Slurry for forming insulating layer, separator for electrochemical device, method for producing the same, and electrochemical device

1. A method for producing an electrochemical device comprising a positive electrode, a negative electrode, and a separator for the electrochemical device,

the method comprising:

applying a slurry for forming an insulating layer to a resin porous base material; and

drying the base material to which the slurry for forming the insulating layer is applied,

wherein the slurry for forming the insulating layer comprises heat-resistant insulating fine particles, a binder, a thickening agent, a dispersion medium, and a dispersing agent,

the resin porous base material is a uniaxially- or biaxially-oriented microporous film,

the microporous film includes a thermoplastic resin with a melting point of 80° C. to 150° C.,

the insulating fine particles are dispersed in the dispersion medium,

the dispersion medium includes water in an amount of 70 mass % or more of the components of the dispersion medium,

a content of the binder in the slurry for forming the insulating layer is 1 to 20 per 100 of the insulating fine particles when expressed as a volume ratio,

a content of the dispersing agent in the slurry for forming the insulating layer is 0.1 to 5 parts by mass per 100 parts by mass of the insulating fine particles,

the slurry for forming the insulating layer has a viscosity of 5 to 500 mPa·s,

a proportion of particles with a particle size of 1 μm or less in the insulating fine particles is 30 vol % or more and a proportion of particles with a particle size of 3 μm or more in the insulating fine particles is 10 vol % or less, and

the insulating layer is formed on both sides or a positive electrode side of the microporous film.

2. The method for producing an electrochemical device according to claim 1 , wherein a proportion of particles with a particle size of 2 μm or more in the insulating fine particles is 10 vol % or less.

3. The method for producing an electrochemical device according to claim 1 , wherein the insulating fine particles are fine particles of at least one selected from the group consisting of alumina, silica, TiO 2 , BaTiO 3 , ZrO 2 , kaoline, zeolite, apatite, and boehmite.

4. The method for producing an electrochemical device according to claim 1 , wherein the insulating fine particles include plate-like particles.

5. The method for producing an electrochemical device according to claim 1 , wherein the insulating fine particles include secondary particles formed by agglomeration of primary particles.

6. The method for producing an electrochemical device according to claim 1 , wherein the slurry for forming the insulating layer comprises as the thickening agent at least one selected from the group consisting of polyethylene glycol, a polyacrylic acid, polyvinyl alcohol, a cellulose derivative, and a natural polysaccharide.

7. The method for producing an electrochemical device according to claim 1 , wherein a content of the thickening agent in the slurry for forming the insulating layer is 0.1 vol % or more of a total volume of solids in the slurry.

8. The method for producing an electrochemical device according to claim 1 , wherein the dispersing agent includes a plurality of ion-dissociable acid groups or salt groups.

9. The method for producing an electrochemical device according to claim 8 , wherein the dispersing agent is at least one selected from the group consisting of polycarboxylate, polyacrylate, and polymethacrylate.

10. The method for producing an electrochemical device according to claim 1 , wherein the slurry for forming the insulating layer comprises as the binder at least one selected from the group consisting of an ethylene-vinyl acetate copolymer having 20 to 35 mol % of a structural unit derived from vinyl acetate, a (meta) acrylic acid copolymer, fluoro-rubber, styrene-butadiene rubber, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, poly-N-vinylacetamide, polyurethane, and an epoxy resin.

11. The method for producing an electrochemical device according to claim 1 , wherein the slurry for forming the insulating layer further comprises an antifoaming agent.