Na-Doped LiNi_0.8Co_0.15Al_0.05O₂ with Excellent Stability of Both Capacity and Potential as Cathode Materials for Li-Ion Batteries

Nickel-rich layered oxides with their large reversible capacity are considered to be some of the most promising cathode materials for high-energy Li-ion batteries. However, the fast decay of capacity and potential of Ni-rich layered oxides occurs unavoidably during long-term cycling, which is harmful to the stable output of energy density of Li-ion batteries. In this work, Na-ion doping is introduced into LiNi0.8Co0.15Al0.05O2 in order to stabilize both the capacity and potential. In this work, 1 wt % Na ions are doped into LiNi0.8Co0.15Al0.05O2 with a gradient distribution from the surface to the bulk. In addition, the morphology of the spherical oxide particle is not damaged by Na-ion doping. Comparing with the pristine sample, Na-doped LiNi0.8Co0.15Al0.05O2 presents lower potential polarization, higher initial Coulombic efficiency, and better rate capability. In particular, the cycle stability of both potential and capacity is greatly enhanced for the Na-doped sample, which is very important for stabilizing the energy density of cathode. In addition, the integrated spherical morphology of the Na-doped sample particle is retained even after long-term cycling, which is attributed to the pillaring effect of Na ions with large radiuses.