JP7771582B2 - Sulfur-based active material, electrode, and lithium-ion secondary battery manufacturing method, and modified polymer, sulfur-based active material, electrode, and lithium-ion secondary battery - Google Patents

Description

This disclosure relates to novel methods for producing sulfur-based active materials, electrodes, and lithium-ion secondary batteries, as well as novel modified polymers, sulfur-based active materials, electrodes, and lithium-ion secondary batteries related to these production methods.

Lithium-ion secondary batteries have a large charge/discharge capacity and are therefore primarily used as batteries for portable electronic devices. Their use as batteries for electric vehicles is also increasing, and improvements in their performance are expected.

Patent Document 1 describes a positive electrode active material for lithium-ion secondary batteries obtained by heating raw material powders containing sulfur powder and polyacrylonitrile powder in a non-oxidizing atmosphere. Furthermore, Patent Document 2 describes an inexpensive positive electrode active material that uses industrial rubber.

On the other hand, it has been proposed to increase the battery capacity of lithium-ion secondary batteries by using materials capable of absorbing and releasing more lithium ions, such as silicon (Si) and tin (Sn), as the negative electrode active material.

International Publication No. 2010/044437 JP 2015-92449 A

However, the positive electrode active material in Patent Document 1 has the problem that the raw material, polyacrylonitrile, is expensive, and polyacrylonitrile with stable quality is even more expensive, making it difficult to provide lithium-ion secondary batteries at low cost. The positive electrode active material in Patent Document 2 still has issues in sufficiently improving cycle characteristics. The above materials proposed as negative electrode active materials have the problem of poor cycle characteristics when repeatedly charged and discharged due to large volume changes associated with the absorption and release of lithium ions. Furthermore, sulfur-based materials generally have low conductivity, posing issues with output characteristics.

The present disclosure seeks to provide a sulfur-based active material that can improve the output characteristics of lithium-ion secondary batteries, an electrode containing the sulfur-based active material (i.e., a positive electrode or negative electrode), and a new method for manufacturing a lithium-ion secondary battery containing the electrode, as well as new modified polymers, sulfur-based active materials, electrodes, and lithium-ion secondary batteries related to these manufacturing methods.

After extensive research, the inventors discovered that the above-mentioned problems could be solved by using titanium(IV) oxide of a specific crystalline form, and after further research, they completed the present disclosure. Specifically, the present disclosure relates to the following method for producing a sulfur-based active material.

A method for producing a sulfur-based active material containing a modified polymer,
(1) mixing a polymer, sulfur, and anatase-type tetragonal titanium (IV) oxide to obtain a calcined raw material; and
(2) a step of calcining the calcined raw material and modifying the polymer with sulfur and anatase-type tetragonal titanium(IV) oxide to obtain a modified polymer;
A method for producing a sulfur-based active material comprising:

This disclosure provides a sulfur-based active material that can improve output characteristics, an electrode containing the sulfur-based active material (i.e., a positive electrode or negative electrode), and a new method for manufacturing a lithium-ion secondary battery containing the electrode, as well as new modified polymers, sulfur-based active materials, electrodes, and lithium-ion secondary batteries related to these manufacturing methods.

In this specification, "output characteristics" refers to the characteristic of a secondary battery that maintains its discharge capacity even when charged and discharged at a high hourly rate (C rate). Therefore, a secondary battery with high output characteristics will experience a small decrease in discharge capacity even when the C rate is increased, and conversely, a secondary battery with low output characteristics will experience a large decrease in discharge capacity when the C rate is increased.

In this disclosure, the upper and lower limit values of "greater than or equal to," "less than or equal to," and "to" used to describe a range of values can be arbitrarily combined, and the values in the examples can also be combined with the upper and lower limit values. Furthermore, when a range of values is specified by "to," unless otherwise specified, both end values are included. Furthermore, in this disclosure, a range of values indicated as including both end values is understood to simultaneously indicate a range that does not include either end value, or even a range that does not include both end values, as long as it does not contradict the spirit of this disclosure.

One embodiment of the present disclosure is a method for producing a sulfur-based active material containing a modified polymer, the method including: step (1) of mixing the polymer, sulfur, and anatase-type tetragonal titanium(IV) oxide to obtain a firing raw material; and step (2) of firing the firing raw material to modify the polymer with sulfur and anatase-type tetragonal titanium(IV) oxide to obtain a modified polymer.

The polymer preferably includes at least one polymer selected from the group consisting of a polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1), a polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and a polymer obtained by polymerizing a monomer containing methacrylonitrile.

_CH2 =C( ^R11 ) ^COOR12 (1)

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.)

This is because the effects of this disclosure are more easily realized.

It is preferred that R ¹² is an alkyl group having 1 to 6 carbon atoms, Y is a hydrocarbylene group having 2 to 6 carbon atoms, the hydrocarbylene group having 1 to 4 substituents, the alkyl group as the substituent having 1 to 4 carbon atoms, and the carbon skeleton constituting the hydrocarbylene group having 1 or 2 ether bonds.

This is because the effects of this disclosure are more easily realized.

The firing is preferably carried out in a non-oxidizing atmosphere.

This is because the effects of this disclosure are more easily realized.

The amount of sulfur relative to the polymer is preferably 50 to 1,000 parts by mass of sulfur per 100 parts by mass of polymer.

This is because the effects of this disclosure are more easily realized.

The firing temperature is preferably 250 to 550°C.

This is because the effects of this disclosure are more easily realized.

The particle size of the polymer is preferably 0.1 to 300.0 μm.

This is because the effects of this disclosure are more easily realized.

Another embodiment of the present disclosure is a method for manufacturing an electrode, comprising the steps of manufacturing a sulfur-based active material by any of the manufacturing methods described above, and manufacturing an electrode using the sulfur-based active material (3).

Another embodiment of the present disclosure is a method for manufacturing a lithium ion secondary battery, the method including the step of manufacturing an electrode by the above-described manufacturing method, and the step (4) of manufacturing a lithium ion secondary battery using the electrode.

Another embodiment of the present disclosure is a modified polymer modified with sulfur and anatase tetragonal titanium(IV) oxide, the modified polymer containing titanium sulfide and 35.0% by mass or more of sulfur.

The modified polymer is preferably at least one polymer selected from the group consisting of polymers obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1), polymers obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and polymers obtained by polymerizing a monomer containing methacrylonitrile, modified with sulfur and anatase tetragonal titanium(IV) oxide.

