Influence of atmospheric pressure on the aging mechanism of LiCoO2/graphite cells

With the application of lithium-ion battery (LIB) in the field of electric aircraft, the aging behavior and mechanism of LIB under low-pressure environment have become an important topic. In this paper, the aging characteristics of LiCoO2/graphite cells under low pressure are investigated. The results show that the decrease of pressure leads to the degradation of cell capacity. With the pressure decreases from 96 kPa to 30 kPa, the capacity loss rate of the cell increases from 0.5% to 17.4%. Coulomb efficiency and differential voltage analysis indicate that low pressure accelerates the loss of lithium inventory. The X-ray computed tomography shows that the cell cycled under low pressure exhibits more significant deformation. The disassembly photos demonstrate that the side reactions of the cell are more obvious under low pressure. The scanning electron microscopy and elemental analysis results confirm that the thickness of solid electrolyte interface film increases with the decrease of pressure. These phenomena indicate that the intensification of battery deformation and internal side reactions under low pressure leads to a decrease in the electrochemical kinetics and long-term cycling ability of the battery.