Study of the electrochemical properties of Ga-doped LiNi0.8Co0.2O2 synthesized by a sol-gel method

The effects of gallium doping on the structure and electrochemical properties of LiNi0.8Co0.2O2 were investigated by X-ray diffraction, cyclic voltammetry and charge-discharge tests. LiNi0.8Co0.2−xGaxO2 (x = 0.01, 0.03, 0.05) was synthesized using a sol-gel method and it showed the average particle size less than 1 μm in diameter. Results showed that gallium-doping had no effect on the crystal structure (α-NaFeO2) of the cathode material in the range x ≤ 0.05. On the other hand, two transitions at 3.7-3.9 and 4.2-4.7 V observed during the cycle test were merged into one when the amount of gallium doping increases to 0.05, implying that the enhanced capacity retention with gallium doping is attributed to the suppression of the phase transition of the cathode. However, the increase of gallium content in LiNi0.8Co0.2O2 slightly decreases the initial discharge capacity.