Electrochemical Properties of the LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Material Modified by Lithium Tungstate under High Voltage

An amount (5 wt %) of lithium tungstate (Li2WO4) as an additive significantly improves the cycle and rate performances of the LiNi0.6Co0.2Mn0.2O2 electrode at the cutoff voltage of 4.6 V. The 5 wt % Li2WO4-mixed LiNi0.6Co0.2Mn0.2O2 electrode delivers a reversible capacity of 199.2 mA h g–1 and keeps 73.1% capacity for 200 cycles at 1 C. It retains 67.4% capacity after 200 cycles at 2 C and delivers a discharge capacity of 167.3 mA h g–1 at 10 C, while those of the pristine electrode are only 44.7% and 87.5 mA h g–1, respectively. It is shown that the structure of the LiNi0.6Co0.2Mn0.2O2 cathode material is not affected by mixing Li2WO4. The introduced Li2WO4 effectively restrains the LiPF6 and carbonate solvent decomposition by consuming PF5 at high cutoff voltage, forming a stable cathode/electrolyte interface film with low resistance.