Mechanisms of the decrease in low-temperature electrochemical performance of LiTiO-based anode materials.

The electrochemical performances of LiTiO (LTO) and LiTiO-rutile TiO (LTO-RTO) composite electrodes at low temperatures were evaluated. The electrochemical performance of both electrodes decreased at low temperatures; regardless, the LTO-RTO electrode performed better than the LTO electrode. First, high viscosity and low ion conductivity of liquid electrolytes at low temperatures significantly reduce electrochemical performance. Second, cycling at low temperatures changes the crystal structure of LTO-based electrodes, impeding lithium ion diffusion and even causing the diffusion path to change from easy to difficult. However, changes in the crystal structure of the LTO-RTO electrode were not sufficient to change this path; thus, diffusion continued along the 8a-16c-8a pathway. Finally, from the perspective of dynamics, aggravation of a side reaction, increase in charge transfer resistance and polarization, and decrease in lithium ion diffusion at low temperatures reduce the electrochemical performance of LTO-based anode materials. However, the activation energy based on lithium ion diffusion is lower in the LTO-RTO electrode than the LTO electrode. The results confirmed that the electrochemical performance of the LTO-RTO electrode was better than that of the LTO electrode at low temperatures.