Interfacial excess charge dynamics as a quantitative descriptor for deciphering lithium dendrite growth

Tracing the origins of Li dendrite growth remains a critical challenge for lithium metal batteries. Existing studies have focused on the mismatch between diffusion and reaction kinetics or on isolated electrode excess charge, overlooking the coupled interfacial processes at nanoscale solid-liquid interface that collectively govern dendrite growth. Herein, we introduce a unified descriptor, the interfacial excess charge distribution factor, to capture the dynamic equilibrium at electrode/electrolyte interface by quantitatively integrating the contributions of electrode excess charge, charge depletion rate and solvation chemistries. We further propose an electrochemical method to monitor Li dendrite growth rates, confirming that electrolytes with rapid excess charge redistribution ability favor planar Li plating. Our findings reveal that, the depletion rate of interfacial excess charge determined by Li⁺-dipole-anion interactions, and the degree of electrode excess charge modulated by solvation structures and cation screening, competitively determine the interfacial excess charge dynamics and Li dendrite growth. Leveraging these insights, we designed an electrolyte with rapid excess charge redistribution ability, which markedly suppressed dendrite formation and achieved superior cycling performance in ~ 6.4 Ah lithium metal batteries. This quantitative framework offers the way for deciphering complex interfacial electroplating and holds promise for other metal-based batteries (e.g., Na, K, Zn, Mg).