Bioinspired gel polymer electrolyte for wide temperature lithium metal battery.

Abstract

Stable operation of Li metal batteries with gel polymer electrolytes in a wide temperature range is highly expected. However, insufficient dynamics of ion transport and unstable electrolyte-electrode interfaces at extreme temperatures greatly hinder their practical applications. We report a bioinspired gel polymer electrolyte that enables high-energy-density Li metal batteries to work stably in a wide temperature range from -30 to 80 °C. The wide-temperature gel polymer electrolyte is fabricated by using a branched polymer of which side chains are double coupled with their asymmetric analogues. The double dipole coupling regulates the Li⁺ coordination environment to form a weak solvation structure that offers fast and uniform Li⁺ deposition at extreme temperatures. Consequently, the non-flammable gel polymer electrolyte displays an ionic conductivity of 1.03 × 10^-4 S cm^-1 at -40 °C and a Li⁺ transference number of 0.83. The Li metal batteries with LiNi_0.8Co_0.1Mn_0.1O₂ positive electrode deliver initial specific discharge capacities of 121.4 mAh g^-1 at -30 °C and 172.2 mAh g^-1 at 80 °C, with corresponding discharge currents of 18.8 mA g^-1 and 188 mA g^-1, respectively. Additionally, a pouch cell delivers a specific energy up to 490.8 Wh kg^-1.