Potassium alloy reference electrodes for potassium-ion batteries

A schematic of the potassium content and the sample made of graphic electrolyte and k metal

Potassium-ion batteries (KIBs) are a promising alternative to conventional lithium-ion batteries with reduced critical mineral dependency, but accurate three-electrode characterisation is hindered by the lack of a suitable reference electrode.

Potassium metal is frequently used as a reference electrode out of necessity, but its high reactivity and unstable potential limit its reliablity.

The authors of 'Potassium Alloy Reference Electrodes for Potassium-Ion Batteries' (published in ACS Materials Letters) investigate the K-In and K-Bi alloy systems, synthesise two-phase In-In₄K and Bi-Bi₂K alloys, and identify Bi-Bi₂K as a promising material owing to its stable potential of 1.07 V vs K+/L. They prove the use of Bi-Bi₂K as a reference electrode by cycling graphite in three-electrode cells and demonstrate that it results in significantly less electrolyte reduction than potassium metal, facilitating the accurate electrochemical characterisation necessary to accelerate KIB development.