Superior electrochemical properties of spherical-like Co₂(OH)₃ Cl-reduced graphene oxide composite powders with ultrafine nanocrystals

Co₂(OH)₃Cl/reduced graphene oxide (RGO) composite powders for use as anodes in lithium ion batteries were prepared directly by spray pyrolysis from a colloidal solution of graphene oxide sheets and cobalt chloride. Co₂(OH)₃Cl nanocrystals less than 10 nm in size were uniformly distributed throughout the spherical Co₂ (OH) ₃Cl/RGO composite powder. CoCl₂ 6H₂-O/RGO, CoCl₂ 6H₂O/Co₃O₄/RGO, and Co₃O₄ powders were also prepared by post-treatment of the Co₂ (OH) ₃Cl/RGO powders at 200, 300, and 400 °C, respectively, in air. The initial discharge capacities of the Co₂(OH)₃Cl/RGO, CoCl₂ 6H₂O/RGO, CoCl₂ 6H₂O/Co₃O₄/RGO, and Co₃O₄ powder electrodes at a current density of 1000 mA g^-1 were 1685, 1518, 1655, and 1046 mA h g^-1, respectively, and their discharge capacities after 200 cycles were 1186, 1030, 884, and 805 mA h g^-1, respectively. The discharge capacities of the Co₂ (OH) ₃Cl/RGO composite powder electrode for the 2nd and 600th cycles at a current density of 5000 mA g^-1 were 1063 and 833 mA h g^-1, respectively. The Co₂ (OH)₃Cl/RGO powders had smaller charge transfer resistance and faster lithium-ion diffusion rate than the other materials.