Suppressing lattice oxygen-induced interfacial degradation via a multifunctional siloxane additive for 4.8 V LRMO‖Li...

Lithium-rich manganese-based oxides (LRMO) are promising cathodes for high-energy-density lithium-metal batteries owing to their high operating voltage and large reversible capacity, but suffer from severe interfacial degradation at high voltages (≥4.8 V), primarily triggered by lattice oxygen release, electrolyte oxidation, and HF-induced corrosion. Herein, we design a multifunctional siloxane-based electrolyte additive, 1,3,5-tris(3,3,3-trifluoropropyl)methylcyclotrisiloxane (TFSO), to regulate these coupled degradation processes. TFSO simultaneously acts as an oxygen scavenger and HF trap, suppressing lattice oxygen reactivity while converting HF into stable SiF/SiO species. Meanwhile, it promotes the formation of robust, inorganic-rich CEI/SEI layers, enabling dual interfacial stabilization and uniform lithium deposition. In addition, TFSO reconstructs the Li⁺ solvation structure, reducing solvent participation in interfacial side reactions. As a result, the LRMO‖Li cell achieves 92.7% capacity retention after 300 cycles at 4.8 V, along with excellent wide-temperature performance (82.7% at 55 °C and 160 mAh g^-1 at 0 °C). This work highlights an effective electrolyte design strategy for mitigating oxygen-triggered interfacial degradation in high-voltage lithium metal batteries.