to _{one (CH 2-} CR ^1-1 ) COR ^1-2 O and three L ^1. When n = 2, Al is chelated with _{two (CH 2-} CR ^1-1 ) COR ^1-2 O and bound to ^{two L 1.} When n = 1, Al is chelated with _{three (CH 2-} CR ^1-1 ) COR ^1-2 O and bound to ^{one L 1.} When n = 0, Al is chelated with _{four (CH 2-} CR ^1-1 ) COR ^{1-2 O.}

The second monomer unit is represented by the general formula (2): (CH _2- CR ^2-1 ) COL ² , and the _{ethylene moiety represented by (CH 2-} CR ^2-1 ) is the main polymer chain. Make up the chain.
L ² in COL ² of the second monomer units are those polymers containing a first monomer unit and the second monomer unit in the crosslinked polyamine, a leaving group. Therefore, the crosslinked polymer of the present invention obtained by cross-linking a polymer containing a first monomer unit and a second monomer unit with a polyamine has an amide group formed by a CO group of the second monomer unit and an amino group of the polyamine. Have.

In the general formula (2), ^R2-1 is an H or an alkyl group. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms.

In the general formula (2), L ² is OH, halogen or OR ^2-2 , and R ^2-2 is a hydrocarbon group which may be substituted with a substituent. Hydrocarbon groups have 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, and 1 to 2 carbon atoms. Can be exemplified. Specific examples of the hydrocarbon group include an alkyl group and an aromatic group such as a benzene ring and a naphthalene ring.
Further, as the substituent, an alkoxy group or fluorine is preferable. Examples of the number of carbon atoms of the alkoxy group include 1 to 6, 1 to 4, and 1 to 2.

In the polymer containing the first monomer unit and the second monomer unit, (the number of the first monomer units) :( the number of the second monomer units) is preferably in the range of 1: 9 to 9: 1. The range of 5: 8.5 to 5: 5 is more preferable, and the range of 2: 8 to 4: 6 is even more preferable. In the crosslinked polymer of the present invention, it can be said that the higher the ratio of the first monomer unit, which is like an ate complex, the smoother the movement of the charge carrier. On the other hand, in the crosslinked polymer of the present invention, it can be said that the higher the ratio of the second monomer unit, the more the crosslinked structure is formed, so that the strength of the crosslinked polymer of the present invention increases.
In the above description, "the number of first monomer units" may be read as "the number of Al". That is, in the polymer containing the first monomer unit and the second monomer unit, (the number of Al) :( the number of the second monomer units) is preferably in the range of 1: 9 to 9: 1, and 1.5. The range of: 8.5 to 5: 5 is more preferable, and the range of 2: 8 to 4: 6 is even more preferable.

Examples of the polyamine that crosslinks the polymer containing the first monomer unit and the second monomer unit include diamine, triamine, and tetraamine. Examples of the amino group constituting the polyamine include _two NH groups and an NHR group (R is an alkyl group), and _two NH groups are preferable from the viewpoint of reactivity.
The chemical structure of a suitable polyamine is (organic group which may be substituted with a substituent)-(NH ₂ ) _n (where n is an integer of 2 or more). Examples of the organic group include those having 2 to 16 carbon atoms. Examples of the organic group include a hydrocarbon group and an organic group in which carbon in the hydrocarbon group is substituted with O, S or NH. Examples of the hydrocarbon group include an alkylene group, an aromatic group, and a combination of an alkylene group and an aromatic group.
As the substituent of the organic group, an alkoxy group or fluorine is preferable. Examples of the number of carbon atoms of the alkoxy group include 1 to 6, 1 to 4, and 1 to 2.

Examples of specific polyamines by taking diamine as an example are alkylene diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophoronediamine, and bis (4-aminocyclohexyl). Saturated carbocyclic diamines such as methane, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-tridine, Examples thereof include aromatic diamines such as 2,4-tolylene diamine, 2,6-tolylene diamine, xylylene diamine and naphthalenediamine.

Regarding the relationship between the amount of the polymer containing the first monomer unit and the second monomer unit and the polyamine, the relationship between the number of the second monomer units and the number of molecules of the polyamine is important. The reason is that the crosslinked polymer is synthesized by the reaction between the second monomer unit and the polyamine.
(Number of second monomer units): (Number of molecules of polyamine) is preferably in the range of 2: 1 to 100: 1, more preferably in the range of 3: 1 to 50: 1, 4: 1 to 10: 1. The range of is more preferable.

The crosslinked polymer of the present invention may contain a monomer unit other than the first monomer unit and the second monomer unit within a range not deviating from the gist of the present invention.

The degree of polymerization of the crosslinked polymer of the present invention can be exemplified in the range of 10 to 1,000,000, 50 to 100,000, 100 to 10000, 500 to 5000, and 1000 to 3000.

Next, a method for producing the crosslinked polymer of the present invention will be described.

The method for producing a crosslinked polymer of the present invention is
a) General formula (1'): M ⁺ [(CH ₂ = CR ^1-1 COR ^1-2 O) _4-n Al (L ¹ ) _n ] ^{-The first monomer represented by −} (general formula (1') ), M is an alkali metal. R ^1-1 is an H or an alkyl group. R ^1-2 is absent or OR ^1-2-1 , SR ^1-2-1 , NR ^{1-. 2-2} R ^{1-2-1 is} selected. R ^1-2-1 is a divalent hydrocarbon group that may be substituted with a substituent. R ^1-2-2 is an H or alkyl group. L ¹ is OH or OR ^1-3 , and R ^1-3 is a hydrocarbon group that may be substituted with a substituent. N is an integer of 0 to 3). Process,
b) The first monomer and the second monomer represented by the general formula (2'): CH ₂ = CR ^2-1 COL ² (in the general formula (2'), ^R2-1 is an H or an alkyl group. L ² is OH, halogen or OR ^2-2 , and R ^2-2 is a hydrocarbon group which may be substituted with a substituent.) A step of copolymerizing to obtain a polymer.
c) A step of cross-linking the polymer with a polyamine to produce a cross-linked polymer.
Have.

a) The process will be described.
^{M, R 1-1} in the general formula (1 ^{'), R} 1-2, description of ^{L 1} and n, ^M in the general formula (1) of the first monomer ^{unit, R 1-1,} R ^1-2, hence the description of L ¹ and n.
In order to prepare the first monomer represented by the general formula (1'), specifically, the first monomer may be synthesized through the following steps a-1) and a-2).

a-1) General formula (3): ^{Compound represented by M +} [AlH _4-n (L ¹ ) _n ] ⁻ (In general formula (3), M is an alkali metal. L ¹ is OH or OR. a ^1-3 step R ^1-3 is to prepare it.) an integer which .n 0-3 a hydrocarbon group which may be substituted with a substituent,
a-2) wherein the general formula (3) and a compound represented _by, CH ² = CR 1-1 ^{COR 1-2} compound represented by OH ^{(R 1-1} is H or an alkyl group ^{.R 1-} or ² is absent, ^{or, oR 1-2-1, SR 1-2-1, .R} 1-2-1 selected from NR ^{1-2-2 R 1-2-1} is substituted with a substituent It is a divalent hydrocarbon group which ^{may be used. R1-2-2} is an H or an alkyl group) and is reacted with the first monomer.

