Nanoscale Morphological Characterization of Coordinated Binder and Solid Electrolyte Interphase in Silicon-Based...

The physical crosslinking of polymeric binders through coordination chemistry significantly improves the electrochemical performance of silicon-based negative electrodes. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy is used to probe the nanoscale morphology of such electrodes. This technique reveals the homogeneous coordination of carboxylated binder with Zn cations and its layering on the silicon surface. The solid electrolyte interphase (SEI) formed after the first cycle is denser with Zn-coordinated binder and preferentially observed on binder-depleted zones. The superiority of coordinated binders can be attributed to their capacity to better stabilize the electrode and the SEI layer due to improved mechanical properties. This results in a lower SEI impedance, a higher first cycle coulombic efficiency, and a 40% improvement of capacity retention after 50 cycles for highly loaded electrodes of over 6 mAh cm^-2 .