WO2022163503A1 - Electrode for secondary battery, and electrochemical device - Google Patents

Abstract

The present invention relates to an electrode for a secondary battery, characterized by having a coating layer formed from a copolymer including repeating units represented by formula (1) and repeating units represented by formula (2), or a coating layer formed from an ionomer of said copolymer and a metal species.　Formula (1): –(CF2–CXY)– Formula (2): –(CH2–CHOH)–

Description

Electrodes for secondary batteries and electrochemical devices

The present invention relates to electrodes for secondary batteries, electrochemical devices, and the like.

Electrochemical devices such as alkali metal ion batteries and electrochemical capacitors have features such as small size, high capacity, and light weight, and are used in various electronic devices. In particular, lithium ion secondary batteries are widely used in electric vehicles (EV) and small electronic devices because of their light weight, high capacity, and high energy density. Portable devices such as smartphones, mobile phones, tablet terminals, video cameras, and laptop computers are examples of small electronic devices.

These electrochemical devices typically have a pair of electrodes and an electrolyte. In an electrochemical device, the electrodes may deteriorate during use or storage, which may cause functional deterioration of the electrochemical device, such as a decrease in capacity retention after charge-discharge cycles.

As a method for suppressing functional deterioration of an electrochemical device, Patent Document 1 discloses that an electrode contains a carboxylate or a sulfonate of a perfluoropolyether group.

Japanese Patent Application Laid-Open No. 2010-44958

However, it cannot be said that the method described in Patent Document 1 can sufficiently suppress deterioration of the function of the electrochemical device.

An object of the present invention is to provide an electrochemical device in which functional deterioration due to use or storage is suppressed.

The present invention relates to the following secondary battery electrode and the like.
[1] A secondary battery electrode comprising a coating layer formed from a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2): .
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl.
[2] Having a coating layer formed from an ionomer of a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), and a metal species: A secondary battery electrode characterized by:
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl.
[3] The secondary battery electrode according to [1] or [2] above, wherein the copolymer has a number average molecular weight of 1,000 to 1,000,000.
[4] The secondary battery electrode according to any one of [1] to [3], wherein X is F and Y is F or Cl.
[5] The secondary battery electrode according to any one of [1] to [4], which is a positive electrode.
[6] The secondary battery electrode according to any one of [1] to [4], which is a negative electrode.
[7] An electrochemical device comprising the secondary battery electrode according to any one of [1] to [6].
[8] An alkali metal ion secondary battery or an alkaline earth metal ion secondary battery comprising the secondary battery electrode according to any one of [1] to [4] as at least one of a positive electrode and a negative electrode. next battery.
[9] The alkali metal ion secondary battery or alkaline earth metal ion secondary battery according to [8] above, wherein the negative electrode contains silicon or lithium.
[10] An ionomer comprising a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), and a metal species.
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl.

According to the present invention, deterioration of the electrode during use or storage can be suppressed by having a coating layer containing a fluorine-containing olefin/vinyl alcohol copolymer with a specific structure. This can suppress functional deterioration of the electrochemical device.

In this specification, the repeating unit represented by formula (X) is also referred to as repeating unit (X).

<Electrode>
The secondary battery electrode of the present disclosure (hereinafter also referred to as “the electrode of the present disclosure”) has a coating layer formed using a fluorinated olefin/vinyl alcohol copolymer having a specific structure. More specifically, the electrode of the present disclosure (hereinafter used to include a positive electrode and a negative electrode) includes an electrode material (hereinafter used to include a positive electrode material and a negative electrode material) and a and a coating layer formed using a fluorine-containing olefin/vinyl alcohol copolymer having a specific structure.
The coating layer may be a coating layer formed from a fluorine-containing olefin/vinyl alcohol copolymer having a specific structure, or a coating formed from an ionomer of a fluorine-containing olefin/vinyl alcohol copolymer having a specific structure and a metal species. layer.

According to the present invention, deterioration of the electrode can be suppressed by having a coating layer containing a fluorine-containing olefin/vinyl alcohol copolymer having a specific structure.
For example, in a lithium ion secondary battery having a negative electrode containing silicon, during use or storage, silicon reacts with lithium to form an alloy, and the volume of the negative electrode expands, which can deteriorate the negative electrode. In addition, in a lithium ion secondary battery having a negative electrode containing lithium, acicular Li dendrites formed on the surface of the electrode during use or storage may penetrate the separator and affect deterioration of the battery. These side reactions that can occur on the electrode surface can be prevented by the coating layer of the present disclosure.

<Fluorine-containing olefin/vinyl alcohol copolymer>
The fluorine-containing olefin/vinyl alcohol copolymer of the specific structure of the present disclosure is a copolymer containing repeating units represented by the following formula (1) and repeating units represented by the following formula (2).
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl. Preferably X is F and Y is F or Cl.

It is believed that the fluorine contained in the repeating unit (1) causes the coating layer to function as a layer that prevents contact between the electrolyte and the electrode. Such a function can suppress side reactions other than the electrochemical reaction essential for functioning as a battery.
It is also believed that the hydroxyl groups contained in the repeating unit (2) allow the coating layer to function as a conductive path for metal ions for functioning as a battery.

The lower limit of the number average molecular weight (Mn) of the fluorine-containing olefin/vinyl alcohol copolymer is preferably 1,000, more preferably 3,000, even more preferably 5,000, and particularly preferably 10,000. 000 is most preferred. The upper limit of Mn is preferably 1,000,000, more preferably 700,000, and particularly preferably 600,000. When the Mn of the fluorine-containing olefin/vinyl alcohol copolymer is at least the above lower limit, the mechanical strength of the coating layer is sufficient, and when it is at most the above upper limit, the electrode material can be sufficiently covered.
In the present disclosure, Mn is measured by gel permeation chromatography (GPC).

In addition, the molecular weight distribution (Mw/Mn) of the fluorine-containing olefin/vinyl alcohol copolymer is preferably 1-5, particularly preferably 1-3. In addition, Mw is a mass average molecular weight.

The fluorine-containing olefin/vinyl alcohol copolymer may be any of random, alternating and block copolymers. From the viewpoint of excellent heat resistance and chemical resistance, random and alternating copolymers are preferred. Coalescing is even more preferred.

In the fluorine-containing olefin/vinyl alcohol copolymer, the molar ratio ((1)/(2)) between the repeating unit (1) and the repeating unit (2) is preferably 10/90 to 90/10, preferably 20/80. ~80/20 is more preferred, and 40/60 to 60/40 is particularly preferred.

