Manganese Phosphide Enables Oxygen Modulation in Co‐Free Li‐Rich Mn‐Based Oxides cathode for Reversible Anionic Redox

ABSTRACT Cobalt‐free lithium‐rich manganese‐based oxides (LRMOs), which have high capacity and cost‐effectiveness, are promising cathode materials for the next generation high energy density lithium‐ion batteries. Nevertheless, their practical application remains hindered by capacity fading, voltage degradation and constrained rate capability. In the present work, it is found that manganese phosphide (Mn 3 P 2 ) can act as an oxygen‐stabilizing agent for LRMO. By simply incorporating it into a Co‐free LRMO during cathode preparation, high capacities of 280 mAh g −1 at 0.1 C and 175 mAh g −1 at 5 C, coupled with the superior capacity retention of 96.8% at 1C after 400 cycles are achieved. P 3− in Mn 3 P 2 reacts with the O (oxygen) in LRMO at the particle surfaces, forming strong P─O covalent bonds and generating high concentrations of oxygen vacancy during the initial cycle, both of which greatly enhance structural stability. The P─O bond localizes the electron accumulation around oxygen, stabilizing the lattice oxygen and enhancing the structural stability. The high concentration of oxygen vacancy favors high electronic conductivity and suppresses the oxygen release additionally. This strategy provides a new avenue for the surface engineering of high performance lithium‐rich manganese‐based cathode materials.