Rate capability of carbon-free lithium titanium oxide electrodes related to formation of electronic conduction paths observed by color change

Abstract

Lithium titanium oxide prepared by the hydrogen reduction synthesis of Li[Li1/3Ti5/3]O4 (LTO) exhibits electronic conductivity. The product demonstrated a superior rate capability than pristine LTO upon the examination of a pellet electrode in the absence of conductive additives. The rate capability of the pristine LTO pellet electrode is poor during the oxidation reaction due to low electronic conductivity of the electrode originated from insufficiently developed electronic conduction paths. In contrast, the rate capability during the reduction reaction is improved due to the formation of electronic conduction paths resulting from transformation to the electronic conductor LTO during the reduction process. Visual inspection indicated that the formation and loss of electronic conduction paths in the electrode are key to determining the rate capability of the LTO pellet electrode in the absence of a conductive additive. Our results confirmed that this LTO exhibiting an electronic conductivity maintains an electronic conduction path in the pellet electrode in the absence of a conductive additive during the redox reaction, thereby resulting in an improved rate capability in both the oxidation and reduction reactions.