Fabrication of spinel Li4−xTi5O12 via ion exchange for high-rate lithium-ion batteries

•The first report on stepwise substitution of lithium ions by proton to obtain Li1Ti5O12.•The Li1Ti5O12 electrode materials exhibit excellent electrochemical performance.•The spinel crystal structure is crucial for the performance of Li4−xTi5O12 anodes.

The present work demonstrates that lithium ions can be stepwise substituted by protons from spinel Li4Ti5O12 crystalline particles though simple ion-exchange in aqueous HCl solution with the aid of heat treatment. This enables us to continuously tune the Li-to-Ti stoichiometric ratios from 0.80 to 0.59, 0.41, 0.21, 0.15, and 0.09, thus transforming Li4Ti5O12 to Li4−xTi5O12 nanocrystals. The resulting nanocrystals maintain the spinel crystal structure when x becomes smaller than 3. Among as-prepared the Li4−xTi5O12 crystalline particles, Li1Ti5O12 shows the highest capacity of 193 mAh g−1 at 1C and 148 mAh g−1 at 20C, lower current impedance (47 Ω), significantly improved rate capability and fairly long cycle life. This excellent electrochemical performance makes spinel Li4−xTi5O12 particles as a promising anode candidate for lithium ion batteries superior.