Exploring Trimethyl-Phosphate-Based Electrolytes without a Carbonyl Group for Li-Rich Layered Oxide Positive Electrodes in Lithium-Ion Batteries.

Li-rich layered oxides (LLOs) are one of the most attractive next-generation positive electrode materials as a result of their high energy density and low cost. However, the deterioration of cycling stability observed in LLOs remains one of the fundamental obstacles to commercialization. Carbonate-based electrolytes reacting with oxygen radicals evolved from the lattice of LLOs is the chief cause of their poor cyclability. Herein, we construct no carbonyl group, trimethyl phosphate (TMP)-based electrolytes with a fluorinated ether co-solvent and apply them to investigate the electrochemical behaviors of LLO batteries. These electrolytes can capture active oxygen species; the initial reversible capacity of cells reaches 295.5 mAh g-1; and the capacity retention remains 96.7% after 100 cycles. In contrast, the capacity retention of cells using carbonate-based electrolytes is only 54.7% after 60 cycles. These results would provide the scientific basis and theoretical support for building electrolytes of LLOs with high properties in the future.