Uniform amorphous MgxByOz coating combined with Vo for highly stable Li-Rich Mn-based cathode material

Abstract

Li-rich Mn-based cathode materials (LRs) have attracted significant research interests owing to high energy density, but their commercial application is limited by capacity/voltage attenuation caused by irreversible lattice oxygen release, structural reconstruction, interface reactions, as well as the dissolution of transition metals (TM). This work proposed a synergistic modification strategy of surface coating by magnesium borate (MgxByOz) cooperated with defect construction of enriched oxygen vacancy (Vo) for Li1.2Mn0.54Ni0.13Co0.13O2 cathode material, and the interior and exterior modification has been achieved in one step through the interaction between reducing agent of BH4- and oxygen at surface. The amorphous MgxByOz coating with good mechanical strength and toughness provides lasting protection and prevents phase degradation from layered to rock-salt phase. The constructed Vo reduce irreversible oxygen release and subsequently slows down capacity decay and voltage degradation. The modified MBO2-LR exhibits superior rate capacity with a specific capacity of 140.6 mAh g−1 at a high current density of 10C and an satisfactory capacity retention of 83.6% after 200 high-voltage cycles at 1C, much higher than the values of the pristine sample. This work offers a viable modifying route for the promising cathode materials with high energy density.