WO2017026253A1 - Manufacturing method for electrode and manufacturing method for electricity storage device - Google Patents

Abstract

The manufacturing method, according to an aspect of the present disclosure, for an electrode forming a capacitor or a battery includes a step for causing, before assembling the capacitor or the battery, an active material to occlude an alkaline metal in a solution obtained by dissolving an alkaline metal salt in an organic solvent. The organic solvent contains a specific organic solvent which is at least one selected from the group consisting of β-keto esters, β-diketones, and compounds each having three or more ether linkages.

Description

Electrode manufacturing method and power storage device manufacturing method Cross-reference of related applications

This international application claims priority based on Japanese Patent Application No. 2015-157162 filed with the Japan Patent Office on August 7, 2015, and is based on Japanese Patent Application No. 2015-157162. The entire contents are incorporated by reference into this international application.

The present disclosure relates to an electrode manufacturing method and an electricity storage device manufacturing method.

2. Description of the Related Art In recent years, electronic devices have been remarkably reduced in size and weight, and accordingly, there has been an increasing demand for downsizing and weight reduction of batteries used as power sources for driving the electronic devices.
In order to satisfy such demands for reduction in size and weight, nonaqueous electrolyte secondary batteries represented by lithium ion secondary batteries have been developed. Moreover, a lithium ion capacitor is known as an electricity storage device corresponding to an application that requires high energy density characteristics and high output characteristics. Further, sodium ion type batteries and capacitors using sodium which is cheaper than lithium and resource-rich are also known.

In such batteries and capacitors, a process (generally referred to as pre-doping) in which an alkali metal is previously occluded in an electrode active material is employed for various purposes. For example, in a lithium ion capacitor, lithium pre-doping is performed to lower the negative electrode potential and increase the energy density. In this case, a method of pre-doping the negative electrode active material in the cell using a current collector having a through hole has become the mainstream (see, for example, Patent Document 1).

Also, in a lithium ion secondary battery, pre-doping is performed to reduce the irreversible capacity of the negative electrode. In this case, in addition to the above method, a method of pre-doping the negative electrode active material before assembling the battery is employed (see, for example, Patent Documents 2 and 3).

Furthermore, when producing a sodium ion type electricity storage device, a method of pre-doping sodium into the negative electrode before assembling the electricity storage device is employed (Patent Document 4).

Further, in Patent Document 5, it is proposed to use a fibrous carbon material in which lithium ions are occluded for the negative electrode in order to suppress the decomposition of the electrolytic solution on the negative electrode during the initial charging of the secondary battery. . In Patent Document 5, a fibrous carbon material is brought into contact with n-butyllithium in a non-aqueous solvent, thereby allowing the fibrous carbon material to occlude lithium ions.

JP 2007-67105 A JP 7-235330 A JP-A-9-293499 JP 2012-69894 A JP 2000-156222 A

In the method using a current collector having a through hole, there is a problem that the manufacturing cost of the capacitor and the battery becomes very high because it is necessary to provide a regular and fine through hole in the current collector. On the other hand, in the method of pre-doping before assembling the capacitor or battery, it is not necessary to use a current collector having a through hole, but there is a problem that it is not suitable for mass production because the dope speed cannot be increased. is there.

One aspect of the present disclosure is a method for manufacturing an electrode in which an alkali metal is occluded in an active material before assembling a battery or a capacitor. In one aspect of the present disclosure, it is desirable to provide a method for manufacturing an electrode that is excellent in mass productivity. .

One embodiment of the present disclosure is a method for manufacturing an electrode constituting a capacitor or battery, and is assembled in a solution in which an alkali metal salt is dissolved in an organic solvent (hereinafter referred to as a pre-dope solution) before the capacitor or battery is assembled. A step of occluding an alkali metal in the substance. The organic solvent contains a specific organic solvent that is at least one selected from the group consisting of a compound having three or more ether bonds, a β-diketone, and a β-ketoester.

According to the electrode manufacturing method of one aspect of the present disclosure, the alkali metal can be occluded in the active material at a high temperature, and thus the occlusion speed of the alkali metal can be increased. Furthermore, since the solvent can be prevented from volatilizing from the pre-dope solution, the exhaust equipment can be omitted or simplified when mass-producing the electrode storing the alkali metal. Moreover, management of the pre-dope solution becomes easy. Therefore, the electrode manufacturing method according to one aspect of the present disclosure is excellent in mass productivity.

