Porous membrane for secondary battery, slurry for secondary battery porous membrane and secondary battery
The porous membrane according to the present invention comprises non-conductive particles, a binder, and a water-soluble polymer, and is characterized in that: the three dimensions of the non-conductive particles, namely the length (L), thickness (t), and width (b), are such that the length (L) is 0.1 to 0 μm, the ratio (b/t) of the width (b) and the thickness (t) is 1.5 to 100; the binder is a copolymer containing (meth)acrylonitrile monomer units and (meth)acrylic acid ester monomer units; and the water-soluble polymer contains sulfonic acid groups, and has a weight average molecular weight of 1000 to 15000. The slurry for a porous membrane according to the present invention is characterized by being formed by dispersing the non-conductive particles, the binder, and the soluble polymer, in water. Thus, the present invention provides: a porous membrane that can be formed into a thin film, has an excellent sliding property, and generates few particles; and a slurry for porous membranes which is capable of producing porous membrane easily and quickly, and has excellent storage stability.
1. A porous membrane for a secondary battery including a non-conductive particle, a binder and an aqueous polymer; wherein:
said non-conductive particle long diameter L is 0.1 to 20 μm and ratio (b/t) between width (b) and thickness (t) is 1.5 to 100,
said binder is a copolymer including (meth)acrylonitrile monomer unit and (meth)acrylate monomer unit; and
said aqueous polymer includes sulfonic acid group and a weight average molecular weight is 1000 to 15000.
2. The porous membrane for the secondary battery as set forth in claim 1 wherein a ratio (=(meth)acrylonitrile monomer unit/(meth)acrylate monomer unit) between (meth)acrylonitrile monomer unit and (meth)acrylate monomer unit in said copolymer is 1/99 to 20/80 in terms of a weight ratio.
3. The porous membrane for the secondary battery as set forth in claim 1 wherein said binder is crosslinkable by heat applying or an energy ray irradiation.
4. The porous membrane for the secondary battery as set forth in claim 1 , wherein said copolymer includes a crosslinking group having heat crosslinking property, and said crosslinking group having heat crosslinking property is at least one selected from the group consisting of epoxy group, N-methylolamide group, and oxazolline group.
5. The porous membrane for the secondary battery as set forth in claim 1 , wherein said copolymer includes a hydrophilic group selected from the group consisting of carboxyl acid group, hydroxyl group and sulfonic acid group.
6. The porous membrane for the secondary battery as set forth in claim 1 , wherein an amount of a repeating unit comprising said sulfonic acid group in said aqueous polymer is 25 wt % or more and 90 wt % or less in terms of sulfonic acid group containing monomer amount.
7. The porous membrane for the secondary battery as set forth in claim 1 , wherein said aqueous polymer includes a repeating unit comprising a carboxyl group.
8. The porous membrane for the secondary battery as set forth in claim 1 including a nonionic surfactant having a cloud point of 30 to 90° C.
9. A slurry for a secondary battery porous membrane including a non-conductive particle, a binder, an aqueous polymer and water; wherein:
said non-conductive particle long diameter L is 0.1 to 20 μm and ratio (b/t) between width (b) and thickness (t) is 1.5 to 100,
said binder is a copolymer including (meth)acrylonitrile monomer unit and (meth)acrylate monomer unit; and
said aqueous polymer includes sulfonic acid group and a weight average molecular weight is 1000 to 15000.
10. The slurry for the secondary battery porous membrane as set forth in claim 9 wherein a TI value of said porous membrane slurry is 1.1 to 3.0.
11. The slurry for the secondary battery porous membrane as set forth in claim 9 wherein a ratio (=(meth)acrylonitrile monomer unit/(meth)acrylate monomer unit) between (meth)acrylonitrile monomer unit and (meth)acrylate monomer unit in said copolymer is 1/99 to 20/80 in terms of a weight ratio.
12. The slurry for the secondary battery porous membrane as set forth in claim 9 wherein said binder is crosslinkable by heat applying or an energy ray irradiation.
13. The slurry for the secondary battery porous membrane as set forth in claim 9 , wherein said copolymer includes a crosslinking group having heat crosslinking property, and said crosslinking group having heat crosslinking property is at least one selected from the group consisting of epoxy group, N-methylolamide group, and oxazolline group.
14. An electrode for a secondary battery, wherein an electrode material mixture layer including a binder for the electrode material mixture layer and an electrode active material is adhered to a current collector, and said electrode comprises the porous membrane as set forth in claim 1 on said electrode material mixture layer.
15. A separator for a secondary battery comprising the porous membrane as set forth in claim 1 on an organic separator.
16. A secondary battery comprising a positive electrode, a negative electrode and an electrolytic solution, wherein at least one of said positive electrode and negative electrode is the electrode for the secondary battery as set forth in claim 14 .
17. A secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolytic solution, wherein said separator is the separator for the secondary battery as set forth in claim 15 .
18. The porous membrane for the secondary battery as set forth in claim 2 wherein said binder is crosslinkable by heat applying or an energy ray irradiation.
19. The porous membrane for the secondary battery as set forth in claim 2 , wherein said copolymer includes a crosslinking group having heat crosslinking property, and said crosslinking group having heat crosslinking property is at least one selected from the group consisting of epoxy group, N-methylolamide group, and oxazolline group.
20. The porous membrane for the secondary battery as set forth in claim 1 , wherein the ratio (b/t) between the width (b) and the thickness (t) is 3 to 100.
21. The porous membrane for the secondary battery as set forth in claim 1 , wherein a ratio (L/b) between the long diameter (L) and the width (b) is 1 to 100.