JP2016009572A - Method for manufacturing electrochemical device electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrochemical device electrode superior in charge and discharge cycle characteristics by allowing an electrochemical device electrode to efficiently adsorb an additive agent.SOLUTION: A method for manufacturing an electrochemical device electrode comprises the steps of: bringing an electrochemical device electrode in contact with a mixture (C) arranged by dispersing or dissolving an additive agent for electrochemical devices in the supercritical or subcritical fluid (B); and then, removing a supercritical or subcritical fluid from the mixture. The supercritical or subcritical fluid is a carbon dioxide and it preferably contains an organic solvent.

Description

  The present invention relates to a method for producing an electrode for an electrochemical device.

  Electrochemical devices such as secondary batteries and capacitors are attracting attention as a tool for solving energy and environmental problems because they can efficiently convert between chemical energy and electrical energy, and are actively developed. .

For example, non-aqueous electrolyte secondary batteries such as lithium secondary batteries are characterized by high voltage and high energy density, and thus are widely used in the field of portable information devices, and their demand is rapidly expanding. Currently, it has established a position as a standard battery for mobile information devices such as mobile phones and notebook computers. Of course, along with the high performance and multi-functionality of portable devices, etc., even higher performance (for example, higher capacity and higher energy density) for non-aqueous electrolyte secondary batteries as its power source It has been demanded.

  In a lithium secondary battery, it is known that by adding vinylene carbonate or the like to an electrolyte, deterioration due to repeated charge / discharge or the like is suppressed, and battery performance can be improved (patent document). In addition, a method of adding an additive to an electrode has been proposed in order to enhance the effect of the additive.

  However, when an additive is added to the electrode, there are problems such as a decrease in the amount added due to evaporation of the additive in the electrode drying step and a deterioration in slurry coating property in the electrode coating step.

JP-A-6-52887

  The present invention solves the problems in the electrode preparation process such as deterioration of coatability due to the addition of the additive for electrochemical devices, evaporation of the additive in the drying process, and the additive as an electrode for electrochemical devices. It aims at providing the method of manufacturing the electrode for electrochemical devices excellent in charging / discharging cycling characteristics by making it adsorb | suck efficiently.

As a result of intensive studies to achieve the above object, the present inventors have reached the present invention. That is, the present invention relates to a supercritical fluid, in which a mixture (C) in which an additive for an electrochemical device is dispersed or dissolved in a supercritical fluid or subcritical fluid (B) is brought into contact with an electrode for an electrochemical device. Or it is the manufacturing method of the electrode for electrochemical devices including the process of removing a subcritical fluid.

Since the manufacturing method of the present invention makes it possible to adsorb the additive for electrochemical devices to the electrode obtained in the existing electrode manufacturing process, it is possible to omit optimization of the electrode manufacturing process due to the additive change it can. The production method of the present invention can also be applied to a compound having a relatively low boiling point that evaporates at the drying temperature because the electrode adsorbing the additive for electrochemical devices does not go through an electrode drying step at a high temperature.
By using the electrode for an electrochemical device produced according to the present invention, an electrochemical device having excellent charge / discharge cycle characteristics can be created.

  The method for producing an electrode for an electrochemical device (A) according to the present invention comprises a mixture (C) in which an additive for an electrochemical device is dispersed or dissolved in a supercritical fluid or a subcritical fluid (B). It includes a step of removing a supercritical fluid or subcritical fluid from the material in contact with (A).

  Examples of the additive for electrochemical devices include sulfone, sultone, sulfate ester, sulfonate ester, sulfite ester, phosphate ester, phosphonate ester, phosphazene, carbonate ester, carboxylate ester, carboxylic anhydride, borate ester, Nitriles, isocyanates, amides, ureas, urethanes, ethers, polyethers and unsaturated hydrocarbons.

  Examples of the sulfone include dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, divinyl sulfone, sulfolane, sulfolene, and dimethyl sulfoxide.

  Examples of the sultone include 1,3-propane sultone and 1,4-butane sultone.

  Examples of the sulfate ester include dimethyl sulfate and diethyl sulfate.

  Examples of the sulfonate include methyl methanesulfonate, ethyl methanesulfonate, propargyl methanesulfonate, methyl benzenesulfonate, ethylene glycol sulfate, 1,2-propanediol sulfate, and the like.

