WO2017073766A1

WO2017073766A1 - Polyimide solution for electricity storage element electrodes, method for producing electricity storage element electrode, and electricity storage element electrode

Info

Publication number: WO2017073766A1
Application number: PCT/JP2016/082163
Authority: WO
Inventors: 健太柴田; 耕竹内; 文子吉野; 睦松下; 山田　宗紀; 朗繁田; 良彰越後
Original assignee: ユニチカ株式会社
Priority date: 2015-10-30
Filing date: 2016-10-28
Publication date: 2017-05-04
Also published as: JPWO2017073766A1; CN108352500A; KR20180075520A

Abstract

The purpose of the present invention is to provide a PI solution which is capable of forming a PI coating film that has a fine phase separation structure, while having a sufficiently decreased ionic resistivity. The present invention relates to a polyimide solution for electricity storage element electrodes, which contains a good solvent and a poor solvent for a polyimide, and which is characterized in that the polyimide contains an oxyalkylene unit and/or a siloxane unit in the main chain.

Description

Storage device electrode polyimide solution, storage device electrode manufacturing method, and storage device electrode

The present invention relates to an electrode used for a power storage element such as a lithium secondary battery, a lithium ion capacitor, a capacitor, or a capacitor.

In the case of thermal runaway due to overcharging or the like in an electrode used for a storage element such as a lithium secondary battery, the electrical insulation of the separator in contact with the electrode due to scratches and / or irregularities on the electrode surface May be destroyed and an electrical internal short circuit may occur.

In order to prevent such an internal short circuit, the surface of the electrode active material layer is made porous by applying a solution of polyimide having heat resistance and a polyimide such as polyamideimide (hereinafter sometimes abbreviated as “PI”). A method for providing a porous PI insulating coating (hereinafter sometimes abbreviated as “porous PI coating”) has been proposed. In such a method, an electrode provided with a PI insulating coating is used as a storage element electrode by filling the pores with an electrolytic solution to develop ionic conductivity. For example, in Patent Document 1, a PI solution is used to form a coating film for forming a film on the surface of the active material layer, and before drying, the film is immersed in a coagulation bath containing a poor solvent for phase separation of the coating film. It has been proposed to cause it to form a porous coating. Patent Document 2 proposes a method of forming a porous film using a coating liquid in which fine particles such as iron oxide, silica, and alumina are used as fillers in a PI solution. However, since the laminated electrode obtained using these coating liquids has low adhesiveness between the active material layer and the porous coating, the effect of preventing short circuit is not always sufficient, and the viewpoint of ensuring the safety of the battery There was a point that should be improved. Further, such an electrode does not have sufficient stress relaxation associated with a change in the volume of the active material, and therefore the improvement of the cycle characteristics of the electrode is not always sufficient. In addition, in a laminated electrode obtained by a method of causing phase separation using a coagulation bath containing a poor solvent such as water and / or alcohol, since the entire active material layer is in contact with the coagulation bath, the poor solvent is inherent to the active material layer. There was a case in which the characteristics of were impaired. Furthermore, since a waste liquid containing a poor solvent is generated from the coagulation bath, this method has a problem as a manufacturing method from the viewpoint of environmental compatibility.

As a method for solving these problems, Patent Document 3 discloses that a specific solution containing PI is used, applied to the surface of the electrode active material layer to form a coating film, and then dried. In addition, a method for obtaining a porous PI coating by causing phase separation in the coating has been proposed.

Since the porous PI coating described in Patent Document 3 does not have sufficient affinity with the electrolyte, the ionic resistivity of the PI coating when the electrolyte is filled in the pores may not be sufficiently low. It was. In addition, since the average pore diameter of the porous coating is slightly larger than 2000 nm, when a lithium foil or a lithium aluminum alloy foil is used as the negative electrode active material layer, dendrite is generated due to insertion and desorption of lithium ions. It was difficult to stop enough. Furthermore, it was difficult to use this coating as a polymer electrolyte.

Japanese Patent Laid-Open No. 11-185731 JP 2011-233349 A International Publication No. 2014/106954

Therefore, the present invention solves the above-described problem, and has a fine phase separation structure and a PI solution capable of forming a PI film having a sufficiently reduced ionic resistivity, and an electricity storage provided with the film An object of the present invention is to provide a device electrode and a manufacturing method thereof.

The present inventors solved the problem by using a PI solution having a specific chemical structure and PI solution of PI and forming a PI film having a phase separation structure obtained therefrom on the electrode active material layer. As a result, the present invention has been completed.

The present invention has the following purpose.

<1> A PI solution containing a good solvent and a poor solvent for PI, wherein the PI contains an oxyalkylene unit and / or a siloxane unit in the main chain. .
<2> The PI solution for a storage element electrode according to <1>, wherein the PI solution further contains a lithium salt.
<3> A method for producing a storage element electrode comprising a step of forming a PI film having a phase separation structure by applying the PI solution according to <1> or <2> to the surface of the active material layer and then drying.
<4> After the PI solution according to <1> or <2> is applied to a substrate and then dried to form a PI coating having a phase separation structure, the PI coating is thermocompression bonded to the active material surface. Then, after that, a method for producing a storage element electrode including a step of peeling the substrate.
<5> The method for producing a storage element electrode according to <3> or <4>, wherein the PI coating having a phase separation structure is a porous PI coating.
<6> The PI film having a phase separation structure has at least two phases, one phase is PI, and at least one of the other phases is a phase containing an electrolyte, according to <3> or <4> A method for producing a storage element electrode.
<7> An electrode in which a PI film having a phase separation structure is laminated and integrated on the surface of an active material layer, wherein the PI contains an oxyalkylene unit and / or a siloxane unit in the main chain. A storage element electrode.

The PI coating having a phase separation structure obtained by applying and drying the PI solution of the present invention on the surface of the electricity storage element active material layer can sufficiently reduce the ionic resistivity of the coating and is excellent in safety. It can be suitably used as a storage element electrode. The PI solution of the present invention can also be used as a solution for forming a polymer electrolyte by previously containing a lithium salt. In addition, an electrode having a PI film formed using the PI solution of the present invention is excellent in charge / discharge characteristics.

