Abstract: The present invention discloses a safe lithium ion battery to solve the short circuit problem of short circuit caused by metal grains produced during the production of the battery on the neck of the lithium ion battery. The lithium ion battery comprises a cylindrical shell, a battery cover, an anode, a membrane, a cathode, an organic electrolyte, and a concave is provided on the round neck of the cylindrical shell, wherein a round tape is provided on the surface of the inner wall of the concave round neck. The lithium ion battery may completely solve the problem of metal grain produced during the production of the neck of the battery shell falling into the shell causing short circuit. It may also solve the problem of damage on the neck of the battery shell during the production of the battery, and short circuit caused by metal grain produced in the using of the battery.