The fluorine-containing olefin/vinyl alcohol copolymer having the specific structure of the present disclosure may further contain other repeating units in addition to the repeating unit (1) and the repeating unit (2) as long as the effect of the present invention is not impaired. good.

Other repeating units include repeating units represented by the following formula (3).
(3) —(CH ₂ —CHOR ¹ )—
In formula (3), R ¹ is selected from the group consisting of a primary or secondary alkyl group having 1 to 12 carbon atoms and a cycloalkyl group having 5 to 12 carbon atoms, which may be substituted with a hydroxyl group or a fluorine atom. It is a group that can be Primary or secondary alkyl groups having 1 to 6 carbon atoms are preferred.

Examples of the repeating unit (3) include units derived from the following vinyl ethers.
Alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, isobutyl vinyl ether and cyclohexyl vinyl ether; functional group-containing vinyl ethers such as hydroxyethyl vinyl ether and hydroxybutyl vinyl ether; fluorine-containing vinyl ethers such as heptafluoropentyl vinyl ether.

Units derived from vinyl ether can be converted to vinyl alcohol units, that is, repeating units (2) by saponification. Therefore, the introduction of vinyl ether-derived units can also be controlled by adjusting the saponification rate.

When the repeating unit (3) is included, the total molar ratio of the repeating unit (1), the repeating unit (2), and the repeating unit (3) [(1)/((2)+(3))] is 40/ 60 to 60/40 is preferred. If the molar ratio [(1)/((2)+(3))] is within the above range, the repeating unit (1) and the repeating unit (2) or the repeating unit (3) are alternately present. A copolymer is easily obtained. In this case, the molar ratio ((2)/(3)) of the repeating unit (2) and the repeating unit (3) is preferably 45/5 to 10/40.

Other repeating units further include repeating units represented by the following formula (4).
(4) —(CH ₂ —CHOCOR ² )—
In formula (4), R ² is selected from the group consisting of a primary or secondary alkyl group having 1 to 24 carbon atoms and a cycloalkyl group having 5 to 12 carbon atoms, which may be substituted with a hydroxyl group or a fluorine atom. It is a group that can be R ² is preferably a primary or secondary alkyl group having 1 to 18 carbon atoms.

Examples of the repeating unit (4) include units derived from the following ester compounds.
vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pentanoate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, vinyl nonanoate, vinyl decanoate, vinyl laurate, vinyl mystylate, vinyl palmitate, vinyl heptadecanoate, Vinyl stearate, vinyl benzoate.

The unit derived from the above ester compound can be converted into a vinyl alcohol unit, that is, the repeating unit (2) by saponification. Therefore, the introduction of units derived from ester compounds can also be controlled by adjusting the saponification rate.

When the repeating unit (4) is included, the total molar ratio of the repeating unit (1), the repeating unit (2), and the repeating unit (4) [(1)/((2)+(4))] is 40/ 60 to 60/40 is preferred. If the molar ratio [(1)/((2)+(4))] is within the above range, the repeating unit (1) and the repeating unit (2) or the repeating unit (4) are alternately present. A copolymer is easily obtained. In this case, the molar ratio ((2)/(4)) of the repeating unit (2) and the repeating unit (3) is preferably 45/5 to 10/40.

The fluorine-containing olefin/vinyl alcohol copolymer of the present disclosure can be synthesized by a known method. Examples thereof include a method of hydrolyzing a fluorine-containing olefin/vinyl acetate copolymer in the presence of an acid or a base, a method of deprotecting a fluorine-containing olefin/vinyl ether copolymer, and the like (e.g., International Publication No. 2013/051669, See Japanese Patent Application Laid-Open No. 2020-102457).

<Ionomer of fluorine-containing olefin/vinyl alcohol copolymer and metal species>
The fluorine-containing olefin/vinyl alcohol copolymer of the present disclosure may be used as it is for the coating layer of the electrode, or may be used as an ionomer of the fluorine-containing olefin/vinyl alcohol copolymer and a metal species.
An ionomer is a complex ion formed by a polymer and a metal ion.
In the present disclosure, it is believed that the ionomer of the copolymer and metal species functions as a conductive path for metal ions in the coating layer to function as a battery.

The metal species forming the ionomer is not limited as long as it is a metal capable of forming a bond with the hydroxyl group contained in the repeating unit (2) in the copolymer. Metal species that are easy to react with are preferred, and polyvalent metals are preferred.

Examples of metal species include group 1 (alkali metals) of the periodic table such as lithium, sodium, and potassium; group 4 of the periodic table such as titanium and zirconium; group 5 of the periodic table such as vanadium and tantalum; molybdenum, cerium; Group 6 of the periodic table such as tungsten, Group 7 of the periodic table such as manganese, Group 8 of the periodic table such as ruthenium, Group 9 of the periodic table such as rhodium and iridium, Group 10 of the periodic table such as palladium, silver, gold Group 11 of the periodic table such as zinc, Group 12 of the periodic table such as zinc, Group 13 of the periodic table such as aluminum, Group 14 of the periodic table such as tin, or elements that exhibit metallic properties such as boron and silicon is mentioned.

In forming an ionomer of a copolymer and a metal species, the metal species can be used in the form of various metal compounds.

Examples of metal compounds include organic acid salts and inorganic acid salts of the above metals, and each of these may be a double salt. Organic metal compounds and inorganic metal compounds of the above metals are also included.
Examples of organic acid salts include titanium acetate, titanium citrate, titanium oxalate, titanium ammonium oxydioxalate, titanium tetraoleate, zirconium octanoate, zirconium acetate, zirconyl acetate, zirconium octylate, zirconyl octylate, and the like. Organic acid salts of metals of group 4 of the periodic table; organic acid salts of metals of group 5 of the periodic table such as vanadium acetate, vanadium oxyoxalate, vanadium octanoate, vanadium naphthenate; molybdenum acetate, molybdenum butyrate, lanthanum octanoate, formic acid Organic acid salts of periodic table group 6 metals such as lanthanum, lanthanum acetate, lanthanum oxalate, lanthanum stearate, cerium acetate, cerium oxalate, and cerium stearate; aluminum acetate, aluminum oxalate, aluminum tartrate, aluminum benzoate, Organic acid salts of Group 13 metals of the periodic table, such as aluminum oleate, aluminum citrate, aluminum gluconate, aluminum stearate, aluminum lactate, aluminum butyrate, aluminum ethoxide, aluminum isopropoxide, and aluminum tris(acetylacetonate) is mentioned.

