Lithium-ion battery longevity is fundamentally limited by lithium plating during high-rate charging, a phenomenon that accelerates aging and compromises safety. Current detection methods are often either too slow for real-time application or require invasive instrumentation. This study presents a non-invasive, time-efficient methodology to detect the onset of lithium plating by isolating the charge transfer overpotential (V_ct) from the total surface overpotential (V_surf). By utilizing pulse-response analysis in the sqrt(t) domain, we effectively isolate surface contributions from diffusive effects. The methodology further refines the signal by removing the SEI overpotential (V_sei) through non-linear models to pinpoint the precise V_ct response.

Experimental results across both commercial 1.2 Ah cells and graphite half-cells reveal a distinct saturation region in the V_ct curve. This “Knee Signature” identifies a sharp transition to a saturation region, providing a clear visual threshold for lithium deposition. This saturation point defines the plating limiting current (I_lim), representing a kinetic boundary where intercalation reaches its maximum capacity. Beyond this I_lim, any incremental current initiates parasitic lithium plating.

We validated these findings by analyzing relaxation signatures; abnormal relaxation potential serves as a definitive physical confirmation that the identified currents triggered plating. By accurately spotting the plating onset current, this methodology enables a new class of physics-informed equivalent circuit models (ECMs) for battery management systems (BMS). This advancement allows for the optimization of fast-charging protocols and cell design by operating at the absolute limit of intercalation without crossing into the degradation zone.