Asymmetric Swelling Behaviors of High‐Energy‐Density Lithium‐Ion Batteries with a SiO_x/Graphite Composite Anode

Abstract The battery swelling originated from the electrode swelling is a big obstacle for the practical application of high‐energy‐density lithium‐ion batteries (HED‐LIBs). Herein, the HED‐LIBs are constructed by SiO_x/graphite composite anode and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode and their swelling behaviors are investigated at the cell, electrode, and particle scales. there are three expansion stages during the charging while one expansion followed by two contraction stages during the discharging process. The expansion ratio is in direct proportion to the ratio of SiO_x content and about 10 times larger than that of the cathode. A 100 nm thick double‐layer solid electrolyte interface, comprises LiF, Li₂O, and Li₂CO₃, forms on the surface of the SiO_x particles, and evolves into a 300 nm thick triple‐layer after cycling. The performance degradation of HED‐LIBs is associated with the expansion of anodes, increase in resistance, and consumption of Li in the anodes during cycling. This study is expected to guide the future selection and design of HED‐LIBs and battery packs.