_CH2 =C( ^R11 ) ^COOR12 (1)

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.)

This is because the effects of this disclosure are more easily realized.

It is preferred that R ¹² is an alkyl group having 1 to 6 carbon atoms, Y is a hydrocarbylene group having 2 to 6 carbon atoms, the hydrocarbylene group having 1 to 4 substituents, the alkyl group as the substituent having 1 to 4 carbon atoms, and the carbon skeleton constituting the hydrocarbylene group having 1 or 2 ether bonds.

This is because the effects of this disclosure are more easily realized.

Another embodiment of the present disclosure is a sulfur-based active material containing the above-described modified polymer.

Another embodiment of the present disclosure is an electrode comprising the above-described sulfur-based active material.

Another embodiment of the present disclosure is a lithium-ion secondary battery comprising the above-described electrode.

[Method of manufacturing sulfur-based active material]
A method for producing a sulfur-based active material containing a modified polymer according to the present disclosure will be described below.

<Polymer>
The polymer is not particularly limited as long as, when heat-treated with sulfur and anatase tetragonal titanium(IV) oxide in a non-oxidizing thermal atmosphere, it takes in sulfur and generates ash (metallic components) through the action of the anatase tetragonal titanium(IV) oxide, thereby forming a modified polymer with improved output characteristics.

Examples of such polymers include those containing at least one polymer selected from the group consisting of a polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1), a polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and a polymer obtained by polymerizing a monomer containing methacrylonitrile, or those consisting only of at least one polymer selected from the same group.

_CH2 =C( ^R11 ) ^COOR12 (1)

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.)

(Acrylate Compound (1))
In formula (1), R ¹¹ is preferably a methyl group, and R ¹² is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, with a methyl group, an n-butyl group, an i-butyl group, or a t-butyl group being preferred. Examples of compounds represented by formula (1) include methyl (meth)acrylate and butyl (meth)acrylate, and more preferably methyl methacrylate and butyl methacrylate. Here, the "(meth)acrylate" in methyl (meth)acrylate and butyl (meth)acrylate refers to either "acrylate" or "methacrylate" (the same applies hereinafter). Of these, methacrylate is preferred. An even more preferred example of a compound represented by formula (1) is butyl methacrylate.

(Diacrylate Compound (2))
In formula (2), both R ²¹ and R ²² are preferably methyl groups. The number of carbon atoms in the hydrocarbylene group of Y is preferably 2 to 6, and more preferably 2 or 3. The number of substituents in Y is preferably 1 to 4, and more preferably 1 or 2. The substituents in Y are preferably one or more substituents selected from the group consisting of hydroxyl groups and alkyl groups having 1 to 4 carbon atoms, and the alkyl groups having 1 to 4 carbon atoms are preferably methyl groups. When the carbon skeleton of Y has an ether bond via an oxygen atom, for example, the portion corresponding to -Y-O- is preferably represented by formula (3) below (however, in formula (3), the substituents in Y are not taken into consideration).

-(CH ₂ ) _l -(CH ₂ CH ₂ O) _m -(CH ₂ CH ₂ CH ₂ O) _n - (3)

(Here, l is a number from 0 to 6, m is a number from 0 to 3, and n is a number from 0 to 2. However, l, m, and n cannot all be 0 at the same time.)

In formula (3), it is preferred that l is 1, 2, 3, 4, 5, or 6, and m and n are 0; alternatively, m is 1, 2, or 3, and l and n are 0; or alternatively, n is 1 or 2, and l and m are 0.

Examples of compounds represented by formula (2) include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyne glycol di(meth)acrylate, and glycerin di(meth)acrylate. Of these, ethylene glycol dimethacrylate is preferred.

(Methacrylonitrile-containing monomers)
For the monomer containing methacrylonitrile, known (meth)acrylic monomers such as acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylamide can be suitably used as monomer components other than methacrylonitrile. Among these, one or more selected from the group consisting of acrylonitrile and (meth)acrylic acid esters are preferred, one or more selected from the group consisting of acrylonitrile and methyl methacrylate are more preferred, and acrylonitrile and methyl methacrylate are even more preferred. Here, "(meth)acrylic" means "acrylic" or "methacrylic." Furthermore, conjugated diene compounds such as butadiene and isoprene can also be used as monomer components other than methacrylonitrile.

(Polymer obtained by polymerizing acrylate compound (1))
Although various polymers can be used as the polymer obtained by polymerizing at least one selected from the group consisting of acrylate compounds represented by formula (1), among them, a homopolymer obtained by polymerizing one kind of acrylate compound is preferred. Examples of such homopolymers include a homopolymer of methyl (meth)acrylate and a homopolymer of butyl (meth)acrylate.

(Polymer of acrylate compound (1) and diacrylate compound (2))
Various polymers can be used as the polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by formula (2), but preferred examples include a copolymer of methyl (meth)acrylate and ethylene glycol di(meth)acrylate, a copolymer of butyl (meth)acrylate and ethylene glycol di(meth)acrylate, etc. A more preferred example is a copolymer of butyl methacrylate and ethylene glycol dimethacrylate.

(Polymer obtained by polymerizing a monomer containing methacrylonitrile)
Examples of polymers obtained by polymerizing a monomer containing methacrylonitrile include polymers obtained by homopolymerizing methacrylonitrile (polymethacrylonitrile) and polymers of methacrylonitrile and one or more monomer components other than methacrylonitrile. The monomer components other than methacrylonitrile can be those mentioned above, with acrylonitrile and (meth)acrylic acid esters being preferred. Therefore, polymers containing methacrylonitrile, acrylonitrile, and (meth)acrylic acid esters are preferred. Here, methyl (meth)acrylate is preferred as the (meth)acrylic acid ester, and in this case, methacrylic is preferred as the "(meth)acrylic." In polymers of methacrylonitrile and one or more monomer components other than methacrylonitrile, the copolymerization ratio of methacrylonitrile is typically 1 to 99 mol%, preferably 10 to 95 mol%, more preferably 20 to 90 mol%, and even more preferably 30 to 80 mol%.

(Production of polymers)
In producing a polymer, the order in which the monomers are polymerized is not particularly limited. For example, all the monomers may be randomly polymerized at once, or specific monomers may be polymerized in advance and then the remaining monomers may be added and polymerized, or specific monomers may be polymerized in advance and then block copolymerized.

