Enhancing cyclic stability of lithium-rich manganese-based cathode materials via a three-in-one strategy with single crystallization, surface coating and bulk phase doping

The common polycrystalline lithium-rich manganese-based cathode materials (LRM) always show various side reactions due to their serious microcracks after cycling, which leads to poor long-cycle stability. Herein, a MgCO 3 molten salt-assisted sintering method is used to achieve a three-in-one modification of LRM by morphological single crystallization, surface MgO coating and bulk-phase Mg 2+ doping. First, MgCO 3 promotes the formation of single-crystallized LRM, and the as-synthetized materials have high mechanical strength to effectively suppress the formation of microcrack. Second, the thermal decomposition of MgCO 3 in-situ results in a uniform MgO coating layer on the LRM surface, avoiding the washing step of removing molten salt , and preventing the direct contact between the material and the electrolyte. Third, a small amount of Mg 2+ enters the lattice structure of LRMs, healing the structural defects caused by the volatilization of lithium during high temperature calcination , and realizing the in-situ trace doping of Mg 2+ at Li sites. As a result, the three-in-one modified materials suppress the corrosion by the electrolyte, inhibit the irreversible loss of oxygen and the migration of transition metal ions , reduce the charge-transfer impedance, and alleviate the phase transition, thus ensuring the excellent electrochemical performances of half-cells. This work not only provides a simple and effective modification strategy to enhance the long cycling performance of LRM at high voltage, but also opens up new perspective for the development of high-energy-density lithium-ion batteries (LIBs).