Ultralong metahewettite CaV6O16·3H2O nanoribbons as novel host materials for lithium storage: Towards high-rate and excellent long-term cyclability

Abstract

The applications of vanadium oxide bronzes as cathode materials for rechargeable lithium-ion batteries are hindered by inferior cyclability and insufficient rate capability, which arised from weak structural stability and sluggish electrochemical kinetics. To address this issue, we incorporate alkaline-earth metals as interlayer materials within the vanadium oxide layered framework, leading to a whole new family of potential Li+ intercalated materials with a general formula MV6O16·nH2O (M=Mg, Ca, Sr, Ba). In these bronze-hydrated compounds, interlayer water can serve as pillars pinning the V–O layers together, coupled with the enhanced divalent cation pillars, maintaining substantial structure stability and leading to excellent long-term stability. Additionally, the interlayer spacing can be further expanded by intercalation of water molecules, offering enhanced Li+ diffusion channel and leading to high rate capability. In this family, we fabricate and study the first such candidate, ultralong metahewettite CaV6O16·3H2O nanoribbons. When evaluated as cathode materials, for the first time, they exhibit high-rate kinetics (103, 78mAhg−1 at 6 and 10Ag−1, respectively) and excellent long-term cyclability (83.6%, 89.5% capacity retention after 1000 cycles at 2 and 6Ag−1, respectively). The electrode shows optimal cycling stability for vanadate-based cathode materials for LIBs ever reported.