Converting CO₂ into functionally valuable materials: a hybrid polymer electrolyte for high-performance lithium metal...

Upcycling CO₂ into battery components promises carbon-neutral energy storage, yet most CO₂-derived polymers require harsh synthesis conditions and have limited electrochemical integration. This work reports a hybrid polymer electrolyte based on a CO₂-derived polyurethane (PCO₂), which is synthesized under ambient conditions (room temperature, 1 atm) as a carbon-utilization strategy. A composite electrolyte (GPCO₂-2) is further constructed by integrating this PCO₂ with a polymer matrix and a deep eutectic solvent component, wherein in situ densification and interfacial reconstruction are established to simultaneously achieve mechanical integrity and electrochemical stability. Benefiting from the abundant coordination sites within GPCO₂-2, a competitive coordination mechanism prevents excessive Li⁺ binding while ensuring continuous ion transport pathways. This unique configuration endows the electrolyte with seamlessly coupled bulk-interface ion transport properties, significantly enhanced Li⁺ dissociation and migration, and promotes the formation of a dense and stable solid-electrolyte interphase. Consequently, the electrolyte delivers outstanding stability, enabling lithium metal to cycle reliably for over 2500 h. At a voltage of 4.3 V, the Li/GPCO₂-2/NCM811 battery achieves 500 stable cycles at 0.5 C. Even under a higher voltage of 4.7 V and at 0.2 C, it still completes 100 stable cycles. Flexible pouch cells assembled with this GPCO₂-2 electrolyte show viability with 71.1% capacity retention after 100 cycles. Beyond cycling performance, the electrolyte's robust oxidative stability also endows the cells with enhanced safety features. Overcharge tests indicate that the GPCO₂-2 cells maintain stable current at high voltages and a lower temperature rise, enhancing safety and oxidative stability through regulated Li⁺ transport.