Composite Li-ion battery cathodes formed via integration of carbon nanotubes or graphene nanoplatelets into chemical preintercalation synthesis of bilayered vanadium oxides

Abstract

Bilayered vanadium oxides are attractive cathode materials for rechargeable batteries. The expanded interlayer space and versatile chemistries of these oxides yield high specific capacities. However, capacity retention and rate performance are limited due to structural instability and low electronic conductivity of these materials. Assembling the oxides with one- and two-dimensional carbon nanoparticles may produce highly efficient heterointerfaces that would enhance electrochemical charge storage properties. Here, we synthesize for the first time bilayered vanadium oxide composites with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The nanostructured carbons were initially functionalized by flash oxidation in air to create polar groups on the carbon surface, producing fCNTs and fGNPs, and improve compatibility with an aqueous chemical preintercalation synthesis route. Lithium preintercalated bilayered vanadium oxide, LVO (LVO = δ-LixV2O5·nH2O), was selected as a redox active oxide component to facilitate Li+ ion diffusion through the interlayer region of δ-V2O5. A one-step process was developed to synthesize LVO/fCNT and LVO/fGNP composites by an in situ low temperature sol-gel method. We observed marked improvements in capacity retention and rate performance in the nanocomposites as compared to the pristine oxide, which were attributed to both improved electron transport and heterointerface stabilization effect enabled by integration with fCNTs and fGNPs. This work illustrates the ability to enhance material functionality through the in situ synthesis of nanocomposites with controllable heterointerface.