The Response of Fast Discharge and Charge Rates of Electrodeposited V2O5 Inverse Opal Networks in Lithium Batteries
Authors: O'Hanlon Sally , McNulty David , O'Dwyer Colm 
Published: December 2020

Cathode materials in Li-ion batteries, especially oxides, are still under intense investigation as electric vehicle and other demanding application require longer cycle life and higher energy density. V2O5 is an important cathode material for Li ion batteries enabling a stable reaction with lithium through a series of phase changes that are Coulombically efficient and reversible. V2O5 can be improved by modifying the physical structure as well as its crystalline structure or stoichiometry. These modifications include macroporous, interconnected networks or the oxide that enhanced stability and mitigate capacity fading under some conditions, as in context we show our recent development with 3DOM battery materials as a comparison to the data presented in this paper. Such improvements are investigated in this work through the development of a unique inverse opal ordered 3D macroporous of V2O5 by electrodeposition. We show the electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of the colloid self-assembled photonic crystal template. Structurally stable electrodeposited vanadium pentoxide inverse opal networks on FTO-coated glass are electrochemically tested as a function of C-Rate, i.e. the inverse of the time (in hours) it takes for the electrode fully discharges or charges (1C = 1/n hours). By selectively controlling whether the inverse opal network is open-worked or overfilled is also of focus in the galvanostatic cycling investigation. Electrochemical analysis shows lithium phase shifts with increasing C-rate in both open and overfilled network cases, which affect specific capacity retention in the electrode. Raman scattering and X-ray diffraction is used to investigate the change in each electrode as a function of C-rate, along with electron microscopy analysis to investigate the effect of C-rate on the structural changes to theV2O5 inverse opal network. Using chronoamperometry, we also show that the nature of the limited response in ordered porous cathodes materials at high rates is governed almost entirely by electronic conductivity, even with advantageous electrolyte access to the material surface.

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