Local electrochemical signatures and SEI formation pathways in silicon-graphite composite negative electrodes

Résumé fourni par la source

The spatial heterogeneity of composite electrodes is a key factor governing their electrochemical performance and stability, yet local electrochemical behavior is difficult to resolve using conventional bulk techniques. This challenge is particularly critical in lithium-ion batteries, especially for composite negative electrodes, where complex distributions of active materials lead to poorly understood interfacial processes such as solid electrolyte interphase (SEI) formation. Here, we employ scanning electrochemical cell microscopy (SECCM) to visualize nanoscale electrochemical activity in silicon-graphite composite electrodes. Localized cyclic voltammetry (CV) enables high-resolution mapping of electrochemical responses, allowing clear classification of graphite-dominant, silicon-dominant, and mixed domains within a single electrode. Furthermore, we demonstrate that SEI formation strongly depends on the local composition. Silicon-rich regions exhibit pronounced irreversible reactions associated with alloying, whereas graphite-dominant regions show more stable behavior. Mixed domains display intermediate characteristics, suggesting their role in mediating interfacial processes. These findings provide direct insight into spatially heterogeneous electrochemical behavior and offer new guidelines for the design of high-performance composite electrodes.

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