Integrated co-modification of PO43− polyanion doping and Li2TiO3 coating for Ni-rich layered LiNi0.6Co0.2Mn0.2O2 cathode material of Lithium-Ion batteries

Abstract Ni-rich layered metal oxide of LiNi0.6Co0.2Mn0.2O2 (NCM) is a promising cathode material for the next-generation lithium-ion batteries. The fast capacity fading caused by interfacial instability, bulk structural degradation and side reactions on electrode/electrolyte interface during cycling hampers its larger scale commercial applications. In this work, a combined modification strategy was implemented by coating with Li2TiO3 on particle surface and doping with PO43− polyanion in bulk of the NCM cathode material. The large tetrahedral PO43− polyanions doped into lattice structure suppresses cationic mixing and structure degradation, while the Li2TiO3 coating layer protects the particle surface and restrains side reactions. The co-modification strengthens overall structure stability for an excellent cycling performance. Moreover, the thin layered Li2TiO3 coating material with three-dimensional channels for ion transport and the enlarged interlayer spacing by PO43−-doping enhance capacity and facilitate Li+ ions diffusing. These factors result in a superior rate capability. With the collaborative cooperation of Li2TiO3 coating and PO43− doping, the sample with 1 mol% coating and 0.03 mol% doping content delivers a reversible specific capacity of 167.2 mAh g−1 at 5C and 157.8 mAh g−1 at 10C, remains a capacity of 147.7 mAh g−1 at 1C after a long term 800 cycles with a retention of 77.4% at a high cut-off voltage of 4.5 V.