Effect of Binder Content on Silicon Microparticle Anodes for Lithium-Ion Batteries

Formulation strongly influences the structure, properties, and electrochemical performance in composite electrodes. The role of polymeric binders is especially critical for electrodes containing high volume change active materials, such as silicon. In this study, we investigated the impact of polyimide binder in silicon microparticle electrodes. The impact of binder content on electrode adhesion to the current collector, cohesion, porosity, electrical resistivity, local electrical connectivity, and silicon utilization was characterized in pristine and cycled electrodes to elucidate the mechanisms driving the electrochemical performance during rate and cycle life tests of Si-NMC622 full cells. We observed that capacity retention improved with increasing binder content, but rate performance suffered with excess binder content, indicating that there is an optimal binder weight fraction to balance the trade-off between these two metrics. Our research reveals important design principles for the optimization of binder content in silicon electrode formulations and can be applied to the development of electrodes containing other active materials and conductive additives.