Water based composition used for modifying diaphragm for lithium ion battery and modified diaphragm and battery

The present invention belongs to the technical field of preparation of lithium-ion batteries, in particular relates to a water based composition used for modifying a diaphragm for a lithium ion battery and a modified polyolefin diaphragm for the lithium ion battery and the lithium ion battery, and aims to improve the strength of the battery core of the lithium ion battery, reduce high temperature expansion of the thickness of the battery core, and simplify the battery production process. The water based composition used for modifying the diaphragm for the lithium ion battery comprises an aqueous binder used for the lithium ion battery and an organic nanoparticle filler dispersed in the aqueous binder, the organic nanoparticle filler is a polymer 1 nanoparticle and a nanoparticle at least coated with a polymer 1; and the particle size of the nanoparticle is 100-2000nm; the polymer 1 is selected from at least one of polymethyl methacrylate, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-butyl acrylate copolymer, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer and polyurethane.