Examples of inorganic acid salts include titanium chloride, titanium hydrofluoric acid, titanium nitrate, titanium oxynitrate, zirconium oxychloride, zircon hydrofluoric acid, zirconium chloride oxide, zirconium phosphate, ammonium zirconium hydroxide carbonate, ammonium zirconium carbonate, Inorganic acid salts of Group 4 metals of the periodic table such as zirconium silicate, zirconium nitrate, zirconium sulfate, and zirconium titanate; vanadium chloride, vanadium dichloride oxide, vanadium trichloride oxide, ammonium metavanadate, vanadyl sulfate, vanadium titanate, etc. Inorganic acid salts of group 5 metals of the periodic table; molybdenum chloride, molybdenum sulfate, molybdenum nitrate, molybdenum phosphate, molybdic acid, ammonium molybdate, lanthanum chloride, lanthanum perchlorate, lanthanum dititanate, lanthanum sulfate, phosphoric acid Periodic Table Group 6 such as lanthanum, cerium chloride, cerium perchlorate, cerium nitrate, cerium sulfate, cerium phosphate, tungsten chloride, tungsten dichloride dioxide, tungsten carbonate, sodium tungstate, ammonium tungstate, and ammonium phosphotungstate Inorganic acid salts of metals: inorganic acid salts of Group 13 metals of the periodic table such as aluminum chloride, aluminum phosphate, aluminum sulfate, aluminum nitrate, aluminum perchlorate and aluminum titanate.

Examples of metal alkoxides include metal alkoxides of Group 4 metals of the periodic table such as titanium methoxide, titanium ethoxide, titanium propoxide, titanium butoxide, zirconium methoxide, zirconium ethoxide, zirconium butoxide, zirconium propoxide; vanadium methoxy; Molybdenum methoxide, molybdenum ethoxide, molybdenum isopropoxide, molybdenum butoxide, molybdenum phenoxide, molybdenum phenyl Ethoxide, molybdenum phenoxyethoxide, cerium methoxide, cerium ethoxide, cerium isopropoxide, cerium butoxide, lanthanum methoxide, lanthanum ethoxide, lanthanum isopropoxide, lanthanum butoxide, tungsten methoxide, tungsten ethoxide, tungsten isopropoxide metal alkoxides of metals of Group 6 of the periodic table such as propoxide and tungsten butoxide; and metal alkoxides of metals of Group 13 of the periodic table such as aluminum ethoxide and aluminum butoxide.

Chelate complexes include, for example, titanium diisopropoxybis(triethanolamine), titanium lactate, titanium tetrakisacetonate, ammonium bis(oxalato)oxotitanate, zirconium tetrakisacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium Chelate complexes of Group 4 metals of the periodic table such as acetylacetonate, tetrakisdimethylaminozirconium, aminocarboxylic acid-based zirconium; chelate complexes of metals of Group 5 of the periodic table such as vanadyl acetylacetate and vanadium acetylacetate; molybdenum dioxide acetylacetonate , lanthanum acetylacetonate, cerium acetylacetonate, ammonium pentanitratocerate, ammonium hexanitratocerate, tungsten acetylacetonate, hexacarbonyltungsten and other chelate complexes of Group 5 metals of the periodic table; aluminum trisacetylacetonate; chelate complexes of Group 13 metals of the periodic table such as

Examples of organometallic compounds include organometallic compounds of Group 4 metals of the periodic table such as tetraisopropyl titanate, tetrabutyl titanate, tetrapropyl zirconate and tetrabutyl zirconate; Organometallic compounds: Organometallic compounds of Group 13 metals of the periodic table, such as triethylaluminum and triisobutylaluminum.

Examples of inorganic metal compounds include inorganic metal compounds of Group 13 metals of the periodic table, such as lithium aluminum hydride, diisobutylaluminum hydride, triethylaluminum, and aluminum trichloride.

Examples of metal compounds containing boron and silicon include boron compounds such as lithium borohydride, sodium borohydride, sodium tetraborate, and lithium tetraborate, and silicon compounds such as triethoxysilane, phenylsilane, and silicon tetrachloride. is mentioned.

Each of the metal compounds described above may be used alone or in combination of two or more.
Moreover, each metal compound can use a commercial item.

The ionomer is a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, or an ether solvent such as diethyl ether and THF. Obtained by mixing in If necessary, pH adjusters, preservatives, and antioxidants may be added.
The mixing ratio of the copolymer and the metal compound is preferably 1/32 to 2 equivalents, more preferably 1/16 to 1 equivalent, and particularly preferably 1 equivalent of the metal compound with respect to 1 equivalent of hydroxyl groups in the copolymer. /8 to 1/2 equivalents.

<Electrode material>
An electrode material means a member that constitutes a main part of an electrode of an electrochemical device, and is a member generally used in various electrochemical devices. Those skilled in the art can appropriately select such an electrode material according to the type of electrochemical device. For example, in an alkali metal ion battery, the electrode material can be an active material-containing portion containing an active material (hereinafter used to include positive electrode active material and negative electrode active material). In the electric double layer capacitor, the electrode material may be a portion that forms an electric double layer at the interface with the electrolyte, such as a portion containing carbon or graphite.

The electrode of the present disclosure can be used as both a positive electrode and a negative electrode in electrochemical devices. When used in the positive electrode and the negative electrode, the oxidative decomposition of the electrolyte can be suppressed, and deterioration of the battery and decomposition of the positive electrode structure due to the decomposition of the electrolyte can be suppressed. In addition, by stabilizing the structure of the film (SEI) formed at the electrode/electrolyte interface and improving the migration of metal ions, it is possible to suppress an increase in resistance. Moreover, when used in combination with a solid electrolyte, the stress caused by the expansion and contraction of the electrode accompanying charging and discharging can be alleviated, and cracks occurring in the solid electrolyte can be suppressed.

Since the electrode of the present disclosure contains a fluorine-containing olefin/vinyl alcohol copolymer on its surface as described above, by using it as a positive electrode and/or a negative electrode of an electrochemical device, the electrochemical device has good electrical properties. and large capacity can be achieved.

<Electrochemical device>
Electrodes of the present disclosure can be used in various electrochemical devices. Accordingly, the present disclosure also provides electrochemical devices comprising electrodes of the present disclosure.

An electrochemical device has at least a pair of electrodes and an electrolyte interposed between the pair of electrodes.

Examples of the electrochemical device include, but are not limited to, batteries, electrochemical sensors, electrochromic elements, electrochemical switching elements, electrolytic capacitors, and electrochemical capacitors.