Polymerization can be carried out by conventional methods such as anionic polymerization or coordination polymerization. There are no particular restrictions on the polymerization method, and any of solution polymerization, emulsion polymerization, gas phase polymerization, and bulk polymerization can be used. Furthermore, the polymerization method may be either batch or continuous.

(Polymer morphology)
The polymer is preferably in the form of fine particles. Here, fine particles refer to particles having a particle diameter of 300.0 μm or less. The particle diameter is preferably 270.0 μm or less, more preferably 200.0 μm or less, even more preferably 100.0 μm or less, even more preferably 50.0 μm or less, even more preferably 20.0 μm or less, even more preferably 15.0 μm or less, even more preferably 13.0 μm or less, even more preferably 10.0 μm or less, and even more preferably 6.0 μm or less. On the other hand, the lower limit of the particle diameter is not particularly limited, but is usually, for example, 0.1 μm or more, preferably 1.0 μm or more. The particle diameter is a value measured using a precision particle size distribution analyzer, Multisizer 3, manufactured by Beckman Coulter, Inc.

The polymer may be spherical microparticles or porous microparticles. When the polymer is porous, its oil absorption is preferably 100 mL/100 g or more, more preferably 110 mL/100 g or more, even more preferably 120 mL/100 g or more, even more preferably 130 mL/100 g or more, and even more preferably 140 mL/100 g or more. The oil absorption is a value measured in accordance with JIS K 5101-13-2:2004. More specifically, it can be measured by the method described in paragraph 0069 of JP 2017-88501 A.

(Polymer weight average molecular weight (Mw))
The Mw of the polymer is not particularly limited as long as it has the above structure. However, the Mw of the polymer is usually within the range of 1,000 to 1,500,000, preferably 2,000 to 1,000,000, and more preferably 10,000 to 300,000. The Mw is a value measured by gel permeation chromatography (GPC) (calibrated with polystyrene).

(Obtaining or manufacturing polymers)
The polymers are commercially available or can be prepared by conventional methods within the knowledge of one skilled in the art, such as those manufactured by Sekisui Plastics Co., Ltd., Kuraray Co., Ltd., and Aica Kogyo Co., Ltd.

<Sulfur>
Sulfur can be used in various forms, such as powdered sulfur, insoluble sulfur, precipitated sulfur, and colloidal sulfur. Of these, precipitated sulfur and colloidal sulfur are preferred. All of these sulfurs are manufactured or sold as elemental sulfur. The amount of sulfur added is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 150 parts by mass or more, even more preferably 200 parts by mass or more, and even more preferably 250 parts by mass or more, per 100 parts by mass of polymer. An amount of sulfur of 100 parts by mass or more tends to improve output characteristics, charge/discharge capacity, and cycle characteristics. On the other hand, there is no particular upper limit to the amount of sulfur added, but it is usually preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 700 parts by mass or less, and even more preferably 600 parts by mass or less. An amount of sulfur of 1000 parts by mass or less tends to be cost-effective. One or more types of sulfur can be used.

<Tetragonal Anatase Titanium Oxide (IV)>
The anatase-type tetragonal titanium(IV) oxide of the present disclosure is a titanium oxide represented by _TiO2 , which has an anatase-type tetragonal crystal structure. Such titanium oxide of the present disclosure is commercially available, and examples thereof include those manufactured by Tokyo Chemical Industry Co., Ltd.

From the perspective of the effects of the present disclosure, the amount of anatase tetragonal titanium(IV) oxide blended is preferably within a specified range. The blended amount is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of polymer. On the other hand, the blended amount is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, and even more preferably 150 parts by mass or less.

<Other ingredients>
When modifying a polymer with sulfur, other materials commonly used in this field may be added to the raw materials to be fired in advance, if desired. Examples of such materials include conductive carbon materials. The use of conductive carbon materials can improve the conductivity of the modified polymer.

Conductive carbon materials are preferably carbon materials with a graphite structure. Examples of such carbon materials that can be used include those with a condensed aromatic ring structure, such as carbon black, acetylene black, ketjen black, graphite, carbon nanotubes (CNT), carbon fiber (CF), graphene, and fullerene. One or more types of conductive carbon materials can be used.

Among these, acetylene black, carbon black, and ketjen black are preferred because they are inexpensive and have excellent dispersibility. Furthermore, small amounts of CNTs or graphene may be used in combination with acetylene black, carbon black, or ketjen black. Such combinations can further improve the cycle characteristics of lithium-ion secondary batteries without significantly increasing costs. The amount of CNTs or graphene used in combination is preferably 8% by mass or more and 12% by mass or less of the total amount of conductive carbon material.

The amount of the conductive carbon material is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of polymer. A blending amount of 5 parts by mass or more tends to further improve charge/discharge capacity and cycle characteristics. On the other hand, the blending amount is preferably 50 parts by mass or less, and more preferably 40 parts by mass or less. A blending amount of 50 parts by mass or less tends to prevent a relative decrease in the proportion of sulfur-containing structures in the modified polymer, and tends to facilitate improvement of charge/discharge capacity and cycle characteristics.

<Step (1)>
Step (1) is a step of mixing a polymer, sulfur, and anatase-type tetragonal titanium dioxide (IV) to obtain a calcined raw material. It is desirable to thoroughly mix the polymer, sulfur, and anatase-type tetragonal titanium dioxide (IV). If other materials are included, they are also mixed. Mixing can be carried out by a conventional method, for example, using a high-speed blender.

<Step (2)>
Step (2) is a step of calcining the calcined raw material to modify the polymer with sulfur and anatase-type tetragonal titanium(IV) oxide to obtain a modified polymer.

(Firing)
The calcination can be carried out by a conventional method, for example, by heating the calcination raw material in a non-oxidizing atmosphere at a predetermined temperature increase rate until a predetermined temperature is reached, maintaining the temperature at the predetermined temperature for a predetermined time, and then allowing it to cool naturally.

(Non-oxidizing atmosphere)
The non-oxidizing atmosphere refers to an atmosphere that is substantially free of oxygen and is adopted to suppress oxidative deterioration of the constituent components and excessive thermal decomposition. Specifically, it refers to an inert gas atmosphere such as nitrogen or argon, a sulfur gas atmosphere, etc. Calcination can be suitably carried out, for example, in an inert gas atmosphere.

