The utility model provides a battery cover plate assembly, which comprises a cover plate, an extraction electrode and a cover plate insulation piece. The cover plate comprises a cover main body and a cover plate rivet. The cover plate insulation piece comprises a cover plate main body upper surface insulation layer, a cover plate main body lower surface insulation layer and a cover plate rivet insulation layer. The cover plate main body upper surface insulation layer, the cover plate main body lower surface insulation layer and the cover plate rivet insulation layer are in an integrated structure. The cover plate insulation piece, the extracting electrode and the cover plate are in an integrated structure. The utility model further provides a lithium ion battery, which comprises a battery cover plate assembly, a casing, a pole core and electrolyte. The pole core and the electrolyte are packaged in a sealing space formed by the casing and the battery cover plate assembly. The battery cover plate assembly has an insulation function, reduces short-circuit risk between the extraction electrode and the cover plate, and avoids the risk of invalid insulation in a using process of the battery.