Description of the general formula M in (3), ^{L 1} and n, M in the general formula (1) of the first monomer unit, hence the description of ^{L 1} and n. In order to prepare the compound represented by the general formula (3), a commercially available compound may be purchased or may be synthesized.

Commercially available compounds represented by the general formula (3) include LiAlH ₄ , LiAlH (OCH ₂ CH ₃ ) ₃ , LiAlH (OC (CH ₃ ) ₃ ) ₃ , and NaAlH ₂ (OCH ₂ CH ₂ OCH ₃ ). ₂ can be exemplified.
As a method for synthesizing the compound represented by the general formula (3), the synthesis method of each of the following reaction formulas can be exemplified. In the synthesis by the second reaction formula, it _{is preferable to carry out the synthesis under the H 2} gas atmosphere and the heating conditions.
LiAlH ₄ + 3R ^1-3 OH → Li ⁺ [AlH (OR ^1-3 ) ₃ ] ⁻ + 3H ₂
Na + Al + 2R ^1-3 OH → Na ⁺ [AlH ₂ (OR ^1-3 ) ₂ ] ⁻

In the a-2) step, the compound represented by the general formula (3) _{reacts with the compound represented by CH 2} = CR ^1-1 COR ^1-2 OH, and hydrogen is released, so that the second step is performed. It becomes one monomer.
An example of the reaction is shown by a reaction formula.
Li ⁺ [AlH (OR ^1-3 ) ₃ ] ⁻ + CH ₂ = CR ^1-1 COR ^1-2 OH →
Li ⁺ [(CH ₂ = CR ^1-1 COR ^1-2 O) Al (OR ^1-3 ) ₃ ] ⁻ + H ₂

The a-2) step is preferably carried out in an organic solvent that is aprotic and difficult to hydride reduction. Examples of the organic solvent include diethyl ether, bis (2-methoxyethyl) ether, chain ether such as 1,2-dimethoxyethane, cyclic ether such as tetrahydrofuran and 1,4-dioxane, dichloromethane, chloroform and carbon tetrachloride. can.
Further, in order to isolate the first monomer, a method of adding a low-polarity organic solvent to precipitate the first monomer is preferable. Examples of low-polarity organic solvents include benzene, toluene, xylene, pentane, hexane, and heptane.

b) The process will be described.
b) The copolymerization reaction in the step may be any method of thermal polymerization, photopolymerization, or polymerization using a polymerization initiator. A method using a polymerization initiator is preferable because of the ease of controlling the polymerization reaction. As the polymerization initiator, a polymerization initiator used for the polymerization of acrylic acid or methacrylic acid may be adopted.
Further, the copolymerization reaction in step b) is preferably random copolymerization.

b) Regarding the molar ratio of the first monomer to the second monomer used in the step, it is preferable that (the number of moles of the first monomer): (the number of moles of the second monomer) is in the range of 1: 9 to 9: 1. The range of 1.5: 8.5 to 5: 5 is more preferable, and the range of 2: 8 to 4: 6 is even more preferable.

b) The step is preferably carried out in an aprotic organic solvent. Examples of the organic solvent include the organic solvent shown in the description of a-2) step, N-methyl-2-pyrrolidone, acetone, and methyl isobutyl ketone.

c) The process will be described.
The c) step is a step of cross-linking the polymer produced in the b) step with a polyamine. c) Specifically considering an example of the step, b) the two ^{amino groups of the second monomer unit COL 2} and the diamine in the two polymer chains produced in the step react with each other to form two amide bonds. It is believed that the formation of the two polymer chains crosslinks the two polymer chains.
An example of the assumed c) step is shown in FIG. 1 by a reaction formula. The reaction formula in FIG. 1 mainly represents the portion required for the crosslinking reaction.

c) The step is preferably carried out in an aprotic organic solvent. Examples of the organic solvent include the organic solvent shown in the description of a-2) step and the organic solvent shown in b) description of the step. Further, the step c) is preferably carried out under heating conditions, and is preferably carried out under conditions under which HL ² by-produced by amide bond formation is removed from the system.

The steps a) to c) are preferably carried out in an atmosphere of an inert gas such as helium, argon or nitrogen.

The crosslinked polymer of the present invention can be used as an electrode material for a power storage device such as a secondary battery, a coating film for an electrode of the power storage device, an additive material for an electrolytic solution, or a solid electrolyte. In particular, since the crosslinked polymer of the present invention contains Al, a coating on a Si-containing negative electrode active material, a coating on a negative electrode active material layer containing a Si-containing negative electrode active material, or a Si-containing negative electrode active material can be used. It is preferable to use the crosslinked polymer of the present invention as an additive material to the electrolytic solution of the power storage device provided. The reason will be explained below.

It is known that under the charge / discharge conditions of a power storage device such as a secondary battery, the constituent components of the electrolytic solution are decomposed to form an SEI (Solid Electrolyte Interphase) film containing oxygen on the surface of the negative electrode active material. .. Here, when the negative electrode active material is a Si-containing negative electrode active material containing silicon, there is a concern that Si may be oxidized and deteriorated by oxygen contained in the SEI film.

However, since the crosslinked polymer of the present invention contains Al, it is considered that the oxidative deterioration of Si is suppressed. The reason is that Al has a lower electronegativity than Si and is considered to preferentially and stably bond with oxygen, and the Al—O bond between Al and oxygen is more stable than the Si—O bond. In addition, it can be said that oxygen forming a stable Al—O bond is less likely to participate in the oxidation of Si, which has a higher electronegativity than Al.

Therefore, the power storage device provided with the crosslinked polymer of the present invention and provided with the Si-containing negative electrode active material can be expected to have a long life. In particular, in a power storage device that uses the crosslinked polymer of the present invention as a coating film on a Si-containing negative electrode active material, or as a coating film on a negative electrode active material layer containing a Si-containing negative electrode active material, the crosslinked polymer of the present invention is used. In addition to the oxidation suppressing effect of suppressing the oxidation of the Si-containing negative electrode active material, the storage device can be expected to have a significantly longer life due to the protective effect of preventing direct contact between the Si-containing negative electrode active material and the electrolytic solution. ..

Examples of the power storage device include a secondary battery and a capacitor. Hereinafter, the power storage device provided with the crosslinked polymer of the present invention is the power storage device of the present invention, the secondary battery provided with the crosslinked polymer of the present invention is the secondary battery of the present invention, and the lithium ion containing the crosslinked polymer of the present invention. The secondary battery may be referred to as the lithium ion secondary battery of the present invention. Further, the electrode coated with the crosslinked polymer of the present invention may be referred to as the electrode of the present invention.
Hereinafter, the power storage device of the present invention including the electrode of the present invention and the electrode of the present invention will be described through the description of the lithium ion secondary battery which is a typical example of the power storage device.

The electrode of the present invention may be a positive electrode or a negative electrode. A specific embodiment of the electrode of the present invention is a layer containing a current collector, an active material layer formed on the surface of the current collector, and a crosslinked polymer of the present invention covering the surface of the active material layer (hereinafter, It is a configuration including simply a "crosslinked polymer layer").

A current collector is a chemically inert electron conductor that keeps current flowing through an electrode during discharge or charging of a secondary battery such as a lithium ion secondary battery. The material of the current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. As the material of the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel. Metallic materials such as can be exemplified. The current collector may be covered with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.

When the potential of the positive electrode is 4 V or more based on lithium, it is preferable to use aluminum as the current collector for the positive electrode.

