Potassium nucleation and growth on substrates of disparate potassiophilicity

Abstract

The increasing demand for batteries in combination with the limited lithium (Li) reserves has motivated the search for alternatives to the conventional Li-ion battery chemistry. Batteries based on potassium (K) have been proposed due to its greater abundance compared to Li in the Earth’s crust. However, the larger weight of K compared to Li necessitates the use of K metal anodes to attain competitive energy densities in K batteries. Metallic anodes are problematic pertaining to rechargeability, as a result of their tendency to form dendritic morphology during cycling. The dendrites are detrimental to the coulombic efficiency of the cells and even hazardous, as they can grow through the separator to the other electrode, causing a short circuit. To control the morphology of K metal, it is imperative to build a fundamental understanding of the electrochemical deposition of K. This work focuses on studying electrochemical deposition of K metal onto various substrates by method of constant current cycling. With this technique, the voltage response is recorded and the peaks during deposition correspond to the nucleation process. The substrate onto which the metal is deposited affects the nucleation and ostensibly the emerging morphology as a consequence. A surprising result is the similarity in depth of the nucleation peaks for the substrates tungsten (W), previously predicted to be superpotassiophobic and gold (Au), expected to be potassiophilic. Another is the both deeper and wider peak for copper (Cu) as compared to W, even though Cu was theoretically estimated to be over 4 times less potassiophobic.