Preparation and characterization of lithium nickel cobalt oxide powders via a wet chemistry processing

Abstract Nickel-rich phases of the solid solutions, LiNi 1− y Co y O 2 ( y =0.1, 0.2, 0.3), were synthesized by a sol–gel method with citric acid as a chelating agent. Various initial conditions were studied in order to find the optimal conditions for the synthesis of LiNi 0.8 Co 0.2 O 2 . The discharge capacity for the compound synthesized under an optimal synthesis condition of 800 °C for 12 h was found to be 187 mAh g −1 in the 1st cycle and it was 176 mAh g −1 after 10 cycles. The other nickel-rich phases, namely, LiNi 0.9 Co 0.1 O 2 and LiNi 0.7 Co 0.3 O 2 showed 1st-cycle discharge capacities of 144 and 163 mAh g −1 , respectively. The corresponding capacity values were 140 and 159 mAh g −1 in the 10th cycle. Excess lithium stoichiometric phases, Li x Ni 0.8 Co 0.2 O 2 , where x =1.10, 1.15 and 1.20, resulted in decreased capacity. Structural and electrochemical properties of the synthesized compounds were compared with those of a commercial LiNi 0.8 Co 0.2 O 2 sample. The effect of calcination temperature and duration, excess lithium stoichiometry and divalent strontium doping in LiNi 0.8 Co 0.2 O 2 are described. Doping with strontium improved both the capacity and cycling performance of LiNi 0.8 Co 0.2 O 2 .