Cyclic Stability of Electrochemically Embedded Nanobeam V2O5 in Polypyrrole Films for Li Battery Cathodes

Abstract

By utilizing a hydrothermal method, V2O5 crystalline powder of nanosized beam shape-termed nanobeam V2O5-was synthesized from a V2O5 xerogel. Then, using an electrochemical polymerization method, a composite film of nanobeam V2O5 embedded in a conductive polypyrrole-termed electrochemically embedded V2O5/polypyrrole (ee-V2O5/PPy)-was grown on anodes from an electrolyte solution containing pyrrole and dispersed nanobeam V2O5. Due to the oxidative catalytic action of V2O5 for the polymerization of pyrrole, a thorough polypyrrole coating simultaneously grew on all the nanobeam V2O5 particles. Both electrochemically and catalytically polymerized polypyrrole can embed and connect the isolated nanobeam V2O5 particles, providing mechanical flexibility during the expanding/shrinking cycles of discharge/charge. The cathode film with 2.6 mg loading of ee-V2O5/PPy had a specific capacity of 294 mAh g(-1) at 0.1 C, which is 99.6% of the theoretical capacity for 2 equiv. of Li intercalation, and had a specific capacity of 195 mAh g(-1) at 5 C. With 6.4 mg of loading, the system revealed superior cyclic stability, with a degradation rate of 2.1% and a specific capacity of 176 mAh g(-1), after 40 battery cycles at the rate of 1 C. The ee-V2O5/PPy cathode performed excellently in terms of both cyclic stability and specific capacity. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3523315] All rights reserved.