V 2 O 5 Nano‐Electrodes with High Power and Energy Densities for Thin Film Li‐Ion Batteries

Nanostructured V 2 O 5 thin films have been prepared by means of cathodic deposition from an aqueous solution made from V 2 O 5 and H 2 O 2 directly on fluorine‐doped tin oxide coated (FTO) glasses followed by annealing at 500°C in air, and studied as film electrodes for lithium ion batteries. XPS results show that the as‐deposited films contained 15% V 4+ , however after annealing all the vanadium is oxidized to V 5+ . The crystallinity, surface morphology, and microstructures of the films have been investigated by means of XRD, SEM, and AFM. The V 2 O 5 thin film electrodes show excellent electrochemical properties as cathodes for lithium ion intercalation: a high initial discharge capacity of 402 mA h g −1 and 240 mA h g −1 is retained after over 200 cycles with a discharging rate of 200 mA g −1 (1.3 C). The specific energy density is calculated as 900 W h kg −1 for the 1 st cycle and 723 W h kg −1 for the 180 th cycle when the films are tested at 200 mA g −1 (1.3 C). When discharge/charge is carried out at a high current density of 10.5 A g −1 (70 C), the thin film electrodes retain a good discharge capacity of 120 mA h g −1 , and the specific power density is over 28 kW kg −1 .