Cooperative Stabilization Of Bi-Electrodes With Robust Interphases For High-Voltage Lithium-Metal Batteries

Stable electrode-electrolyte interphases on both electrodes are indispensable to warrant cycling stability of high -voltage Li-metal batteries. Here, we reveal a unique cooperative reaction mechanism to form protective interphase layers on both Li-metal anode and high-voltage cathodes, which is exemplified by a multifunctional additive ethoxy(pentafluoro)cyclotriphosphazene (PFPN). The F-rich PFPN first reacts with Li-metal anode to form LiF-rich solid electrolyte interphase (SEI), which stabilizes the Li deposition/dissolution processes. Meanwhile, the in-situ generated PFPN derivatives with a de-fluorated structure are prone to be oxidized on cathode, forming a robust cathode-electrolyte interphase (CEI) to prevent electrolyte oxidation and electrode degradation at high voltage. With PFPN to harness the aggressive battery electrodes, Li-metal batteries with high-voltage LiCoO2 (4.5 V) and LiNi0.5Mn1.5O2 (4.9 V) cathodes exhibit improved cycling stability and rate capability. In particular, the LiNi0.5Mn1.5O2 vertical bar Li full cell with limited Li supply (N/P = 7.6) demonstrates outperformed capacity retention of 90.7 % after 100 cycles, which is almost twice that of the cell using PFPN-free conventional electrolyte (47.5 %).