Research on Electrochemical Properties and Fade Mechanisms of Li-rich Cathode Materials at Low-temperature

In recent years, Li-rich layered cathode materials have caught more and more attention; however, their low-temperature performance have hardly been researched and reported. In this work, typical layered Li-rich oxides (0.55Li 2 MnO 3 ·0.45LiNi 1/3 Co 1/3 Mn 1/3 O 2 ) are successfully synthesized by co-precipitation method. And their electrochemical properties have been investigated emphatically at 25   °C and 0   °C. Results show that the reversible capacity of as-prepared Li-rich oxides exhibit much dependence on temperature from ∼230 mAh·g −1 (25   °C), ∼160   mAh·g −1 (10   °C), ∼70   m   mAh·g −1 (0   °C) to ∼50   mAh·g −1 (−5   °C). Our analyses indicate that there are several factors responsible for the capacity loss at low temperature: (1) the deactivation of Li 2 MnO 3 component; (2) the limited kinetic of Li + intercalation into MnO 2 ; (3) the increase of electrochemical impendences, especially the charge-transfer resistance ( R ct ); (4) the decrease of Li ion diffusion coefficient ( D Li+ ). And we find that pre-activation at room temperature is a quite effective way to improve its electrochemical performances at low temperature. In addition to the above four factors, for the first time, we suggest that the lattice contraction with decreasing temperature should also be considered.