Abstract: The present invention is to provide a lithium battery can be exempted from short circuit problems caused by metallic particles agitated through the manufacturing process and later usage. Said lithium battery includes a battery cover, anode films, separators, cathode films, an organic electrolyte, a cylindrical housing with a neck portion formed on an upper portion of the cylindrical housing. Said neck portion is spread with a layer of polymeric based composite materials onto an inner wall inside the neck portion, damages happened to the neck portion will not cause short circuit also.