Polyoxometalate-Based Bottom-Up Fabrication of Graphene Quantum Dot/Manganese Vanadate Composites as Lithium Ion Battery Anodes.

Lithium ion battery (LIB) electrodes require a stable connection between a redox-active metal oxide for charge storage and an electrically conductive (often carbon-based) material for charge transport. As charge transfer within the metal oxide is often a performance-limiting factor, one promising concept is the linking of charge transfer and charge storage components on the nanoscale. This would maximize the interfacial contact area and improve charging/discharging behavior. This work presents a one-step, room-temperature route giving nanostructured manganese vanadium oxide/graphene quantum dot (GQD) composite electrodes. Manganese vanadium oxide clusters are used as solution-processable precursors, which are deposited on GQDs using a sonication-driven conversion leading to electroactive, lightweight composites. Incorporation of the composites as anodes in LIBs shows high electrochemical performance featuring discharge capacities of 970 mAh g-1 over 100 cycles with coulombic efficiencies near 100 %. The study shows how 3d-metal oxide/GQD nanostructures can be accessed by a scalable sonication route starting from soluble, chemically tunable metal oxide clusters and graphene quantum dots.