Enhanced High Voltage Performance of Chlorine/Bromine Co-Doped Lithium Nickel Manganese Cobalt Oxide

摘要

The chlorine (Cl) and bromine (Br) co-doped lithium nickel manganese cobalt oxide (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ) was successfully synthesized by the molten salt method. The synthesized LiNi 1/3 Co 1/3 Mn 1/3 O 2 compound demonstrates spherical morphology, which is formed by aggregated spherical-like or polygon primary particles. Halogen substitution would contribute to the growth of the primary particles. The LiNi 1/3 Co 1/3 Mn 1/3 O 2 compound has the typical hexagonal layered structure, and no impurity phase is detected. The surface oxidation state of the compound is improved after Cl and Br substitution. Moreover, the Cl and Br co-doped LiNi 1/3 Co 1/3 Mn 1/3 O 2 compound exhibits both improved rate capacity and cycle stability at a high voltage (4.6 V) compared with the pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The initial discharge capacities of Cl and Br co-doped LiNi 1/3 Co 1/3 Mn 1/3 O 2 are 208.9 mAh g ?1 , 200.6 mAh g ?1 , 188.2 mAh g ?1 , 173.3 mAh g ?1 , and 157.1 mAh g ?1 at the corresponding rates of 0.1C, 0.2C, 0.5C, 1C, and 3C respectively. The capacity retention at 1C after 50 cycles is increased from 81.1% to 93.2% by co-doping. The better contact between the electroactive particles of the electrode and the smaller resistance enhance the electric conductivity of the Cl and Br co-doped LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode. The synthesized LiNi 1/3 Co 1/3 Mn 1/3 O 2 is a promising cathode material for a high-power and large-capacity lithium-ion battery.