(Temperature increase rate)
The temperature rise rate is preferably, for example, within the range of 50 to 500°C/h. The temperature rise rate is more preferably 100°C/h or higher. On the other hand, the temperature rise rate is more preferably 400°C/h or lower, even more preferably 300°C/h or lower, and even more preferably 200°C/h or lower. When the temperature rise rate is within such a range, the effects of the present disclosure tend to be easily achieved.

(Baking temperature and time)
The calcination temperature refers to the temperature after the temperature rise of the calcination raw material is completed, and is maintained for a certain period of time to calcinate the calcination raw material. The temperature is preferably in the range of 250 to 550°C. A temperature of 250°C or higher tends to avoid insufficient sulfurization reaction and prevent a decrease in the charge/discharge capacity of the target product. On the other hand, a temperature of 550°C or lower tends to prevent decomposition of the calcination raw material and prevent a decrease in yield and a decrease in charge/discharge capacity. The temperature is more preferably 300°C or higher, and even more preferably 350°C or higher. On the other hand, the temperature is more preferably 500°C or lower, and more preferably 450°C or lower.

The time for which the firing temperature is maintained can be set appropriately depending on the type of firing raw material, the firing temperature, etc., but is preferably 1 to 6 hours, for example. A time of 1 hour or more tends to allow firing to proceed sufficiently, while a time of 6 hours or less tends to prevent excessive thermal decomposition of the constituent components.

(Device)
The calcination can be carried out using a muffle furnace, or alternatively, using a continuous device such as a twin-screw extruder. The use of a continuous device has the advantage that the modified polymer can be continuously produced through a series of operations, such as kneading, pulverizing, and mixing the calcination raw materials while calcining them. On the other hand, a muffle furnace is a furnace partitioned by a hot plate or the like so that the heat source (heater) is not exposed inside the furnace. The use of a muffle furnace can prevent contamination of the calcined material and also suppress changes in the atmosphere inside the furnace, contributing to more precise calcination.

<Residue removal process>
The treated product obtained after calcination contains unreacted sulfur, which is the sulfur that sublimed during calcination and then cooled and precipitated. These residues are a factor in reducing cycle characteristics, so it is desirable to remove them as much as possible. The removal of residues can be carried out by conventional methods, such as reduced-pressure heating drying, hot air drying, and solvent washing.

<Crushing and classification>
The resulting modified polymer can be pulverized to a predetermined particle size and classified to obtain particles of a size suitable for the production of electrodes. The preferred particle size distribution is a median diameter of about 5 to 40 μm. In the firing method using the twin-screw extruder described above, the modified polymer can be pulverized simultaneously with the production of the modified polymer by shearing during kneading.

<Sulfur-based active material>
The modified polymer obtained by the above process can be used as a sulfur-based active material as it is. The sulfur-based active material of the present disclosure may contain the modified polymer, and may optionally contain a sulfur-based active material other than the modified polymer, as long as the effect of the present disclosure is not affected. Furthermore, the sulfur-based active material of the present disclosure may consist solely of the modified polymer.

[Electrode manufacturing method]
The electrode of the present disclosure can be produced by using the sulfur-based active material of the present disclosure as an electrode active material for a lithium-ion secondary battery, i.e., as a positive electrode active material or a negative electrode active material. That is, the electrode of the present disclosure can be produced in the same manner as in the production of a general electrode for a lithium-ion secondary battery, except that the sulfur-based active material of the present disclosure is used.

<Method of manufacturing positive electrode>
When the sulfur-based active material of the present disclosure is used as a positive electrode active material for a lithium-ion secondary battery, the positive electrode can be manufactured in the same manner as a typical positive electrode for a lithium-ion secondary battery, except that the sulfur-based active material of the present disclosure is used as the positive electrode active material. For example, the positive electrode can be manufactured by mixing particulate sulfur-based active material with a conductive additive, a binder, and a solvent to prepare a paste-like positive electrode material, applying the positive electrode material to a current collector, and drying it. Alternatively, the positive electrode can be manufactured by kneading the sulfur-based active material of the present disclosure together with a conductive additive, a binder, and a small amount of solvent in a mortar or the like, forming it into a film, and then pressing it onto a current collector using a press or the like.

(Conductive additive)
Examples of the conductive additive include vapor grown carbon fiber (VGCF), carbon powder, carbon black (CB), acetylene black (AB), ketjen black (KB), graphite, or fine powder of a metal that is stable at a positive electrode potential, such as aluminum or titanium. These conductive additives can be used alone or in combination.

(binder)
Examples of binders include polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyimide (PI), polyamideimide (PAI), carboxymethyl cellulose (CMC), polyvinyl chloride (PVC), acrylic resin, methacrylic resin (PMA), polyacrylonitrile (PAN), modified polyphenylene oxide (PPO), polyethylene oxide (PEO), polyethylene (PE), polypropylene (PP), etc. These binders can be used alone or in combination of two or more.

(solvent)
Examples of the solvent include N-methyl-2-pyrrolidone, N,N-dimethylformaldehyde, alcohol, hexane, water, etc. These solvents can be used alone or in combination of two or more.

(Amount)
The amounts of the materials constituting the positive electrode are not particularly limited, but for example, it is preferable to mix 2 to 100 parts by mass of a conductive additive, 2 to 50 parts by mass of a binder, and an appropriate amount of a solvent with 100 parts by mass of a sulfur-based active material.

(Current collector)
As the current collector, a material commonly used for lithium-ion secondary battery positive electrodes may be used. Examples of current collectors include aluminum foil, aluminum mesh, punched aluminum sheet, aluminum expanded sheet, stainless steel foil, stainless steel mesh, punched stainless steel sheet, stainless steel expanded sheet, foamed nickel, nickel nonwoven fabric, copper foil, copper mesh, punched copper sheet, copper expanded sheet, titanium foil, titanium mesh, carbon nonwoven fabric, and carbon woven fabric. Among these, current collectors made of highly graphitized carbon nonwoven fabric and carbon woven fabric are suitable as current collectors when the sulfur-based active material of the present disclosure is used as a positive electrode active material because they do not contain hydrogen and have low reactivity with sulfur. As raw materials for highly graphitized carbon fibers, various pitches (i.e., by-products of petroleum, coal, coal tar, etc.) and polyacrylonitrile fiber (PAN), which are used as carbon fiber materials, can be used. One type of current collector can be used, or two or more types can be used in combination.

