Self-shutdown function based on overcharge-triggered electrochemical nano-switch for safer Li-ion batteries

• A novel overcharge self-protection strategy for LIBs is proposed. • The overcharge-triggered electrochemical nano-switch is inserted between current collector and active material. • The electrochemical nano-switch switch can permanently eliminate the safety hazards caused by the overcharged battery. • The working mechanism of electrochemical nano-switch is revealed by a combination of experiments and theoretical calculations. Overcharge abuse is one of the most common initiators of thermal runaway in lithium ion batteries (LIBs). Much efforts have been devoted to the developments of advanced Battery Management System (BMS) and redox shuttles to provide overcharge protection for LIBs. However, the current overcharge protection strategies are not able to permanently eliminate the safety hazards caused by overcharge abuse. Herein, we propose a new overcharge protection mechanism based on the overcharge-triggered electrochemical nano-switch (denoted as OTENS). The results demonstrate that the insertion of OTENS into between the current collector and the active mass has a little negative effect on the electrochemical performances of battery under normal and slight overcharge conditions. More importantly,the OTENS will be activated under deep overcharge condition, permanently shutting down the overcharged cell and consequently avoiding the continuous cell damage. Such a overcharge-triggered shutdown mechanism originates from the overoxidation of electrically conductive polymer that causes the loss of its electrochemical activity and electric conduction. This electrode design for constructing safer LIBs is simple and also fully compatible with the present industrial manufacture process.