10 is a cross-sectional SEM image of an electrode “A-1” obtained in Example 9. 10 is a cross-sectional SEM image of a porous PI coating portion of an electrode “A-1” obtained in Example 9. FIG.

Hereinafter, the present invention will be described in detail.

In the present invention, a PI solution is used. Here, PI is a heat-resistant polymer having an imide bond in the main chain or a precursor thereof, and is usually a polycondensation of a diamine component, which is a monomer component, with a tetracarboxylic acid component and / or a tricarboxylic acid component. Is obtained. These PIs include, in addition to normal PI (soluble polyimide, thermoplastic polyimide, non-thermoplastic polyimide, etc.), polyamide imide (hereinafter sometimes abbreviated as “PAI”), polyester imide, And PI precursors, and the like, and PI precursors and PAI are preferably used. These PIs are copolymer PIs containing oxyalkylene units and / or siloxane units in the main chain and using monomers containing oxyalkylene units and / or siloxane units as copolymerization components.

The PI precursor is one that generates an imide bond by heating at a temperature of 100 ° C. or higher. In the present invention, polyamic acid (hereinafter sometimes abbreviated as “PAA”) is preferably used. PAA is obtained by reacting tetracarboxylic dianhydride and diamine in a solvent. PAA may be partially imidized.

PIs such as PI precursors (for example PAA) and PAI contain oxyalkylene units and / or siloxane units in the main chain. For a PAA solution containing an oxyalkylene unit in the main chain, for example, a PI solution as disclosed in Japanese Patent No. 5944613 can be used. The patent gazette has the following <1> and <2>, and a PI solution containing an oxyalkylene unit described in detail here can also be used in the present invention. That is, in the present invention, the entire text of the patent publication is referred to and incorporated.
<1> A porous PI film comprising PI containing an oxyalkylene unit, having a porosity of 45% to 95% by volume, and an average pore size of 10 nm to 1000 nm.
<2> A solution comprising PI containing an oxyalkylene unit and a mixed solvent containing the good solvent and the poor solvent, wherein the poor solvent ratio in the mixed solvent is 65% by mass or more and 95% by mass or less. A method for producing a porous PI film, characterized by drying at a temperature of less than 350 ° C. after coating on the top.

The PAA containing an oxyalkylene unit and / or a siloxane unit contains an oxyalkylene unit and / or a siloxane unit as a tetracarboxylic dianhydride in the reaction of tetracarboxylic dianhydride and diamine in an approximately equimolar amount. Copolymerization using tetracarboxylic dianhydride and tetracarboxylic dianhydride containing neither oxyalkylene unit nor siloxane unit, or diamine and oxyalkylene unit containing oxyalkylene unit and / or siloxane unit as diamine It is a PAA obtained by copolymerization using a diamine that does not contain any siloxane unit or by copolymerization using both the above-described tetracarboxylic dianhydride and the above-described diamine. Here, a tetracarboxylic dianhydride or diamine containing an oxyalkylene unit and / or a siloxane unit is “monomer A”, and a tetracarboxylic dianhydride or diamine containing neither an oxyalkylene unit nor a siloxane unit is “monomer B”. And may be abbreviated respectively. A tetracarboxylic dianhydride containing neither an oxyalkylene unit nor a siloxane unit may be abbreviated as “TA”, and a diamine containing neither an oxyalkylene unit nor a siloxane unit may be abbreviated as “DA”.

Although the present invention does not prevent monomer A from containing both oxyalkylene units and siloxane units in one molecule, monomer A usually contains one of oxyalkylene units or siloxane units in one molecule. . Among the monomers A, as the monomer A containing an oxyalkylene unit (hereinafter sometimes abbreviated as “monomer A-1”), for example, a tetracarboxylic dianhydride containing an oxyalkylene unit (hereinafter referred to as “TA”). -1 ”) and diamines containing oxyalkylene units (hereinafter sometimes abbreviated as“ DA-1 ”). Among the monomers A, as the monomer A containing a siloxane unit (hereinafter sometimes abbreviated as “monomer A-2”), for example, a tetracarboxylic dianhydride containing a siloxane unit (hereinafter referred to as “TA-2”). And a diamine containing a siloxane unit (hereinafter sometimes abbreviated as “DA-2”). As monomer A, one or both of monomer A-1 and monomer A-2 may be used, and usually one of them is used.

In other words, the PAA containing an oxyalkylene unit and / or a siloxane unit is a monomer component comprising one or more monomers selected from the group consisting of TA-1, DA-1, TA-2 and DA-2. You may contain as. A PAA containing a preferred oxyalkylene unit and / or siloxane unit contains one or more monomers selected from the group consisting of DA-1 and DA-2 as the monomer component.

The PAA containing an oxyalkylene unit is, for example, a copolymerized PAA obtained by copolymerizing TA-1 and / or DA-1 with TA and / or DA (hereinafter abbreviated as “PAA-1”). There are things).

PAA containing a siloxane unit is, for example, a copolymerized PAA obtained by copolymerizing TA-2 and / or DA-2 with TA and / or DA (hereinafter abbreviated as “PAA-2”). Is).

PAA-1 and PAA-2 can be used in combination.

The PAA solution contains a mixed solvent obtained by mixing a good solvent that dissolves the solute PAA and a solute that is a poor solvent. Here, the good solvent refers to a solvent having a solubility in PAA of 1% by mass or more at 25 ° C., and the poor solvent refers to a solvent having a solubility in PAA of less than 1% by mass at 25 ° C. The poor solvent preferably has a higher boiling point than the good solvent. Moreover, the boiling point difference is preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and further preferably 50 ° C. or higher.

As the good solvent, an amide solvent or a urea solvent is preferably used. Examples of the amide solvent include N-methyl-2-pyrrolidone (NMP boiling point: 202 ° C.), N, N-dimethylformamide (DMF boiling point: 153 ° C.), N, N-dimethylacetamide (DMAc boiling point: 166 ° C.). Is mentioned. Examples of urea solvents include tetramethylurea (TMU boiling point: 177 ° C) and dimethylethyleneurea (boiling point: 220 ° C). These good solvents may be used alone or in combination of two or more.