Specifically, it is preferable to use a current collector for the positive electrode made of aluminum or an aluminum alloy. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or higher is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is called an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, Al—Mg—Si, and Al—Zn—Mg.

Further, as aluminum or an aluminum alloy, specifically, for example, A1000 series alloys such as JIS A1085 and A1N30 (pure aluminum series), A3000 series alloys such as JIS A3003 and A3004 (Al-Mn series), JIS A8079, A8021 and the like. A8000 series alloy (Al—Fe series) can be mentioned.

The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, 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 preferably used. When the current collector is in the form of a foil, a sheet, or a film, the thickness thereof is preferably in the range of 1 μm to 100 μm.

The active material layer contains an active material that can occlude and release charge carriers such as lithium ions, and, if necessary, a binder and a conductive auxiliary agent. The active material layer preferably contains the active material in an amount of 60 to 99% by mass, more preferably 70 to 95% by mass, based on the total mass of the active material layer.

As the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c M} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, M is Mn and / or Al and D are W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Lithium composite metal represented by at least one element selected from Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P and V, 1.7 ≦ f ≦ 3). Oxides, Li ₂ MnO ₃ can be mentioned. Further, as the positive electrode active material, _{a metal oxide having a spinel structure such as LiMn 2} O ₄ , a solid solution composed of a mixture of the metal oxide having a spinel structure and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (in the formula). M is selected from at least one of Co, Ni, Mn, and Fe) and the like. Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as the basic composition, and those in which the metal element contained in the basic composition is replaced with another metal element can also be used. Further, as the positive electrode active material, a material that does not contain a charge carrier (for example, lithium ions that contribute to charging / discharging) may be used. For example, elemental sulfur, compounds complexed with sulfur and carbon, metal sulfides such as TiS _2, oxides such as V 2 _{O 5,} MnO _2, polyaniline and anthraquinone and compounds containing these aromatic in chemical structure, conjugated double Conjugated materials such as acetic acid-based organic substances and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronylnitroxide, galbinoxyl, phenoxyl and the like may be adopted as the positive electrode active material. When a positive electrode active material that does not contain a charge carrier such as lithium is used, it is necessary to add a charge carrier to the positive electrode and / or the negative electrode in advance by a known method. The charge carrier may be added in an ionic state or may be added in a nonionic state such as a metal. For example, when the charge carrier is lithium, a lithium foil may be attached to the positive electrode and / or the negative electrode to integrate them.

From the viewpoint of excellent and high capacity, and durability, as the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c M} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, M is Mn and / or Al, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Nb, Mg, Ta, Ti, La, Zr, Cu, At least one element selected from Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f It is preferable to use the lithium composite metal oxide represented by ≦ 3).

In the above general formula, the values of b, c, and d are not particularly limited as long as they satisfy the above conditions, but those having 0 <b <1, 0 <c <1, 0 <d <1 are used. Good, and at least one of b, c, and d is in the range of 10/100 <b <90/100, 10/100 <c <90/100, 5/100 <d <70/100. More preferably, the range is 20/100 <b <80/100, 12/100 <c <70/100, 10/100 <d <60/100, and 30/100 <b <70/100, It is more preferably in the range of 15/100 <c <50/100 and 12/100 <d <50/100.

As for a, e, and f, any numerical value within the range specified by the above general formula may be used, and preferably 0.5 ≦ a ≦ 1.5, 0 ≦ e <0.2, 1.8 ≦ f ≦ 2. 5.5, more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, 1.9 ≦ f ≦ 2.1 can be exemplified respectively.

_{As a positive electrode active material, Li x} Mn _{2-y Ay} O ₄ (A is Ca, Mg, S, Si, Na, K, Al, P, Ga) having a spinel structure is excellent in terms of high capacity and durability. , At least one element selected from Ge, and at least one metal element selected from transition metal elements such as Ni. 0 <x≤2.2, 0≤y≤1) can be exemplified. Examples of the range of the value of x include 0.5 ≦ x ≦ 1.8, 0.7 ≦ x ≦ 1.5, and 0.9 ≦ x ≦ 1.2, and the range of the value of y is 0. Examples thereof include ≦ y ≦ 0.8 and 0 ≦ y ≦ 0.6. As specific compounds having a spinel structure, LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ can be exemplified.

Specific examples of the positive electrode active material include LiFePO ₄ , Li ₂ FeSiO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ , Li ₂ MnPO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F. As another specific positive electrode active material, Li ₂ MnO _3- LiCoO ₂ can be exemplified.

As the negative electrode active material, a material capable of occluding and releasing charge carriers can be used. Therefore, there is no particular limitation as long as it is a simple substance, an alloy or a compound capable of occluding and releasing a charge carrier such as lithium ion. For example, Li, Group 14 elements such as carbon, silicon, germanium, and tin, Group 13 elements such as aluminum and indium, Group 12 elements such as zinc and cadmium, Group 15 elements such as antimony and bismuth, and magnesium as negative electrode active materials. , Alkaline earth metals such as calcium, and Group 11 elements such as silver and gold may be used alone. Specific examples of alloys or compounds include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, and Co-Sn alloys, carbon-based materials such as various graphites, elemental silicon, and SiO _{x that disproportionates to elemental silicon and silicon dioxide.} Examples thereof include a silicon-based material such as 0.3 ≦ x ≦ 1.6), a simple substance of silicon, or a composite of a silicon-based material and a carbon-based material. Further, the negative electrode active material is an oxide such as _{Nb 2} O ₅ , TIO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O _{3 , or Li 3-x} M _x N (M =). A nitride represented by Co, Ni, Cu) may be adopted. One or more of these can be used as the negative electrode active material.

From the viewpoint of the possibility of increasing the capacity, preferred negative electrode active materials include graphite, Si-containing negative electrode active material, and Sn-containing material. As described above, the Si-containing negative electrode active material is particularly preferable because the crosslinked polymer of the present invention contains Al. The Si-containing material that can be used as the Si-containing negative electrode active material will be described below.

As a specific example of the Si-containing material, Si alone or SiO _x (0.3 ≦ x ≦ 1.6) disproportionated into two phases of a Si phase and a silicon oxide phase can be exemplified. The Si phase in SiO _x can occlude and release lithium ions, and its volume changes with the charging and discharging of the secondary battery. The silicon oxide phase has less volume change due to charging and discharging than the Si phase. _{That is, SiO x} as the negative electrode active material realizes a high capacity by the Si phase and suppresses the volume change of the entire negative electrode active material by having the silicon oxide phase. If x is less than the lower limit, the ratio of Si becomes excessive, so that the volume change during charging / discharging becomes too large, and the cycle characteristics of the secondary battery deteriorate. On the other hand, when x exceeds the upper limit value, the Si ratio becomes too small and the energy density decreases. The range of x is more preferably 0.5 ≦ x ≦ 1.5, and even more preferably 0.7 ≦ x ≦ 1.2.

In the above-mentioned SiO _x , it is considered that an alloying reaction occurs between lithium and silicon in the Si phase during charging and discharging of the lithium ion secondary battery. It is believed that this alloying reaction contributes to the charging and discharging of the lithium ion secondary battery.

As a specific example of the Si-containing material, a silicon material disclosed in International Publication No. 2014/08608 or the like (hereinafter, simply referred to as “silicon material”) can be mentioned.