<Method of manufacturing negative electrode>
When the sulfur-based active material of the present disclosure is used as the negative electrode active material of a lithium-ion secondary battery, the negative electrode can be manufactured in the same manner as a general negative electrode for a lithium-ion secondary battery, except that the sulfur-based active material of the present disclosure is used as the negative electrode active material. For example, the negative electrode can be manufactured by mixing particulate sulfur-based active material with a conductive additive, a binder, and a solvent to prepare a paste-like negative electrode material, applying the paste to a current collector, and drying the paste. Alternatively, the negative electrode can be manufactured by kneading the sulfur-based active material of the present disclosure together with the conductive additive, the binder, and a small amount of solvent in a mortar or the like, forming a film, and then pressing the film onto a current collector using a press or the like.

The conductive additive, binder, and solvent can be the same as those described in the positive electrode manufacturing method above, and the amounts of these ingredients are also as described above. The current collector can also be the same as those described in the positive electrode manufacturing method above.

[Method of manufacturing lithium ion secondary battery]
The lithium ion secondary battery of the present disclosure can be manufactured in the same manner as in the manufacture of a general lithium ion secondary battery, except that the lithium ion secondary battery electrode is used as the lithium ion secondary battery electrode.

<When a sulfur-based active material is used as a positive electrode active material>
The lithium ion secondary battery of the present disclosure can be manufactured according to a conventional method using a positive electrode containing the sulfur-based active material (positive electrode active material) of the present disclosure, a negative electrode, an electrolyte, and, if desired, components such as a separator.

(Negative electrode)
Examples of anode materials that can be used include known metallic lithium, carbon-based materials such as graphite, silicon-based materials such as silicon thin films, and alloy-based materials such as copper-tin and cobalt-tin. Lithium-free materials, such as carbon-based, silicon-based, and alloy-based materials among the above-mentioned anode materials, are advantageous in that they are less likely to cause short circuits between the positive and negative electrodes due to dendrite formation. However, when these lithium-free anode materials are used in combination with the positive electrode of the present disclosure, neither the positive nor negative electrodes contain lithium. Therefore, a lithium pre-doping process is required to pre-insert lithium into either the negative electrode or the positive electrode, or both. Known methods for pre-doping lithium can be used. For example, when doping lithium into the anode, lithium can be inserted into a half-cell assembled using metallic lithium as the counter electrode by electrochemical doping, or by a pre-doping method in which lithium is inserted by attaching a metallic lithium foil to the electrode and then leaving it in an electrolyte solution, thereby utilizing the diffusion of lithium into the electrode. The above-mentioned electrolytic doping method can also be used when pre-doping the positive electrode with lithium. As a lithium-free negative electrode material, a silicon-based material, which is a high-capacity negative electrode material, is particularly preferred, and among them, thin-film silicon, which has a thin electrode thickness and is advantageous in terms of capacity per volume, is more preferred.

(electrolyte)
The electrolyte used in lithium ion secondary batteries can be an organic solvent containing an electrolyte alkali metal salt dissolved therein. The organic solvent is preferably at least one selected from non-aqueous solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl ether, γ-butyrolactone, and acetonitrile. Examples of the electrolyte that can be used include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiI, and LiClO ₄ . The electrolyte concentration may be approximately 0.5 mol/L to 1.7 mol/L. The electrolyte is not limited to a liquid form. For example, when the lithium ion secondary battery is a lithium polymer secondary battery, the electrolyte is solid (e.g., polymer gel).

(separator)
In addition to the negative electrode, positive electrode, and electrolyte described above, a lithium-ion secondary battery may also include components such as a separator. The separator is interposed between the positive electrode and negative electrode, allowing ions to move between the positive electrode and negative electrode and preventing internal short-circuiting between the positive electrode and negative electrode. If the lithium-ion secondary battery is a sealed type, the separator is also required to have the function of retaining the electrolyte. As the separator, a thin, microporous or nonwoven membrane made of a material such as polyethylene, polypropylene, polyacrylonitrile, aramid, polyimide, cellulose, or glass is preferably used.

(shape)
The shape of the lithium ion secondary battery is not particularly limited, and it can be in various shapes such as a cylindrical type, a laminated type, a coin type, a button type, and the like.

<When a sulfur-based active material is used as a negative electrode active material>
The lithium ion secondary battery of the present disclosure can be manufactured according to a conventional method by using a negative electrode containing the sulfur-based active material (negative electrode active material) of the present disclosure, a positive electrode, an electrolyte, and, if desired, components such as a separator.

(positive electrode)
The positive electrode material is not particularly limited as long as it is, for example, a lithium-containing transition metal oxide or solid solution oxide, or a substance capable of electrochemically absorbing and releasing lithium ions. Examples of lithium-containing transition metal oxides include Li-Co-based composite oxides _such as _LiCoO2 , Li _- Ni-Co _{- Mn} -based composite oxides such as _LiNiO2 , Li-Ni-based composite oxides such as LiNiO2, and Li-Mn- _based composite oxides such as _LiMn2O4 . Examples of solid solution _oxides include _{LiaMnxCoyNizO2 ( 1.150} ≦a≦1.430 _{, 0.450} ≦x≦0.600, _0.100 ≦y≦0.150, 0.200≦z≦0.280) _{, LiMnxCoyNizO2} (0.300≦x≦0.850, 0.100≦y≦0.300, 0.100≦z≦ _0.300 ), and _{LiMn1.5Ni0.5O4 .} These compounds may be used alone or in combination.

The electrolyte, separator, and shape of the lithium-ion secondary battery can be the same as those described above when the sulfur-based active material of the present disclosure is used as the positive electrode active material.

[Modified polymer]
The modified polymer of the present disclosure is a modified polymer modified with sulfur and anatase-type tetragonal titanium(IV) oxide, and contains titanium sulfide and 35.0 mass% or more of sulfur.

The modified polymer of the present disclosure contains titanium sulfide, which is produced during the process of modifying the polymer with sulfur and anatase tetragonal titanium(IV) oxide.

The modified polymer of the present disclosure exhibits a predetermined amount of ash content (amount of metal components). The higher the ash content produced using anatase-type tetragonal titanium(IV) oxide, the more likely the output characteristics will improve. Therefore, it is presumed that a higher ash content is preferable. Generally, the preferred range of ash content in the modified polymer is 10.0% by mass or more, more preferably 15.0% by mass or more, even more preferably 20.0% by mass or more, even more preferably 21.0% by mass or more, even more preferably 22.0% by mass or more, even more preferably 22.5% by mass or more, and even more preferably 23.0% by mass or more. There is no particular upper limit for the ash content, but it may typically be, for example, approximately 50.0% by mass or less, approximately 45.0% by mass or less, or approximately 42.0% by mass or less. In the present disclosure, the ash content is determined by the method described in the Examples section below.

