Chemical integration of reduced graphene oxide sheets encapsulated ZnCo2O4 quantum dots achieving excellent capacity storage for lithium-ion batteries

Chemically integrated hybrid quantum dots ZnCo 2 O 4 /reduced graphene oxide (QDs ZCO/rGO) sheets nanocomposites are synthesized through polyol processes. rGO sheets grow and interweave to form basic skeletons. Ultrafine ZCO particles with a size of around 3.66   nm grow and embed on both sides of the rGO sheets, and the rGO sheets restrain the reunion of ZCO nanoparticles . The existence of rGO sheets and ZCO nanoparticles can engender the mutual synergistic effects so that hybrid QDs ZCO/rGO electrodes exhibit the excellent electrochemical properties . Owing to this special nanoparticles-on-sheets structure, the hybrid QDs ZCO/rGO electrodes exhibit an excellent initial discharge capacity for rechargeable lithium-ion batteries (1325.9   mAh   g −1 at the current density of 200   mA   g −1 ), high rate stability (532.3/566.1   mAh   g −1 at 4000   mA   g −1 ) and outstanding electrochemical cyclic stability (657.6/668.2   mAh   g −1 at 2000   mA   g −1 after 2000 cycles with a capacity retention of 68.6%). For full-cells, high initial reversible discharging capacity (646   mAh   g −1 at 200   mA   g −1 ) and good cyclic stability (514   mAh   g −1 at 200   mA   g −1 after 100 cycles) are obtained. The superior performance of the as-prepared electrodes is ascribed to the advantage of nano-sized particles. With the successful synthesis of hybrid QDs ZCO/rGO nanocomposites, the facile synthetic route and unique growth of nanostructuring method can be extended to high electrochemical performance electrodes for commercial lithium-ion batteries.