Synergistic enhancement of Li-rich manganese-based cathode materials through single crystallization and in-situ spinel coating

Lithium-rich manganese-based cathode (LRM) materials are considered the most promising cathode for the next-generation high-energy-density Li-ion batteries due to their high specific discharge capacity. However, the current mainstream LRM materials exhibit a polycrystalline morphology, and the degradation of this morphology during extended cycling exacerbates structural distortions, leading to poor cycle stability. Herein, a spinel phase encapsulated single-crystal LRM material with a particle size of about 500 nm is prepared through a simple molten-salt assistant solid-state synthesis method utilizing traditional polycrystalline LRM precursor, followed by boric acid treatment. Combined with various characterizations, the surface coating layer of obtained single-crystal LRM materials is identified as spinel Li4Mn5O12 with a thickness of about 5 nm, which effectively enhances Li+ diffusion kinetics. Benefited from the collaborative strategy of single crystallization and spinel coating which strength Li+ conduction and suppresses particle cracking, the single-crystal LRM materials achieve a specific discharge capacity of 296.3 mAh g−1 at 0.1 C (1 C = 250 mA g−1), yielding a capacity retention of 97.4% after 300 cycles at 1 C. This study offers a universal and easy industrial scale-up approach for developing single-crystal LRM cathode materials with long cycling stability, which promotes the commercial utilization of single-crystal LRM cathode.