The silicon material has a structure in which a plurality of plate-shaped silicon bodies are laminated in the thickness direction. The silicon material is, for example, _{subjected to a step of reacting CaSi 2} with an acid to synthesize a layered silicon compound containing polysilane as a main component, and a step of heating the layered silicon compound at 300 ° C. or higher to release hydrogen. It is manufactured.

The ideal reaction formula when hydrogen chloride is used as the acid shows the method for producing the silicon material as follows.
3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl _{2
Si 6 H 6 → 6Si + 3H} 2 ↑

_{However, in the upper reaction for synthesizing Si 6} H ₆ which is polysilane, water is usually used as a reaction solvent from the viewpoint of removing by-products and impurities. Since Si ₆ H ₆ can react with water, the layered silicon compound is rarely produced as containing only _{Si 6} H ₆ in the step of synthesizing the layered silicon compound including the reaction in the upper stage, and is layered. Silicon compounds are represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from an acid anion, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6). Manufactured as a compound. In the above chemical formula, unavoidable impurities such as Ca that may remain are not considered. The silicon material obtained by heating the layered silicon compound also contains an element derived from an anion of oxygen or acid.

As described above, the silicon material has a structure in which a plurality of plate-shaped silicon bodies are laminated in the thickness direction. In order to efficiently occlude and release a charge carrier such as lithium ion, the plate-shaped silicon body preferably has a thickness in the range of 10 nm to 100 nm, and more preferably in the range of 20 nm to 50 nm. The length of the plate-shaped silicon body in the longitudinal direction is preferably in the range of 0.1 μm to 50 μm. Further, the plate-shaped silicon body preferably has (length in the longitudinal direction) / (thickness) in the range of 2 to 1000. The laminated structure of the plate-shaped silicon body can be confirmed by observation with a scanning electron microscope or the like. Further, this laminated structure is considered to be a remnant of the Si layer in _{the raw material CaSi 2.}

The silicon material preferably contains amorphous silicon and / or silicon crystallites. In particular, in the plate-shaped silicon body, it is preferable that amorphous silicon is used as a matrix and silicon crystallites are scattered in the matrix. The size of the silicon crystallite is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, further preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scheller's equation using the half width of the diffraction peak on the Si (111) plane of the obtained X-ray diffraction chart by performing X-ray diffraction measurement on the silicon material. ..

The abundance and size of the plate-shaped silicon body, amorphous silicon and silicon crystallites contained in the silicon material mainly depend on the heating temperature and the heating time. The heating temperature is preferably in the range of 350 ° C to 950 ° C, more preferably in the range of 400 ° C to 900 ° C.

The average particle size of the silicon material is preferably in the range of 2 to 7 μm, more preferably in the range of 2.5 to 6.5 μm. If a silicon material having an average particle size too small is used, it may be difficult to manufacture a negative electrode from the viewpoint of cohesiveness and wettability. Specifically, in the slurry prepared at the time of manufacturing the negative electrode, the silicon material having an average particle size too small may aggregate. On the other hand, a lithium ion secondary battery provided with a negative electrode using a silicon material having an average particle size too large may not be able to perform suitable charging / discharging. In a silicon material having an average particle size too large, it is presumed that the cause is that lithium ions cannot sufficiently diffuse into the inside of the silicon material. The average particle size in the present specification means _{D 50} when the sample is measured by a general laser diffraction type particle size distribution measuring device.

The Si-containing material is preferably combined with a carbon material to form a negative electrode active material. Due to the compounding, the structure of silicon is particularly stable, and the durability of the negative electrode is improved. The above compounding may be performed by a known method. As the carbon material used for the composite, graphite, hard carbon, soft carbon or the like may be adopted. The graphite may be natural graphite or artificial graphite.
Further, the Si-containing material may be coated with carbon. The carbon-coated Si-containing material has excellent conductivity.

Examples of the binder include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins and carboxymethyl cellulose. , A known material such as styrene-butadiene rubber may be adopted.

Further, a polymer obtained by cross-linking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid with a polyamine such as diamine disclosed in International Publication No. 2016/06382 may be used as a binder.

Examples of the diamine include alkylene diamines such as ethylenediamine, propylenediamine and hexamethylenediamine, saturated carbocyclic diamines such as 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophoronediamine and bis (4-aminocyclohexyl) methane. m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-tridine, 2,4-tolylene diamine, 2 , 6-Tollylene diamine, xylylene diamine, naphthalenediamine and other aromatic diamines.

The mixing ratio of the binder in the active material layer is preferably a mass ratio of active material: binder = 1: 0.005 to 1: 0.3. This is because if the amount of the binder is too small, the moldability of the electrode is lowered, and if the amount of the binder is too large, the energy density of the electrode is lowered.

Conductive aids are added to increase the conductivity of the electrodes. Therefore, the conductive auxiliary agent may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. The conductive auxiliary agent may be a chemically inert electron high conductor, and examples thereof include carbon black, which are carbonaceous fine particles, graphite, Vapor Grown Carbon Fiber, and various metal particles. To. Examples of carbon black include acetylene black, Ketjen black (registered trademark), furnace black, and channel black. These conductive auxiliary agents can be added to the active material layer alone or in combination of two or more. The mixing ratio of the conductive auxiliary agent in the active material layer is preferably a mass ratio of active material: conductive auxiliary agent = 1: 0.01 to 1: 0.5. This is because if the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

In order to form an active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used to collect current. The active material may be applied to the surface of the body. Specifically, an active material, a binder, a solvent, and, if necessary, a conductive auxiliary agent are mixed to form a slurry, and then the slurry is applied to the surface of a current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried one may be compressed.

A crosslinked polymer layer that covers the surface of the active material layer will be described. Since the crosslinked polymer layer is formed on the surface of the active material layer, direct contact between the electrolytic solution and the active material can be suppressed, so that deterioration of the positive electrode active material, the negative electrode active material or the electrolytic solution can be prevented. In the case of a positive electrode formed on the surface of the positive electrode active material layer, the crosslinked polymer layer can mainly suppress oxidative decomposition of the electrolytic solution, and the crosslinked polymer layer is formed on the surface of the negative electrode active material layer. In the case of the negative electrode, it is possible to mainly suppress the reductive decomposition of the electrolytic solution.

The thickness of the crosslinked polymer layer is not particularly limited, but is preferably 0.01 to 20 μm, more preferably 0.05 to 15 μm, further preferably 0.1 to 10 μm, and particularly preferably 0.5 to 5 μm.

To provide a crosslinked polymer layer on the surface of the active material layer, for example, the reaction solution after the reaction step of the method for producing a crosslinked polymer of the present invention is appropriately prepared at an appropriate concentration and applied to the surface of the active material layer. After carrying out the coating step, the drying step may be carried out. In the coating step, conventionally known methods such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method may be used. The drying step may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. The drying temperature may be appropriately set within a range in which the crosslinked polymer does not decompose, and is preferably a temperature equal to or higher than the boiling point of the reaction solvent. The drying time may be appropriately set according to the coating amount and the drying temperature.

The secondary battery of the present invention comprises the electrodes of the present invention. In the secondary battery of the present invention, both the positive electrode and the negative electrode may be the electrodes of the present invention, or one of the electrodes is the electrode of the present invention and the other is not provided with the crosslinked polymer layer. It may be an electrode.

