Separator, process for preparing the same, lithium ion secondary battery, battery module, battery pack and apparatus
The present embodiments provide a separator, a process for preparing the same, a lithium ion secondary battery, a battery module, a battery pack and an apparatus. The separator provided by the present application comprises a porous base film and a functional coating disposed on at least one surface of the porous base film, wherein the functional coating comprises polyimide nanosheets, and the polyimide nanosheets are stacked irregularly to form a lamellar loose structure; and a thickness ratio of the functional coating to the porous base film is from 0.1 to 1.0. The present application also provides a process for preparing the separator, and a lithium ion secondary battery and an apparatus comprising the separator.
1. A separator, comprising a porous base film and a functional coating disposed on at least one surface of the porous base film, wherein,
the functional coating comprises polyimide nanosheets, and the polyimide nanosheets are stacked irregularly to form a lamellar loose structure; and a thickness ratio of the functional coating to the porous base film is from 0.1 to 1.0,
the functional coating further comprises a binder; and the binder comprises one or more of polyfluoroolefin binders, polyacrylate binders, polyacrylic acid binders, polyurethane binders, silicone binders, epoxy binders and cellulose-derived binders, and
a mass percentage of the binder in the functional coating is from 5% to 40%; and a mass percentage of the polyimide nanosheets in the functional coating is from 60% to 95%.
2. The separator according to claim 1 , wherein the porous base film has a thickness of 2 μm to 16 μm, and the functional coating has a thickness of 1 μm to 10 μm.
3. The separator according to claim 1 , wherein the polyimide nanosheets have an average monolithic area of 3 μm 2 to 12 μm 2 .
4. The separator according to claim 3 , wherein the polyimide nanosheets have a length of 5 μm to 10 μm and a width of 1 μm to 5 μm.
5. The separator according to claim 1 , wherein the polyimide nanosheets have a thickness of 100 nm to 300 nm.
6. The separator according to claim 1 , wherein the porous base film is selected from polyolefin base films.
7. The separator according to claim 1 , wherein the porous base film is selected from one of polypropylene film, polyethylene film and polyethylene-propylene copolymer film.
8. A lithium ion secondary battery, comprising a positive electrode plate, a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein the separator is the separator according to claim 1 .
9. A battery module, comprising the lithium ion secondary battery according to claim 8 .
10. A battery pack, comprising the battery module according to claim 9 .
11. An apparatus, comprising the lithium ion secondary battery according to claim 8 .
12. A process for the preparation of the separator according to claim 1 , comprising:
(1) mixing polyimide nanosheets and a binder with deionized water to obtain an aqueous dispersion of polyimide nanosheets; and
(2) applying the aqueous dispersion of polyimide nanosheets to at least one surface of a porous base film to form a functional coating, in which a thickness ratio of the functional coating to the porous base film is from 0.1 to 1.0, and drying it to obtain the separator,
the functional coating further comprises a binder; and the binder comprises one or more of polyfluoroolefin binders, polyacrylate binders, polyacrylic acid binders, polyurethane binders, silicone binders, epoxy binders and cellulose-derived binders, and
a mass percentage of the binder in the functional coating is from 5% to 40%; and a mass percentage of the polyimide nanosheets in the functional coating is from 60% to 95%.