Removing α-H in Carboxylate-Based Electrolytes for Stable Lithium Metal Batteries

Although carboxylate esters greatly improve the cold weather performance of graphite-based lithium-ion batteries utilized in arctic expeditions, the underlying cause of the incompatibility between carboxylates and lithium (Li) anodes has not been sufficiently explained, resulting in the greatly restricted usage of carboxylate in lithium metal batteries (LMBs). Herein, we reveal the serious parasitic reactions between carboxylate α-H atoms and Li metal are the culprits that render carboxylate-based ineffectiveness for LMBs. By replacing all α-H atoms with fluorine atoms and methyl groups, we successfully construct inert carboxylates and find the ions/molecules distribution in electric-double-layer (EDL) can be manipulated at a molecular-level. The unique structure ensuring more anions are positioned closer to the Li surface in the EDL of the inert carboxylate-based electrolyte, the morphology of the deposited Li is significantly regulated and the chemical corrosion gets effectively inhibited, as a consequence of remarkable extending lifespan of carboxylate-based LMBs with routine salt concentration and few additives. More generally, using carboxylates lacking α-H atoms offer a realistic approach to increase the variety of solvents that can be used in LMBs electrolytes.