Pre-lithiated Li(Ni_xMn_yCo_z)O₂ nanoparticles with a double-layer lithium structure

Li(Ni_xMn_yCo_z)O₂ cathode materials (NMC) have advantages such as the good Li ion diffusivity, stable reversible capacity, and environmental compatibility in spite of a low actual capacity. Although a double-layer lithium structure can be generated by pre-lithiation, the thickness is very small and the capacity improvement is limited. In this work, a series of Li(Ni0.6Mn0.2Co0.2)O₂ nanoparticles are prepared by the sol-gel method and centrifugation and the pre-lithiation process are monitored by transmission electron microscope (TEM). A double lithium structure of about 10 nanometers thick is produced on the NMC materials with different sizes. With decreasing NMC particle size, the proportion of the double-layer lithium structure increases and reaches 48% for a particle diameter of 100nm. The results reveal a viable means to improve the capacity of NMC materials in charging and discharging.