The battery is not particularly limited as long as it has an electrode and an electrolyte, but examples include alkali metal batteries, alkali metal ion batteries, alkaline earth metal ion batteries, radical batteries, solar cells, and fuel cells. In a preferred embodiment, the battery is in particular an alkali metal battery, an alkali metal ion battery or an alkaline earth metal battery, such as a lithium battery, a lithium ion battery, a sodium ion battery, a magnesium battery, a lithium air battery, a sodium sulfur battery. , a lithium sulfur battery, preferably a lithium ion battery. The above battery may be a primary battery or a secondary battery. Preferably, the battery is an alkali metal ion secondary battery, especially a lithium ion secondary battery.

<Alkali metal ion secondary battery>
The electrochemical device of the present disclosure will be described in more detail by taking an alkali metal ion secondary battery as an example.

In the alkali metal ion secondary battery of the present disclosure, at least one of the positive electrode and the negative electrode is the electrode of the present disclosure.

The alkali metal ion secondary battery of the present disclosure can have a general structure as an alkali metal ion secondary battery. For example, an alkali metal ion secondary battery can have a positive electrode, a negative electrode, a separator, an electrolytic solution, etc. in an exterior case. In addition, the alkali metal ion secondary battery of the present disclosure further includes other members such as a positive electrode current collecting tab, a negative electrode current collecting tab, and a battery lid, or a member for protecting the battery such as an internal pressure release valve or a PTC element. etc.

An electrode material in an alkali metal ion secondary battery can be composed of an active material-containing portion containing an active material (hereinafter used including a positive electrode active material and a negative electrode active material) and a current collector. The active material-containing portion exists, for example, as a layer on the current collector.

<Positive electrode>
The positive electrode has a positive electrode material including a positive electrode active material-containing portion. In addition, when the positive electrode is the electrode of the present disclosure, a coating layer formed from a fluorine-containing olefin/vinyl alcohol copolymer or an ionomer of the copolymer and a metal species is formed on the surface of the positive electrode material. It further has a coating layer.

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release alkali metal ions. For example, a material containing an alkali metal and at least one transition metal is preferable. Specific examples include alkali metal-containing transition metal composite oxides and alkali metal-containing transition metal phosphate compounds. Among them, as the positive electrode active material, an alkali metal-containing transition metal composite oxide that produces a high voltage is particularly preferable. Examples of the alkali metal ions include lithium ions, sodium ions, and potassium ions. In preferred embodiments, the alkali metal ions may be lithium ions. That is, in this aspect, the alkali metal ion secondary battery is a lithium ion secondary battery.

Examples of the alkali metal-containing transition metal composite oxide include:
Formula: M _a Mn _2-b M ¹ _b O ₄
(Wherein M is at least one metal selected from Li, Na or K; 0.9 ≤ a; 0 ≤ b ≤ 1.5; M ¹ is Fe, Co, Ni, Cu, Zn , Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, at least one metal selected from the group consisting of Si and Ge) lithium-manganese spinel composite oxide represented by
Formula: MNi _1-c M ² _c O ₂
(wherein M is at least one metal selected from Li, Na or K; 0 ≤ c ≤ 0.5; M ² is Fe, Co, Mn, Cu, Zn, Al, Sn, Cr , V, Ti, Mg, Ca, Sr, B, Ga, In, at least one metal selected from the group consisting of Si and Ge), or
Formula: MCo _1-d M ³ _d O ₂
(wherein M is at least one metal selected from Li, Na or K; 0 ≤ d ≤ 0.5; M ³ is Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr , V, Ti, Mg, Ca, Sr, B, Ga, In, at least one metal selected from the group consisting of Si and Ge). In the above, M is preferably one metal selected from Li, Na or K, more preferably Li or Na, and still more preferably Li.

Among them, MCoO ₂ , MMnO ₂ , MNiO ₂ , MMn ₂ O ₄ , MNi _0.8 Co _0.15 Al _0.05 O ₂ from the point of being able to provide an alkali metal ion secondary battery with high energy density and high output. , or MNi _1/3 Co _1/3 Mn _1/3 O ₂ .

Other _{positive electrode} active _{materials include MFePO4} , _{MNi0.8Co0.2O2} , _{M1.2Fe0.4Mn0.4O2 , MNi0.5Mn1.5O2 and MV3 .} O ₆ , M ₂ MnO ₃ and the like.

The active material-containing portion containing the positive electrode active material is preferably formed from a positive electrode mixture containing the positive electrode active material. For example, it can be obtained by applying a positive electrode mixture onto a current collector and drying it. The positive electrode mixture may further contain a binder, a thickener, and a conductive material.

<Negative Electrode>
The negative electrode has a negative electrode material including a portion containing a negative electrode active material. Further, when the negative electrode is the electrode of the present disclosure, a coating layer formed from a fluorine-containing olefin/vinyl alcohol copolymer or an ionomer of the copolymer and a metal species is formed on the surface of the negative electrode material. It further has a coating layer.

Examples of the negative electrode active material include thermal decomposition products of organic substances under various thermal decomposition conditions, artificial graphite, alkali metals such as natural graphite, preferably carbonaceous materials capable of absorbing and releasing lithium; tin oxide, silicon oxide, etc. metal oxide materials capable of absorbing and releasing alkali metals; alkali metals; various alkali metal alloys; and metal composite oxide materials containing alkali metals. These negative electrode active materials may be used in combination of two or more.

Carbonaceous materials capable of absorbing and desorbing alkali metals include artificial graphite or purified natural graphite produced by high-temperature treatment of graphitizable pitch obtained from various raw materials, or surface treatment of these graphites with pitch or other organic matter. Those obtained by carbonization after treatment are preferable, and natural graphite, artificial graphite, artificial carbonaceous materials, and carbonaceous materials obtained by heat-treating artificial graphite materials one or more times in the range of 400 to 3,200 ° C., negative electrode active materials. The material layer is made of carbonaceous materials having at least two or more different crystallinities, and/or the carbonaceous material has an interface where the carbonaceous materials with different crystallinities are in contact, and the negative electrode active material layer is composed of at least two or more kinds of carbonaceous materials. A carbonaceous material having an interface where carbonaceous matter with different orientations are in contact with each other is more preferable because it has a good balance between initial irreversible capacity and high current density charge/discharge characteristics. Moreover, these carbon materials may be used singly, or two or more of them may be used in any combination and ratio.

Carbonaceous materials obtained by heat-treating the above artificial carbonaceous substances and artificial graphite substances at least once within the range of 400 to 3,200° C. include coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and these pitches. oxidized, needle coke, pitch coke and partially graphitized carbon agents, furnace black, acetylene black, pitch-based carbon fiber and other organic matter thermal decomposition products, carbonizable organic matter and their carbides, or Examples thereof include solutions obtained by dissolving carbonizable organic substances in low-molecular organic solvents such as benzene, toluene, xylene, quinoline and n-hexane, and carbonized products thereof.