Specific configurations other than the electrodes in the lithium ion secondary battery of the present invention include a separator and an electrolytic solution.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit due to contact between the two electrodes. As the separator, a known one may be adopted, and synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester and polyacrylonitrile, polysaccharides such as cellulose and amylose, and fibroin , Natural polymers such as keratin, lignin, and sverin, porous bodies using one or more electrically insulating materials such as ceramics, non-woven fabrics, and woven fabrics. Further, the separator may have a multi-layer structure.

The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

As the non-aqueous solvent, cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers and the like can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and examples of the cyclic ester include gamma-butyrolactone, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethylmethyl carbonate, and examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetate alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which some or all of the chemical structure of the specific solvent is replaced with fluorine may be adopted.

Examples of the electrolyte include lithium salts such _{as LiClO 4} , LiAsF ₆ , LiPF _{6 , LiBF 4} , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) _2.

As the electrolytic solution, 0.5 mol / mol / mol of lithium salts such as _{LiClO 4} , LiPF ₆ , LiBF ₄ , and LiCF ₃ SO _{3 is} added to a non-aqueous solvent such as fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate. An example is an example of a solution dissolved at a concentration of about 1.7 mol / L from L.

A specific method for manufacturing the lithium ion secondary battery of the present invention will be described.
For example, a separator is sandwiched between a positive electrode and a negative electrode to form an electrode body. The electrode body may be either a laminated type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a laminated body of a positive electrode, a separator and a negative electrode is wound. After connecting the positive electrode collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collector lead or the like, an electrolytic solution is added to the electrode body to form a lithium ion secondary battery. good.

The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical type, a square type, a coin type, and a laminated type can be adopted.

The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, it is advisable to connect a plurality of lithium ion secondary batteries in series to form an assembled battery. In addition to vehicles, devices equipped with lithium-ion secondary batteries include various battery-powered home appliances such as personal computers and portable communication devices, office devices, and industrial devices. Further, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydraulic power generation and other power storage devices and power smoothing devices, power supply sources for power and / or auxiliary equipment such as ships, aircraft, and aircraft. Power supply sources for spacecraft and / or auxiliary equipment, auxiliary power sources for vehicles that do not use electricity as power sources, power sources for mobile home robots, power sources for system backup, power sources for non-disruptive power sources, It may be used as a power storage device that temporarily stores the electric power required for charging in a charging station for an electric vehicle or the like.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. As long as it does not deviate from the gist of the present invention, it can be carried out in various forms with modifications, improvements, etc. that can be made by those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

(Example 1)
The crosslinked polymer of Example 1 was produced as follows. In principle, the reagents and solvents used in the examples of the present specification are dehydrated with a molecular sieve. In addition, each step such as the examples of the present specification is performed in an inert gas atmosphere in principle.

a-1) Step _{A tetrahydrofuran solution containing LiAlH 4} at a concentration of 2 mol / L was prepared. 3 mL of the solution was taken and mixed with 10 mL of tetrahydrofuran to prepare a mixed solution. The mixture contains 6 mmol of LiAlH ₄ .
The mixture was cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.58 g (18 mmol) of methanol was added dropwise to the mixture under stirring. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
LiAlH ₄ + 3CH ₃ OH → Li [AlH (OCH ₃ ) ₃ ] + 3H ₂

a-2) Step The reaction solution obtained in step a-1) is cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.43 g (6 mmol) of acrylic acid is added dropwise to the reaction solution with stirring. did. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
Li [AlH (OCH ₃ ) ₃ ] + CH ₂ = CHCO ₂ H →
Li [(CH ₂ = CHCO ₂ ) Al (OCH ₃ ) ₃ ] + H ₂

Toluene was added to the reaction solution to precipitate a white first monomer. Then, filtration and toluene washing were performed to isolate 1.15 g of the white first monomer of Example 1.

b) Step 0.99 g (5 mmol) of the first monomer of Example 1 and 0.84 g (11.7 mmol) of acrylic acid as the second monomer were dissolved in 10 g of N-methyl-2-pyrrolidone. It was used as a solution. The molar ratio of the first monomer to the second monomer in the solution is 3: 7.
Azobisisobutyronitrile (17.5 mg), which is a polymerization initiator, was added to this solution and heated to 75 ° C. under nitrogen atmosphere conditions and stirring to initiate a random copolymerization reaction. The reaction solution maintained at 75 ° C. was stirred for 6 hours and then cooled to room temperature to obtain a polymer solution of Example 1 containing a polymer in which the first monomer and the second monomer were copolymerized.

c) Step A polyamine solution was prepared by dissolving 0.28 g (1.4 mmol) of 4,4'-diaminodiphenylmethane, which is a polyamine, in 1 g of N-methyl-2-pyrrolidone. A polyamine solution was added to 5 g of the polymer solution of Example 1 (containing 0.77 g of the polymer), and the mixture was stirred for 30 minutes, then heated to 110 ° C. and stirred for 3 hours. The reaction solution was cooled to room temperature to prepare a crosslinked polymer solution containing the crosslinked polymer of Example 1.

_{-Production of Si-containing negative electrode active material CaSi 2} was added to a concentrated hydrochloric acid solution at 0 ° C. under stirring conditions and reacted for 1 hour. Water was added to the reaction solution, filtration was performed, and the yellow powder was collected by filtration. The yellow powder was washed with water, further washed with ethanol, and then dried under reduced pressure to obtain a layered silicon compound containing layered polysilane. Next, the layered silicon compound was heated at 500 ° C. under an argon atmosphere to release hydrogen to produce a silicon material. By heating the silicon material at 880 ° C. in a propane gas atmosphere, a carbon-coated silicon material which is a Si-containing negative electrode active material was produced.

-Manufacture of binder solution Polyacrylic acid containing polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in N-methyl-2-pyrrolidone in an amount of 15% by mass. A solution was produced. Further, 4,4'-diaminodiphenylmethane (Tokyo Chemical Industry Co., Ltd.) is dissolved in N-methyl-2-pyrrolidone, and 4,4'-diaminodiphenylmethane is contained in 50% by mass of 4,4'-diamino. A diphenylmethane solution was produced. Under a nitrogen atmosphere, the mixture of 12.7 parts by mass of the polyacrylic acid solution and 1.05 parts by mass of the 4,4'-diaminodiphenylmethane solution was stirred at room temperature for 30 minutes, and further stirred at 110 ° C. for 2 hours. , A binder solution was produced.

-Manufacturing of negative electrode The above-mentioned binder solution in an amount of 72.5 parts by mass of carbon-coated silicon material as a negative electrode active material, 13.5 parts by mass of acetylene black as a conductive auxiliary agent, and 14 parts by mass of a solid content as a binder. And, an appropriate amount of N-methyl-2-pyrrolidone was mixed to prepare a slurry. A copper foil having a thickness of 30 μm was prepared as a current collector for the negative electrode. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the copper foil coated with the slurry. Then, the copper foil was pressed to obtain a joint. The obtained bonded material was dried by heating in a vacuum dryer at 180 ° C. for 2 hours to produce a negative electrode precursor having a negative electrode active material layer having a thickness of 20 μm. The mixture of polyacrylic acid used as a binder and 4,4'-diaminodiphenylmethane was dehydrated by the above-mentioned heat drying, and the polyacrylic acid was crosslinked with 4,4'-diaminodiphenylmethane. Transforms into a polymer.

