Effects of ratios of Li2MnO3 and Li(Ni1/3Mn1/3Co1/3)O2 phases on the properties of composite cathode powders in spray pyrolysis

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

The chlorine (Cl) and bromine (Br) co-doped lithium nickel manganese cobalt oxide (LiNi1/3Co1/3Mn1/3O2) was successfully synthesized by the molten salt method. The synthesized LiNi1/3Co1/3Mn1/3O2 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 LiNi1/3Co1/3Mn1/3O2 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 LiNi1/3Co1/3Mn1/3O2 compound exhibits both improved rate capacity and cycle stability at a high voltage (4.6 V) compared with the pristine LiNi1/3Co1/3Mn1/3O2. The initial discharge capacities of Cl and Br co-doped LiNi1/3Co1/3Mn1/3O2 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 LiNi1/3Co1/3Mn1/3O2 cathode. The synthesized LiNi1/3Co1/3Mn1/3O2 is a promising cathode material for a high-power and large-capacity lithium-ion battery.

AlF3 surface-coated Li[Li0.2 Ni0.17 Co0.07 Mn0.56 ]O2 nanoparticles with superior electrochemical performance for lithium-ion batteries

Li-rich layered cathode materials have already drawn considerable attention owing to their high capacity performance for Li-ion batteries (LIBs). In this work, layered Li-rich Li[Li0.2 Ni0.17 Co0.07 Mn0.56 ]O2 nanoparticles are surface-modified with AlF3 through a facile chemical deposition method. The AlF3 surface layers have little impact on the structure of the material and act as buffers to prevent the direct contact of the electrode with the electrolyte; thus, they enhance the electrochemical performance significantly. The 3 wt % AlF3 -coated Li-rich electrode exhibits the best cycling capability and has a considerably enhanced capacity retention of 83.1 % after 50 cycles. Moreover, the rate performance and thermal stability of the 3 wt % AlF3 -coated electrode are also clearly improved. Surface analysis indicates that the AlF3 coating layer can largely suppress the undesirable growth of solid electrolyte interphase (SEI) film and, therefore, stabilizes the structure upon cycling.

Fabrication and electrochemical performance of 0.6Li2MnO3-0.4Li(Ni1/3Co1/3Mn1/3)O2 microspheres by two-step spray-drying process

0.6Li2MnO3-0.4Li(Ni1/3Co1/3Mn1/3)O2 composite microspheres with dense structures are prepared by a two-step spray-drying process. Precursor powders with hollow and porous structures prepared by the spray-drying process are post-treated at a low temperature of 400 °C and then wet-milled to obtain a slurry with high stability. The slurry of the mixture of metal oxides is spray-dried to prepare precursor aggregate powders several microns in size. Post-treatment of these powders at high temperatures (>700 °C) produces 0.6Li2MnO3-0.4 Li(Ni1/3 Co1/3 Mn1/3)O2 composite microspheres with dense structures and high crystallinity. The mean size and geometric standard deviation of the composite microspheres post-treated at 900 °C are 4 μm and 1.38, respectively. Further, the initial charge capacities of the aggregated microspheres post-treated at 700, 800, 900, and 1000 °C are 336, 349, 383, and 128 mA h g(-1), respectively, and the corresponding discharge capacities are 286, 280, 302, and 77 mA h g(-1), respectively. The discharge capacity of the composite microspheres post-treated at an optimum temperature of 900 °C after 100 cycles is 242 mA h g(-1), and the corresponding capacity retention is 80%.