Zero Voltage-Degradation of Li₂MnO₃ with Ultrathin Amorphous Li─Mn─O Coating

Manganese-based lithium-rich layered oxides (Mn-LLOs) are promising candidate cathode materials for lithium-ion batteries, however, the severe voltage decay during cycling is the most concern for their practical applications. Herein, an Mn-based composite nanostructure constructed Li₂MnO₃ (LMO@Li₂MnO₃) is developed via an ultrathin amorphous functional oxide Li_xMnO_y coating at the grain surface. Due to the thin and universal LMO amorphous surface layer etched from the lithiation process by the high-concentration alkaline solution, the structural and interfacial stability of Li₂MnO₃ are enhanced apparently, showing the significantly improved voltage maintenance, cycle stability, and energy density. In particular, the LMO@Li₂MnO₃ cathode exhibits zero voltage decay over 200 cycles. Combining with ex situ spectroscopic and microscopic techniques, the Mn^2+/4+ coexisted behavior of the amorphous LMO is revealed, which enables the stable electrochemistry of Li₂MnO₃. This work provides new possible routes for suppressing the voltage decay of Mn-LLOs by modifying with the composite functional unit construction.