As the metal material used as the negative electrode active material, if it is possible to occlude and release alkali metals, simple alkali metals, simple metals and alloys forming alkali metal alloys, or oxides, carbides, nitrides, and silicons thereof. It may be any compound such as a compound, a sulfide, or a phosphide, and is not particularly limited. Single metals and alloys that form alkali metal alloys are preferably materials containing group 13 and group 14 metal/metalloid elements, more preferably aluminum, silicon and tin (hereinafter referred to as "specific metal elements"). abbreviations) and alloys or compounds containing these atoms. One of these may be used alone, or two or more thereof may be used in any combination and ratio.

As the negative electrode active material having at least one atom selected from the specific metal elements, any one metal simple substance of the specific metal element, an alloy composed of two or more specific metal elements, one or two or more specific metal elements Alloys composed of metallic elements and other one or more metallic elements, compounds containing one or more specific metallic elements, and oxides, carbides, nitrides, and silicides of these compounds , sulfides or phosphides. By using these metal simple substances, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

In addition, compounds in which these complex compounds are intricately combined with several kinds of elements such as simple metals, alloys, or non-metallic elements are also included. Specifically, for silicon and tin, for example, an alloy of these elements and a metal that does not act as a negative electrode can be used. For example, in the case of tin, it is possible to use a complex compound containing 5 to 6 elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not act as a negative electrode, and a non-metallic element. can.

Specifically, Si simple substance, _SiB4 , _SiB6 , _Mg2Si , _Ni2Si , _TiSi2 , _MoSi2 , _CoSi2 , _NiSi2 , _CaSi2 , _CrSi2 , _Cu6Si , _FeSi2 , _MnSi2 , NbSi2, _TaSi2 , _VSi2 , _WSi2 , _ZnSi2 , SiC _{, Si3N4} , _Si2N2O , _SiOv ( ₀ < _v≤2 ), LiSiO or tin alone, _SnSiO3 , _LiSnO , Mg2 Sn, SnO _w (0<w≦2) can be mentioned.

Composite materials containing Si or Sn as a first constituent element and additionally containing second and third constituent elements can also be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum and phosphorus.

In particular, since a high battery capacity and excellent battery characteristics can be obtained, as the metal material, silicon or tin alone (which may contain trace amounts of impurities), SiO _v (0 < v ≤ 2), SnO _w (0 ≤w≤2), Si--Co--C composite materials, Si--Ni--C composite materials, Sn--Co--C composite materials, and Sn--Ni--C composite materials are preferred.

The alkali metal-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release alkali metals, but from the viewpoint of high current density charge-discharge characteristics, materials containing titanium and alkali metals. is preferred, more preferably an alkali metal-containing composite metal oxide material containing titanium, and more preferably a composite oxide of alkali metal and titanium (hereinafter abbreviated as "alkali metal titanium composite oxide"). That is, it is particularly preferable to contain an alkali metal titanium composite oxide having a spinel structure in the negative electrode active material for electrolyte batteries because the output resistance is greatly reduced.

The alkali metal titanium composite oxide has the general formula:
_{MxTiyM3zO4 _} ^_ _{_ _}
[wherein M is at ^least one metal selected from Li, Na or K; M3 is Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and represents at least one element selected from the group consisting of Nb; ] It is preferable that it is a compound represented by.

In the above, M is preferably one metal selected from Li, Na or K, more preferably Li or Na, and still more preferably Li.

Among the above compositions,
(i) 1.2≤x≤1.4, 1.5≤y≤1.7, z=0
(ii) 0.9≦x≦1.1, 1.9≦y≦2.1, z=0
(iii) 0.7≦x≦0.9, 2.1≦y≦2.3, z=0
is particularly preferred because it has a good balance of battery performance.

Particularly preferred compositions of the above compounds are M _4/3 Ti _5/3 O ₄ for (i), M ₁ Ti ₂ O ₄ for (ii) and M _4/5 Ti _11/5 O ₄ for (iii) . Moreover, as for the structure of Z≠0, for example, M _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

The active material-containing portion containing the negative electrode active material is preferably formed from a negative electrode mixture containing the negative electrode active material. For example, it can be obtained by applying a negative electrode mixture onto a current collector and drying it. The negative electrode mixture may further contain a binder, a thickener, and a conductive material.

<Coating layer>
The electrode of the present disclosure has a coating layer formed from a fluorine-containing olefin/vinyl alcohol copolymer or a coating layer formed from an ionomer of the copolymer and a metal species. The coating layer is preferably formed on the electrode material, more specifically on the active material-containing portion.

An electrode having a coating layer may be produced by surface-treating an electrode material coated with an active material with a fluorine-containing olefin/vinyl alcohol copolymer or an ionomer of the copolymer and a metal species. In the step of forming the coating layer of the material mixture, it may be produced by applying an electrode material mixture obtained by mixing a fluorine-containing olefin/vinyl alcohol copolymer or an ionomer of the copolymer and a metal species.

Since the electrode of the present disclosure has the coating layer, by using it as the positive electrode and/or the negative electrode of an alkali metal ion secondary battery, preferably a lithium ion secondary battery, the alkali metal ion secondary battery has good cycle characteristics. and large battery capacity, and good storage characteristics.

<Separator>
The separator separates the positive electrode and the negative electrode and allows passage of alkali metal ions, preferably lithium ions, while preventing current short circuit due to contact between the two electrodes. The separator may be, for example, a porous film made of synthetic resin or ceramic, or a laminated film in which two or more kinds of porous films are laminated. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene.

<Electrolyte>
The above positive electrode, negative electrode and separator are preferably impregnated with an electrolytic solution, which is a liquid electrolyte. This electrolytic solution is obtained by dissolving an electrolytic salt in a solvent, and may contain other materials such as various additives as necessary.

The solvent may be, for example, one type of non-aqueous solvent such as an organic solvent, or may contain two or more types of non-aqueous solvents.

Examples of the solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, and tetrahydrofuran. 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane or 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate or ethyl trimethyl acetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, and dimethylsulfoxide. By using these solvents, excellent battery capacity, cycle characteristics, storage characteristics and the like can be obtained.

The solvent may further contain unsaturated carbon-bonded cyclic carbonates, halogenated chain carbonates, halogenated cyclic carbonates, sultones (cyclic sulfonates), acid anhydrides, and the like.

<Electrolyte salt>
The electrolyte salt may contain, for example, any one or more of the alkali metal salts described below. However, the electrolyte salt may be a salt other than the alkali metal salt (for example, a light metal salt other than the alkali metal salt).