  Examples of the sulfite include dimethyl sulfite, diethyl sulfite, ethylene sulfite, propylene sulfite, and vinylene sulfite.

  Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, dimethyl propyl phosphate, diethyl methyl phosphate, ethyl methyl propyl phosphate, trifluoroethyl dimethyl phosphate, bis (trifluoroethyl phosphate). ) Methyl, tris phosphate (trifluoroethyl), pentafluoropropyldimethyl phosphate, trifluoroethyl methyl phosphate, pentafluoropropyl methyl ethyl phosphate, trifluoroethyl methyl phosphate, trifluoroethyl diethyl phosphate, etc. Is mentioned.

  Examples of the phosphonic acid ester include dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl (difluoromethane) phosphonate.

  Examples of the phosphazene include hexafluorocyclotriphosphazene, hexachlorocyclotriphosphazene, hexaphenoxycyclotriphosphazene and the like.

Examples of the carbonate ester include vinylene carbonate, fluoroethylene carbonate, allyl ethyl carbonate, and allyl methyl carbonate.

Examples of the carboxylic acid ester include methyl acetate, ethyl acetate, vinyl acetate, methyl propionate, ethyl propionate, vinyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, diethyl malonate, diethyl succinate, and dimethyl maleate. Etc.

Examples of the carboxylic acid anhydride include malonic anhydride, succinic anhydride, maleic anhydride, and phthalic anhydride.

Examples of the boric acid ester include trimethyl borate, triethyl borate, triisopropyl borate, trinormal propyl borate, trinormal butyl borate, tripentyl borate, trihexyl borate, triheptyl borate, trioctyl borate, boric acid Trinonyl, tridecyl borate, tris borate (2-monofluoroethyl), tris borate (2,2-difluoroethyl), tris borate (2,2,2-trifluoroethyl), tris borate (2,2 , 3,3-tetrafluoropropyl), tris borate (2,2,3,3,3-pentafluoropropyl), tris borate (hexafluoroisopropyl), tris borate (2,2,3,3, 4,4,5,5-octafluoropentyl), tris borate (2,2,2,3,3,4,4,5,5- Nafluoropentyl), tris borate (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl), tris borate (2,2,3,3, 4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl), tris borate (2,2,3,3,4,4,5,5,5) 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11-eicosadecafluoroundecyl) and the like.

Examples of the nitrile include acrylonitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, octanenitrile, undecanenitrile, decanenitrile, cyclohexanecarbonitrile, benzonitrile, phenylacetonitrile, succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethyl Succinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,5-dimethyl-2 5-hexanedicarbonitrile, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-didianobenzene, 1,3-dicyanobenzene, 1 , 4-dicyanobenzene and the like.

Examples of the isocyanate include hexamethylene diisocyanate, dicyclohexylmethane 4,4′-diisocyanate, isophorone didiisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, xylylene diisocyanate, α, α, α ′, α′-tetramethylxylylene diisocyanate, and the like. It is done.

Examples of the amide include N, N-dimethylformamide, N, N-dimethylacetamide, acrylamide, N-methylacetanilide, N-ethylacetanilide, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone and the like. .

Examples of the urea include N, N-dimethylimidazolidinone.

Examples of the urethane include methyl-N, N-dimethylcarbamate and N-methyloxazolidinone.

Examples of the ether include dimethyl ether, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

Examples of the polyether include polyethylene glycol dimethyl ether, polypropylene glycol dimethyl ether, polyethylene glycol methyl ethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol dibutyl ether.

Examples of the unsaturated hydrocarbon include styrene, biphenyl, cyclohexylbenzene terphenyl, and t-butylbenzene.

  The electrode for an electrochemical device contains a positive electrode active material or a negative electrode active material.

Examples of the positive electrode active material include composite oxides of lithium and transition metals (for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ and LiMn ₂ O ₄ ), transition metal oxides (for example, MnO ₂ and V ₂ O ₅ ), and transition metals. Examples thereof include sulfides (for example, MoS ₂ and TiS ₂ ), and conductive polymers (for example, polyaniline, polyvinylidene fluoride, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polycarbazole).

  The content of the positive electrode active material contained in the electrode is preferably 20 to 99% by weight, more preferably 45 to 95% by weight from the viewpoint of battery capacity.

