Comparative studies of tungsten and zirconium doping on single crystal cobalt-free cathode material

In this study, the cobalt-free single crystal cathode materials LiNi0.75Mn0.25O2 (NM), W-doped LiNi0.75Mn0.25O2 (NMW) and Zr-doped LiNi0.75Mn0.25O2 (NMZ) were prepared by a high-temperature solid-state method. The effects of W and Zr elements to the cathode material LiNi0.75Mn0.25O2 were studied systematically. The results show that W doping can improve the reversible specific capacity slightly. Nevertheless, it is not conducive to the cyclic stability. Meanwhile, although the reversible specific capacity of the material decreases slightly with the Zr doping, its cyclic stability and high rate capability can be improved significantly. Cyclic voltammetry (CV) results reveal that the improvement originates from the mitigated electrode polarization phenomenon and enhanced Li+ kinetics. In addition, direct current resistance (DCR) analyses verify that Zr doping can effectively inhibit the increase of DCR, which is beneficial to the rate capability and cycle stability.