Syndiotactic Polystyrene-Based Ionogel Membranes for High Temperature Electrochemical Applications

This work focuses on ionogel membranes for use in Li-ion batteries fabricated from syndiotactic polystyrene (sPS) gels filled with ionic liquids (ILs). The aim is to increase the operating temperature of Li-ion batteries. Thermal stability and safe operation of Li-ion batteries are two key attributes for their success in hybrid vehicles and other high-temperature applications. The volatility of the liquid electrolytes in current lithium-ion battery technology causes thermal runaway leading to fire, explosion, and swelling of the cell. The approach followed in this work combines the thermal stability and ruggedness of sPS and the extremely low volatility of ILs. The performances of lithium metal/graphite half-cells fabricated with ionogel membranes and those with Celgard-3501 membranes are evaluated at both room temperature and at elevated temperatures of 100 °C. Our data show that the cells with ionogel membranes can be operated continuously at 100 °C without failure. In addition, better charge-discharge capacity is obtained due to high ionic conductivity and high electrolyte retention both derived from high porosity of sPS gels and better wetting of sPS by the ILs.