Novel Flowerlike Metastable Vanadium Dioxide (B) Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries

Abstract

Novel flowerlike VO2 (B) micro-nanostructures assembled by single-crystalline nanosheets have been successfully synthesized via a hydrothermal route using polymer polyvinyl pyrrolidone (PVP, K30) as capping reagent. Detailed proofs indicated that the process of crystal growth was dominated by a nucleation and growth, self-assembly, and then Ostwald ripening growth mechanism. For the first time, the flowerlike micro-nanostructures VO2 (B) was applied as the active material into aqueous lithium ion battery applications, which showed improved electrochemical properties with the first discharge capacity reaching 74.9 mAhg−1, a quite outstanding value for aqueous lithium ion battery systems in light of previous reports (usually <65 mAhg−1). In addition, corresponding VO2 (B) nanostructures with better crystallinity were obtained by calcining the precursor of flowerlike VO2 (B) structures. The post-treated flowerlike VO2 (B) electrode shows fascinating advantages in electrochemical properties with the first discharge capacity reaching 81.3 mAhg−1, which is higher than that of the flowerlike VO2 (B) sample before annealing. Furthermore, we have investigated the electrochemical intercalation and deintercalation properties with Li+ the synthesized VO2 (B) nanobelts and carambola-like VO2 (B) structure. The unique flowerlike structure plays a basic role in the morphology requirement to serve as transport paths for lithium ion in aqueous lithium ion batteries. It was observed that the morphologies and crystallinity of the synthesized products had an evident influence on the electrochemical intercalation and deintercalation properties with lithium ions.