Quantifying Interfacial Ion Transfer at Operating Potassium-Insertion Battery Electrodes within Highly Concentrated...

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Interfacial ion transfer is critical for battery electrode performance.
• Quantifying ion transfer, especially at high electrolyte concentrations, remains challenging.

Purpose of the Study:

• To develop a scanning electrochemical microscope (SEM) method for tracking alkali ion transfer.
• To measure ion concentration changes at high electrolyte concentrations (up to 3 mol dm⁻³).

Main Methods:

• Utilized a ferri/ferrocyanide (FeCN) redox mediator in an aqueous electrolyte.
• Employed voltammetry at a platinum microelectrode to monitor ion concentration shifts.
• Applied a 2D axisymmetric finite element model to estimate insertion rates.

Main Results:

• Observed a reversible 60 mV per decade shift in half-wave potential (E½) with K⁺ concentration changes.
• Demonstrated tracking of local K⁺ concentration changes during insertion/deinsertion on a potassium-insertion electrode.
• The FeCN mediator method showed stability and similar behavior in various aqueous electrolytes.

Conclusions:

• The developed SEM method effectively tracks interfacial ion transfer kinetics at high electrolyte concentrations.
• This technique provides a valuable tool for characterizing a key parameter in battery development.
• Future work could adapt this method for non-aqueous electrolytes and even higher concentrations.