It is sectional drawing showing the structure of a capacitor.

DESCRIPTION OF SYMBOLS 1 ... Capacitor, 3 ... Electrode unit, 5 ... Exterior container, 7 ... Electrolyte, 9 ... Positive electrode, 11 ... Negative electrode, 13 ... Separator, 15 ... Lithium ion supply source, 17 ... positive electrode terminal, 19 ... connecting member, 21 ... negative electrode terminal

An embodiment of the present disclosure will be described.
1. Electrode Manufacturing Method The electrode manufacturing method of the present disclosure includes a step of occluding an alkali metal in an active material in a solution in which an alkali metal salt is dissolved in an organic solvent (hereinafter referred to as a pre-dope solution).

電極 The electrode manufactured by the electrode manufacturing method of the present disclosure may be a positive electrode or a negative electrode. In the method for producing an electrode of the present disclosure, when a positive electrode is produced, an alkali metal is occluded in the positive electrode active material, and when a negative electrode is produced, an alkali metal is occluded in the negative electrode active material.

The active material is not particularly limited as long as it is an electrode active material applicable to a battery or a capacitor using insertion / extraction of alkali metal ions, and may be a negative electrode active material or a positive electrode active material. It may be.

The negative electrode active material is not particularly limited, and examples thereof include carbon materials, metals or metalloids that can be alloyed with lithium, and materials containing these oxides. Examples of the carbon material include graphite, graphitizable carbon, non-graphitizable carbon, and composite carbon material in which graphite particles are coated with pitch or resin carbide. Examples of the metal or metalloid capable of being alloyed with lithium or a material containing these oxides include materials described in JP-A-2005-123175 and JP-A-2006-107795. Examples of the metal or semimetal that can be alloyed with lithium include Si and Sn.

Examples of the positive electrode active material include alkali metal transition metal composite oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, sodium cobalt oxide, sodium nickel oxide, and sodium manganese oxide. .

Either the positive electrode active material or the negative electrode active material may be composed of a single material, or may be a mixture of two or more materials. The manufacturing method of the electrode of this indication is suitable when making a negative electrode active material occlude alkali metal, and it is especially preferred that a negative electrode active material is a material containing carbon material, Si, or its oxide.

Generally, when a carbon material is used as an active material, if the particle size of the carbon material is reduced, an electricity storage device having a low internal resistance can be obtained, but there may be a problem. The problem is, for example, a problem that the irreversible capacity increases or a problem that the amount of gas generated when the power storage device is held in a charged state increases. By using the electrode manufacturing method of the present disclosure, such a problem can be suppressed even when a carbon material having a 50% volume cumulative diameter D50 of 0.1 to 10 μm is used as the active material. The 50% volume cumulative diameter D50 is a value measured by a laser diffraction / scattering method.

Also, when using a material containing Si or its oxide as an active material, the irreversible capacity generally tends to increase. If the manufacturing method of the electrode of this indication is used, this tendency can be controlled.

As the alkali metal occluded in the active material, lithium or sodium is preferable, and lithium is particularly preferable.
In the electrode manufacturing method of the present disclosure, the organic solvent in the pre-dope solution is at least one selected from the group consisting of a compound having three or more ether bonds, a β-diketone, and a β-ketoester (hereinafter referred to as a specific organic solvent). ).

When the organic solvent contains the specific organic solvent, the active material can occlude the alkali metal at a high temperature. Thereby, the occlusion speed of the alkali metal can be increased. Furthermore, since the solvent can be prevented from volatilizing from the pre-dope solution, the exhaust equipment can be omitted or simplified when mass-producing the electrode storing the alkali metal. Moreover, management of the pre-dope solution becomes easy.

The reason why such an effect (hereinafter referred to as a desired effect) is obtained is thought to be that ether oxygen or carbonyl oxygen contained in the specific organic solvent strongly interacts with alkali metal ions.

The compound having three or more ether bonds may be a chain compound or a cyclic compound (for example, crown ether), but is preferably a chain compound. Examples of the chain compound include polyalkylene glycol dialkyl ether, and more specifically, diethylene glycol dimethyl ether (diglyme), diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether (triglyme), triethylene glycol butyl methyl ether, Examples include polyethylene glycol dialkyl ethers such as tetraethylene glycol dimethyl ether (tetraglyme); polypropylene glycol dialkyl ethers such as dipropylene glycol dimethyl ether. Of these, polyethylene glycol dialkyl ether is preferred.