N-Methyl-2-pyrrolidone was added to the crosslinked polymer solution containing the crosslinked polymer of Example 1 to prepare a solution containing 10% by mass of the crosslinked polymer of Example 1. Example 1 includes a negative electrode active material layer coated with a crosslinked polymer layer having a thickness of several μm by applying the solution in a film form on the surface of the negative electrode precursor and then heating to remove the solvent. A negative electrode was manufactured.

-Manufacturing of a lithium ion secondary battery The negative electrode of Example 1 was cut to a diameter of 11 mm and used as an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut into a diameter of 16 mm and used as a counter electrode. As a separator, a glass filter (Hoechst Celanese Co., Ltd.) and a single-layer polypropylene celgard 2400 (Polypore Co., Ltd.) were prepared. Further, an electrolytic solution prepared by dissolving _{LiPF 6} at 1 mol / L in a solvent in which 50 parts by volume of ethylene carbonate and 50 parts by volume of diethyl carbonate was mixed was prepared. Two types of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, the celgard 2400, and the evaluation electrode to form an electrode body. This electrode body was housed in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolytic solution was further injected to obtain a coin-type battery. This was used as the lithium ion secondary battery of Example 1.

(Example 2)
The crosslinked polymer of Example 2 was produced as follows.

a-1) Step _{A tetrahydrofuran solution containing LiAlH 4} at a concentration of 2 mol / L was prepared. 3 mL of the solution was taken and mixed with 10 mL of tetrahydrofuran to prepare a mixed solution. The mixture contains 6 mmol of LiAlH ₄ .
The mixture was cooled to −10 ° C., and then a tetrahydrofuran solution containing 1.37 g (18 mmol) of monomethylethylene glycol was added dropwise to the mixture under stirring. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
LiAlH ₄ + 3CH ₃ OCH ₂ CH ₂ OH → Li [AlH (OCH ₂ CH ₂ OCH ₃ ) ₃ ] + 3H ₂

a-2) Step The reaction solution obtained in step a-1) is cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.43 g (6 mmol) of acrylic acid is added dropwise to the reaction solution with stirring. did. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
Li [AlH (OCH ₂ CH ₂ OCH ₃ ) ₃ ] + CH ₂ = CHCO ₂ H →
Li [(CH ₂ = CHCO ₂ ) Al (OCH ₂ CH ₂ OCH ₃ ) ₃ ] + H ₂

Toluene was added to the reaction solution to precipitate a white first monomer. Then, filtration and toluene washing were performed to isolate the white first monomer of Example 2.

b) Step 1.65 g (5 mmol) of the first monomer of Example 2 and 0.84 g (11.7 mmol) of acrylic acid as the second monomer are dissolved in 10 g of N-methyl-2-pyrrolidone. It was used as a solution. The molar ratio of the first monomer to the second monomer in the solution is 3: 7.
Azobisisobutyronitrile (17.5 mg), which is a polymerization initiator, was added to this solution and heated to 75 ° C. under nitrogen atmosphere conditions and stirring to initiate a random copolymerization reaction. The reaction solution maintained at 75 ° C. was stirred for 6 hours and then cooled to room temperature to obtain a polymer solution of Example 2 containing a polymer in which the first monomer and the second monomer were copolymerized.

c) Step A polyamine solution was prepared by dissolving 0.26 g (1.3 mmol) of 4,4'-diaminodiphenylmethane, which is a polyamine, in 1 g of N-methyl-2-pyrrolidone. A polyamine solution was added to 5 g of the polymer solution of Example 2 (containing 1 g of the polymer), and the mixture was stirred for 30 minutes, then heated to 110 ° C. and stirred for 3 hours. The reaction solution was cooled to room temperature to prepare a crosslinked polymer solution containing the crosslinked polymer of Example 2.

Hereinafter, the negative electrode and the lithium ion secondary battery of Example 2 were manufactured by the same method as in Example 1 except that the crosslinked polymer solution containing the crosslinked polymer of Example 2 was used.

(Example 3)
The crosslinked polymer of Example 3 was produced as follows.

a-1) Step _{A tetrahydrofuran solution containing LiAlH 4} at a concentration of 2 mol / L was prepared. 3 mL of the solution was taken and mixed with 10 mL of tetrahydrofuran to prepare a mixed solution. The mixture contains 6 mmol of LiAlH ₄ .
The mixture was cooled to −10 ° C., and then a tetrahydrofuran solution containing 1.8 g (18 mmol) of 2,2,2-trifluoroethanol was added dropwise to the mixture under stirring. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
LiAlH ₄ + 3CF ₃ CH ₂ OH → Li [AlH (OCH ₂ CF ₃ ) ₃ ] + 3H ₂

a-2) Step The reaction solution obtained in step a-1) is cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.43 g (6 mmol) of acrylic acid is added dropwise to the reaction solution with stirring. did. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
Li [AlH (OCH ₂ CF ₃ ) ₃ ] + CH ₂ = CHCO ₂ H →
Li [(CH ₂ = CHCO ₂ ) Al (OCH ₂ CF ₃ ) ₃ ] + H ₂

Toluene was added to the reaction solution to precipitate a white first monomer. Then, filtration and toluene washing were performed to isolate the white first monomer of Example 3.

b) Step 2.01 g (5 mmol) of the first monomer of Example 3 and 0.84 g (11.7 mmol) of acrylic acid as the second monomer were dissolved in 15 g of N-methyl-2-pyrrolidone. It was used as a solution. The molar ratio of the first monomer to the second monomer in the solution is 3: 7.
Azobisisobutyronitrile (17.5 mg), which is a polymerization initiator, was added to this solution and heated to 75 ° C. under nitrogen atmosphere conditions and stirring to initiate a random copolymerization reaction. The reaction solution maintained at 75 ° C. was stirred for 6 hours and then cooled to room temperature to obtain a polymer solution of Example 3 containing a polymer in which the first monomer and the second monomer were copolymerized.

c) Step A polyamine solution was prepared by dissolving 0.19 g (0.96 mmol) of 4,4'-diaminodiphenylmethane, which is a polyamine, in 1 g of N-methyl-2-pyrrolidone. A polyamine solution was added to 5 g of the polymer solution of Example 3 (containing 0.8 g of the polymer), and the mixture was stirred for 30 minutes, then heated to 110 ° C. and stirred for 3 hours. The reaction solution was cooled to room temperature to prepare a crosslinked polymer solution containing the crosslinked polymer of Example 3.

Hereinafter, the negative electrode and the lithium ion secondary battery of Example 3 were manufactured by the same method as in Example 1 except that the crosslinked polymer solution containing the crosslinked polymer of Example 3 was used.

