Impact of Maturation on Si-Based Negative Electrodes for LIBs: Contributions of Binder Migration and Cu Corrosion

Abstract The maturation treatment, which involves exposing the composite electrode to high-humidity environment after casting slurry onto Al/Cu foil, has been reported to improve the charge-discharge performance of Si-based anodes that undergo significant volume changes during lithiation cycling. The precise mechanisms underlying this enhancement are not yet fully understood. Historically, two primary mechanisms have been proposed for the maturation process: (1) binder migration, which improves the uniformity and strength of the composite electrode, and (2) the dissolution of Cu2+ from the Cu current collector in the presence of an acidic binder, leading to cross-linking within the binder that reinforces the electrode. However, the dominance of these mechanisms remains unresolved. In this study, we investigated the contributions of these factors by applying maturation treatments to electrodes both with and without ball milling and employing polyacrylate-based binders of varying neutralization degrees. Maturation treatment significantly enhanced reversible capacity and capacity retention in electrodes without ball milling. Even in electrodes that underwent ball milling to obtain uniformity, a partial improvement was observed using polyacrylate binders of appropriate acidity, while non-acidic binders did not improve the cyclability. These results indicate that both mechanisms contribute significantly and that maturation treatment is beneficial even in well-dispersed electrodes.