The modified polymer of the present disclosure exhibits a predetermined sulfur content. The sulfur content is preferably 35.0% by mass or more, more preferably 35.5% by mass or more, even more preferably 36.0% by mass or more, even more preferably 36.5% by mass or more, and even more preferably 36.8% by mass or more. Having a sulfur content within the above range tends to make it easier to achieve the effects of the present disclosure. Meanwhile, the upper limit of the sulfur content is not particularly limited, but may be, for example, 50.0% by mass or less, 49.5% by mass or less, 49.0% by mass or less, 48.5% by mass or less, 48.0% by mass or less, or 47.9% by mass or less. In the present disclosure, the sulfur content is determined by the method described in the Examples section below.

The modified polymer of the present disclosure is produced by the method described above in the section on the method for producing a sulfur-based active material. Therefore, the explanation in the section on the method for producing a sulfur-based active material above can also be used to explain the modified polymer, provided there is no contradiction.

[Sulfur-based active material]
The sulfur-based active material of the present disclosure contains the modified polymer. Therefore, the sulfur-based active material of the present disclosure may contain a sulfur-based active material other than the modified polymer, or may consist solely of the modified polymer, as desired.

The sulfur-based active material of the present disclosure is manufactured by the method described above in the section on manufacturing methods for sulfur-based active materials. Therefore, the explanation in the section on manufacturing methods for sulfur-based active materials above can also be used to describe sulfur-based active materials, as long as there are no contradictions.

[electrode]
The electrode of the present disclosure comprises the sulfur-based active material of the present disclosure.

The electrodes disclosed herein are manufactured using the method described in the electrode manufacturing method section above. Therefore, the explanation in the electrode manufacturing method section above can also be used to describe the electrodes, provided there are no contradictions.

[Lithium-ion secondary battery]
The lithium ion secondary battery of the present disclosure comprises the electrode of the present disclosure.

The lithium-ion secondary battery disclosed herein is manufactured by the method described above in the section on manufacturing methods for lithium-ion secondary batteries. Therefore, the explanation in the section on manufacturing methods for lithium-ion secondary batteries above can also be used to describe lithium-ion secondary batteries, provided there are no contradictions.

This disclosure will be described based on examples, but is not limited to these examples.

The various chemicals used in the examples and comparative examples are listed below. Where necessary, the various chemicals were purified according to standard methods.

[Materials used in the test]
Polymer 1: Spherical acrylic resin consisting of butyl methacrylate and ethylene glycol dimethacrylate copolymer (Techpolymer BM30X-5 manufactured by Sekisui Plastics Co., Ltd., particle size: 5 μm)
Polymer 2: Spherical acrylic resin consisting of a homopolymer of methyl methacrylate (Techpolymer MB-8 manufactured by Sekisui Plastics Co., Ltd., particle size: 8 μm)
Sulfur: precipitated sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Titanium oxide (anatase): tetragonal anatase titanium(IV) oxide manufactured by Tokyo Chemical Industry Co., Ltd.
Titanium oxide (rutile): rutile-type tetragonal titanium(IV) oxide manufactured by Tokyo Chemical Industry Co., Ltd.

[Example 1]
<Production of raw materials>
According to the formulation in Table 1, the materials were mixed in a blender to obtain a raw material for firing (a raw material for firing).

(Reaction Apparatus)
A muffle furnace was used to sinter the raw materials. A muffle furnace is a furnace that is partitioned with a hot plate or the like so that the heat source (heater) is not exposed inside the furnace to prevent contamination of the samples. The muffle furnace used has a heater at the bottom of the furnace, which is partitioned with a hot plate. A lid is installed on the front of the furnace, and the furnace is designed to maintain an inert gas atmosphere inside. A thermocouple is attached to the lid, which allows the temperature inside the furnace to be measured during sintering. Two tiers of SUS rectangular trays, an upper tier and a lower tier, are installed inside the furnace to sinter the raw materials.

Gas (e.g., argon (Ar) gas) can be continuously supplied to and discharged from the furnace from outside through a gas inlet pipe and a gas outlet pipe. The gas outlet pipe is connected to a trap tank containing an aqueous sodium hydroxide solution, and exhaust gas attempting to escape from the muffle furnace through the gas outlet pipe first passes through the aqueous sodium hydroxide solution in the trap tank before being released to the outside. Therefore, even if the exhaust gas contains hydrogen sulfide gas generated by the reaction, it is neutralized by the aqueous sodium hydroxide solution and removed from the exhaust gas.

(Firing process)
First, with the firing raw materials contained in a SUS container, the atmosphere in the muffle furnace was replaced with Ar gas three times using a vacuum pump. Then, Ar gas was continuously supplied from the gas inlet tube at a flow rate of 100 mL/min, and 30 minutes after the start of supply, heating of the muffle furnace began. The temperature was increased at a rate of 5 ° C/min, and when the temperature of the firing raw materials reached 400 ° C, heat treatment was performed for 2 hours while maintaining the temperature at 400 ° C. Next, while adjusting the flow rate of Ar gas, the temperature of the fired product was naturally cooled to 25 ° C under an Ar gas atmosphere, and the fired product was then removed from the muffle furnace.

(Removal of unreacted sulfur)
To remove unreacted sulfur (free elemental sulfur) remaining in the calcined product, the following process was carried out. The calcined product was pulverized in a mortar, and 2 g of the pulverized product was placed in a glass tube oven and heated at 250°C for 3 hours while evacuating to obtain a calcined product from which unreacted sulfur had been removed (or which contained only a trace amount of unreacted sulfur). The heating rate was 10°C/min.

(Classification work)
In order to remove coarse particles from the fired product, the fired product was classified using a 32 μm mesh stainless steel sieve to obtain Modified Polymer 1.

<Manufacturing of lithium-ion secondary batteries>
A lithium ion secondary battery was manufactured as follows.