(Example 4)
The crosslinked polymer of Example 4 was produced as follows.

a-1) Step _{A tetrahydrofuran solution containing LiAlH 4} at a concentration of 2 mol / L was prepared. 3 mL of the solution was taken and mixed with 10 mL of tetrahydrofuran to prepare a mixed solution. The mixture contains 6 mmol of LiAlH ₄ .
The mixture was cooled to −10 ° C., and then a tetrahydrofuran solution containing 2.38 g (18 mmol) of 2,2,3,3-tetrafluoropropanol was added dropwise to the mixture under stirring. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
LiAlH ₄ + 3CHF ₂ CF ₂ CH ₂ OH → Li [AlH (OCH ₂ CF ₂ CHF ₂ ) ₃ ] + 3H ₂

a-2) Step The reaction solution obtained in step a-1) is cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.43 g (6 mmol) of acrylic acid is added dropwise to the reaction solution with stirring. did. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
Li [AlH (OCH ₂ CF ₂ CHF ₂ ) ₃ ] + CH ₂ = CHCO ₂ H →
Li [(CH ₂ = CHCO ₂ ) Al (OCH ₂ CF ₂ CHF ₂ ) ₃ ] + H ₂

Toluene was added to the reaction solution to precipitate a white first monomer. Then, filtration and toluene washing were performed to isolate the white first monomer of Example 4.

b) Step 2.49 g (5 mmol) of the first monomer of Example 4 and 0.84 g (11.7 mmol) of acrylic acid as the second monomer are dissolved in 15 g of N-methyl-2-pyrrolidone. It was used as a solution. The molar ratio of the first monomer to the second monomer in the solution is 3: 7.
Azobisisobutyronitrile (17.5 mg), which is a polymerization initiator, was added to this solution and heated to 75 ° C. under nitrogen atmosphere conditions and stirring to initiate a random copolymerization reaction. The reaction solution maintained at 75 ° C. was stirred for 6 hours and then cooled to room temperature to obtain a polymer solution of Example 4 containing a polymer in which the first monomer and the second monomer were copolymerized.

c) Step A polyamine solution was prepared by dissolving 0.18 g (0.91 mmol) of 4,4'-diaminodiphenylmethane, which is a polyamine, in 1 g of N-methyl-2-pyrrolidone. A polyamine solution was added to 5 g of the polymer solution of Example 4 (containing 0.91 g of the polymer), and the mixture was stirred for 30 minutes, then heated to 110 ° C. and stirred for 3 hours. The reaction solution was cooled to room temperature to prepare a crosslinked polymer solution containing the crosslinked polymer of Example 4.

Hereinafter, the negative electrode and the lithium ion secondary battery of Example 4 were manufactured by the same method as in Example 1 except that the crosslinked polymer solution containing the crosslinked polymer of Example 4 was used.

(Example 5)
The crosslinked polymer of Example 5 was produced as follows.

a-1) Step A reaction solution was produced in the same manner as in step a-1) of Example 4.

a-2) Step The reaction solution obtained in step a-1) is cooled to −10 ° C., and then a tetrahydrofuran solution containing 0.61 g (6 mmol) of hydroxymethylacrylamide is added to the reaction solution with stirring. Dropped. After the dropping, the temperature of the reaction solution was raised to room temperature, and the mixture was stirred for 2 hours. The reaction here is shown below by the reaction formula.
Li [AlH (OCH ₂ CF ₂ CHF ₂ ) ₃ ] + CH ₂ = CHCONHCH ₂ OH → Li [(CH ₂ = CHCONHCH ₂ O) Al (OCH ₂ CF ₂ CHF ₂ ) ₃ ] + H ₂

Toluene was added to the reaction solution to precipitate a white first monomer. Then, filtration and toluene washing were performed to isolate the white first monomer of Example 5.

b) Step 2.64 g (5 mmol) of the first monomer of Example 5 and 0.84 g (11.7 mmol) of acrylic acid as the second monomer are dissolved in 15 g of N-methyl-2-pyrrolidone. It was used as a solution. The molar ratio of the first monomer to the second monomer in the solution is 3: 7.
Azobisisobutyronitrile (17.5 mg), which is a polymerization initiator, was added to this solution and heated to 75 ° C. under nitrogen atmosphere conditions and stirring to initiate a random copolymerization reaction. The reaction solution maintained at 75 ° C. was stirred for 6 hours and then cooled to room temperature to obtain a polymer solution of Example 5 containing a polymer in which the first monomer and the second monomer were copolymerized.

c) Step A polyamine solution was prepared by dissolving 0.18 g (0.91 mmol) of 4,4'-diaminodiphenylmethane, which is a polyamine, in 1 g of N-methyl-2-pyrrolidone. A polyamine solution was added to 5 g of the polymer solution of Example 5 (containing 0.94 g of the polymer), and the mixture was stirred for 30 minutes, then heated to 110 ° C. and stirred for 3 hours. The reaction solution was cooled to room temperature to prepare a crosslinked polymer solution containing the crosslinked polymer of Example 5.

Hereinafter, the negative electrode and the lithium ion secondary battery of Example 5 were manufactured by the same method as in Example 1 except that the crosslinked polymer solution containing the crosslinked polymer of Example 5 was used.

(Comparative Example 1)
The negative electrode of Comparative Example 1 (corresponding to the negative electrode precursor in the production of the negative electrode of Example 1) and the lithium ion secondary battery were manufactured by the same method as in Example 1 except that the crosslinked polymer was not used. ..

(Comparative Example 2)
c) The negative electrode and the lithium ion secondary battery of Comparative Example 2 were applied in the same manner as in Example 1 except that the uncrosslinked polymer solution of Example 1 was applied to the surface of the negative electrode precursor without performing the step. Manufactured.

(Comparative Example 3)
Polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) was dissolved in N-methyl-2-pyrrolidone to produce a polyacrylic acid solution containing 15% by mass of polyacrylic acid. Further, 4,4'-diaminodiphenylmethane was dissolved in N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution containing 4,4'-diaminodiphenylmethane in an amount of 50% by mass. Under a nitrogen atmosphere, a mixture of 12.7 parts by mass of the polyacrylic acid solution and 1.7 parts by mass of the 4,4'-diaminodiphenylmethane solution was stirred at room temperature for 30 minutes, and further stirred at 110 ° C. for 2 hours. , A crosslinked polymer solution containing the crosslinked polymer of Comparative Example 3 was produced.

Hereinafter, the negative electrode and the lithium ion secondary battery of Comparative Example 3 are manufactured by the same method as in Example 1 except that the crosslinked polymer solution containing the crosslinked polymer of Comparative Example 3 is applied to the surface of the negative electrode precursor. did.

(Reference example 1)
A polyacrylic acid solution was prepared by dissolving 0.5 parts by mass of polyacrylic acid (weight average molecular weight 250,000, Wako Pure Chemical Industries, Ltd.) in 4.5 parts by mass of ethanol. Further, a diphosphorus pentoxide solution was prepared by dissolving 0.985 parts by mass of diphosphorus pentoxide in 2 parts by mass of ethanol. A diphosphorus pentoxide solution was added dropwise to the polyacrylic acid solution, and then the mixture was stirred for 2 hours to prepare the polymer solution of Reference Example 1. The ethanol used had a water content of 100 ppm or less.
In the polymer solution of Reference Example 1, the ratio of the number of moles of the acrylic acid monomer constituting the polyacrylic acid to the number of moles of diphosphorus pentoxide is 1: 1. In other words, the value of (the number of moles of carboxylic acid group in the carboxylic acid group-containing polymer used) / (the number of moles of phosphorus in the pentavalent phosphorus compound used) is 1/2.

The polymer solution of Reference Example 1 was applied in the form of a film on the surface of an aluminum foil, and then heated to remove ethanol, and the solution was subjected to an infrared spectrophotometer for analysis. From the analysis results, it was considered that the polymer of the polymer solution of Reference Example 1 _{contained the -CO-O-PO (OCH 2} CH ₃ ) _{2 structure.}

Hereinafter, the negative electrode of Reference Example 1 and the lithium ion secondary battery were manufactured by the same method as in Example 1 except that the polymer solution of Reference Example 1 was applied to the surface of the negative electrode precursor.

