Stabilization of silicon-graphite blended anode performance using self-healing binders

Sharp capacity decay during the first cycles due to the huge expansion of silicon particles (ΔV > 300 %) is the main problem for the commercialization of silicon-based anodes. Although the combination of silicon with graphite is a good solution to minimize the pulverization effect, better integrity should be provided by using effective binder systems for a longer lifetime. Recently, self-healing binders have been studied to obtain breathing electrodes to alleviate expansion-shrinkage during cycling. In this study, we proposed newly synthesized binders to stabilize the structure and improve the capacity decay performance. Biopolymers were chemically modified to create additional functional groups providing good adhesion, ionic conductivity and promoting self-healing properties based on different mechanisms. Binders were characterized by mechanical testing, electrolyte uptake test, and FTIR analysis. Anode slurries were prepared in deionized water by addition of silicon-graphite powders (20:80 wt%) as active material, synthesized binders, and carbon as a conductive agent. Galvanostatic charge-discharge tests were carried out between 0.01-1.5 V vs. Li/Li+ potential window at different current densities from 0.1 to 2 C-rate. Cycling voltammetry was performed at 0.1 mV/s. It was found that the synthesized binders have better capacity decay performance compared to commonly used CMC/SBR binders, particularly at lower C-rates which mostly depend on charge transfer resistance because of electrical contact loss.

Acknowledgments:
The work was supported by APVV-19-0461 and VEGA 2/0167/22 grants.