Effect of Si doping on the structure and electrochemical performance of high-voltage LiNi0.5Mn0.5O2 cathode

Abstract

Despite its high energy density, high-voltage LiNi0.5Mn0.5O2 cathode which suffers from a poor cycle performance that originated from the cathode structural collapse is still far from commercialization. Doping heteroatom into the lattice of LiNi0.5Mn0.5O2 is believed to be a valid strategy in overcoming this bottleneck. Herein, Si was employed as a dopant to comprehensively improve the electrochemical performance of LiNi0.5Mn0.5O2. X-ray diffraction and Rietveld refinement revealed that doping Si into LiNi0.5Mn0.5O2 can optimize its structure, which reduced the degree of Li/Ni cation mixing. As a result, an enhanced interfacial reaction kinetics of Li-ion intercalation/de-intercalation could be achieved, rendering the doped LiNi0.5Mn0.5O2 a remarkably improved reversible capacity in comparison with its pristine. Moreover, it was found that Li0.99Si0.01Ni0.5Mn0.5O2 showed a significantly higher capacity than LiNi0.5Mn0.5O2 does at 25 °C. It is believed that this work affords an effective strategy for high-performance LiNi0.5Mn0.5O2 cathode.