Examples of the negative electrode active material include graphite, amorphous carbon, polymer compound fired bodies (for example, those obtained by firing and carbonizing phenol resin and furan resin), cokes (for example, pitch coke, needle coke, and petroleum coke), carbon fibers. , Conductive polymers (for example, polyacetylene and polypyrrole), tin, silicon, and metal alloys (for example, lithium-tin alloy, lithium-silicon alloy, lithium-aluminum alloy, and lithium-aluminum-manganese alloy).

  The content of the negative electrode active material contained in the electrode is preferably 20 to 99% by weight and more preferably 50 to 98% by weight from the viewpoint of battery capacity.

The additive amount of the electrochemical device additive is preferably 0.05 to 20% by weight, more preferably 0.1%, from the viewpoint of charge / discharge cycle characteristics, based on the weight of the active material contained in the electrode. -10% by weight.

The supercritical fluid or subcritical fluid (B) used in the present invention may be a mixture (C1) of a supercritical fluid or subcritical fluid (B) and an organic solvent (D). Examples of the organic solvent (D) include ketone solvents (acetone, methyl ethyl ketone, etc.), ether solvents (tetrahydrofuran, diethyl ether, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, cyclic ether, etc.), ester solvents (acetate ester, pyrubin). Acid esters, 2-hydroxyisobutyric acid esters, lactic acid esters, etc.), amide solvents (dimethylformamide, etc.), alcohol solvents (methanol, ethanol, isopropanol, fluorine-containing alcohols, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.) and Aliphatic hydrocarbon solvents (octane, decane, etc.) are listed.

  The content of the organic solvent based on the total weight of the supercritical fluid or subcritical fluid (B) and the organic solvent (D) is from 0 to 90 from the viewpoint of the cycle characteristics of the battery using the electrode produced by this production method. % By weight is preferred, more preferably 0 to 50% by weight.

Examples of the supercritical fluid used for dispersing or dissolving the additive for electrochemical devices in the present invention include supercritical water and supercritical carbon dioxide. Among these, carbon dioxide in a supercritical state is preferable from the viewpoint of charge / discharge cycle characteristics of a battery using an electrode according to the production method of the present invention.

In the present invention, as a method of bringing a mixture obtained by dispersing or dissolving an additive for an electrochemical device into a supercritical fluid or a subcritical fluid (B) into contact with the electrode for an electrochemical device, for example, the electrode is placed in a pressure-resistant reaction vessel. It arrange | positions on a holding stand and the said additive is prepared in a container. Carbon dioxide is introduced into the container and maintained at 20 MPa by adjusting the pressure. The carbon dioxide fluid that has become a supercritical fluid becomes a pressurized fluid in which the additive is dissolved or dispersed, contacts the electrode, and can impregnate the electrode surface or inside the electrode.

It is sufficient if the time required for mixing the additive for electrochemical devices and the supercritical fluid or subcritical fluid in the mixture (C) is longer than the time during which the additive dissolves or disperses and no pressure drop occurs over time. It is.

  In this invention, the temperature at the time of contact with a mixture (C) and the electrode for electrochemical devices is 30-120 degreeC from a soluble or dispersible viewpoint of the additive for electrochemical devices, More preferably, it is 50-100 degreeC. The contact time is preferably 1 to 120 minutes, more preferably 10 to 60 minutes, from the viewpoint of charge / discharge cycle characteristics of the battery using the electrode according to the production method of the present invention. The pressure at the time of contact is preferably 2 to 20 MPa.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these. Hereinafter, unless otherwise specified, “%” represents “% by weight” and “parts” represents “parts by weight”.

[Production of positive electrode for electrochemical devices]
Lithium cobaltate (LiCoO ₂ ) powder 90.0 parts, Ketjen black [Sigma-Aldrich Co., Ltd.] 5 parts, polyvinylidene fluoride [Sigma-Aldrich Co., Ltd.] 5 parts and the number of parts shown in Table 2 (D ) In a mortar, 70.0 parts of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] was added, and further mixed well in a mortar to obtain a slurry. The obtained slurry was applied to one side of an aluminum electrolytic foil having a thickness of 20 μm using a wire bar in the air, dried at 80 ° C. for 1 hour, and further under reduced pressure (1.3 kPa) at 80 ° C. It was dried for 2 hours and punched out to 15.95 mmφ to produce a positive electrode for electrochemical devices.

