Electrochemical oscillation during galvanostatic charging and discharging of Zr-modified Li4Ti5O12 in Li-ion batteries

Abstract

The electrochemical oscillation in Li-ion batteries has been reported for two-phase electrode materials of Li₄Ti₅O₁₂ and LiCrTiO₄, which is originated from the group-by-group phase transition in a multi-particle electrode. For both Li₄Ti₅O₁₂ and LiCrTiO₄, the electrochemical oscillation exhibits usually during charging, while rarely for discharging. Herein, a series of Zr-modified Li₄Ti₅O₁₂ 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 Li₄Ti₅O₁₂, the specific capacity of Zr-modified Li₄Ti₅O₁₂ 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 ZrO₂ nanoparticles, rather than dope into the bulk phase of Li₄Ti₅O₁₂, which makes Li₄Ti₅O₁₂ 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 Li₂TiO₃ phase will suppress the electrochemical oscillation. Therefore, the Li excess can induce the electrochemical oscillation during both charging and discharging of Zr-modified Li₄Ti₅O₁₂, which can be adopted to investigate the electrochemical oscillation of other materials in LIBs.