Diagnostic Identification of Reversible Lithium Stripping Kinetics under Cold Operation
Reversible lithium stripping under cold operation requires voltage relaxation or dQ/dV diagnostic tracking to adjust BMS derating and protect cycle life.
Mixed Potential
Meaning
Steady-state electric potential established at an electrode surface where multiple distinct electrochemical reactions exchange charge simultaneously at equal and opposite net rates. Corrosion processes and self-discharge mechanisms in battery cells shift measured open-circuit voltages away from thermodynamic equilibrium potentials. At this steady state, mixed potential reflects the balance between localized anodic oxidation and cathodic reduction currents, terminating where one dominant electrochemical reaction eliminates competing charge transfer pathways.
Electrodynamic Equilibrium
Polarized interfaces where oxidation and reduction reactions occur on the same conductor do not follow simple Nernstian equilibrium equations. Butler-Volmer kinetics describe how individual partial current densities vary with electrode potential until total anodic current balances total cathodic current. When evaluating mixed potential, researchers plot Evans diagrams to identify the intersection of partial polarization curves representing simultaneous oxidation and reduction reactions.
Corrosion Kinetics
Impurity species in battery electrolytes induce localized parasitic reactions that degrade active materials over long storage periods. Transition metal dissolution at the cathode creates parasitic micro-galvanic couples on graphite anodes. Quantifying mixed potential identifies self-discharge rates and structural degradation without requiring destructive cell disassembly.
Measurement Threshold
Reference electrode placement and electrolyte conductivity directly influence the accuracy of measured surface potentials. Uncompensated ohmic resistance across thin liquid films masks local potential gradients at active sites. Calculating mixed potential yields kinetic rate data without separating individual species transfer coefficients.