As the poor solvent, an ether solvent is preferably used. Examples of ether solvents include diethylene glycol dimethyl ether (boiling point: 162 ° C), triethylene glycol dimethyl ether (boiling point: 216 ° C), tetraethylene glycol dimethyl ether (boiling point: 275 ° C), diethylene glycol (boiling point: 244 ° C), triethylene glycol. (Boiling point: 287 ° C.), tripropylene glycol (boiling point: 273 ° C.), diethylene glycol monomethyl ether (boiling point: 194 ° C.), tripropylene glycol monomethyl ether (boiling point: 242 ° C.), triethylene glycol monomethyl ether (boiling point: 249 ° C.), and the like. These may be used alone or in combination of two or more.

The blending amount of the poor solvent in the mixed solvent is preferably 15 to 95% by mass, and more preferably 60 to 90% by mass with respect to the mass of the mixed solvent. By doing in this way, phase separation occurs efficiently in the drying process after application to the substrate.

As the PAA-1 solution, monomers such as tetracarboxylic dianhydride (a mixture of TA-1 and TA, or only TA) and diamine (a mixture of DA-1 and DA, or DA only) are approximately equimolar. A solution obtained by blending and polymerizing the mixture in the mixed solvent at a temperature of 10 to 70 ° C. can be used.

TA-1 is a tetracarboxylic dianhydride containing an oxyalkylene unit. Specific examples of TA-1 include ethylene glycol bisanhydro trimellitate (TMEG), diethylene glycol bis anhydro trimellitate, triethylene glycol bis anhydro trimellitate, tetraethylene glycol bis anhydro trimellitate, polyethylene Glycol bisanhydro trimellitate, propylene glycol bis anhydro trimellitate, dipropylene glycol bis anhydro trimellitate, tripropylene glycol bis anhydro trimellitate, tetrapropylene glycol bis anhydro trimellitate, polypropylene glycol bis In addition to anhydrotrimellitate, etc., any of the compounds described below, “diamine containing oxyalkylene unit” (DA-1), and trimellitic anhydride And Doo acid is obtained by amide-forming reaction, the tetracarboxylic dianhydride having two amide bonds. These may be used alone or in combination of two or more. Of these, TMEG is preferred. These compounds can use a commercial item and can also manufacture it by a well-known method.

TA is not particularly limited as long as it is a tetracarboxylic dianhydride containing neither an oxyalkylene unit nor a siloxane unit. Specific examples of TA include, for example, pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3 ′, 4′- Biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and 3,3 ′, 4,4′-diphenylsulfonetetra Examples thereof include carboxylic dianhydrides. These may be used alone or in combination of two or more. Of these, one or more compounds selected from the group consisting of PMDA and BPDA are preferred. These compounds can use a commercial item and can also manufacture it by a well-known method.

DA-1 is a diamine containing oxyalkylene units. Specific examples of DA-1 include ethylene glycol bis (2-aminoethyl) ether, diethylene glycol bis (2-aminoethyl) ether, triethylene glycol bis (2-aminoethyl) ether, tetraethylene glycol bis (2-amino). Ethyl) ether, polyethylene glycol bis (2-aminoethyl) ether, propylene glycol bis (2-aminoethyl) ether, dipropylene glycol bis (2-aminoethyl) ether, tripropylene glycol bis (2-aminoethyl) ether, Examples thereof include tetrapropylene glycol bis (2-aminoethyl) ether and polypropylene glycol bis (2-aminoethyl) ether (PPGME). These may be used alone or in combination of two or more. Of these, PPGME is preferred. These compounds can use a commercial item and can also manufacture it by a well-known method. For example, PPGME is available as Jeffamine D2000 (number average molecular weight 2000: manufactured by Huntsman).

DA is not particularly limited as long as it is a diamine containing neither an oxyalkylene unit nor a siloxane unit. Specific examples of DA include, for example, 4,4′-diaminodiphenyl ether (DADE), 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane (BAPP), 4,4′-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, p-phenylenediamine, m-phenylenediamine, 2,4-diamino Toluene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-diaminobiphenyl, 4 , 4'-Diamino-2,2'-bis (trifluoromethyl) biphenyl, 4,4'-bis 4-aminophenoxy) biphenyl, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl Sulfone, 4,4′-diaminodiphenyl sulfide, and the like. These may be used alone or in combination of two or more. Of these, one or more compounds selected from the group consisting of DADE and BAPP are preferred. These compounds can use a commercial item and can also manufacture it by a well-known method.

As the PAA-2 solution, a monomer tetracarboxylic dianhydride (a mixture of TA-2 and TA, or only TA) and a diamine (a mixture of DA-2 and DA, or only DA) are approximately equimolar. A solution obtained by blending and polymerizing the mixture in the mixed solvent at a temperature of 10 to 70 ° C. can be used.

TA-2 is a tetracarboxylic dianhydride containing siloxane units. Specific examples of TA-2 include 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, 1,3-bis (3,4- Dicarboxyphenyl) -1,1,3,3-tetraethylsiloxane dianhydride, bis (3,4-dicarboxyphenyl) dimethylpolysiloxane dianhydride, bis (3,4-dicarboxyphenyl) diethylpolysiloxane An anhydride etc. are mentioned. These may be used alone or in combination of two or more. These compounds can use a commercial item and can also manufacture it by a well-known method.

DA-2 is a diamine containing siloxane units. Specific examples of DA-2 include 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane, 1,3-bis (4-aminobutyl) -1,1, Examples include 3,3-tetramethyldisiloxane, 1,3-bis (4-aminophenoxy) -1,1,3,3-tetramethyldisiloxane, and a compound represented by the following general formula (1). . These may be used alone or in combination of two or more. In DA-2, in the following general formula (1), R ¹ and R ² are trimethylene groups, R ³ , R ⁴ , R ⁵ and R ⁶ are methyl groups, n is 3 to 100, and compounds thereof A mixture (hereinafter sometimes abbreviated as “DASM”) is preferred, and among these, compounds having a number average molecular weight of 300 to 5000 and mixtures thereof are more preferred. DA-2 can be a commercially available product or can be produced by a known method. For example, DASM is available as KF-8010 (number average molecular weight 860: manufactured by Shin-Etsu Chemical Co., Ltd.).