[Production of negative electrode for electrochemical devices]
92.5 parts of graphite powder having an average particle diameter of about 8 to 12 μm, 7.5 parts of polyvinylidene fluoride, 200 parts of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] and the number of parts shown in Table 2 ( D) was thoroughly mixed in a mortar to obtain a slurry. The obtained slurry was applied to one side of a 20 μm-thick copper foil in the air using a wire bar, dried at 80 ° C. for 1 hour, and further under reduced pressure (1.3 kPa) at 80 ° C. for 2 hours. It was dried, punched to 16.15 mmφ, and made a negative electrode for an electrochemical device with a thickness of 30 μm using a press.

<Example 1>
The positive electrode for the lithium secondary battery is placed in a pressure-resistant reaction vessel, 0.9 part of 1,3-propane sultone [manufactured by Tokyo Chemical Industry Co., Ltd.] is charged into the pressure-resistant reaction vessel, and the temperature in the kettle is raised to 40 ° C Warm up. After raising the temperature, carbon dioxide was supplied to 20 MPa to form a supercritical fluid, which was held for 30 minutes with stirring. Carbon dioxide was removed and the pressure was returned to normal pressure to obtain an electrode for electrochemical devices (A-1).

<Example 2>
An electrode for an electrochemical device was prepared in the same manner as in Example 1 except that 0.9 part of ethylene sulfite [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of 1,3-propane sultone. A-2) was obtained.

<Example 3>
An electrode for an electrochemical device was prepared in the same manner as in Example 1 except that 0.9 part of tributyl phosphate [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of 1,3-propane sultone. A-3) was obtained.

<Example 4>
For electrochemical devices, except that 0.9 part of hexafluorocyclotriphosphazene [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of 1,3-propane sultone. An electrode (A-4) was obtained.

<Example 5>
The same procedure as in Example 1 was carried out except that 0.9 part of maleic anhydride [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of 1,3-propane sultone. A-5) was obtained.

<Example 6>
An electrode for electrochemical devices was carried out in the same manner as in Example 1 except that 0.9 part of triisopropyl borate [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of 1,3-propane sultone. (A-6) was obtained.

<Example 7>
The negative electrode for a lithium secondary battery was placed in a pressure-resistant reaction vessel, 0.9 part of succinonitrile [manufactured by Tokyo Chemical Industry Co., Ltd.] was charged into the pressure-resistant reaction vessel, and the temperature in the kettle was raised to 40 ° C. After raising the temperature, carbon dioxide was supplied to 20 MPa to form a supercritical fluid, which was held for 30 minutes with stirring. Carbon dioxide was extracted and the pressure was returned to normal pressure to obtain an electrode for electrochemical devices (A-7).

<Example 8>
For electrochemical devices, except that 0.9 part of methyl-N, N-dimethylcarbamate [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of succinonitrile. An electrode (A-8) was obtained.

<Example 9>
An electrode for electrochemical devices was carried out in the same manner as in Example 7 except that 0.9 part of 1,2-diethoxyethane [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of succinonitrile. (A-9) was obtained.

<Example 10>
An electrode for an electrochemical device (A-) was prepared in the same manner as in Example 7 except that 0.9 part of polyethylene glycol dimethyl ether (Mn 500) [manufactured by Sigma-Aldrich] was used instead of 0.9 part of succinonitrile. 10) was obtained.

<Example 11>
Electrode for electrochemical devices (A-11), except that 0.9 part of cyclohexylbenzene [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of succinonitrile. Got.

<Example 12>
Electrode for electrochemical devices (A-12), except that 0.9 part of vinylene carbonate [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 0.9 part of succinonitrile. Got.

<Comparative Example 1>
A comparative electrochemical device electrode (A′-1) was obtained in the same manner as in Example 1 except that 0.9 part of 1,3-propane sultone was not used.

<Comparative Example 2>
The positive electrode for electrochemical devices and the negative electrode for electrochemical devices were used as comparative electrochemical device electrodes (A′-2).

<Comparative Example 3>
A comparative electrochemical device electrode (A′-3) was obtained in the same manner as in Example 7 except that 0.9 part of succinonitrile was not used.

Table 1 summarizes the electrodes (A-1) to (A-12) for electrochemical devices and the electrodes (A′-1) to (A′-3) for comparative electrochemical devices of Examples 1 to 12.

