Defects in Li4Ti5O12 induced by carbon deposition: An analysis of unidentified bands in Raman spectra

Lithium titanate (Li4Ti5O12, LTO) has already occupied its niche as anode material for high-power and long-lifespan lithium batteries, but some novel directions for basic and applied research are still open. One of the most promising approaches in improving its properties, e.g., electronic conductivity and rate capability, is based on the controllable defect engineering. The “defects” may be intentionally introduced in LTO via doping, surface modifications, and the synergy between them. However, the defects, sensitive to the electrical and electrochemical properties, are usually extremely dilute. Reliable materials characterizations are essential and challenging, but the instrumental tools for revealing dilute defects are still insufficient. Herein, detailed analyses upon the surface or subsurface defects of carbon-coated LTO were performed using various materials characterization methods. Raman spectroscopy has been identified as a unique tool for the structural defects probing.