(However, in formula (1), n represents an integer of 1 or more. Further, ^{R 1} and ^{R 2} are the same or different and each represents a lower alkylene group or a phenylene ^{^{^{group, R 3, R 4, R}}} 5 And R ⁶ each represents the same or different lower alkyl group, phenyl group or phenoxy group.

In particular, when one of TA-1 or DA-1 is used as the monomer A-1 containing an oxyalkylene unit in a PAA containing only an oxyalkylene unit among oxyalkylene units or siloxane units, TA-1 or The amount of DA-1 used (copolymerization ratio) is preferably 0.5 to 20 mol%, more preferably 1 to 10 mol%. The mol% indicating the copolymerization ratio refers to a value calculated according to the following formula. When both TA-1 and DA-1 are used, the amount used (copolymerization ratio) is preferably 0.5 to 20 mol%, and preferably 1 to 10 mol%. Is more preferable.

In addition, when one of TA-2 or DA-2 is used as a monomer A-2 containing a siloxane unit in a PAA containing only a siloxane unit among oxyalkylene units or siloxane units, TA-2 or DA- The amount of 2 used (copolymerization ratio) is preferably 0.5 to 20 mol%, more preferably 1 to 10 mol%. The mol% indicating the copolymerization ratio refers to a value calculated according to the following formula. When both TA-2 and DA-2 are used, the amount used (copolymerization ratio) is preferably 0.5 to 20 mol%, and preferably 1 to 10 mol%. Is more preferable.

In PAA containing both oxyalkylene units and siloxane units, the amount of TA-1, TA-2, DA-1 and DA-2 used (copolymerization ratio) is 0.5 to 20 mol%, respectively. It is preferably 1 to 10 mol%, more preferably.

As described above, in the copolymerized PAA, the copolymerization ratio of monomers containing oxyalkylene units or siloxane units is preferably 0.5 to 20 mol% based on the above formula, More preferably, it is 1 to 10 mol%. That is, in PAA containing an oxyalkylene unit and / or a siloxane unit, among the used amounts (copolymerization ratios) of TA-1, DA-1, TA-2 and DA-2 defined by the above formula, It is preferable that at least one use amount (copolymerization ratio) is within the above range.

In the above, examples of PAA have been described, but for PIs other than PAA, such as soluble PI and / or PAI, the same method as PAA can be used. The same applies to the preferred use amount (copolymerization ratio) of monomers containing oxyalkylene units or siloxane units.

For example, as the PAI solution, a PAI solution as disclosed in JP-A-2016-145300 can be used. The gazette has the gist of <1> and <2> below, and a PAI solution containing an oxyalkylene unit described in detail here can also be used in the present invention. That is, in the present invention, the entire text of the publication is referred to and incorporated.
<1> A porous PAI obtained by a dry porosification process, comprising a PAI containing an oxyalkylene unit, having a porosity of 20% by volume to 95% by volume and an average pore size of 10 nm to 1000 nm. A porous PAI film characterized by being.
<2> A method for producing a porous PAI film, wherein a solution containing an oxyalkylene unit and a good solvent and a poor solvent is applied on a substrate and then dried at a temperature of 200 ° C. or lower.

In the present invention, PAI containing a siloxane unit can also be used. This is a copolymerized PAI obtained by copolymerizing the tricarboxylic acid component, the DA-2 and the DA.

The PI solution is obtained by polymerizing in a good solvent to obtain a solution, and then adding a poor solvent thereto, obtaining a suspension by polymerizing in the poor solvent and then adding a good solvent thereto, etc. Can also be obtained.

The concentration of PI in the PI solution is preferably 3 to 45% by mass, more preferably 5 to 40% by mass.

The viscosity of the PI solution at 30 ° C. is preferably in the range of 0.01 to 100 Pa · s, more preferably 0.1 to 50 Pa · s.

In the PI solution, if necessary, known additives such as various surfactants and / or silane coupling agents may be added as long as the effects of the present invention are not impaired. Moreover, you may add other polymers other than PI to the PI solution in the range which does not impair the effect of this invention as needed.

In order to laminate and integrate the electrode active material layer and the porous PI coating, for example, a PI solution is applied to the surface of the electrode active material layer and dried to induce phase separation to form the porous PI coating. What is necessary is just to form. Also, a PI solution is applied onto a substrate (for example, a release film such as a polyester film) and dried to induce phase separation to form a porous PI coating, which is used as an electrode active material layer. After thermocompression bonding, the substrate (release film) can be peeled off to be laminated and integrated. In thermocompression bonding, an adhesive may be applied to the surface of the porous PI coating in the form of dots and then thermocompression bonded to the electrode active material layer. For the point application of the adhesive, for example, methods disclosed in Japanese Patent Application Laid-Open Nos. 2003-151638, 2014/014118, and 2016-42454 can be used.

As a method of applying the PI solution to the electrode active material layer, a method of applying continuously by roll-to-roll or a method of applying in a sheet form can be adopted, and any method may be used. As the coating apparatus, a known method using a die coater, a multilayer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater or the like can be used.

In the case where a PI precursor solution is used as the PI solution, the drying step includes inducing the phase separation by volatilizing the solvent contained in the coating film to form a porous PAA coating and the porous coating. And Step 2 in which the PAA coating is thermally imidized to form a porous PI coating. The temperature in step 1 is preferably about 100 to 200 ° C., and the temperature in step 2 is preferably less than 350 ° C., for example, 200 to 320 ° C. In addition, when PI other than PI precursors, such as soluble polyimide and PAI, is used, the step 2 is not necessary. In Step 2, the copolymerized PAA does not need to be 100% imidized, and a copolymerized PAA component that is not imidized may remain. Here, the imidization ratio can be adjusted by selecting drying conditions, thermal imidization conditions, and the like.

The PI used in the present invention preferably has a Tg of 150 ° C. or higher, more preferably 200 ° C. or higher. By doing in this way, favorable heat resistance is securable. In addition, the value measured by DSC (differential thermal analysis) can be used for Tg.

