Carbon Composite Anodes with Tunable Microstructures for Potassium-Ion Batteries

Abstract

Among the post-lithium battery technologies, potassium-ion batteries are promising for cost-effective large-scale energy storage, as potash is an abundant resource. However, a major challenge is to understand the structure-performance relationships of carbon anodes for potassium-ion storage. In this study, we have designed a variety of carbon composite materials from 100 % graphite to 100 % soft carbon and in between, with tunable structural features to fundamentally understand the roles of different carbon structural features in potassium ion insertion. We have found that the graphite-soft carbon composites (G-SC) show a high charge capacity of 280.2 mAh g−1 with an increased initial coulombic efficiency, representing the best reversibility among different carbon composites. Electrochemical impedance spectroscopy, cyclic voltammetry, and ex-situ structural characterizations have been applied to substantiate that the presence of soft carbon in G-SC inhibits the solid electrolyte interface layer formation and provides structural protection to the graphitic layers.