SoC dependent kinetic parameters of insertion electrodes from staircase — GITT

• A staircase galvanostatic intermittent titration technique is introduced.
• Ohmic resistance, exchange current and charge transfer coefficients are obtained.
• A significant SoC dependence of the kinetic parameters is revealed.
• Staircase (SC) — GITT is well suited to study insertion/extraction kinetics.

A staircase galvanostatic intermittent titration technique (SC-GITT) is introduced and exemplarily examined using the well-known half-cell reaction, LiCoO2 | Li. SC-GITT expands the common GITT and complements the number of accessible kinetic parameters by the ohmic resistance, the exchange current density and the charge transfer coefficient. In contrast to conventional GITT, the magnitude of the applied current is rapidly varied in a staircase like manner previously to the actual titration step. The overpotentials obtained within the staircase regime are fitted to a modified Butler–Volmer equation to determine the kinetic parameters. In the case of LiCoO2, the results reveal a significant lithium concentration dependence of the charge transfer kinetics and the ohmic resistance. The proposed experimental technique appears to be well suited for the investigation of electrochemical kinetics for all kinds of insertion electrodes.

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