Thermally Aged Li-Mn-O Cathode with Stabilized Hybrid Cation and Anion Redox

Though low-cost and environmentally friendly, Li-Mn-O cathodes suffer from low energy density. Although synthesized Li₄Mn₅O₁₂-like overlithiated spinel cathode with reversible hybrid anion- and cation-redox (HACR) activities has a high initial capacity, it degrades rapidly due to oxygen loss and side-reaction-induced electrolyte decomposition. Herein, we develop a two-step heat treatment to promote local decomposition as Li₄Mn₅O₁₂ → 2LiMn₂O₄ + Li₂MnO₃ + 1/2 O₂↑, which releases near-surface reactive oxygen that is harmful to cycling stability. The produced nanocomposite delivers a high discharge capacity of 225 mAh/g and energy density of over 700 Wh/kg at active-material level at a current density of 100 mA/g between 1.8 to 4.7 V. Benefiting from suppressed oxygen loss and side reactions, 80% capacity retention is achieved after 214 cycles in half cells. With industrially acceptable electrolyte amount (6 g/Ah), full cells paired with Li₄Ti₅O₁₂ anode have a good retention over 100 cycles.