Desolvation Kinetics Governs Propylene Carbonate Co-Intercalation in Graphite Anodes

The long-standing ethylene carbonate-propylene carbonate (EC-PC) disparity in graphite anodes exemplifies a broader challenge: whether solvated ions can be stripped efficiently enough to avoid solvent-assisted insertion. Here, through systematic screening of commercial graphites, PC-based electrolytes, and polymer binders, we show that solvent co-intercalation in graphite is a system-level kinetic outcome arising from competition between conventional Li⁺ intercalation and solvent-assisted insertion under galvanostatic polarization. We introduce the "lowest achievable potential" (P_LA), a semi-quantitative operational descriptor of how far a graphite-electrolyte system can be polarized before PC co-intercalation becomes dominant under defined testing conditions. Through integrated experimental and computational analysis, we show that the observed electrolyte-dependent P_LA trends arise from coupled changes in Li⁺ solvation and interphasial chemistry. Temperature-switching and electrolyte-exchange experiments indicate that neither bulk solvation nor the preformed interphase alone determines graphite stability. Instead, their relative contributions depend on the electrolyte formulation and operating conditions. Graphite surface disorder, carbon coatings, and binder chemistry provide additional electrode-side regulation. These findings establish a unified kinetic framework linking bulk solvation, interfacial regulation, and operating conditions to destructive PC co-intercalation.