Examples of alkali metal salts include the following compounds.
_MPF6 , MBF4, _MClO4 , _MAsF6 , MB _{( C6H5} ) ₄ , _{MCH3SO3 , MCF3SO3 , MAlCl4} , _M2SiF6 , _MCl , _MBr . (Wherein, M is at least one metal selected from Li, Na or K, preferably one metal selected from Li, Na or K, more preferably Li or Na , and more preferably Li.)
By using these alkali metal salts, excellent battery capacity, cycle characteristics, storage characteristics and the like can be obtained. Among them, at least one selected from MPF ₆ , MBF ₄ , MClO ₄ and MAsF ₆ is preferred, and MPF ₆ is more preferred. By using these alkali metal salts, the internal resistance is further lowered and higher effects can be obtained.

<Solid electrolyte>
In the battery of the present disclosure, a solid electrolyte may be used as the electrolyte instead of the liquid electrolyte described above. Examples of solid electrolytes include inorganic electrolytes and organic electrolytes. Examples of inorganic electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, and hydride-based solid electrolytes. Organic electrolytes include, for example, polymer-based solid electrolytes.
Examples of oxide-based solid electrolytes include perovskite-type oxides, NASICON-type oxides, LISICON-type oxides, and garnet-type oxides.
Examples of sulfide solid electrolytes include Li ₂ SP ₂ S ₅ based compounds, Li ₂ S—SiS ₂ based compounds, Li ₂ S—GeS ₂ based compounds, Li ₂ S—B ₂ S ₃ based compounds, Li ₂ SP ₂ S ₃ compounds, LiI-Si ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₁₀ GeP ₂ S ₁₂ are mentioned.
Examples of hydride solid electrolyte materials include LiBH ₄ , LiBH ₄ -3KI, LiBH ₄ -PI ₂ , LiBH ₄ -P ₂ S ₅ , LiBH ₄ -LiNH ₂ , 3LiBH ₄ -LiI, LiNH ₂ and Li ₂ AlH. ₆ , Li( _NH2 )2I, _Li2NH , _LiGd (BH4) _3Cl , Li2(BH4)( _NH2 ), _{Li3 ( NH2} ) _I , _{Li4 (} BH4) _{( NH2} ) ₃ can be mentioned.
Polymer-based solid electrolytes include, for example, polyethylene oxide-based polymer compounds, polymer compounds containing one or more selected from the group consisting of polyorganosiloxane chains and polyoxyalkylene chains, vinylidene fluoride (VdF)-derived repeating units. organic polymer electrolytes such as fluorine-containing polymer compounds such as fluorine-containing polymers having

<Battery design>
The electrode group may have either a laminate structure in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, or a structure in which a positive electrode plate and a negative electrode plate are spirally wound with a separator interposed therebetween. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as "electrode group occupancy") is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80% or less. is preferred.

The current collecting structure is not particularly limited, but a structure that reduces the resistance of the wiring part and the joint part is preferable in order to more effectively improve the charge/discharge characteristics of the electrolyte solution at high current density.

When the electrode group has the above laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to a terminal is preferably used. When the area of one electrode increases, the internal resistance increases, so a plurality of terminals may be provided within the electrode to reduce the resistance. In the case of the electrode group having the wound structure described above, the internal resistance can be reduced by providing a plurality of lead structures for each of the positive electrode and the negative electrode and bundling them around the terminal.

The material of the exterior case is not particularly limited as long as it is stable with respect to the electrolyte used. Specifically, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminate films of resin and aluminum foil are used. From the viewpoint of weight reduction, aluminum or aluminum alloy metals and laminate films are preferably used.

Exterior cases that use metals are those that weld metals together by laser welding, resistance welding, or ultrasonic welding to form a sealed structure, or that uses the above metals via a resin gasket to form a caulked structure. things are mentioned. Examples of exterior cases using the laminate film include those having a sealing and airtight structure by heat-sealing the resin layers to each other. A resin different from the resin used for the laminate film may be interposed between the resin layers in order to improve the sealing property. In particular, when the resin layer is heat-sealed through the current collector terminal to form a closed structure, the metal and the resin are joined together. A resin is preferably used.

The shape of the alkali metal ion secondary battery of the present disclosure is arbitrary, and examples thereof include cylindrical, rectangular, laminated, coin-shaped, and large-sized shapes. The shape and configuration of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

Next, the present invention will be described with reference to examples, but the present invention is not limited only to such examples.

<Synthesis of fluorine-containing olefin/vinyl alcohol copolymer>
(Synthesis example 1)
With reference to the description of Example 2 of WO 2011/126056, repeating units derived from tetrafluoroethylene (TFE) and repeating units derived from t-butyl vinyl ether (TBVE) are 97% or more saponified vinyl alcohol and TBVE-derived repeating units remaining unsaponified were synthesized.

(Synthesis example 2)
With reference to the description of Example 4 of International Publication No. 2011/126056, repeating units derived from TFE and repeating units derived from tetrahydropyranyl vinyl ether (THPVE) are saponified at least 95% and converted to vinyl alcohol. and THPVE-derived repeating units remaining without saponification were synthesized.

(Synthesis Example 3)
With reference to the description of Example 5 of WO 2011/126056, repeating units derived from chlorotrifluoroethylene (CTFE) and units in which 95% or more of repeating units derived from TBVE are saponified and converted to vinyl alcohol and a TBVE-derived repeating unit remaining without saponification was synthesized.

(Synthesis Example 4)
With reference to the description of Example 6 of WO 2011/126056, repeating units derived from CTFE, units in which 95% or more of repeating units derived from TBVE are saponified and converted to vinyl alcohol, and unsaponified A copolymer containing repeating units derived from TBVE remaining in and repeating units derived from cyclohexyl vinyl ether (CHVE) was synthesized.

(Synthesis Example 5)
With reference to the descriptions of Synthesis Example 2 and Synthesis Example 9 of WO 2013/175962, repeating units derived from TFE and repeating units derived from vinyl acetate are 100% saponified and converted to vinyl alcohol. A copolymer containing

(Synthesis Example 6)
With reference to the descriptions of Synthesis Example 1 and Synthesis Example 13 of International Publication No. WO 2013/175962, repeating units derived from TFE and units obtained by saponifying 96% of repeating units derived from vinyl acetate into vinyl alcohol, A copolymer containing repeating units derived from vinyl acetate remaining without being saponified was synthesized.

(Synthesis Example 7)
With reference to the descriptions of Synthesis Example 3 and Synthesis Example 14 of International Publication No. WO 2013/175962, repeating units derived from TFE and units obtained by saponifying 96% of repeating units derived from vinyl acetate and converting them into vinyl alcohol, A copolymer containing repeating units derived from vinyl acetate remaining without being saponified was synthesized.

