Influence of working temperature on the electrochemical characteristics of Al2O3-coated LiNi0.8Co0.1Mn0.1O2 cathode materials for Li-ion batteries

Abstract

The influence of working temperature on the electrochemical performance of commercial Al2O3-coated Li[Ni0.8Co0.1Mn0.1]O2 cathode material is investigated. This cathode material is characterized using XRD, SEM, TEM, EDS, XPS, and ICP-AES. The electrochemical degradation mechanism is determined using electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The results indicate that the minimum aging rate of cycled cells is 0.12 at 25 °C, and the rate performance enhances with increasing operating temperature. Three kinds of different equivalent circuits could be adopted to explain the EIS spectra at low temperature, room temperature, and elevated temperature. The charge-transfer resistance (Rct) of the cell at the 10th cycle drops from 684.6 Ω to 95.1 Ω when the temperature rises from −15 °C to 25 °C. Especially at elevated temperatures (45 °C and 55 °C), the Rct value of the 10th and 50th cycles decreases remarkably, which is attributed to that the side reaction between Li[Ni0.8Co0.1Mn0.1]O2 material and electrolyte is inhibited by Al2O3 coating layer. The performance degradation of Al2O3-modified Li[Ni0.8Co0.1Mn0.1]O2 at low temperature and elevated temperature is due to the sharp increase of Rct and the consumption of active lithium in the decomposition reaction of electrolyte, respectively. It is concluded that the optimum operating temperature of the battery with the Al2O3-coated Li[Ni0.8Co0.1Mn0.1]O2 cathode material is 15–35 °C.