The average pore diameter of the porous PI coating is 10 nm or more and 2000 nm or less, preferably 20 nm or more and 1300 nm or less, and more preferably 20 nm or more and 1000 nm or less. By making the average pore diameter in this way, the ionic resistivity of the PI coating can be made sufficiently low, and this PI coating can be used as a polymer electrolyte. The average pore diameter was obtained by obtaining a SEM (scanning electron microscope) image of the cross section of the porous PI coating at a magnification of 5000 to 20000, and separating it into a pore portion and a PI portion using commercially available image processing software. This can be confirmed.

The porosity of the porous PI coating is preferably 30 to 90% by volume, more preferably 40 to 80% by volume, and still more preferably 45 to 80% by volume. By setting the porosity in this way, good mechanical properties and good cushioning properties for stress relaxation accompanying the volume change of the active material can be ensured at the same time. For this reason, the electrode which is excellent in safety | security and has a favorable cycling characteristic can be obtained. The porosity of the porous PI coating is a value calculated from the apparent density of the porous PI coating and the true density (specific gravity) of PI constituting the coating. Specifically, the porosity (volume%) is calculated by the following formula when the apparent density of the PI coating is A (g / cm ³ ) and the true density of PI is B (g / cm ³ ).

It is preferable that the porous PI coating is firmly bonded to the active material layer. That is, from the viewpoint of improving battery safety, the adhesive strength between the electrode active material layer and the porous PI coating is preferably higher than the strength of the electrode active material layer. Whether or not the adhesive strength is higher than the strength of the electrode active material layer can be determined by whether cohesive failure or interface peeling occurs at the interface when the electrode active material layer is peeled from the PI coating. . When cohesive failure occurs, it is determined that the strength of the adhesive interface is higher than the strength of the electrode active material layer. A cohesive failure is determined when a piece of the active material layer adheres to a part of the surface of the PI coating after peeling (adhesion surface with the electrode active material layer). In the electrode of the present invention, such high adhesive strength greatly contributes to the improvement of battery safety.

The thickness of the porous PI coating is preferably 0.5 to 100 μm, more preferably 1 to 20 μm.

The porous PI coating may be either insulating or conductive. When the porous PI coating is insulative, this layer is advantageous because it also has a function as a separator that prevents electrical contact between the positive electrode and the negative electrode of a storage element (for example, a lithium secondary battery). When making the porous PI coating conductive, for example, 5 to 50% by mass of conductive particles such as carbon (graphite, carbon black, etc.) particles and / or metal (silver, copper, nickel, etc.) particles are porous. What is necessary is just to mix | blend with quality PI film. From the viewpoint of ensuring cushioning properties and adhesion of the porous PI coating, the amount of these conductive particles is preferably 20% by mass or less.

When the porous PI coating formed on the electrode surface is used as a power storage element electrode, when creating a cell of the power storage element, a known electrolytic solution (in a solvent such as ethylene carbonate and dimethyl carbonate, A solution in which a lithium salt such as LiPF ₆ is dissolved). Thereby, ion conductivity develops and it can be used as a storage element electrode. As described above, the storage element electrode on which the porous PI film is formed may be a film having ionic conductivity at the time of cell preparation. A conductive film (this PI film may be abbreviated as “polymer electrolyte PI film”) may be used. In order to do this, the porous PI film may be impregnated with a solution containing an electrolyte and filled in the pores. Such a technique is publicly known, and for example, a method as described in Electrochimica Acta 45 (2000) 1347-1360 and Electrochimica Acta 204 (2016) 176-182 can be used. The solution containing the electrolyte may contain a “gelling polymer” as described in, for example, JP-A-2006-289985. Further, by using a solution containing an electrolyte such as a lithium salt in a PI solution for forming a porous film (this solution may be abbreviated as “PI-L solution”), A polymer electrolyte PI coating can also be obtained. That is, by applying and drying the PI-L solution on the surface of the electrode active material layer, a PI coating having a phase separation structure and having at least two phases, wherein one phase of the PI coating is PI, A PI coating consisting of a phase (solid or liquid) in which at least one of the other phases contains an electrolyte can be obtained.

Specific examples of the lithium salt in the PI-L solution include LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ . These may be used alone or in combination of two or more. Among these, LiPF ₆ and LiN (CF ₃ SO ₂ ) ₂ are preferable. The lithium salt content is preferably 5 to 200% by mass and more preferably 20 to 150% by mass with respect to the mass of the poor solvent in the PI solution. A polymer electrolyte PI coating is obtained by applying a solution having such a composition to the surface of the electrode active material layer and drying. In this polymer electrolyte PI coating, a part of the solvent (good solvent and poor solvent) in the PI-L solution may remain in the polymer electrolyte PI coating in a form solvated with the lithium salt.

Porous PI film (as electrolytic solution is filled in the pores) and polymer electrolyte PI film, it ionic resistivity becomes ion conductivity indicators, it is preferably 5Omucm ² or less, 4Omucm ² or less Is more preferably 3 Ωcm ² or less. When the ionic resistivity is within the above range, good charge / discharge characteristics of the lithium secondary battery using the electrode of the present invention can be ensured. The ionic resistivity (Rs-PI) of these PI coatings can be calculated using, for example, the following method. That is, assuming that the ionic resistivity of only the active material layer filled with the electrolytic solution formed on the current collector is Rs-1, and the ionic resistivity of the laminate having the PI film formed on the surface thereof is Rs-2. , Rs-PI is calculated by subtracting Rs-1 from Rs-2. Rs-1 and Rs-2 are determined by configuring a measurement cell using a lithium foil and the current collector as an electrode, using a commercially available separator as necessary, and measuring impedance at 25 ° C. and 100 KHz. can do.

The electrode active material layer on which the PI film having a phase separation structure is laminated is a layer formed on the current collector of the storage element (for example, lithium secondary battery) electrode of the present invention, and the positive electrode active material layer and the negative electrode A general term for active material layers.

