Meaning
Relative capacity shifts quantify the progressive misalignment between positive and negative electrode operating windows caused by unequal parasitic side reactions. Battery degradation analysis relies on state of charge slippage to explain full cell capacity loss that occurs independent of active material degradation. The metric measures relative endpoint shifts on voltage capacity curves, applying to full cells while excluding single electrode half cell measurements where infinite lithium reservoirs exist.
Thermodynamic Shift
Solid electrolyte interphase growth continuously consumes active lithium at the anode during charge cycles. When positive and negative electrode voltage curves shift relative to one another, state of charge slippage alters the voltage boundaries where cell cutoff limits are reached.
Diagnostic Detection
Differential capacity analysis identifies peak shifts across voltage profiles over extended cycling history. Asymmetric side reactions cause the anode potential curve to drift relative to the cathode balance. By comparing full cell voltage features against reference half cell profiles, state of charge slippage reveals whether capacity loss stems from lithium inventory depletion or electrode breakdown.
Higher operational temperatures accelerate this drift mechanism by speeding up parasitic electrolyte oxidation.
Capacity Retention
Rebalancing cell stoichiometry through secondary formation steps can offset temporary alignment losses. Uncorrected electrode drift leads to premature cell voltage cutoff during normal operation.