(positive electrode)
Modified polymer 1 was used as the sulfur-based active material, acetylene black as the conductive additive, and acrylic resin as the binder. These were weighed so that the ratio of active material: conductive additive: binder = 90:5:5 (mass%), placed in a container, and stirred and mixed using a centrifugal mixer (ARE-250 manufactured by Thinky Corporation) using milliQ water as a dispersant to produce a uniform slurry. The produced slurry was applied to a 20 μm aluminum foil using an applicator with a slit width of 60 μm, and the compressed electrode was heated in a dryer at 120 ° C. for 3 hours, dried, and punched out to φ11 to obtain an electrode (positive electrode). Then, the weight of the electrode was measured, and the amount of active material in the electrode was calculated from the above ratio.

(Negative electrode)
As the negative electrode, a metallic lithium foil (disk-shaped, 14 mm in diameter and 500 μm in thickness, manufactured by Honjo Metals Co., Ltd.) was used.

(electrolyte)
The electrolyte used was a non-aqueous electrolyte prepared by dissolving _LiPF6 in a mixed solvent of ethylene carbonate and diethyl carbonate. The ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1:1. The concentration of _LiPF6 in the electrolyte was 1.0 mol/L.

(lithium ion secondary battery)
A coin battery was fabricated using the above positive and negative electrodes. Specifically, in a dry room, a separator (Celgard 2400, a 25 μm thick polypropylene microporous membrane manufactured by Celgard) and a glass nonwoven fabric filter (440 μm thick, GA100 manufactured by Advantec) were sandwiched between the positive and negative electrodes to form an electrode battery. This electrode battery was housed in a battery case (CR2032 type coin battery material, manufactured by Hosen Co., Ltd.) made of a stainless steel container. The above electrolyte solution was poured into the battery case. The battery case was sealed using a crimping machine to obtain the lithium ion secondary battery of Example 1.

[Examples 2 to 6 and Comparative Examples 1 to 3]
Except for making appropriate changes according to the formulations and conditions in Table 1, the same procedures as in Example 1 were carried out to produce the respective firing raw materials, modified polymers, and lithium ion secondary batteries.

[evaluation]
<Sulfur content analysis>
The amount of sulfur in the modified polymer was determined by calculating the mass ratio (%) of the sulfur content to the total amount of the modified polymer from the mass measured using an ion chromatograph DX-320 manufactured by Dionex Corporation and a column (IonPac AS12A) manufactured by the same company.

<Ash content (metal content)>
The modified polymers produced in the examples and comparative examples were subjected to thermogravimetry to determine the ash content (%).

The thermogravimetric measurement was performed using a TGA Q500 manufactured by TA Instruments. The measurement conditions were as follows: heating to 750°C in an Ar atmosphere at a temperature increase rate of 70°C/min, then introducing air and maintaining the same temperature for an additional 5 minutes to decompose the modified polymer. The remaining amount was taken as the ash content (amount of metal components), and the ash content (%) was calculated.

<Charge/discharge capacity measurement test>
The coin-type lithium ion secondary batteries produced in each of the Examples and Comparative Examples were charged and discharged at a current value equivalent to 50 mA (0.1 C) per 1 g of positive electrode active material under the conditions of a test temperature of 30°C, a discharge cut-off voltage of 1.0 V, and a charge cut-off voltage of 3.0 V, and the discharge capacity (mAh) up to the 10th charge was observed.

The battery was also charged and discharged in the same manner at a current value equivalent to 250 mA at 0.5 C, a current value equivalent to 500 mA at 1.0 C, and a current value equivalent to 1000 mA at 2.0 C, and the discharge capacity (mAh) up to the 10th cycle was observed.

As can be seen from Table 1, the examples of the present disclosure show little decrease in battery capacity and excellent output characteristics even when charged and discharged at high current values of 0.5C, 1.0C, and 2.0C.

<Embodiment>
Examples of embodiments of the present disclosure are provided below.

[1] A method for producing a sulfur-based active material containing a modified polymer,
(1) mixing a polymer, sulfur, and anatase-type tetragonal titanium (IV) oxide to obtain a calcined raw material; and
(2) a step of calcining the calcined raw material and modifying the polymer with sulfur and anatase-type tetragonal titanium(IV) oxide to obtain a modified polymer;
A method for producing a sulfur-based active material comprising:
[2] The polymer is
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1):
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and
The method for producing a sulfur-based active material according to [1] above, which contains at least one polymer selected from the group consisting of polymers obtained by polymerizing a monomer containing methacrylonitrile.

_CH2 =C( ^R11 ) ^COOR12 (1)

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.)
[3] R ¹² is an alkyl group having 1 to 6 carbon atoms, preferably 1 to 4, and Y is a hydrocarbylene group having 2 to 6 carbon atoms, preferably 2 or 3, and in the hydrocarbylene group, the number of substituents is 1 to 4, preferably 1 or 2, the number of carbon atoms in the alkyl group that is the substituent is 1 to 4, preferably 1, and the number of ether bonds in the carbon skeleton that constitutes the hydrocarbylene group is 1 to 2. The method for producing a sulfur-based active material according to [1] or [2] above.
[4] The method for producing a sulfur-based active material according to any one of [1] to [3] above, wherein the firing is carried out in a non-oxidizing atmosphere.
[5] The amount of sulfur relative to the polymer is 50 to 1000 parts by mass, preferably 100 to 800 parts by mass, more preferably 150 to 700 parts by mass, still more preferably 200 to 600 parts by mass, and still more preferably 250 to 600 parts by mass, relative to 100 parts by mass of the polymer. [1] to [4] The method for producing a sulfur-based active material according to any one of the above.
[6] The method for producing a sulfur-based active material according to any one of [1] to [5] above, wherein the firing temperature is 250 to 550 ° C, preferably 300 to 500 ° C, more preferably 350 to 450 ° C.
[7] The particle diameter of the polymer is 0.1 to 300.0 μm, preferably 0.1 to 270.0 μm, more preferably 0.1 to 200.0 μm, even more preferably 0.1 to 100.0 μm, even more preferably 0.1 to 50.0 μm, even more preferably 0.1 to 20.0 μm, even more preferably 0.1 to 15.0 μm, even more preferably 0.1 to 13.0 μm, even more preferably 0.1 to 10.0 μm, even more preferably 0.1 to 6.0 μm, even more preferably 1.0 to 6.0 μm. [1] The method for producing a sulfur-based active material according to any one of [6] to [6] above.
[8] A method for manufacturing an electrode, comprising:
A step of producing a sulfur-based active material by the production method according to any one of [1] to [7] above; and
Step (3) of producing an electrode using the sulfur-based active material
A method for manufacturing an electrode comprising the steps of:
[9] A method for manufacturing a lithium ion secondary battery, comprising:
A step of producing an electrode by the production method described in [8] above; and
(4) producing a lithium ion secondary battery using the electrode;
A method for manufacturing a lithium ion secondary battery comprising:
[10] A modified polymer modified with sulfur and anatase-type tetragonal titanium(IV) oxide,
The modified polymer contains titanium sulfide and has a sulfur content of 35.0% by mass or more, preferably 35.5% by mass or more, more preferably 36.0% by mass or more, even more preferably 36.5% by mass or more, and still more preferably 36.8% by mass or more.
[11] The modified polymer is
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1):
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and
The modified polymer according to [10] above, wherein at least one polymer selected from the group consisting of polymers obtained by polymerizing a monomer containing methacrylonitrile is modified with sulfur and anatase-type tetragonal titanium(IV) oxide.

