Realization of a high voltage Ni rich layer LiNi0.5Co0.2Mn0.3O2 single crystalline cathode for LIBs by surface modification

Single crystalline ternary cathode material LiNi0.5Co0.2Mn0.3O2(NCM523) can operate at extremely high voltages and could offer exceptional energy density. The single crystal morphology is less easy to form the cracks and could express better structure stability compared to the polycrystalline counterpart. However, irreversible parasitic side reactions in the interface during cycling may lead to rapid electrochemical degradations. Herein, a simple chemical wet method that modifies the single-crystal NCM523 particles with Al2O3 coating is proposed. The coating layer can effectively suppress the phase transformation and irreversible phase transition on the NCM surface during cycling. Furthermore, the cladding layer can prevent the erosion of by-products such as HF. As a result, the Al2O3 modified NCM523 delivers a high specific capacity of 192.5mAh g−1, excellent cycling stability and rate capability. The capacity retention was 91.7% after 50 cycles even at ultra-high cut-off voltage of 4.7 V. This surface engineering strategy paves the way to promote the development of small size single crystal NCM523 materials for next generation LIBs.