Tailored Mesoporous Carbon/Vanadium Pentoxide Hybrid Electrodes for High Power Pseudocapacitive Lithium and Sodium Intercalation

摘要

In this study, atomic layer deposition (ALD) is employed to synthesize hybrid electrode materials of especially tailored mesoporous carbon and vanadium oxide. The highly conformal and precise character of ALD allowed for depositing up to 65 mass % of vanadium oxide inside the 5-20 nm mesopores of the carbon particles, without substantially obstructing internal surface area. The deposited phase was identified as orthorhombic V2O5, and an increasing crystalline order was detected for higher mass loadings. Employing the hybrid material as lithium and sodium intercalation hosts at a rate of 0.5C yielded specific capacities of 310 and 250 mAh/g per V2O5, respectively, while showing predominantly pseudocapacitive behavior, that is, capacitor-like voltage profiles. C-rate benchmarking revealed a retention of about 50% of the maximum capacity for both lithium and sodium at a high rate of 100C. When testing for longevity in lithium-containing electrolyte, a steadily increasing capacity was observed to 116% of the initial value after 2000 cycles. In sodium electrolyte, the capacity faded to 75% after 2000 cycles, which represents one of the most stable performances for sodium intercalation in the literature. Homogeneously distributed vanadium oxide that is locally confined in the tailored carbon mesopores was identified as the reason for enhanced cyclability and rate behavior of the hybrid material.