Design of a Sodium-ion Cell with a Carbon-free Li₄Ti₅O₁₂ Negative Electrode

Abstract

In order to design a safe and practical Na-ion cell, the electrochemical properties of a conduction additive-free Li₄Ti₅O₁₂ (LTO) electrode were investigated. The charge-discharge properties of LTO electrodes with/without conductive carbon additives are similar to each other in half-cell experiments, while the irreversible capacity fading of the carbon-free electrode is much smaller than that of the carbon-added electrode. A full cell consisting of α-NaFeO₂ and carbon-free LTO electrodes shows a capacity of more than 90 mAh g⁻¹ after 50 cycles without Na-metal deposition. The current density capabilities of both electrodes are comparable, indicating that the rate-determining process of the charge-discharge reaction is the ionic conduction of Na⁺ in the Li₄Ti₅O₁₂ crystal, not electronic conduction.