Quantifying Localized Lithium Plating Onset via Differential Voltage Tracking
Differential voltage tracking identifies localized lithium plating onset by detecting subtle slope shifts during charge and characteristic dV/dt relaxation plateaus.
Mixed Potential Relaxation
Meaning
Dynamic equilibration of unequal local surface potentials across an electrode following current interruption reflects the simultaneous occurrence of multiple electrochemical processes across different particle locations. Mixed potential relaxation captures the process whereby transient surface-plated metallic lithium chemically dissolves and intercalates into adjacent under-lithiated graphite particles during cell rest periods. The diagnostic application ceases once the electrode reaches uniform internal chemical equilibrium and local potential gradients drop to zero.
Equilibration Physics
Aggressive charging creates pronounced potential non-uniformities across the thickness of porous electrodes, leaving outer particle surfaces heavily polarized while core regions remain under-utilized. If metallic lithium plates during charging, the electrode establishes a mixed potential governed by the reversible metallic lithium potential and the local graphite intercalation potential. During subsequent rest, a spontaneous local corrosion-like cell develops, where metallic lithium oxidizes and transfers electrons to the graphite matrix, allowing lithium ions to insert into vacant host sites.
Relaxation Observation
High-precision open-circuit voltage tracking records this chemical reintercalation as a characteristic extended voltage plateau during the initial minutes of rest. The duration and shape of the plateau reflect the quantity of reversible plated lithium and the kinetic ease of chemical reintercalation. Once all accessible metallic lithium intercalates, cell voltage transitions toward the true thermodynamic equilibrium of the graphite host.
Quality Standard
Battery module assemblers use mixed potential relaxation signatures during end-of-line quality screening to verify cell safety after fast-charging formation protocols. Cells that exhibit extended relaxation plateaus contain elevated levels of surface plating, signaling inadequate electrode balance or poor electrolyte wetting. Purchasing contracts specify strict thresholds for permissible relaxation durations to prevent deploying cells prone to rapid capacity loss.
Differential Capacity Voltage Relaxation Analysis for Detecting Low Temperature Plating
Differential capacity voltage relaxation analysis detects sub-zero lithium plating by identifying chemical re-intercalation peaks during post-charge rest.