(Evaluation example 1)
The lithium ion secondary batteries of Examples 1 to 5, Comparative Examples 1 to 3, and Reference Example 1 are charged to 0.01 V at a constant current of 0.05 C rate, and then charged to 0.05 C rate. An initial charge / discharge test was performed in which the battery was discharged to 1.5 V at a constant current. The initial charge / discharge efficiency shown by the charge capacity, the discharge capacity, and the ratio of the discharge capacity to the charge capacity in the initial charge / discharge test was calculated.

Next, the lithium ion secondary batteries of Examples 1 to 5, Comparative Examples 1 to 3, and Reference Example 1 were charged to 0.01 V at a constant current of 0.3 C rate, and then 0.3 C. The charge / discharge cycle of discharging to 1.5 V at a constant current of the rate was repeated 20 times. The capacity retention rate was calculated according to the following formula.
Capacity retention rate (%) = 100 x (discharge capacity in the 20th cycle) / (discharge capacity in the 1st cycle)

The above results are shown in Tables 1 and 2 together with the characteristics of each polymer.

From the results of Tables 1 and 2, the lithium ion secondary batteries of Examples 1 to 5 using the crosslinked polymer of the present invention were compared with the lithium ion secondary batteries of Comparative Example 1 using no polymer. Therefore, it can be seen that excellent characteristics were exhibited in both the initial charge / discharge efficiency and the capacity retention rate.
Further, as compared with the lithium ion secondary battery of Comparative Example 2 using a polymer containing the first monomer unit and the second monomer unit but not cross-linked with polyamine, Examples 1 to 5 It can be seen that the lithium ion secondary battery exhibits a remarkably excellent capacity retention rate.

From these results, the importance of cross-linking with polyamines can be understood. It is considered that the crosslinked polymer of the present invention was able to withstand the expansion and contraction of the negative electrode active material due to charging and discharging because the crosslinked polymer of the present invention was excellent in physical strength due to the crosslinking with polyamine.

Compared with the lithium ion secondary battery of Comparative Example 3 using a polymer that has been cross-linked with polyamine but does not contain the first monomer unit, the lithium ion secondary batteries of Examples 1 to 5 have been replaced with the lithium ion secondary batteries of Examples 1 to 5. It can be seen that excellent characteristics were exhibited in both the initial charge / discharge efficiency and the capacity retention rate.
Further, as compared with the lithium ion secondary battery of Reference Example 1 using a polymer containing P, which does not contain the first monomer unit and has a higher electronegativity than Si, lithium of Examples 1 to 5 is used. It can be seen that the ion secondary battery showed excellent characteristics in both the initial charge / discharge efficiency and the capacity retention rate. In particular, the capacity retention rate of the lithium ion secondary batteries of Examples 1 to 5 is significantly superior to the capacity retention rate of the lithium ion secondary battery of Reference Example 1.

From these results, the importance of the first monomer unit can be understood.
It is suggested that the ate complex-like chemical structure in the first monomer unit is suitable for the movement of charge carriers, and since Al, which has a lower electronegativity than Si, is present in the first monomer unit, the Si-containing negative electrode is present. It is considered that the suppression of the oxidation of the active material was reflected in the test results.

Claims (6)

Formula _{^{(1): M + [(}} (CH 2 = CR 1-1) COR 1-2 O) 4-n Al (L 1) n] - first monomer over represented by (formula (1) In, M is an alkali metal. R ^1-1 is an H or an alkyl group. R ^1-2 is absent or OR ^1-2-1 , SR ^1-2-1 , NR ^{1-2. -2} R ^{1-2-1 is} selected. R ^1-2-1 is a divalent hydrocarbon group that may be substituted with a substituent. R ^1-2-2 is an H or an alkyl group. L ¹ is OH or OR ^1-3 , and R ^1-3 is a hydrocarbon group that may be substituted with a substituent. N is an integer of 0 to 3). ₍₂₎ in :( ^{CH 2 =} CR 2-1) the second monomer over represented by COL ² (general formula ^{(2), R 2-1} is H or an alkyl group .L ² is OH, halogen or OR ^2-2 , where R ^2-2 is a hydrocarbon group which may be substituted with a substituent), and a polymer obtained by polymerizing the polymer.
A crosslinked polymer characterized by being crosslinked with a polyamine. The current collector, the Si-containing negative electrode active material layer formed on the surface of the current collector, and the crosslinked polymer according to claim 1 that covers the surface of the Si-containing negative electrode active material layer are provided. Characterized negative electrode. A power storage device comprising the crosslinked polymer according to claim 1. a) General formula (1'): M ⁺ [(CH ₂ = CR ^1-1 COR ^1-2 O) _4-n Al (L ¹ ) _n ] ^{-The first monomer represented by −} (general formula (1') ), M is an alkali metal. R ^1-1 is an H or an alkyl group. R ^1-2 is absent or OR ^1-2-1 , SR ^1-2-1 , NR ^{1-. 2-2} R ^{1-2-1 is} selected. R ^1-2-1 is a divalent hydrocarbon group that may be substituted with a substituent. R ^1-2-2 is an H or alkyl group. L ¹ is OH or OR ^1-3 , and R ^1-3 is a hydrocarbon group that may be substituted with a substituent. N is an integer of 0 to 3). Process,
b) The first monomer and the second monomer represented by the general formula (2'): CH ₂ = CR ^2-1 COL ² (in the general formula (2'), ^R2-1 is an H or an alkyl group. L ² is OH, halogen or OR ^2-2 , and R ^2-2 is a hydrocarbon group which may be substituted with a substituent.) A step of copolymerizing to obtain a polymer.
c) A step of cross-linking the polymer with a polyamine to produce a cross-linked polymer.
A method for producing a crosslinked polymer, which comprises. a-1) General formula (3): ^{Compound represented by M +} [AlH _4-n (L ¹ ) _n ] ⁻ (In general formula (3), M is an alkali metal. L ¹ is OH or OR. a ^1-3 step R ^1-3 is to prepare it.) an integer which .n 0-3 a hydrocarbon group which may be substituted with a substituent,
a-2) wherein the general formula (3) and a compound represented _by, CH ² = CR 1-1 ^{COR 1-2} compound represented by OH ^{(R 1-1} is H or an alkyl group ^{.R 1-} or ² is absent, ^{or, oR 1-2-1, SR 1-2-1, .R} 1-2-1 selected from NR ^{1-2-2 R 1-2-1} is substituted with a substituent A divalent hydrocarbon group which ^{may be used. R1-2-2} is an H or an alkyl group) and is reacted to form a first monomer.
b) The first monomer and the second monomer represented by the general formula (2'): CH ₂ = CR ^2-1 COL ² (in the general formula (2'), ^R2-1 is an H or an alkyl group. L ² is OH, halogen or OR ^2-2 , and R ^2-2 is a hydrocarbon group which may be substituted with a substituent.) A step of copolymerizing to obtain a polymer.
c) A step of cross-linking the polymer with a polyamine to produce a cross-linked polymer.
A method for producing a crosslinked polymer, which comprises. The steps a) to c) according to claim 4, or the steps a-1) to c) according to claim 5.
And d) the step of coating the Si-containing negative electrode active material layer with the crosslinked polymer,
A method for manufacturing a negative electrode, characterized by having.

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