(Synthesis Example 8)
With reference to the descriptions of Synthesis Example 4 and Synthesis Example 15 of WO 2013/175962, repeating units derived from TFE, repeating units derived from hexafluoropropylene (HFP), and repeating units derived from vinyl stearate are 97. % saponified units converted to vinyl alcohol and vinyl stearate-derived repeating units remaining unsaponified were synthesized.

(Synthesis Example 9)
With reference to the descriptions of Synthesis Example 5 and Synthesis Example 16 of WO 2013/175962, repeating units derived from TFE and repeating units derived from vinyl stearate are saponified by 95% and converted to vinyl alcohol. , and repeating units derived from vinyl stearate remaining unsaponified.

(Synthesis Example 10)
With reference to the descriptions of Synthesis Example 6 and Synthesis Example 17 of WO 2013/175962, a repeating unit derived from HFP and a unit obtained by saponifying 94% of a repeating unit derived from vinyl acetate to vinyl alcohol, A copolymer containing repeating units derived from vinyl acetate remaining without being saponified was synthesized.

(Synthesis Example 11)
With reference to the descriptions of Synthesis Example 7 and Synthesis Example 18 of WO 2013/175962, CTFE-derived repeating units, vinyl acetate-derived repeating units converted to vinyl alcohol by 96% saponification, A copolymer containing repeating units derived from vinyl acetate remaining without being saponified was synthesized.

Table 1 shows the properties and composition of each copolymer synthesized in Synthesis Examples 1 to 11.
Mn and Mn/Mw were measured by polystyrene gel conversion gel permeation chromatography (GPC) using a high-speed GPC apparatus "HLC-8220GPC" manufactured by Tosoh Corporation. Tetrahydrofuran was used as the eluent.
The copolymer composition of the copolymer obtained in each example was calculated from the measurement results of ¹ H NMR (nuclear magnetic resonance) spectrum and ¹⁹ F NMR spectrum of the obtained copolymer.
The alternating ratio was obtained by sequence analysis by the Monte Carlo method based on the copolymerization reactivity ratio calculated from the Q value and e value, which are numerical values specific to the monomers.

<Production and evaluation of electrical devices>
<Si-based negative electrode>
(Preparation of electrolytic solution)
LiPF ₆ was added to a mixed solvent (30:70 volume ratio) of ethylene carbonate, which is a high dielectric constant solvent, and ethyl methyl carbonate, which is a low viscosity solvent, so as to give a concentration of 1.0 mol/liter. got

(Production of lithium ion secondary battery)
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material, carbon black was used as the conductive material, and N-methyl-2-pyrrolidone dispersion of polyvinylidene fluoride (PVdF) was used as the binder. , a conductive material and a binder at a solid content ratio of 92/3/5 (mass % ratio) to prepare a positive electrode mixture slurry. The obtained positive electrode material mixture slurry was uniformly applied onto a 20 μm-thick aluminum foil current collector, dried, and then compression-molded with a press to form a positive electrode laminate. A positive electrode laminate having a diameter of 1.6 cm was punched out from the positive electrode laminate by a punching machine to prepare a circular positive electrode material.

Artificial graphite powder and amorphous silicon (SiO) as a negative electrode active material, an aqueous dispersion of carboxymethylcellulose sodium (concentration of sodium carboxymethylcellulose of 1% by mass) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (styrene - using a butadiene rubber concentration of 50% by mass), and mixing the active material, the thickener and the binder at a solid content ratio of 93/4.6/1.2/1.2 (mass% ratio) A negative electrode mixture slurry was prepared. After uniformly coating a copper foil with a thickness of 20 μm and drying at 25° C., it was compression-molded with a press and punched out into a size of 1.6 cm in diameter with a punch to produce a circular negative electrode material.

At least one of the positive electrode material and the negative electrode material obtained above was subjected to coating treatment by method 1 or method 2 described later to obtain a positive electrode and a negative electrode. The positive electrode material and the negative electrode material that were not coated were used as the positive electrode and the negative electrode as they were.

The above-mentioned circular positive electrode and negative electrode are opposed to each other via a 20 μm thick microporous polyethylene film (separator), and the electrolytic solution obtained above is injected. Sealed, precharged and aged to produce a coin-type lithium ion secondary battery.

(Measurement of battery characteristics)
The obtained coin-type lithium ion secondary battery was examined for cycle capacity retention and resistance increase rate as follows.

(Cycle capacity retention rate)
The secondary battery produced above is charged at 25 ° C. with a constant current-constant voltage charge (hereinafter referred to as “CC/CV charge”) to 4.2 V at a current equivalent to 0.5 C (0.1 C cut ), the battery was discharged to 3 V at a constant current of 0.5 C, and this cycle was regarded as one cycle, and the initial discharge capacity was obtained from the discharge capacity of the first cycle. Here, 1C represents a current value that discharges the standard capacity of the battery in one hour, and 0.5C represents half that current value, for example. After CC/CV charging (0.1C cut) was performed again to 4.2 V, charging and discharging were performed in the same manner, and the discharge capacity after 200 cycles was measured. Based on the following formula, the ratio of the discharge capacity after 200 cycles to the initial discharge capacity was determined and defined as the cycle capacity retention (%). The measurement temperature was 60°C.
Cycle capacity retention (%) = (discharge capacity after 200 cycles) / (initial discharge capacity) x 100

(Resistance increase rate)
A charge-discharge cycle performed under predetermined charge-discharge conditions (charge at a predetermined voltage at 0.5 C until the charge current reaches 0.1 C and discharge at a current equivalent to 1 C to 3.0 V) is defined as one cycle. The resistance after cycling and the resistance after 200 cycles were measured. The measurement temperature was 25°C. A resistance increase rate was obtained based on the following formula.
Resistance increase rate (%) = Resistance (Ω) after 200 cycles/Resistance (Ω) after 3 cycles x 100

<Example 1-1 to Example 1-13>
At least one of the positive electrode material and the negative electrode material was coated with the fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example by the method described below, and battery characteristics were evaluated.
Table 2 shows the types and evaluation results of the fluorine-containing olefin/vinyl alcohol copolymer.

Method 1: Coating treatment 1
After immersing the electrode material in a 0.1% by mass THF solution of the fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example for 1 minute, excess compounds attached to the surface of the electrode material were washed away with THF and dried. to obtain an electrode surface-treated with a copolymer.

