Rate capability for Na-doped Li1.167Ni0.18Mn0.548Co0.105O2 cathode material and characterization of Li-ion diffusion using galvanostatic intermittent titration technique

Spherical Li1.167−xNaxNi0.18Mn0.548Co0.105O2 (0 ⩽ x ⩽ 0.1) particles were prepared by spray pyrolysis, and subjected to electrochemical characterization for lithium battery applications. It was confirmed that Na doping enhances the charge/discharge rate capability. The structure of prepared samples was characterized by XRD: the c-axis lattice parameter increases with increase in the amount of Na ions (parameterized by x, above). The Na-doped sample with x = 0.05 shows capacities of 208 and 184 mA h g−1 at high current densities of 1.0 C and 2.0 C, respectively. These values are enhanced, compared to values of 189 and 167 mA h g−1 for the bare sample. The ratio of the capacity at 1.0 C to that at 0.1 C is enhanced from 77% for the bare sample to 84% for the Na-doped sample with x = 0.05. The Li diffusion coefficients obtained from the galvanostatic intermittent titration technique (GITT) are higher for Na-doped samples than for the bare sample. In particular, the Na-doped sample (x = 0.05), in the potential range around 4 V, has a higher DLi+ value of 3.34 × 10−9 cm2 s−1, compared with 1.35 × 10−9 cm2 s−1 for the bare sample. The Na-doped samples (0 < x < 0.075) show high capacity retention: the Na-doped sample (x = 0.05) shows a capacity retention of 92% compared to 83% for the bare sample.