A facile electrochemical modification route in molten salt for Ti3+ self-doped spinel lithium titanate

Ti3+ self-doped spinel Li4Ti5O12 (LTO) particles were synthesized through a facile electrochemical modification route in NaCl-KCl molten salt electrolysis, and the formation mechanism is explored. Alternating Ti3+ self-doping significantly improves the electrochemical performance of the spinel Li4Ti5O12 (LTO) particle, especially at high charge/discharge rates. According to the report, LTO, once introduced with oxygen vacancies or Ti3+, will decrease the band gap about to 1.54 eV, which can dramatically improve the inherent electronic conductivity. Through the molten salt electrochemical modification technique, the Ti3+ species will be doped onto the surface of LTO, which was confirmed through transmission electron microscopy with EPR (namely electron spin resonance) spectra, X-ray photoelectron spectroscopy, X-ray analysis. As anodes in lithium-ion batteries (LIBs), the spinel Li4Ti5O12 (LTO) particle electrode with self-doped Ti3+ can deliver stable discharge capacities of 168, 152, 131, 120, 102, 93 and 78 mAh g−1 at different rates of 0.5, 1, 5, 10, 15 and 20C, respectively. Meanwhile, like pure spinel LTO, they also carry strong cycling stability and demonstrate the capacity retention of 92.0%, though after 900 cycles under 5C. Our results indicate that pure-phase LTO is prepared by a molten salt method, and it is then electrochemically modified by a constant current to obtain conductive Ti3+. Self-doped spinel Li4Ti5O12 particles are a good alternative to facilitate the transfer of electrons, especially under high-rate conditions, because it shows good electronic and ionic conductivities. In addition, the molten salt synthesis and the electrochemical modification steps of this method are conducted in the same reactor with a simple process, strong operability and environmental friendly process.