Pyrrhotite Fe1−xS microcubes as a new anode material in potassium-ion batteries

Potassium-ion batteries are an emerging energy storage technology that could be a promising alternative to lithium-ion batteries due to the abundance and low cost of potassium. Research on potassium-ion batteries has received considerable attention in recent years. With the progress that has been made, it is important yet challenging to discover electrode materials for potassium-ion batteries. Here, we report pyrrhotite Fe 1− x S microcubes as a new anode material for this exciting energy storage technology. The anode delivers a reversible capacity of 418 mAh g −1 with an initial coulombic efficiency of ~70% at 50 mA g −1 and a great rate capability of 123 mAh g −1 at 6 A g −1 as well as good cyclability. Our analysis shows the structural stability of the anode after cycling and reveals surface-dominated K storage at high rates. These merits contribute to the obtained electrochemical performance. Our work may lead to a new class of anode materials based on sulfide chemistry for potassium storage and shed light on the development of new electrochemically active materials for ion storage in a wider range of energy applications. Energy storage: Developing electrodes for potassium-based batteries Energy storage: Developing electrodes for potassium-based batteries. Microcubes of iron sulfide pyrrhotite constitute a promising electrode material for potassium-ion batteries. Potassium-ion (K + ) batteries are being investigated as an alternative to lithium-ion batteries due to potassium’s abundance and low cost, but a challenge lies in discovering suitable materials for the battery’s electrodes. Yang Xu, and a team from University College London, United Kingdom, and Northeast Normal University, China, fabricated microcubes of pyrrhotite to use in K + battery anodes to store ions. The anodes constructed by the team demonstrated a high capacity, with fast charge/discharge characteristics and stability that withstood repeated K + insertion/extraction. Employing metal sulfides has cost and sustainability benefits, and the authors hope that their study can fuel further studies to realize the potential of K + energy storage.