As the current collector, a metal foil such as a copper foil, a stainless steel foil, a nickel foil, or an aluminum foil can be used. Aluminum foil is preferably used for the positive electrode, and copper foil is used for the negative electrode. The thickness of these metal foils is preferably 5 to 50 μm, more preferably 9 to 18 μm. The surface of these metal foils may be subjected to a surface roughening treatment and / or a rust prevention treatment for improving the adhesion to the active material layer.

The positive electrode active material layer is, for example, a layer obtained by binding positive electrode active material particles with a resin binder. The material used as the positive electrode active material particles is preferably a material capable of occluding and storing lithium ions. For example, an oxide system (LiCoO ₂ , LiNiO ₂ etc.), an iron phosphate system (LiFePO ₄ etc.), a polymer compound system ( Active material particles such as polyaniline and polythiophene). Among these, LiCoO ₂ , LiNiO ₂ , and LiFePO ₄ are preferable. In order to reduce the internal resistance of the positive electrode active material layer, conductive particles such as carbon (graphite, carbon black, etc.) particles and / or metal (silver, copper, nickel, etc.) particles are contained in an amount of about 1 to 30% by mass. It may be blended.

The negative electrode active material layer is, for example, a layer obtained by binding negative electrode active material particles with a resin binder. The material used as the negative electrode active material particles is preferably a material capable of occluding and storing lithium ions. Examples thereof include graphite, amorphous carbon, silicon-based, and tin-based active material particles. Among these, graphite particles and silicon-based particles are preferable. Examples of the silicon-based particles include particles of silicon alone, a silicon alloy, a silicon / silicon dioxide composite, and the like. Among these silicon-based particles, particles of silicon alone are preferable. Silicon alone means crystalline or amorphous silicon having a purity of 95% by mass or more. The negative electrode active material layer contains about 1 to 30% by mass of conductive particles such as carbon (graphite, carbon black, etc.) particles and / or metal (silver, copper, nickel, etc.) particles in order to reduce the internal resistance. It may be blended. Moreover, lithium foil and lithium alloy foil can be used as the negative electrode active material layer.

The particle diameters of the active material particles and the conductive particles are preferably 50 μm or less for both the positive electrode and the negative electrode, and more preferably 10 μm or less. Even if the particle diameter is too small, binding with a resin binder becomes difficult, so it is usually 0.1 μm or more, preferably 0.5 μm or more.

The porosity of the electrode active material layer is preferably 5 to 50% by volume for both the positive electrode and the negative electrode, and more preferably 10 to 40% by volume.

The layer thickness of the electrode active material layer is usually about 20 to 200 μm.

As the above-mentioned resin binder for binding the active material particles, for example, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene Examples thereof include butadiene copolymer rubber (SBR), polytetrafluoroethylene, polypropylene, polyethylene, and PI. Among these, PVDF, SBR, and PI are preferable.

The laminate in which the active material layer is formed on the current collector as described above can use a commercially available product. For example, it can be manufactured by a known method such as the following, but a commercially available product is used. You can also.

That is, a dispersion containing the above-mentioned binder, active material particles, and solvent (hereinafter sometimes abbreviated as “active material dispersion”) is applied to the surface of a metal foil as a current collector and dried to obtain a metal. An electrode active material layer can be formed on the foil.

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

The electrode active material layers (for positive electrode and negative electrode) formed on the current collector used in the following Examples and Comparative Examples were obtained as follows.

(Positive electrode active material layer)
86 parts by mass of LiFePO ₄ particles (average particle size 0.5 μm) as a positive electrode active material, 8 parts by mass of carbon black (acetylene black) as a conductive additive, and 6 parts by mass of PVDF as a binder resin are uniformly in NMP. To obtain a positive electrode active material dispersion. This dispersion was applied to a positive electrode current collector 15 μm thick aluminum foil, and the resulting coating film was dried at 130 ° C. for 10 minutes and then hot pressed to obtain a positive electrode active material layer having a thickness of 50 μm. .

(Negative electrode active material layer-1)
85 parts by mass of graphite particles (average particle size 8 μm) as a negative electrode active material, 5 parts by mass of carbon black (acetylene black) as a conductive auxiliary agent, and 10 parts by mass of PI as a binder resin are uniformly dispersed in NMP. Thus, a negative electrode active material dispersion having a solid content concentration of 25% by mass was obtained. This dispersion was applied to a negative electrode current collector 18 μm thick copper foil, and the resulting coating film was dried at 120 ° C. for 10 minutes, heat-treated at 300 ° C. for 60 minutes, and hot-pressed to have a thickness of 50 μm. The negative electrode active material layer was obtained. As the PI, “Uimide varnish CR” manufactured by Unitika Ltd. was used.

(Negative electrode active material layer-2)
98 parts by mass of graphite particles (average particle size: 8 μm) as a negative electrode active material, 1 part by mass of carboxymethylcellulose, and 1 part by mass of SBR as a binder resin are uniformly dispersed in water, and a negative electrode having a solid content concentration of 25% by mass An active material dispersion was obtained. This dispersion was applied to a 10 μm-thick copper foil as a negative electrode current collector, and the obtained coating film was dried at 120 ° C. for 10 minutes and then hot pressed to obtain a negative electrode active material layer having a thickness of 40 μm. .

(Electrode evaluation method)
The characteristics of the electrodes obtained in the following examples and comparative examples were evaluated by the following methods.
The electrode was punched into a circle having a diameter of 16 mm, and a separator made of a polyethylene porous film and a lithium foil were sequentially laminated on the porous PI coating surface side, and this was stored in a stainless steel coin-type outer container. An electrolytic solution (1M LiPF ₆ solution using a solvent in which ethylene carbonate and dimethyl carbonate are mixed at a volume ratio of 1: 1) as a solvent is injected into the outer container, and the outer container is made of stainless steel via a packing. The cap was covered and fixed, the battery can was sealed, and the cell for evaluation was obtained. Using this cell, the ion resistivity (Rs-PI) was calculated by measuring the impedance at 100 KHz by the method described above. In addition, discharge capacity and cycle characteristics were evaluated using this cell.

