CoO Quantum Dots Anchored on Reduced Graphene Oxide Aerogels for Lithium-Ion Storage

Lithium-ion capacitor (LIC) is an efficient hybrid electrochemical energy storage device, which dominates high power and energy density simultaneously. In this work, a method of liquid phase fragmentation combined with solvothermal and freeze drying treatment is used to fabricate CoO quantum dots/reduced graphene oxide composite (CoO QDs/rGO) anode. Liquid phase fragmentation plays an important role in the controllable formation of ultrafine CoO nanoparticles and their uniform anchoring on three-dimensional (3D) rGO aerogels. The CoO/rGO anode exhibits an initial discharge specific capacity of 1233.6 mA h g^–1 and a discharge specific capacity of 726.1 mA h g^–1 after 700 cycles at 1.0 A g^–1. The high specific capacity and good cycle performance are attributed to the CoO QDs with short ion transport paths, low stress change, and large interaction area between the electrode and electrolyte as well as a flexible conductive rGO with a large active surface area and abundant active sites. Metal oxide quantum dots formed by liquid phase fragmentation and the corresponding 3D multichannel metal oxide/rGO composite aerogels could be developed as superior candidates for efficient energy storage in LIC.