Lithium ion battery composite cathode with overdischarge energy to 0V and preparation method and application thereof

A lithium ion battery composite cathode with overdischarge energy to 0V and a preparation method and application thereof. The present invention relates to a cathode material for lithium ion battery, and solves the problem that existing lithium cobalt oxide battery and other high voltage lithium ion battery above 3.45V, in overdischarge to 0V, have serious loss of storage capacity, leading to the failure. The composite cathode is a laminate structure composite cathode composed of lithium cobalt oxide or lithium manganese oxide spinel layer/active isolation layer / lithium iron phosphate layer. The preparation method is as below: mixing a super capacitor carbon material, a conductive agent, a binder and a liquid dispersant to prepare an isolation layer slurry; coating the isolation layer slurry on the surface of positive electrode sheet and drying; and then coating the lithium iron phosphate slurry on the active isolation layer surface; and finally drying and tabletting. The active separating layer in the composite cathode can effectively isolate the surface layer lithium iron phosphate and underlying lithium cobalt oxide and other active substances, and allow discharge to 0V and no store failure at 0V, so as to improve the durability of the lithium ion battery.