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

• NCM was integratedly modified by combination of Li 2 TiO 3 coating and PO 4 3− doping. • Fast ion conductor coating suppresses side reactions and decreases ion transferring impedance. • PO 4 3− stabilizes crystal structure, reduces cation mixing and improves ionic conductivity. • The modified NCM shows excellent rate capability and cycling stability at high cut-off voltage. Ni-rich layered metal oxide of LiNi 0.6 Co 0.2 Mn 0.2 O 2 (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 Li 2 TiO 3 on particle surface and doping with PO 4 3− polyanion in bulk of the NCM cathode material. The large tetrahedral PO 4 3− polyanions doped into lattice structure suppresses cationic mixing and structure degradation, while the Li 2 TiO 3 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 Li 2 TiO 3 coating material with three-dimensional channels for ion transport and the enlarged interlayer spacing by PO 4 3− -doping enhance capacity and facilitate Li + ions diffusing. These factors result in a superior rate capability. With the collaborative cooperation of Li 2 TiO 3 coating and PO 4 3− 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.