Moreover, as a compound which has 3 or more ether bonds, the compound which has 4 or more ether bonds is preferable from the point which can raise the density | concentration of an alkali metal salt, and it has especially 4 or 5 ether bonds. Compounds are preferred.

Examples of the β-diketone include acetylacetone, 5-methyl-2,4-hexanedione, and 2,6-dimethyl-3,5-heptanedione. Examples of the β-ketoester include alkyl acetoacetates such as methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, and isopropyl acetoacetate.

As the specific organic solvent, a compound having three or more ether bonds is preferable from the viewpoint of enhancing a desired effect. The boiling point at 1 atm of the specific organic solvent is preferably 100 to 300 ° C. from the viewpoint of enhancing the desired effect. The specific organic solvent may be composed of a single component or a mixed solvent of two or more components.

In the electrode manufacturing method of the present disclosure, the pre-dope solution may contain an organic solvent other than the specific organic solvent. As the organic solvent other than the specific organic solvent, an aprotic organic solvent is preferable. Examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like. .

The organic solvent other than the specific organic solvent may be composed of a single component or a mixed solvent of two or more components.
The mass ratio of the specific organic solvent to the total amount of the organic solvent in the pre-dope solution is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more from the viewpoint of enhancing a desired effect.

In the electrode manufacturing method of the present disclosure, in the step of occluding an alkali metal in the active material, the pre-dope solution is preferably heated, the temperature of the pre-dope solution is preferably 40 to 110 ° C., and 50 to 100 It is particularly preferable that the temperature is set to ° C. When the temperature of the pre-dope solution is set within the above range, safety is ensured and occlusion of alkali metal proceeds efficiently.

The heating of the pre-dope solution may be heating the pre-dope solution in a state mixed with the active material, or may be heating the pre-dope solution in a state separated from the active material.

The alkali metal salt dissolved in the pre-dope solution is preferably a lithium salt or a sodium salt. Examples of the anion moiety constituting the alkali metal salt include phosphorus anions having a fluoro group such as PF ₆ ⁻ , PF ₃ (C ₂ F ₅ ) ₃ ⁻ , PF ₃ (CF ₃ ) ₃ ⁻ , and the like; BF ₄ ⁻ , Boron anions having a fluoro group or a cyano group such as BF ₂ (CF) ₂ ⁻ , BF ₃ (CF ₃ ) ⁻ , B (CN) ₄ ^—, etc .; N (FSO ₂ ) ₂ ⁻ , N (CF ₃ SO ₂ ) _{2 ^{-, N (C 2 F 5}} SO 2) 2 - sulfonyl imide anion having a fluoro group such as; _{CF 3} SO 3 ^- is an organic sulfonate anion having a fluoro group and the like. Among these, a sulfonylimide anion having a fluoro group is preferable from the viewpoint of enhancing a desired effect.

The concentration of the alkali metal salt in the pre-dope solution is preferably 10 to 50 mol%, particularly preferably relative to the specific organic solvent, when the specific organic solvent is a compound having three ether bonds, β-diketone or β-ketoester. Is 40 to 50 mol%. Further, when the specific organic solvent is a compound having four or more ether bonds, it is preferably 50 to 100 mol%, particularly preferably 80 to 100 mol%, based on the specific organic solvent. If it is within this range, the desired effect can be enhanced.

The pre-dope solution further contains additives such as vinylene carbonate, vinyl ethylene carbonate, 1-fluoroethylene carbonate, 1- (trifluoromethyl) ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, diethyl sulfone. Can do.

The step of occluding the alkali metal in the active material in the pre-dope solution is not particularly limited, and examples thereof include the following doping step A and doping step B. The occlusion amount of the alkali metal is preferably 70 to 95% with respect to the theoretical capacity of the negative electrode active material when lithium is stored in the negative electrode active material of the lithium ion capacitor. Further, when the lithium is occluded in the negative electrode active material of the lithium ion secondary battery, the alkali metal occlusion amount is preferably 10 to 30% with respect to the theoretical capacity of the negative electrode active material.

