Electrochemical oscillation during galvanostatic charging and discharging of Zr-modified Li 4 Ti 5 O 12 in Li-ion batteries.

The electrochemical oscillation in Li-ion batteries has been reported for two-phase electrode materials of Li 4 Ti 5 O 12 and LiCrTiO 4 , which is originated from the group-by-group phase transition in a multi-particle electrode. For both Li 4 Ti 5 O 12 and LiCrTiO 4 , the electrochemical oscillation exhibits usually during charging, while rarely for discharging. Herein, a series of Zr-modified Li 4 Ti 5 O 12 samples are prepared by using the spray-drying combined with high-temperature sintering method, and the electrochemical oscillation is observed during not only the charging process, but also the discharging process, which gradually grows up and then disappears by increasing the Li content. Compared with Li 4 Ti 5 O 12 , the specific capacity of Zr-modified Li 4 Ti 5 O 12 decreases gradually by increasing the Zr/Ti ratio, owing to the impurity phases. According to the XRD, XPS and STEM results, the Zr element tends to accumulate on the surface to form ZrO 2 nanoparticles, rather than dope into the bulk phase of Li 4 Ti 5 O 12 , which makes Li 4 Ti 5 O 12 particles well dispersive. In contrast to the Li deficiency for only charging, the electrochemical oscillation during both charging and discharging should be attributed to the Li excess, but too much Li 2 TiO 3 phase will suppress the electrochemical oscillation. Therefore, the Li excess can induce the electrochemical oscillation during both charging and discharging of Zr-modified Li 4 Ti 5 O 12 , which can be adopted to investigate the electrochemical oscillation of other materials in LIBs.