Electrochemical Impedance Analysis of V2O5 and PEDOT Composite Film Cathodes

Abstract

Composite films of nanobeam V2O5 and poly-3,4-ethylenedioxythiophene (PEDOT) were grown using an electrochemical polymerization method. PEDOT in the composite film connects the isolated V2O5 nanobeams and gives rise to a conductive network, improved Li-ion accessibility and transport pathways in the electrode. The nanobeamV(2)O(5)/ PEDOT composite film cathodes have high capacities, excellent rate capabilities and cycling stabilities at various C rates: their specific capacities were 262 mAh g(-1) at 0.1 C, 239 mAh g(-1) at 1 C, 186 mAh g(-1) at 10 C, and 141 mAh g(-1) at 100 C. After testing the battery for more than 150 battery cycles at a rate of 10 C, the degradation rate was found to be approximately 9%. The diffusion coefficient of the nanobeam-V2O5 crystalline electrode was calculated to be approximately 4.6x10(-8); and those of alpha-, epsilon-, and delta-LixV2O5 crystalline phases, were estimated to be in the range of (2.1-9.8)x10(-10). Under the conditions of PEDOT coating and networking in the composite film, the diffusion coefficients of each phase of LixV2O5 that reversibly formed during the discharging and charging processes were able to be estimated.