(Doping process A)
First, a layer containing an active material before occluding an alkali metal (hereinafter referred to as a precursor layer) is formed on a current collector. The precursor layer and the current collector are combined into an electrode precursor. This electrode precursor is brought into electrochemical contact with an alkali metal source in a pre-dope solution. At this time, an alkali metal is occluded in the active material contained in the precursor layer, and the electrode precursor becomes an electrode.

If the doping step A is used, after the doping step A, the manufactured electrode is used as it is (without passing through a step of forming a layer containing an active material on the current collector) as an electrode of a battery or a capacitor. Can do.

In addition, when the electrode manufacturing method of the present disclosure is used for the purpose of reducing the irreversible capacity or suppressing the decomposition of the electrolyte during charging / discharging, the active material is reversibly applied after the doping step A. After further performing the step of desorbing part or all of the occluded alkali metal as alkali metal ions, the produced electrode can be used as an electrode of a battery or a capacitor.

The precursor layer can be prepared, for example, by preparing a slurry containing an active material before occluding an alkali metal, a binder, and the like, applying the slurry on a current collector, and drying the slurry.

Examples of the binder include rubber-based binders such as styrene-butadiene rubber (SBR) and NBR; fluorine-based resins such as polytetrafluoroethylene and polyvinylidene fluoride; polypropylene, polyethylene, disclosed in JP2009-246137A Fluorine-modified (meth) acrylic binder as described above.

The slurry may contain other components in addition to the active material and the binder. Examples of other components include a conductive agent and a thickener. Examples of the conductive agent include carbon black, graphite, vapor grown carbon fiber, and metal powder. Examples of the thickener include carboxymethyl cellulose, its Na salt or ammonium salt, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.

The thickness of the precursor layer is not particularly limited, but is, for example, 5 to 500 μm, preferably 10 to 200 μm, particularly preferably 10 to 100 μm.
As the current collector, for example, a metal foil such as copper, nickel, and stainless steel is preferable. Further, the current collector may be one in which a conductive layer mainly composed of a carbon material is formed on the metal foil. The thickness of the current collector can be, for example, 5 to 50 μm.

The form of the alkali metal supply source is not particularly limited. For example, an alkali metal plate, an alkali metal alloy plate, or the like can be used as the alkali metal supply source. These thicknesses can be set to 0.03 to 3 mm, for example. The alkali metal supply source is preferably disposed on the conductive substrate. The conductive substrate may be porous. Examples of the material of the conductive substrate include copper, stainless steel, nickel, and the like.

Examples of the method of bringing the electrode precursor and the alkali metal supply source into electrochemical contact include a method of short-circuiting the electrode precursor and the alkali metal supply source in a pre-dope solution containing an alkali metal salt, Examples thereof include a method in which a direct current is passed between the electrode precursor and the alkali metal supply source in a pre-dope solution containing a salt.

As a method of short-circuiting the electrode precursor and the alkali metal supply source in the pre-dope solution containing the alkali metal salt, for example, the current collector is used as one terminal and the conductive substrate on which the alkali metal supply source is arranged is the other. As a terminal, there is a method in which both terminals are electrically connected by a conductor such as a metal wire to cause a short circuit. The short-circuiting time can be appropriately set according to the area, thickness, and the like of the precursor layer, and can be, for example, 1 to 1000 hours, preferably 5 to 500 hours.

Further, as a method of passing a direct current between the electrode precursor and the alkali metal supply source in the pre-dope solution containing the alkali metal salt, for example, a positive terminal of a direct current stabilized power source is used, and an alkali metal supply source is used. There is a method of connecting a conductive base material arranged and connecting a negative terminal of a direct current stabilized power source to a current collector to energize. The current at the time of energization can be appropriately set according to the area, thickness, etc. of the precursor layer.

If the electrode manufacturing method of the present disclosure is used, problems such as precipitation of alkali metal are suppressed even when high-speed energization is performed at a constant current of 5C or more, and further at a constant current of 10C or more. Metal can be occluded. Here, “C” is a charge / discharge coefficient, and a current value for charging or discharging the storage battery in one hour is represented as “1C”.

(Doping process B)
In the pre-dope solution, the active material itself is brought into contact with an alkali metal supply source to cause the active material to occlude the alkali metal. For the specific method, for example, the method described in JP2012-209195A can be referred to.

The method described in the publication includes a mixture containing at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, and dimethyl carbonate, a lithium salt, metallic lithium, and an active material. This is a method in which lithium is occluded in the active material by electrically contacting the material with the metallic lithium. In this method, a specific organic solvent may be used instead of ethylene carbonate.

