Performance of quasi-solid-state silicon-based lithium-ion batteries under different operating external pressure

Silicon-based anodes are the core materials for enhancing the energy density of lithium-ion batteries, but their volume expansion during lithiation easily results in performance degradation, which limits practical application. This work intends to clarify the regulation mechanism of external pressure on the electrochemical performance, long-cycle stability, and stress characteristics of quasi-solid-state silicon-based lithium-ion pouch batteries, as well as specifically address the key issue of battery performance degradation induced by the volume expansion of silicon-based anodes. The 10 Ah silicon-based quasi-solid-state pouch cells are tested, combining electrochemical tests and characterization, the influence of external pressure and its internal mechanism are systematically explored. The results suggest that appropriately increasing the external pressure can effectively optimize the internal interface contact of the battery, reduce the ohmic impedance and charge transfer impedance, and significantly improve the charge-discharge performance and energy efficiency. There is an optimal regulation range for the external pressure, and the initial external pressure of 300–400 kgf is correlated with the best balance between the charge-discharge performance and long-cycle stability. When the external pressure exceeds this range (e.g., 800 kgf), it leads to anode cracking and an unstable solid electrolyte interphase film structure, thereby accelerating performance degradation. The quasi-solid electrolyte exhibits excellent stress-buffering capability, which can effectively suppress electrode expansion and limit the peak-to-valley difference. Especially under the pressure of 50 kgf, the maximum stress difference is 50 kgf, which is much lower than that of batteries with liquid electrolyte. The obtained mechanical expansion characteristics and pressure optimization rules are highly consistent with practical manufacturing scenarios, and these findings can provide direct engineering guidance for the large-scale assembly and industrialization of quasi-solid batteries.