Binder and preparation method thereof, separator, electrode assembly, battery cell, battery, and electric apparatus
This application relates to the field of battery technologies, and in particular, to a binder and a preparation method thereof, and a separator, electrode assembly, battery cell, battery, and electric apparatus containing such binder. The binder includes a core layer structure and a shell layer structure provided on surface of the core layer structure, where the core layer structure includes a polyvinylidene fluoride polymer, and the shell layer structure includes a polyacrylate polymer. Polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, resulting in insufficient adhesion force. Therefore, in this application, the polyacrylate polymer is used to encapsulate the polyvinylidene fluoride polymer to obtain a core-shell-structured binder, so that the crystallinity of the polyvinylidene fluoride polymer in the core-shell-structured binder is improved, and adhesion performance of the core-shell-structured binder is improved, thereby increasing adhesion force between a separator and an electrode plate via the binder.
1 . A binder, wherein the binder comprises a core layer structure and a shell layer structure provided on surface of the core layer structure, wherein the shell layer structure comprises a polyacrylate polymer, and the core layer structure comprises a polyvinylidene fluoride polymer;
constituent monomers of the polyacrylate polymer comprise a first polymeric flexible monomer, a second polymeric polar monomer, and a third polymeric molecular weight regulating monomer;
a molar ratio of the first polymeric flexible monomer, the second polymeric polar monomer, and the third polymeric molecular weight regulating monomer is 1:(0.01-0.8):(0.01-0.15); and
the first polymeric flexible monomer contains an ester bond in structure, the second polymeric polar monomer contains a cyano group in structure, and the third polymeric molecular weight regulating monomer contains an amide bond.
2 . The binder according to claim 1 , wherein the shell layer structure comprises multiple shells, the multiple shells being spaced apart on the surface of the core layer structure.
3 . The binder according to claim 1 , wherein a mass ratio of the polyvinylidene fluoride polymer to the polyacrylate polymer is (2-100):1.
4 . The binder according to claim 1 , wherein a median particle size by volume D v 50 of the binder is 0.5 μm-50 μm.
5 . The binder according to claim 1 , wherein a molar ratio of the first polymeric flexible monomer, the second polymeric polar monomer, and the third polymeric molecular weight regulating monomer is 1:(0.05-0.7):(0.05-0.12).
6 . The binder according to claim 1 , wherein the first polymeric flexible monomer is an acrylate monomer, the second polymeric polar monomer is an acrylonitrile monomer, and the third polymeric molecular weight regulating monomer is an acrylamide monomer.
7 . The binder according to claim 6 , wherein the acrylate monomer comprises at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate;
and/or the acrylonitrile monomer comprises at least one of acrylonitrile and methacrylonitrile;
and/or the acrylamide monomer comprises at least one of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.
8 . The binder according to claim 1 , wherein the polyvinylidene fluoride polymer comprises at least one of vinylidene fluoride polymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer, vinylidene fluoride-tetrafluoropropylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-perfluorobuttene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trifluorochloroethylene copolymer, or vinylidene fluoride-fluoroethylene copolymer.
9 . A separator, wherein the separator comprises the binder according to claim 1 .
10 . An electrode assembly, wherein the electrode assembly comprises the separator according to claim 9 .
11 . A battery, wherein the battery comprises the battery cell according to claim 10 .
12 . An electric apparatus, wherein the electric apparatus comprises the battery cell according to claim 10 .
13 . A preparation method of binder, comprising:
adding water, an emulsifier, an initiator, and constituent monomers of a polyvinylidene fluoride polymer into a reaction vessel, stirring, and heating under a reaction pressure for polymerization reaction, to obtain a seed emulsion for later use;
mixing and stirring water, an emulsifier, and constituent monomers of a polyacrylate polymer to obtain a shell-layer monomer pre-emulsion for later use; and
putting the shell-layer monomer pre-emulsion and an initiator into the seed emulsion, and performing stirring and heating for reaction, to obtain a core-shell-structured binder, wherein
constituent monomers of the polyacrylate polymer comprise a first polymeric flexible monomer, a second polymeric polar monomer, and a third polymeric molecular weight regulating monomer;
a molar ratio of the first polymeric flexible monomer, the second polymeric polar monomer, and the third polymeric molecular weight regulating monomer is 1:(0.01-0.8):(0.01-0.15); and
the first polymeric flexible monomer contains an ester bond in structure, the second polymeric polar monomer contains a cyano group in structure, and the third polymeric molecular weight regulating monomer contains an amide bond.
14 . The preparation method of binder according to claim 13 , wherein a mass ratio of the constituent monomers of the polyvinylidene fluoride polymer to the constituent monomers of the polyacrylate polymer is (2-100):1.
15 . The preparation method of binder according to claim 13 , wherein the constituent monomers of the polyvinylidene fluoride polymer comprise vinylidene fluoride;
or the constituent monomers of the polyvinylidene fluoride polymer comprise at least one of vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, tetrafluoropropylene, trifluoropropylene, perfluorobutene, tetrafluoroethylene, trifluoroethylene, trifluorochloroethylene, and fluoroethylene.
16 . A separator, wherein the separator comprises the binder prepared using the preparation method of binder according to claim 13 .
17 . A battery cell, wherein the battery cell comprises the electrode assembly according to claim 16 .