In the method described in the publication, the lithium salt is composed of LiBF ₄ , LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiC ₄ BO ₈ , (C ₂ F ₅ SO ₂ ) ₂ NLi, and (FSO ₂ ) ₂ NLi. At least one selected from the group can be mentioned. Among them, it is preferable to use (FSO ₂ ) ₂ NLi. Moreover, as the metal lithium, lithium metal powder coated with Li ₂ CO ₃ or lithium metal foil can be used.

In the method described in the publication, during occlusion, the electrode active material and the metallic lithium can be brought into electrical contact by applying ultrasonic vibration to the mixture.
An electrode can be manufactured by preparing a slurry containing an active material after occlusion of an alkali metal and a binder and the like by the doping step B, applying the slurry on a current collector, and drying the slurry. The electrode includes an active material layer containing the active material, the binder, and the like, and a current collector.

The thickness of the active material layer is not particularly limited, but is, for example, 5 to 500 μm, preferably 10 to 200 μm, particularly preferably 10 to 100 μm.
Examples of the binder include the same binders as those contained in the slurry used in the dope step A. The slurry may contain other components in addition to the active material and the binder. Examples of other components include the same components as those contained in the slurry used in the dope step A. The material, thickness, etc. of the current collector can also be the same as the current collector used in the doping step A.

The electrode manufacturing method of the present disclosure is suitable for manufacturing a negative electrode included in an alkali ion type capacitor or battery, and more suitable for manufacturing a negative electrode included in an alkali ion type capacitor or secondary battery. It is particularly suitable for the production of a negative electrode provided in an ion secondary battery.

When the electrode obtained by the electrode manufacturing method of the present disclosure is used for a lithium ion secondary battery, the density of the active material layer is preferably 1.50 to 2.00 g / cc, particularly preferably 1.60. To 1.90 g / cc.

When the electrode obtained by the electrode manufacturing method of the present disclosure is used for a lithium ion capacitor, the density of the active material layer is preferably 0.50 to 1.50 g / cc, particularly preferably 0.70. ˜1.20 g / cc.

2. Capacitor The capacitor of the present disclosure corresponds to an electricity storage device. The capacitor includes a positive electrode, a negative electrode, and an electrolyte. A negative electrode can be manufactured by the manufacturing method of the electrode of this indication. The capacitor is not particularly limited as long as it is a capacitor using insertion / extraction of alkali metal ions, and examples thereof include a lithium ion capacitor and a sodium ion capacitor. Among these, a lithium ion capacitor is preferable.

基本 The basic configuration of the positive electrode constituting the capacitor of the present disclosure is the same as the configuration of the electrode described in the above-mentioned “electrode manufacturing method”, but it is preferable to use activated carbon as the positive electrode active material.

The form of the electrolyte constituting the capacitor of the present disclosure is usually a liquid electrolyte. The basic configuration of the electrolytic solution is the same as the configuration of the pre-dope solution described in the above “electrode manufacturing method”, but from the viewpoint of the cost and the electrochemical characteristics of the cell at a low temperature of 0 ° C. or lower, the organic solvent is It is preferable to use an organic solvent other than the specific organic solvent. The concentration of alkali metal ions (alkali metal salt) is preferably 0.1 mol / L or more, more preferably in the range of 0.5 to 1.5 mol / L. The electrolyte may have a gel or solid form for the purpose of preventing leakage.

キ ャ パ シ タ The capacitor of the present disclosure can include a separator for suppressing physical contact between the positive electrode and the negative electrode. As a separator, the nonwoven fabric or porous film which uses a cellulose rayon, polyethylene, a polypropylene, polyamide, polyester, a polyimide etc. as a raw material can be mentioned, for example.

As a structure of the capacitor, for example, three or more plate-like constitutional units composed of a positive electrode and a negative electrode and a separator interposed therebetween are laminated to form a laminated body, and the laminated body is enclosed in an exterior film. A stacked cell may be mentioned.

In addition, as a capacitor structure, for example, a band-shaped structural unit composed of a positive electrode and a negative electrode, and a separator interposed therebetween is wound to form a multilayer body, and the multilayer body is stored in a rectangular or cylindrical container. The wound type cell etc. which were made are mentioned.

