Direct Growth of MoO₂/Reduced Graphene Oxide Hollow Sphere Composites as Advanced Anode Materials for Potassium‐Ion Batteries

Hollow MoO₂ /reduced graphene oxide (MoO₂ /rGO) sub-microsphere composites have been fabricated through a simple hydrothermal approach followed by a heat treatment process. When employed as an anode material for potassium-ion batteries, the as-synthesized MoO₂ /rGO composite can deliver an initial charge specific capacity of 367.2 mAh g^-1 at 50 mA g^-1 , and its reversible capacity is 218.9 mAh g^-1 after 200 cycles. Even when cycled at 500 mA g^-1 , a high charge specific capacity of 104.2 mAh g^-1 is achieved after 500 cycles. The excellent cycling capability and rate performance may be ascribed to the synergistic effects of the reduced graphene oxide and the hollow MoO₂ spheres, which can increase the electrical conductivity of the composite, as well as resisting the strain arising from the repeated discharge-charge processes. These results indicate that the MoO₂ /rGO hollow sphere composites are promising negative electrode materials for potassium-ion batteries.