Electrochemical device comprising separator with laminated porous layers
An electrochemical device of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. The separator includes a first porous layer composed mainly of a thermoplastic resin and a second porous layer composed mainly of insulating particles with a heat-resistant temperature of 150° C. or higher. The first porous layer is disposed to face the negative electrode.
1. An electrochemical device comprising:
a positive electrode;
a negative electrode;
a non-aqueous electrolyte; and
a separator between the positive electrode and the negative electrode,
wherein the separator comprises a first porous layer that includes 50 vol % or more of a thermoplastic resin and a second porous layer that includes insulating particles with a heat-resistant temperature of 150° C. or higher and an organic binder for binding the insulating particles,
the first porous layer is composed of a microporous film that includes a resin with a melting point of 100 to 140° C.,
a content of the insulating particles in the second porous layer is 90 vol % or more,
the second porous layer is not formed on surfaces of the positive electrode and the negative electrode, and is formed on a surface of the microporous film and integrated with the microporous film,
the second porous layer and the microporous film are larger in width than the positive electrode and the negative electrode,
the second porous layer is disposed to face the positive electrode, and
the microporous film is disposed to face the negative electrode.
2. The electrochemical device according to claim 1 , wherein the resin with a melting point of 100 to 140° C. has a melt viscosity of 1000 mPa·s or more at 140° C.
3. The electrochemical device according to claim 1 , wherein the resin with a melting point of 100 to 140° C. has a melt viscosity of 1000000 mPa·s or less at 140° C.
4. The electrochemical device according to claim 1 , wherein a part or the whole of the insulating particles included in the second porous layer is made of inorganic particles.
5. The electrochemical device according to claim 1 , wherein the second porous layer includes secondary particles formed by agglomeration of primary particles.
6. The electrochemical device according to claim 1 , wherein the first porous layer includes a thermoplastic resin with a melting point of higher than 140° C.
7. The electrochemical device according to claim 1 , wherein the insulating particles include particles of at least one inorganic oxide selected from the group consisting of alumina, silica, titanium oxide, barium titanate, zirconium oxide, and boehmite.
8. The electrochemical device according to claim 1 , wherein the insulating particles have a number average particle size of 0.01 to 5 μm.
9. The electrochemical device according to claim 1 , wherein the thermoplastic resin includes at least one resin selected from the group consisting of polyethylene, polypropylene, and copolymerized polyolefin.
10. The electrochemical device according to claim 1 , wherein the first porous layer is a polyolefin microporous film.
11. The electrochemical device according to claim 1 , wherein at least one of the first porous layer and the second porous layer includes a porous matrix that is formed of a woven fabric or a nonwoven fabric and has a heat-resistant temperature of 150° C. or higher.
12. The electrochemical device according to claim 1 , wherein the first porous layer is a microporous film obtained by laminating a polyethylene layer and a layer made of a resin with a higher melting point than that of the polyethylene.
13. The electrochemical device according to claim 1 , wherein the resin with a melting point of 100 to 140° C. is 30 mass % or more of the thermoplastic resin.
14. The electrochemical device according to claim 1 , wherein a ratio X/Y of a thickness X of the first porous layer to a thickness Y of the second porous layer is 10 or less.
15. The electrochemical device according to claim 1 , wherein the microporous film has a surface that faces the negative electrode and the surface is integrated with the negative electrode.
16. The electrochemical device according to claim 1 , wherein the negative electrode comprises a negative electrode active material containing layer, and the first porous layer is in contact with the negative electrode active material containing layer.
17. The electrochemical device according to claim 1 , wherein the separator has a thermal shrinkage ratio of 5% or less at 150° C.
18. The electrochemical device according to claim 1 , wherein the separator has a Gurley value of 10 to 300 sec.
19. The electrochemical device according to claim 1 , wherein the first porous layer has a thickness of 16 μm or less.
20. The electrochemical device according to claim 1 , wherein the second porous layer has a thickness of 6 μm or less.
21. The electrochemical device according to claim 1 , wherein the organic binder is at least one selected from the group consisting of an ethylene-acrylic acid copolymer, fluoro-rubber, styrene-butadiene rubber, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, a cross-linked acrylic resin, polyurethane, and an epoxy resin.
22. The electrochemical device according to claim 1 , wherein the positive electrode comprises a positive electrode active material containing layer, and the second porous layer is in contact with the positive electrode active material containing layer.
23. An electrochemical device comprising:
a positive electrode;
a negative electrode;
a non-aqueous electrolyte; and
a separator between the positive electrode and the negative electrode,
wherein the separator comprises a first porous layer that includes 50 vol % or more of a thermoplastic resin and a second porous layer that includes insulating particles with a heat-resistant temperature of 150° C. or higher and an organic binder for binding the insulating particles,
the first porous layer is composed of a microporous film that includes a resin with a melting point of 100 to 140° C.,
a content of the insulating particles in the second porous layer is 90 vol % or more,
the second porous layer is not formed on surfaces of the positive electrode and the negative electrode, and is formed on a surface of the microporous film and integrated with the microporous film,
the second porous layer includes plate-like particles,
the second porous layer is disposed to face the positive electrode, and
the microporous film is disposed to face the negative electrode.
24. An electrochemical device comprising:
a positive electrode;
a negative electrode;
a non-aqueous electrolyte; and
a pair of separators present on both sides of the positive electrode,
wherein each of the separators comprises a first porous layer that includes 50 vol % or more of a thermoplastic resin and a second porous layer that includes insulating particles with a heat-resistant temperature of 150° C. or higher and an organic binder for binding the insulating particles,
each of the separators has a thermal shrinkage ratio of 5% or less at 150° C.,
the first porous layer is composed of a microporous film that includes a resin with a melting point of 100 to 140° C.,
a content of the insulating particles in the second porous layer is 70 vol % or more,
the second porous layer is formed on a surface of the microporous film,
the second porous layer and the microporous film are larger in width than the positive electrode and the negative electrode,
the second porous layer is disposed to face the positive electrode, and
the microporous film is disposed to face the negative electrode.
25. The electrochemical device according to claim 24 , wherein the positive electrode, the negative electrode, and the separator form a spiral electrode body, and
the two separators on both sides of the positive electrode are wound so that the respective second porous layers come into contact with each other at the beginning of the winding.
26. The electrochemical device according to claim 24 , wherein the negative electrode comprises a negative electrode active material containing layer, and each of the first porous layers of the two separators on both sides of the positive electrode is in contact with the negative electrode active material containing layer.
27. The electrochemical device according to claim 24 , wherein each of the microporous films of the two separators on both sides of the positive electrode has a surface that faces the negative electrode and is integrated with the negative electrode.
28. An electrochemical device comprising:
a positive electrode;
a negative electrode;
a non-aqueous electrolyte; and
a pair of separators present on both sides of the positive electrode,
wherein each of the separators comprises a first porous layer that includes 50 vol % or more of a thermoplastic resin and a second porous layer that includes insulating particles with a heat-resistant temperature of 150° C. or higher and an organic binder for binding the insulating particles,
each of the separators has a thermal shrinkage ratio of 5% or less at 150° C.,
the first porous layer is composed of a microporous film that includes a resin with a melting point of 100 to 140° C.,
a content of the insulating particles in the second porous layer is 70 vol % or more,
the second porous layer is formed on a surface of the microporous film,
the insulating particles of the second porous layer include plate-like particles,
the second porous layer is disposed to face the positive electrode, and
the microporous film is disposed to face the negative electrode.