This invention discloses a binder, its preparation method, and its application. The binder comprises the following raw materials: a compound containing soft segments, a compound containing hard segments, and a chain
extender. The compound containing soft segments includes polyether polyols and
polyester polyols, wherein the polyether polyols are end-capped with amino or hydroxyl groups, and the
polyester polyols are end-capped with amino or hydroxyl groups. The compound containing hard segments is a diisocyanate, and the chain
extender is a chain
extender containing phenolic groups. This binder helps solve the interface problem of the positive
electrode during battery operation and is expected to improve the cycle life and stability of the battery.