Improvement of electrochemical reversibility of the Ni-Rich cathode material by gallium doping

Abstract

This manuscript introduces a simple and facile strategy to greatly upgrade the electrochemical reversibility of the cathode material by doping trace quantity of Ga3+ to partially replace Mn4+ in LiNi0.8Co0.1Mn0.1O2. X-ray diffraction and X-ray photoelectron spectroscopy results reveal that the engaging of Ga3+ in the lattice inhibits the oxygen release and reduces the cation disorder, consequently increasing structural stability of the LiNi0.8Co0.1Mn0.1O2 sample. Electrochemical results show that rate capability and cycling stability of Ga-doped samples are remarkably improved. In particular, the LiNi0.8Co0.1Mn0.07Ga0.03O2 material exhibits the optimized electrochemical performance with a capacity retention of 91.2%, and the average discharge voltage kept at 3.69 V that is 0.27 V higher than that of LiNi0.8Co0.1Mn0.1O2 after 100 cycles at 1 C in voltage of 2.8–4.3 V. Surprisingly, its capacity retention even increases from 63.6% to 89.5% after 100 cycles at 1 C in 2.8–4.5 V, indicating that the Ga-doped cathode exhibits cycle stability and reduces the polarization of electrochemistry during charge-discharge process. This results from improving the stability of crystal structure by the support of gallium ion to defend layered structures against collapsing during the oxidation-reduction of Ni.