Solid-State Lithium Metal Batteries with Improved Performance via Polymer Electrolyte Interface Modification

Modification of lithium metal (LM) with a stable solid electrolyte interface leading to the possibilities of ambient assembly of a lithium metal battery (LMB) is of tremendous interest in the development of low-cost, safe batteries. Herein, LM surface modifications via direct as well as polymer electrolyte surface modification approaches consisting of hot pressing in air are demonstrated for the development of a stable solid electrolyte interface (SEI). The SEI at the polymer-lithium metal interface has in situ formed LiF and defective graphene, making the solid-state batteries cyclable even at high current densities (10 mA cm^-2). This modification brings enhanced cyclability (>1000 cycles (1 h per cycle) for Li||Li cells at 6 mA cm^-2; and >200 cycles for Li||NMC at 1 C) with a high Li⁺ transference number (0.62 ± 0.08) to the electrolyte operating at room temperature. Here, an optimized thin film of fluorinated graphite polymer was used for the modification, bringing air stability to the lithium anode along with fire resistance after the modification, addressing the key safety concerns with the direct use of metallic lithium. This method opens the possibilities of high performance LMBs with their assembly devoid of high inert conditions, thereby bringing down the cost of battery technology.