High-performance composite polymer membranes for solid-state lithium-metal batteries

Ceramic-polymer composite electrolytes are among the strong contenders for the development of safe and high-energy density solid-state Li-metal batteries (SSLB). Current composite electrolytes suffer, however, from low conductivity and thermodynamic instability versus cathode materials. In order to overcome the current limitations, we report the preparation of electrolyte membranes based on lithium garnet (LLZO) nanowires synthesized via electrospinning technique, poly (ethylene oxide) (PEO) and a sulfonic-based plasticizer enabled with high Li-ion conductivity of 0.1 mS cm^-1 at room temperature. The fabricated flexible membranes show improved electrochemical performances. For example, the cyclic voltammetry results confirm the electrochemical stability of the developed electrolyte membrane in a voltage window of 3 V to 5.5 V that potentially enables utilization of high voltage cathodes such as LiCoPO₄. To extend, the electrochemical stability towards low voltage to enable the use of cathode materials operating in a larger or lower voltage range, we engineered the lithium metal surface by a thin layer of Li₃N layer that stabilized the developed membranes down to 1.5 V. Integration of the developed electrolyte membranes with high specific capacity cathodes could potentially enable the next generation Li-metal batteries with high energy density.