<Examples 1-14 to 1-16, Examples 1-18 to 1-19>
At least one of the positive electrode material and the negative electrode material was coated with a reaction solution of the fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example and LiAlH ₄ by the following method, and battery characteristics were evaluated.
Table 2 shows the types and evaluation results of the fluorine-containing olefin/vinyl alcohol copolymer.

Method 2: Coating treatment 2
In a glove box, a 1 M LiAlH ₄ THF solution was slowly added dropwise at room temperature to a 0.1% by mass THF solution (20 mL) of the fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example. Each addition amount is as described in Tables 2 and 3. After stirring for 12 hours at room temperature, the resulting solution was filtered through a 0.45 μm PTFE filter to obtain a reaction solution of the copolymer and LiAlH ₄ . After the electrode material was immersed in the obtained reaction solution for 1 minute, excess compounds adhering to the surface of the electrode material were washed away with THF, dried, and the electrode surface-treated with the reaction product of the copolymer and LiAlH ₄ got

Among Examples 1-1 to 1-19, Examples 1-1 to 1-16 and Examples 1-18 to 1-19 are examples, and Example 1-17 is a comparative example. From the above results, the coating layer in which at least one of the positive electrode and the negative electrode is formed of a copolymer or the ionomer of the copolymer and the metal species is better than the battery of Example 1-17 using the positive electrode and the negative electrode without a coating layer. The batteries of Examples 1-1 to 1-16 and Examples 1-18 to 1-19 having a coating layer formed by the above had a high cycle capacity retention rate and a low resistance increase rate. Further, from a comparison between Examples 1-1 and 1-2, it was confirmed that the cycle capacity retention rate is higher and the resistance increase rate is lower when the negative electrode has a coating layer than when the positive electrode has a coating layer. From the comparison between Examples 1-14 and 1-18, it was confirmed that the resistance increase rate was lower when the negative electrode had the coating layer than when the positive electrode had the coating layer.

<Li-based negative electrode>
(Preparation of electrolytic solution)
LiN (SO ₂ F) ₂ (LiFSI) was added to give a concentration of 1.0 mol/liter to obtain an electrolytic solution.

(Production of lithium ion secondary battery)
LiCoO ₂ , a conductive agent (Super-P; Timcal Ltd.), PVdF and N-methylpyrrolidone were mixed to obtain a composition for forming a positive electrode active material layer. In the composition for forming a positive electrode active material layer, the ratio of LiCoO ₂ , the conductive agent and PVDF was 97/1.5/1.5 (mass ratio), and the content of N-methylpyrrolidone was 97 g of LiCoO ₂ . 137 g was used for
The composition for forming a cathode active material layer was coated on an aluminum foil having a thickness of 15 μm and dried at 25° C. The dried resultant was heat-treated in a vacuum at 110° C. and punched with a puncher to have a diameter of 1.6 cm. A circular positive electrode material was produced by punching out to a size of .

In a glove box, a lithium metal thin film with a thickness of 15 μm was punched out with a punching machine to a size of 1.6 cm in diameter to produce a circular negative electrode material.

At least one of the positive electrode material and the negative electrode material obtained above was subjected to coating treatment by method 1 or method 2 described above to obtain a positive electrode and a negative electrode. The positive electrode material and the negative electrode material that were not coated were used as the positive electrode and the negative electrode as they were.

A polyethylene separator (porosity: about 48%) is interposed between the positive electrode and the negative electrode obtained by the above process, and the electrolytic solution obtained above is injected. It was sealed, precharged, and aged to produce a coin-type lithium ion secondary battery.

(Measurement of battery characteristics)
The obtained coin-type lithium ion secondary battery was examined for cycle capacity retention and resistance increase rate in the same manner as described above.

<Example 2-1 to Example 2-13>
The fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example was applied to at least one of the positive electrode material and the negative electrode material in the same manner as in Example 1-1, and battery characteristics were evaluated.
Table 3 shows the types and evaluation results of the fluorine-containing olefin/vinyl alcohol copolymer.

<Examples 2-14 to 2-16, Examples 2-18 to 2-19>
At least one of the positive electrode material and the negative electrode material was coated with the reaction solution of the fluorine-containing olefin/vinyl alcohol copolymer produced in each synthesis example and LiAlH ₄ in the same manner as in Examples 1-14, and the battery characteristics were evaluated. did.
The types of fluorine-containing olefin/vinyl alcohol copolymers and evaluation results are shown in Table 3 below.

Among Examples 2-1 to 2-19, Examples 2-1 to 2-16 and Examples 2-18 to 2-19 are examples, and Example 2-17 is a comparative example. From the above results, the coating layer in which at least one of the positive electrode and the negative electrode is formed of a copolymer or the ionomer of the copolymer and the metal species is better than the battery of Example 2-17 using the positive electrode and the negative electrode without a coating layer. The batteries of Examples 2-1 to 2-16 and Examples 2-18 to 2-19 having the coating layer formed by the above had a high cycle capacity retention rate and a low resistance increase rate. Further, from the comparison between Examples 2-1 and 2-2 and between Examples 2-14 and 2-18, the cycle capacity retention rate is higher when the negative electrode has a coating layer than when the positive electrode has a coating layer. was high and the resistance increase rate was low.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2021-013487) filed on January 29, 2021, the contents of which are incorporated herein by reference.

A secondary battery using the secondary battery electrode of the present disclosure has excellent cycle characteristics and can be used for electric vehicles (EV) and electronic devices. As electronic devices, it is particularly useful for frequently used smartphones, mobile phones, tablet terminals, video cameras, notebook computers, and the like.

Claims (10)

A secondary battery electrode comprising a coating layer formed from a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl. It has a coating layer formed from an ionomer of a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), and a metal species. Electrodes for secondary batteries.
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl. The secondary battery electrode according to claim 1 or 2, wherein the copolymer has a number average molecular weight of 1,000 to 1,000,000. The secondary battery electrode according to any one of claims 1 to 3, wherein said X is F and said Y is F or Cl. The secondary battery electrode according to any one of claims 1 to 4, which is a positive electrode. The secondary battery electrode according to any one of claims 1 to 4, which is a negative electrode. An electrochemical device comprising the secondary battery electrode according to any one of claims 1 to 6. An alkali metal ion secondary battery or an alkaline earth metal ion secondary battery comprising the secondary battery electrode according to any one of claims 1 to 4 as at least one of a positive electrode and a negative electrode. The alkali metal ion secondary battery or alkaline earth metal ion secondary battery according to claim 8, wherein the negative electrode contains silicon or lithium. An ionomer comprising a copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), and a metal species.
(1)-(CF ₂ -CXY)-
(2) —(CH ₂ —CHOH)—
In the above formula (1), X and Y are each independently H, F, _CF3 or Cl.