_CH2 =C( ^R11 ) ^COOR12 (1)

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.)
[12] The modified polymer according to the above [10] or [11], wherein R ¹² is an alkyl group having 1 to 6 carbon atoms, preferably 1 to 4, and Y is a hydrocarbylene group having 2 to 6 carbon atoms, preferably 2 or 3, and the hydrocarbylene group has 1 to 4, preferably 1 or 2, substituents, the alkyl group as the substituent has 1 to 4, preferably 1, carbon atom, and the carbon skeleton constituting the hydrocarbylene group has 1 or 2 ether bonds.
[13] A sulfur-based active material comprising the modified polymer according to any one of [10] to [12] above.
[14] An electrode comprising the sulfur-based active material according to [13] above.
[15] A lithium ion secondary battery comprising the electrode according to [14] above.

Claims (15)

A method for producing a sulfur-based active material containing a modified polymer,
(1) mixing a polymer, sulfur, and anatase-type tetragonal titanium (IV) oxide to obtain a calcined raw material; and
(2) a step of calcining the calcined raw material and modifying the polymer with sulfur and anatase-type tetragonal titanium(IV) oxide to obtain a modified polymer;
A method for producing a sulfur-based active material comprising:
The polymer
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1):
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and
Polymers made by polymerizing monomers containing methacrylonitrile
A method for producing a sulfur-based active material, comprising:

CH2 =C(R11 ₎ ^COOR12 ( ¹ )

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.) the polymer obtained by polymerizing a monomer containing methacrylonitrile is a polymer obtained by homopolymerizing methacrylonitrile or a polymer of methacrylonitrile and one or more monomer components other than methacrylonitrile,
2. The method for producing a sulfur-based active material according to claim 1, wherein the monomer component other than methacrylonitrile is selected from the group consisting of acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylamide . 3. The method for producing a sulfur-based active material according to claim 1 or 2, wherein R ¹² is an alkyl group having 1 to 6 carbon atoms, Y is a hydrocarbylene group having 2 to 6 carbon atoms, the hydrocarbylene group has 1 to 4 substituents, the alkyl group that is the substituent has 1 to 4 carbon atoms, and the carbon skeleton constituting the hydrocarbylene group has 1 to 2 ether bonds. The method for producing a sulfur-based active material according to any one of claims 1 to 3, wherein the calcination is carried out in a non-oxidizing atmosphere. The method for producing a sulfur-based active material according to any one of claims 1 to 4, wherein the amount of sulfur relative to the polymer is 50 to 1,000 parts by mass of sulfur per 100 parts by mass of polymer. The method for producing a sulfur-based active material according to any one of claims 1 to 5, wherein the firing temperature is 250 to 550°C. The method for producing a sulfur-based active material according to any one of claims 1 to 6, wherein the particle diameter of the polymer is 0.1 to 300.0 μm. A method for manufacturing an electrode, comprising:
A step of producing a sulfur-based active material by the production method according to any one of claims 1 to 7; and
Step (3) of producing an electrode using the sulfur-based active material
A method for manufacturing an electrode comprising the steps of: A method for manufacturing a lithium ion secondary battery, comprising:
producing an electrode by the method of claim 8; and
(4) producing a lithium ion secondary battery using the electrode;
A method for manufacturing a lithium ion secondary battery comprising: A modified polymer modified with sulfur and anatase tetragonal titanium(IV) oxide,
The modified polymer contains titanium sulfide and has a sulfur content of 35.0% by mass or more,
The modified polymer is
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1):
A polymer obtained by polymerizing at least one compound selected from the group consisting of acrylate compounds represented by the following formula (1) and at least one compound selected from the group consisting of diacrylate compounds represented by the following formula (2), and
Polymers made by polymerizing monomers containing methacrylonitrile
1. A modified polymer , wherein at least one polymer selected from the group consisting of: is modified with sulfur and anatase-type tetragonal titanium(IV) oxide .

CH2 =C(R11 ₎ ^COOR12 ( ¹ )

(wherein R ¹¹ is a hydrogen atom or a methyl group, and R ¹² is an alkyl group.)

CH ₂ =C(R ²¹ )COO-Y-OCO(R ²² )C=CH ₂ (2)

(wherein R ²¹ and R ²² are the same or different and each represent a hydrogen atom or a methyl group; Y is a hydrocarbylene group; the hydrocarbylene group may have at least one substituent selected from the group consisting of a hydroxyl group and an alkyl group; and the carbon skeleton constituting the hydrocarbylene group may have an ether bond via an oxygen atom; however, when there are two or more ether bonds, there are always two or more carbon atoms between adjacent oxygen atoms.) the polymer obtained by polymerizing a monomer containing methacrylonitrile is a polymer obtained by homopolymerizing methacrylonitrile or a polymer of methacrylonitrile and one or more monomer components other than methacrylonitrile,
The modified polymer according to claim 10, wherein the monomer component other than methacrylonitrile is selected from the group consisting of acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylamide . The modified polymer according to claim 10 or 11, wherein R ¹² is an alkyl group having 1 to 6 carbon atoms, Y is a hydrocarbylene group having 2 to 6 carbon atoms, the hydrocarbylene group has 1 to 4 substituents, the alkyl substituents have 1 to 4 carbon atoms, and the carbon skeleton constituting the hydrocarbylene group has 1 or 2 ether bonds. A sulfur-based active material containing the modified polymer described in any one of claims 10 to 12. An electrode comprising the sulfur-based active material according to claim 13. A lithium ion secondary battery comprising the electrode according to claim 14.