<Examples 13-24, Comparative Examples 4-8>
[Preparation of electrolyte]
An electrolyte solution additive was blended in 87.5 parts of a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1) in the number of parts shown in Table 2, and LiPF ₆ was added as an electrolyte so as to be 12% by weight. It was made to melt | dissolve and the electrolyte solution of Examples 13-24 and Comparative Examples 4-8 was prepared.

[Production of lithium secondary battery]
A lithium metal is disposed at one end of the 2032 type coin cell, and the positive or negative electrodes of Examples 1 to 12 and Comparative Examples 1 to 3 are disposed at the other end so that the coated surfaces face each other, and a separator (polypropylene nonwoven fabric) is provided between the electrodes. Was inserted to prepare a lithium secondary battery half cell. Liquid injection was sealed in a cell prepared with a previously prepared electrolyte. The results of evaluating the charge / discharge cycle characteristics by the following method are shown in Table 2.

<Evaluation of charge / discharge cycle characteristics of positive-electrode side lithium secondary battery half cell>
Using a charge / discharge measuring device “Battery Analyzer 1470” [manufactured by Toyo Technica Co., Ltd.], the battery voltage is charged to 0.1 V with a current of 0.1 C, and after a pause of 10 minutes, the battery voltage is 0.1 C. Was discharged to 3.0 V, and this charge / discharge was repeated. At this time, the battery capacity at the first charge and the battery capacity at the 50th cycle charge were measured, and the charge / discharge cycle characteristics were calculated from the following formula. It shows that charging / discharging cycling characteristics are so favorable that a numerical value is large.
Charging / discharging cycle characteristics (%) = (battery capacity at the 50th cycle charge / battery capacity at the first charge) × 100

<Evaluation of charge / discharge cycle characteristics of negative electrode side lithium secondary battery half cell>
Using a charge / discharge measuring device “Battery Analyzer 1470 type”, the battery voltage was discharged to 0.1 V with a current of 0.1 C to a voltage of 0.05 V. This charge / discharge was repeated. At this time, the battery capacity at the first charge and the battery capacity at the 50th cycle charge were measured, and the charge / discharge cycle characteristics were calculated from the following formula. It shows that charging / discharging cycling characteristics are so favorable that a numerical value is large.
Charging / discharging cycle characteristics (%) = (battery capacity at the 50th cycle charge / battery capacity at the first charge) × 100

  It turned out that the electrode for lithium secondary batteries produced using the manufacturing method of this invention is excellent in charging / discharging cycle performance from the result of the said Example and comparative example.

The manufacturing method of the electrode for electrochemical devices of this invention is suitable for manufacture of the electrode for lithium secondary batteries. Electrochemical devices other than those disclosed in the present invention (lithium ion capacitors, electric double layer capacitors, all solid state batteries, lead acid batteries, nickel metal hydride batteries, nickel cadmium batteries, air batteries, alkaline batteries, dye-sensitized solar cells, fuels It can also be applied to the electrode of a battery or the like.

Claims (6)

The supercritical fluid or subcritical fluid is removed from the mixture (C) in which the additive for electrochemical device is dispersed or dissolved in the supercritical fluid or subcritical fluid (B) and brought into contact with the electrode for electrochemical device. The manufacturing method of the electrode for electrochemical devices including the process to make. The additive for electrochemical devices is sulfone, sultone, sulfate ester, sulfonate ester, sulfite ester, phosphate ester, phosphonate ester, phosphazene, carbonate ester, carboxylate ester, carboxylic anhydride, borate ester, nitrile The production method according to claim 1, which is an additive containing at least one compound selected from the group consisting of styrene, isocyanate, amide, urea, urethane, ether, polyether and unsaturated hydrocarbon.   The electrode for an electrochemical device contains a positive electrode active material, and the active material is at least selected from the group consisting of a composite oxide of lithium and a transition metal, a transition metal oxide, a transition metal sulfide, and a conductive polymer. The production method according to claim 1, wherein the production method is one active material.   The electrode for an electrochemical device contains a negative electrode active material, and the active material is made of graphite, amorphous carbon, polymer compound fired body, coke, carbon fiber, conductive polymer, tin, silicon, and metal alloy. The production method according to claim 1, wherein the production method is at least one active material selected. The mixture (C) is a mixture (C1) in which an additive for electrochemical devices is dispersed or dissolved in a supercritical fluid or subcritical fluid (B) and an organic solvent (D). The production method according to item.   The manufacturing method according to claim 1, wherein the supercritical fluid or the subcritical fluid is carbon dioxide.