This study developed a novel branched additive membrane, which can be electrochemically self-synthesized to a solid electrolyte interface (SEI), to reduce the danger of lithium-ion batteries. The additive can be manufactured efficiently, and the membrane provides a high degree of safety, by reducing the probability of batteries suffering an internal short circuit. A composite electrode of LiCoO(2) with the proposed self-polymerized SEI delivers excellent energy density near 150 mAh/g, without any side effects. In addition, open circuit potential (OCP) and charge-discharge curve behavior in full cell tests have revealed favorable electrochemical properties. Measurements to detect internal short circuits show that the self-polymerized SEI in a full cell is initiated within 1 s of a nail penetrating the battery. This novel membrane and self-polymerized SEI techniques make batteries safer for future applications. (C) 2010 Elsevier B.V. All rights reserved.