(3-Aminopropyl)triethoxysilane as an Electrolyte Additive for Enhancing the Thermal Stability of Silicon Anode in Lithium-Ion Batteries

Silicon (Si), which can give a high capacity, is a potential next-generation anode material for lithium-ion batteries (LIBs), though there is a growing concern over the safety of Si-based batteries with higher energy density, where the reaction between the electrolytes and the charged electrodes can cause thermal issues. In our study, we developed an electrolyte additive which effectively improves the thermal stability of Si electrodes. Specifically, addition of 5 wt % (3-aminopropyl)triethoxysilane (APTES) into a commercial carbonate-based electrolyte reduces the heat generation from the Si electrode significantly while not affecting its charge and discharge capacities. NMR and X-ray photoelectron spectroscopy characterizations suggest that APTES serves as a PF₅/HF scavenger, stabilizing the electrolyte and suppressing its decomposition at a high temperature. At the same time, moisture in the electrolyte triggers the polymerization of APTES, forming a protective network covering the electrodes. Moreover, APTES improves thermal stability of the electrode by forming a SiO₂-rich solid-electrolyte interphase on the surface of the Si particles. The knowledge of the decomposition mechanism between the electrolyte and electrode from this study allows us to design stable electrolyte systems for battery applications in the future.