Designing an Al-Rich In Situ Coating for Stabilizing High-Energy-Density Li Metal Battery Electrodes via Electrolyte Modulation

High-energy-density Li metal batteries with high charge voltage and fast charge/discharge rates are of great significance to the energy storage market. However, traditional carbonate-based electrolytes suffer from severe performance decay due to their oxidation and decomposition under high working voltages, and they are unable to prevent Li dendrite growth. Herein, we report an advanced concentrated ternary salt ether-based electrolyte which is compatible with a high charge voltage and exhibits a high rate capability in a Li metal-based Li||LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) battery. Advanced electron microscopy reveals a stable Al-rich interphase in situ coated on the cathode surface due to the design of the electrolyte. This interphase suppresses the surface side effect and thus improves cell cyclability. Benefiting from the in situ coated interphase, the cell exhibits good capacity retention of ∼85% after 300 cycles with a charge voltage of 4.4 V (C/3 charge and 1 C discharge). This work offers a promising strategy for developing practical secondary batteries based on Li metal with outstanding high voltage and rate performance.