Incremental Capacity Analysis

Incremental Capacity Analysis (ICA) is a non-destructive/damaging method used to investigate the state of health. It is based on the differentiation of the battery capacity over the battery voltage. Can be used for a full or a partial cycle. Frequently used alongside Differential Voltage Analysis (DVA) for estimating State of Health (SOH). Note ICA is the inverse of DVA.

Definition:

  • rate of change of charge with voltage (dQ/dV)
  • peaks correspond to phase transitions / equilibria (intercalation)
  • used to study cell electrochemistry changes over lifetime

Sensitivity and limitations:

  • requires low C-rates (C/24) for accuracy
    • higher C-rate result in peak shift, broadening, magnitude reduction and loss of peaks
  • data differentiation amplifies noise, hence need for filtering / smoothing
  • strict monotonicity required in differential techniques
  • application to multicell configurations is complex due to heterogeneity / noise

Krupp et al [1] give an overview of the technique:

(a) Charge and discharge voltage curve versus state of charge (b) incremental capacity (IC) curve versus cell voltage for a fresh lithium iron phosphate (LFP) cell cycled at C/20 and 25 °C.

Influence of loss of lithium inventory (LLI) (a), resistance increase (RI) (b), loss of active material at anode (LAMNE) (c), and loss of active material at cathode (LAMPE) (d) on the charge IC peaks of a typical LFP cell.

References

  1. Krupp, A.; Ferg, E.; Schuldt, F.; Derendorf, K.; Agert, C. Incremental Capacity Analysis as a State of Health Estimation Method for Lithium-Ion Battery Modules with Series-Connected Cells. Batteries 2021, 7, 2

See also: Cell Measurement Techniques