The capacitor of the present disclosure can be manufactured, for example, by forming a basic structure including at least a negative electrode and a positive electrode and injecting an electrolyte into the basic structure.
FIG. 1 shows an example of the configuration of the capacitor 1. The capacitor 1 is a multilayer storage device. The capacitor 1 includes an electrode unit 3, an outer container 5, and an electrolyte 7.

The electrode unit 3 is a stacked electrode unit having a structure in which a plurality of units in which the positive electrode 9 and the negative electrode 11 are stacked via the separator 13 are further stacked. A film-like lithium ion supply source 15 is laminated on each of the upper and lower surfaces of the electrode unit 3.

The outer container 5 accommodates the electrode unit 3. The electrolyte 7 is filled in the outer container 5. The positive electrode 9 extends toward one end of the outer container 5 and is connected to the positive electrode terminal 17. The positive electrode terminal 17 is fixed to the exterior container 5 by a connecting member 19.

The negative electrode 11 extends toward the end of the outer container 5 opposite to the one, and is connected to the negative electrode terminal 21. The battery described later can also have the configuration shown in FIG. 1, for example.

3. Battery The battery of the present disclosure corresponds to an electricity storage device. The battery includes a positive electrode, a negative electrode, and an electrolyte. A negative electrode can be manufactured by the manufacturing method of the electrode of this indication. The battery is not particularly limited as long as it uses insertion / extraction of alkali metal ions, and may be a primary battery or a secondary battery. Examples of the battery include a lithium ion secondary battery, a sodium ion secondary battery, and an air battery. Among these, a lithium ion secondary battery is preferable.

The basic configuration of the positive electrode constituting the battery of the present disclosure is the same as the configuration of the electrode described in the above-mentioned “electrode manufacturing method”, but as the positive electrode active material, in addition to those already exemplified, a nitroxy radical compound Organic active materials such as oxygen and oxygen can also be used.

The configuration of the electrolyte constituting the battery of the present disclosure and the configuration of the battery itself are the same as those described in the above “capacitor”.
The battery of the present disclosure can be manufactured, for example, by forming a basic structure including at least a negative electrode and a positive electrode and injecting an electrolyte into the basic structure.

Hereinafter, embodiments of the present disclosure will be described more specifically with reference to examples. However, the present disclosure is not limited to the following examples. In the following examples and comparative examples, various physical properties of the active material were measured by the following methods. The negative electrode was produced in an air environment controlled at a temperature of 23 ° C. and a dew point of −40 ° C.

Example 1
(i) Production of Negative Electrode Precursor A 40 μm thick precursor layer was formed on a current collector made of a copper foil having a surface roughness Ra = 0.1 μm. The precursor layer is a layer containing graphite (negative electrode active material, 50% volume cumulative diameter D50 = 5 μm), carboxymethylcellulose, acetylene black (conductive agent) and a dispersant in a mass ratio of 88: 4: 5: 3. It is. The precursor layer was formed by preparing a slurry containing the above components, applying the slurry onto a current collector, and drying the slurry. The graphite contained in the precursor layer is in a state before occluding the alkali metal. The current collector and the precursor layer formed thereon are collectively referred to as a negative electrode precursor below.

(ii) Production and Evaluation of Negative Electrode The negative electrode precursor obtained in (i) above was cut into a circle having a diameter of 15.9 mm. Further, a counter electrode was prepared by cutting lithium metal into a circle having a diameter of 16.1 mm. And the tripolar flat cell was produced combining the negative electrode precursor, the counter electrode, and the lithium reference electrode.

The pre-dope solution was injected into the flat cell. The pre-dope solution is a solution obtained by mixing equimolar amounts of LiN (FSO ₂ ) ₂ and triglyme. The pre-dope solution is an example of a solution in which an alkali metal salt is dissolved in an organic solvent.

The obtained flat cell was connected to a charge / discharge tester. Moreover, the flat cell was installed in the 80 degreeC thermostat, and left still for 2 hours. Thereafter, the battery was charged with a constant current of 1C. The charging time was set such that the lithium occlusion rate was 76% with respect to the theoretical capacity of graphite (372 mAh / g).

As a result, a negative electrode including a current collector and a layer containing a negative electrode active material occluded with lithium (a negative electrode active material layer) formed thereon was obtained. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.088V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.04 mAh.

(Example 2)
A negative electrode was produced in the same manner as in Example 1 except that the current value during charging was changed from 1 C to 50 C. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.087V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.02 mAh.

