Mesoporous lithium vanadium oxide as a thin film electrode for lithium-ion batteries: comparison between direct synthesis of LiV2O5 and electrochemical lithium intercalation in V2O5

Abstract

Research in the field of lithium-ion batteries favours electrode materials with high surface area. In this context, this paper is dedicated to mesoporous thin films (MTFs) and compares the electrochemical performance of γ-LiV₂O₅ MTFs with post-synthesis electrochemical lithium intercalation in α-V₂O₅ MTFs. Formation of vanadium oxide MTFs by soft-chemistry is notoriously difficult. However, it is shown that wormlike vanadium oxide (V–O) and lithium vanadium oxide (Li–V–O) MTFs can be obtained on silicon substrates by a direct sol–gel soft-templating route (evaporation-induced micelle assembly) using a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) structuring agent. Heat treatment for 1 minute at 400 °C (Li–V–O system) or 30 minutes at 350 °C (V–O system) leads to the crystallization of γ-LiV₂O₅ or α-V₂O₅, respectively. These calcination conditions ensure the degradation of the structuring agent while preventing the collapse of the mesostructure, yielding MTFs with pore size diameter in the 30–35 nm range. Using the same set of synthesis conditions, films can be deposited on conductive glass substrates for electrochemical investigation: the α-V₂O₅ films display better specific capacities, while the cyclability is good for both compositions, even at a current density as high as 30 C-rate.