Competitive adsorption within electrode slurries and impact on cell fabrication and performance

Abstract

Why do battery researchers use 10–20 wt% binder in research cells when commercial chemistries use much less? This report seeks to explore this question by understanding the ordering and structure of polyimide binder with a silicon/pitch-carbon black electrode system. Correlating the effect of binder concentration on electrode architecture and electrochemical properties is vital to enhancing silicon anode cycle and calendar life. Using ultra-small angle neutron scattering (USANS) and binder adsorption isotherms an optimal region of polyimide (PI) binder coverage was found. Further, there is a preferential adsorption of PI to carbon black that has to be completed before PI binds to the silicon. Optimizing the concentration of binder leads to a 50% increase in capacity due to the optimization of binder-silicon-carbon interactions. • First direct measurement of polyimide binder adsorption in slurry • Polyimide binder selectively adsorbs to carbon black over silicon • Need to optimize binder ratio with each material to evaluate cell performance • Polyimide acts as a dispersant during slurry fabrication