(Example 3)
A negative electrode was produced in the same manner as in Example 1 except that the temperature of the thermostatic chamber was changed from 80 ° C to 25 ° C. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.084V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.10 mAh.

Example 4
A negative electrode was produced in the same manner as in Example 1 except that the same amount of tetraglyme was used instead of triglyme. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.087V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.04 mAh.

(Example 5)
A negative electrode was produced in the same manner as in Example 1 except that the same amount of tetraglyme was used instead of triglyme and the current value during charging was changed from 1C to 10C. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.087V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.01 mAh.

(Comparative Example 1)
A flat cell was prepared basically in the same manner as in Example 1. However, the pre-dope solution to be injected into the flat cell contains 1.2 M LiPF ₆ and also contains a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate as an organic solvent. The volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 30:40:30.

The obtained flat cell was connected to a charge / discharge tester. Moreover, the flat cell was installed in the 80 degreeC thermostat, and left still for 2 hours. Then, the negative electrode was manufactured by charging similarly to Example 1. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.095V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 0.49 mAh.

Although the current value at the time of charging was low (1C), compared with Example 1, the potential of the negative electrode was higher and the discharge capacity of the negative electrode was halved. It is considered that the lithium ions were consumed by causing some irreversible reaction by heating the pre-dope solution to 80 ° C.

(Comparative Example 2)
Except for changing the current value during charging from 1 C to 50 C, an attempt was made to manufacture the negative electrode in the same manner as in Comparative Example 1, but during the charging, the negative electrode potential dropped below the measurement limit and lithium could be occluded. lost. When the cell was disassembled and the surface of the negative electrode was observed, white lithium metal deposition was observed on the negative electrode.

This is considered to be a phenomenon caused by the occurrence of lithium that cannot be intercalated between the graphite layers when the occlusion speed is increased by high-speed charging because the diffusion resistance of lithium ions inside the graphite particles is high.

(Comparative Example 3)
A negative electrode was produced in the same manner as in Comparative Example 1 except that the temperature of the thermostatic chamber was changed from 80 ° C to 25 ° C. The potential of the obtained negative electrode with respect to the lithium reference electrode was 0.084V. Moreover, the discharge capacity of the negative electrode when discharged using lithium metal as a counter electrode was 1.10 mAh.

(Comparative Example 4)
Except for changing the current value during charging from 1 C to 50 C, an attempt was made to manufacture the negative electrode in the same manner as in Comparative Example 3, but during the charging, the negative electrode potential dropped below the measurement limit and lithium could be occluded. lost. When the cell was disassembled and the surface of the negative electrode was observed, white lithium metal deposition was observed on the negative electrode. If the current value at the time of charging was low (1C), lithium could be occluded, but lithium could not be occluded at high rate (50C).

Claims (9)

1. A method of manufacturing an electrode constituting a capacitor or battery,
   Before assembling the capacitor or battery, including the step of occluding the alkali metal in the active material in a solution in which the alkali metal salt is dissolved in an organic solvent,
   A method for producing an electrode, wherein the organic solvent contains at least one specific organic solvent selected from the group consisting of a compound having three or more ether bonds, a β-diketone, and a β-ketoester.
2. The method for producing an electrode according to claim 1, wherein the boiling point of the specific organic solvent is 100 to 300 ° C.
3. The method for producing an electrode according to claim 1 or 2, wherein a mass ratio of the specific organic solvent to the total amount of the organic solvent is 50 mass% or more.
4. 4. The method for producing an electrode according to claim 1, wherein the specific organic solvent contains a compound having 4 or 5 ether bonds.
5. The method for producing an electrode according to any one of claims 1 to 3, wherein the specific organic solvent contains a polyalkylene glycol dialkyl ether.
6. The method for producing an electrode according to any one of claims 1 to 5, wherein the alkali metal salt is a lithium salt or a sodium salt.
7. The method for producing an electrode according to any one of claims 1 to 6, wherein the solution is heated in the step of occluding an alkali metal in the active material.
8. The method for producing an electrode according to any one of claims 1 to 7, wherein the electrode is a capacitor or a negative electrode of a battery.
9. A method for producing an electricity storage device comprising a negative electrode, a positive electrode, and an electrolyte,
   A method for manufacturing an electricity storage device, wherein the negative electrode is manufactured by the manufacturing method according to any one of claims 1 to 7.
   

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