Effect of operation voltage on the practical performance of high-energy-density LiCoO2/artificial graphite pouch cells at various temperatures

To achieve wide applications of LiCoO2-based high-voltage lithium-ion batteries, three questions remain to be answered: how to stabilize the cathode/electrolyte interphase upon cycling, what is the practical performance at the pouch cell level and various temperatures, and why the charge cutoff voltage is limited at 4.4 V. Thus, an ~3 Ah LiCoO2/artificial graphite pouch cell has been developed, whose performances at different temperatures and voltages have been studied. It is observed that the cell at 4.5 V exhibits ultrahigh area capacity and energy-density, good discharge abilities at high rates and at − 20 °C, and high cyclic stability. Investigation reveals that the bulk structure and interface of LiCoO2 are stabilized by using LiCoO2, which is composed of monocrystalline and polycrystalline powders, and a combination of multiple electrolyte additives. We also find that the real barriers for a commercial application are the inferior high-rate charge ability due to the aggravated electrochemical polarization and poor storage stability at 60 °C caused by the side reactions. Undoubtedly, this work will deepen the understanding of the overall performance of LiCoO2-based high-energy-density pouch cells and direct further optimization of LiCoO2.