<Example 1>
In a glass reaction vessel, under a nitrogen atmosphere, DADE: 0.97 mol, PPGME: 0.03 mol (number average molecular weight 2000: Jeffamine D2000 manufactured by Huntsman), DMAc and tetraethylene glycol dimethyl ether mixed solvent (DMAc / The mixing ratio of tetraethylene glycol dimethyl ether was 2/8) in mass ratio and stirred to dissolve the diamine component. While this solution was cooled to 30 ° C. or lower with a jacket, PMDA: 1.01 mol was gradually added, followed by polymerization at 40 ° C. for 5 hours to obtain a copolymerized PAA solution (P-1: The solid content concentration was 15% by mass).

<Example 2>
A copolymer PAA solution (P-2) was obtained in the same manner as in Example 1 except that “DADE: 0.97 mol” was changed to “DADE: 0.8 mol and BAPP: 0.17 mol”. .

<Example 3>
A copolymer PAA solution (P-3) was obtained in the same manner as in Example 1 except that “PMDA: 1.01 mol” was changed to “PMDA: 0.81 mol and BPDA: 0.20 mol”. .

<Example 4>
A copolymer PAA solution (P-4) was obtained in the same manner as in Example 1 except that “PMDA: 1.01 mol” was changed to “BPDA: 1.01 mol”.

<Example 5>
A copolymer PAA solution (in the same manner as in Example 1 except that “DADE: 0.97 mol, PPGME: 0.03 mol” was changed to “DADE: 0.94 mol, PPGME: 0.06 mol”. P-5) was obtained.

<Example 6>
Copolymerization was carried out in the same manner as in Example 1 except that the mixing ratio of the mixed solvent (DMAc / tetraethylene glycol dimethyl ether) was 1/9 by mass and the solid content concentration of the copolymerized PAA solution was 10% by mass. A PAA solution (P-6) was obtained.

<Example 7>
Copolymerization was carried out in the same manner as in Example 2, except that the mixing ratio of the mixed solvent (DMAc / tetraethylene glycol dimethyl ether) was 1/9 by mass and the solid content concentration of the copolymerized PAA solution was 10% by mass. A PAA solution (P-7) was obtained.

<Example 8>
In a glass reaction vessel, under a nitrogen atmosphere, DADE: 0.97 mol, DASM: 0.03 mol (number average molecular weight: about 860: KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd.), a mixed solvent consisting of DMAc and tetraethylene glycol dimethyl ether ( The mixing ratio of DMAc / tetraethylene glycol dimethyl ether was 3/7) by mass and stirred. To this solution, PMDA: 1.03 mol was gradually added at room temperature, and then a polymerization reaction was carried out at 60 ° C. for 5 hours to give a copolymer PAA solution into which a siloxane unit was introduced (P-8: solid content concentration was 16% by mass) )

<Example 9>
P-1 obtained in Example 1 was applied to the surface of the negative electrode active material layer-1, dried at 130 ° C. for 10 minutes, and heat-treated at 250 ° C. for 60 minutes in a nitrogen atmosphere to obtain a porous film having a thickness of 15 μm. An electrode (negative electrode) “A-1” having a porous PI film formed on the surface of the negative electrode active material layer-1 was obtained. This porous PI film was firmly bonded to the surface of the negative electrode active material layer. The SEM image of the negative electrode “A-1” cross section and the SEM image of the cross section of the PI coating part are shown in FIGS. When the pore portion and the PI portion were separated and analyzed by image processing software, the average pore diameter of the porous PI coating was 450 nm. The porosity was 65% by volume.

When a cell was prepared by the above-described method using the negative electrode “A-1” and the ionic resistivity was measured, the Rs-PI of this porous PI coating was 2.8 Ωcm ² . Using this cell, a charge / discharge cycle was performed in which the battery was charged to 2.5 V at 30 ° C. with a constant current of 0.1 C and discharged to 0.03 V. As a result, the negative electrode “A-1” had an initial discharge capacity of 310 [mAh / g-active material], a discharge capacity after 10 cycles of 232 [mAh / g-active material], a high initial discharge capacity and a good cycle. The characteristics were confirmed. The voltage represents a voltage with respect to the ionization potential of lithium.

<Example 10>
P-2 obtained in Example 2 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-2” in which a porous PI coating having a thickness of 10 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of the negative electrode “A-2” was 360 nm, and Rs-PI was 2.6 Ωcm ² .

<Example 11>
P-3 obtained in Example 3 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-3” in which a porous PI coating having a thickness of 8 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of the negative electrode “A-3” was 560 nm, and Rs-PI was 2.9 Ωcm ² .

<Example 12>
P-4 obtained in Example 4 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-4” in which a porous PI coating having a thickness of 8 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of negative electrode “A-4” was 880 nm, and Rs-PI was 2.5 Ωcm ² .

<Example 13>
P-5 obtained in Example 5 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-5” in which a porous PI coating having a thickness of 10 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of the negative electrode “A-5” was 670 nm, and Rs-PI was 2.9 Ωcm ² .

<Example 14>
P-6 obtained in Example 6 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-6” in which a porous PI coating having a thickness of 4 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of the negative electrode “A-6” was 270 nm, and Rs-PI was 2.1 Ωcm ² .

<Example 15>
P-7 obtained in Example 7 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “A-7” in which a porous PI coating having a thickness of 4 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the porous PI coating of the negative electrode “A-7” was 310 nm, and Rs-PI was 2.4 Ωcm ² .

<Example 16>
P-1 obtained in Example 1 was applied to the surface of an aluminum foil with a release layer, dried at 130 ° C. for 10 minutes, heat-treated at 250 ° C. for 60 minutes in a nitrogen atmosphere, and porous having a thickness of 7 μm. A laminate having a PI coating formed on the surface of an aluminum foil was obtained. The porous PI coating and the negative electrode active material layer-2 were thermocompression bonded at 200 ° C., and then the aluminum foil was peeled off to adhere the porous PI coating to the surface of the negative electrode active material layer-2. Electrode (negative electrode) “A-8” was obtained. The average pore diameter of the porous PI coating of the negative electrode “A-8” was 370 nm, and Rs-PI was 2.7 Ωcm ² .

