Si/Graphite Anodes for Solid-State Batteries: Composition Selection via Electrochemical and Chemo-Mechanical Properties

Silicon-graphite composites are among the most widely used anode materials in conventional lithium-ion batteries and recently have been considered as promising candidates in lithium-ion solid-state batteries. In this work, we investigate the influence of the silicon content on the electrochemical and chemo-mechanical behaviors of different Si/graphite composites in solid-state batteries. All anode composites show that an increase of Si presence in the composite enhances the cyclability at a high current density. Using direct-current (DC) polarization and temperature-dependent electrochemical impedance spectroscopy, we observe that both electronic and ionic conductivities are sufficient across the composition series. Operando stress measurements demonstrate how the internal pressure of the anode in a solid-state battery changes as a function of the Si content. Less Si (e.g., ≤10 wt %) in the blended matrix offers smaller internal stress, while it is significantly increased at 20 wt % of Si. This study emphasizes the importance of optimizing the silicon/graphite ratio in the anode composites to balance high battery performance with stable chemo-mechanical properties.