LAUSR

Abstract The lattice doping has been widely used to improve the electrochemical performances of Li-rich cathode materials but the roles of the introduced foreign atoms are still not very clear. Herein, a series of Li2Ru1-xTixO3 solid solutions have been synthesized and the roles of Ti doping on the structural and electrochemical properties of Li2RuO3 have been comprehensively investigated. The Rietveld refinement exhibits that the interlayer spacing gradually shortens with increasing Ti content. This shrinkage is favorable to the layered structure stability but increases the lithium diffusion barrier. Galvanostatic measurements show that Li2Ru0.8Ti0.2O3 possesses the best cyclability with 196.9 and 196.1 mAh g−1 for charge and discharge capacity retaining after 90 cycles, respectively. Cyclic voltammetry scanning indicates that Ti dopant promotes the formation of more peroxo- or superoxo-like species but reduces the initial coulumbic efficiency. Results of electrochemical impedance spectroscopy display that Ti doping reduces the charge transfer impedance, which facilitates the lithium-ion diffusion across the electrolyte-electrode interface and improves the electronic conductivity. Li2Ru0.8Ti0.2O3 exhibits the best electrochemical performance owing to the balance among all the factors discussed above. This study also offers some new insights into optimizing the electrochemical performances of Li-rich cathode materials through the lattice doping.