Stabilizing Protic and Aprotic Liquid Electrolytes at High-Bandgap Oxide Interphases

Approaches for regulating electrochemical stability of liquid electrolytes in contact with solid-state electrodes are a requirement for efficient and reversible electrical energy storage in batteries. Such methods are particularly needed in electrochemical cells in which the working potentials of the electrodes lie outside the thermodynamic stability limits of the liquid electrolyte. Here we study electrochemical stability of liquids at electrolyte/electrode interfaces protected by nanometer thick, high electrical bandgap ceramic phases. We report that well-designed ceramic interphases extend the oxidative stability limits for both protic and aprotic liquid electrolytes, in some cases by as much as 1.5 V. It is shown further that such interphases facilitate stable electrodeposition of reactive metals such as lithium at high Coulombic efficiency and in electrochemical cells subject to extended galvanostatic cycling at a current density of 3 mA cm–2 and at capacities as high as 3 mAh cm–2. High-resolution cryo-FIB-SEM characterization reveals that solid/compact Li electrodeposits anchored by the ceramic interphase are the source of the enhanced Li deposition stability. The results enable a proof-of-concept “anode-free” Li metal rechargeable battery in which Li initially provided in the cathode is the only source of lithium in the cell.