<Example 17>
P-1 obtained in Example 1 was applied to the surface of the positive electrode active material layer, dried at 130 ° C. for 10 minutes, and heat-treated at 200 ° C. for 60 minutes in a nitrogen atmosphere to obtain a porous PI having a thickness of 12 μm. An electrode (positive electrode) “A-9” having a coating formed on the surface of the positive electrode active material layer was obtained. The average pore diameter of the PI coating of the positive electrode “A-9” was 920 nm.

A cell was prepared by the above-described method using the positive electrode “A-9”, and the ionic resistivity was measured. As a result, the Rs-PI of this PI film was 3.0 Ωcm ² . Using this cell, a charge / discharge cycle was performed at 30 ° C. with a constant current of 0.1 C to 4.5 V, and with a constant current of 0.1 C, discharging to 3.0 V. As a result, the initial discharge capacity of the positive electrode “A-9” was 146 [mAh / g-active material], the discharge capacity after 10 cycles was 159 [mAh / g-active material], and the high initial discharge capacity and good cycle were obtained. The characteristics were confirmed. The voltage represents a voltage with respect to the ionization potential of lithium.

<Example 18>
P-1 obtained in Example 1 was applied to the surface of the positive electrode active material layer and dried at 150 ° C. for 10 minutes to form a porous PI coating having a thickness of 4 μm on the surface of the positive electrode active material layer. Electrode (positive electrode) “A-10” was obtained. The average pore diameter of the PI coating of the positive electrode “A-10” was 540 nm, and Rs-PI was 1.8 Ωcm ² .

<Example 19>
P-8 obtained in Example 8 was applied to the surface of the negative electrode active material layer-1, dried at 150 ° C. for 10 minutes, and heat-treated at 250 ° C. for 60 minutes in a nitrogen atmosphere, and having a thickness of 3 μm. An electrode (negative electrode) “A-11” having a PI film formed on the surface of the negative electrode active material layer was obtained. The average pore diameter of the PI coating of the negative electrode “A-11” was 1200 nm, and Rs-PI was 2.5 Ωcm ² .

<Example 20>
A PAI solution was obtained according to the method described in JP-A-2016-145300 and Example 1. That is, in a glass reaction vessel, trimellitic anhydride (TMA): 0.96 mol, 4,4′-diphenylmethane diisocyanate (MDI): 1 mol, polytetramethylene glycol (molecular weight 1000): 0 in a nitrogen atmosphere. 0.04 mol of NMP was added and stirred. The obtained solution was heated to 200 ° C., reacted for 7 hours, and then cooled to obtain a PAI solution into which oxytetramethylene units were introduced. Tetraethylene glycol dimethyl ether was added to this, and oxyalkylene was added. A copolymerized PAI solution (P-9: 11% by mass) into which units were introduced was obtained. The mass ratio of tetraethylene glycol dimethyl ether in this solution was 70% by mass with respect to the mixed solvent (NMP and tetraethylene glycol dimethyl ether).

<Example 21>
P-9 obtained in Example 20 was applied to the surface of the negative electrode active material layer-1, dried at 150 ° C. for 10 minutes, and heat-treated at 250 ° C. for 60 minutes in a nitrogen atmosphere, and having a thickness of 3 μm. An electrode (negative electrode) “A-12” having a PI film formed on the surface of the negative electrode active material layer was obtained. The average pore diameter of the PI coating of the negative electrode “A-12” was 1800 nm, and Rs-PI was 2.8 Ωcm ² .

<Comparative Example 1>
A PAA solution (R-1) was obtained in the same manner as in Example 1 except that “DADE: 0.97 mol, PPGME: 0.03 mol” was changed to “DADE: 1.00 mol”.

<Comparative Example 2>
R-1 obtained in Comparative Example 1 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “B-1” in which a porous PI coating having a thickness of 15 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the PI coating of the negative electrode “B-1” was 3200 nm, and Rs-PI exceeded 10 Ωcm ² .

<Comparative Example 3>
R-1 obtained in Comparative Example 1 was used in the same manner as in Example 9 to obtain an electrode (negative electrode) “B-2” in which a porous PI coating having a thickness of 4 μm was formed on the surface of the negative electrode active material layer. It was. The average pore diameter of the PI coating of the negative electrode “B-2” was 3100 nm, and Rs-PI exceeded 10 Ωcm ² .

As described above in Examples and Comparative Examples, the storage element electrode of the present invention, such as a lithium secondary battery, has an average pore diameter and an oxyalkylene unit or siloxane unit having a high affinity for the electrolyte. The ionic resistivity of the formed porous PI coating is low. Therefore, it can be suitably used as a storage element electrode of a lithium secondary battery, a lithium ion capacitor or the like having excellent safety and high discharge capacity and good cycle characteristics.

The PI solution of the present invention is useful for the production of electrodes used for power storage elements such as lithium secondary batteries, lithium ion capacitors, capacitors, and capacitors.

Claims

A polyimide solution containing a good solvent and a poor solvent for a polyimide, wherein the polyimide contains an oxyalkylene unit and / or a siloxane unit in the main chain.
The polyimide solution for a storage element electrode according to claim 1, wherein the polyimide solution further contains a lithium salt.
A method for producing a storage element electrode comprising a step of forming a polyimide film having a phase separation structure by applying the polyimide solution according to claim 1 or 2 to the surface of the active material layer and then drying.
After the polyimide solution according to claim 1 or 2 is applied to a substrate and then dried to form a polyimide coating having a phase separation structure, the polyimide coating is thermocompression bonded to the active material surface, A method for producing an electricity storage element electrode, comprising a step of peeling a material.
The method for producing a storage element electrode according to claim 3 or 4, wherein the polyimide coating having a phase separation structure is a porous polyimide coating.
The production of a storage element electrode according to claim 3 or 4, wherein the polyimide coating having a phase separation structure has at least two phases, one phase is polyimide, and at least one of the other phases is an electrolyte-containing phase. Method.
An electrode in which a polyimide film having a phase separation structure is laminated and integrated on the surface of an active material layer, wherein the polyimide contains an oxyalkylene unit and / or a siloxane unit in its main chain. Storage element electrode.