Polytriphenylamine used as an electroactive separator material for overcharge protection of rechargeable lithium battery

An electroactive polytriphenylamine (PTPAn) was synthesized and used as separator material for providing a self-activating overcharge protection of rechargeable lithium batteries. The experimental results from the Li–LiFePO4 cells demonstrated that the electroactive separator could transform from an electronically isolating state to a conductive state at overcharge, producing an resistive internal short circuit to maintain the cellʹs voltage at the safety value of ~3.75 V. In addition, the electroactive PTPAn separator works reversibly and has no negative influences on the normal charge–discharge behaviors of the Li–LiFePO4 cells.