Synergy of Cu-foam/Sb2O3/rGO for stable potassium anodes of high-rate and low-temperature potassium metal batteries

Abstract

Potassium (K) with higher abundance than lithium has been explored as an anode material for K metal batteries (KMBs) for possible application in large-scale energy storage. However, the unstable solid electrolyte interface (SEI) at the K anode due to uncontrolled growth of K dendrites is a challenge in KMB development. In this paper, a multifunctional interface containing Sb₂O₃ and reduced graphene oxide (rGO) on Cu foam to form a current collector (Cu@Sb₂O₃@rGO) is developed for a KMB anode through structural regulation, where the Cu form with a large surface area can reduce the volume change during charge and discharge processes, Sb₂O₃ can provide potassiophilicity toward uniform K plating and stripping to give a dendrite-free K anode, and rGO can provide abundant defects for increasing the ion transport and reaction kinetics. Such a Cu@Sb₂O₃@rGO current collector exhibits a remarkable reversibility of K plating/stripping for up to 600 cycles at 0.5 mA cm⁻²/2 mA h cm⁻², and the formed Cu@Sb₂O₃@rGO@K anode demonstrates an extended cycle lifespan of 1300 hours under 0.2 mA cm⁻²/0.2 mA h cm⁻² in symmetric cells. This anode-constructed PTCDA‖ Cu@Sb₂O₃@rGO@K full battery exhibits both exceptional cycling stability (over 2000 cycles) and outstanding rate capability (112.8 mA h g⁻¹ at 10 C). Furthermore, even under extremely low temperature (−20 °C), this battery can still maintain an impressive 55% of its room temperature capacity. In situ Raman spectroscopic techniques and electrochemical methods including in situ EIS, half cell, symmetric cell, and full cell tests and theoretical DFT calculations are carried out to probe the structure–performance relationship and the reaction mechanisms for fundamental understanding toward further optimizing the performance of such the K anode and the corresponding KMBs. The strategy for stabilizing the K metal anode in this work may provide a guidance for further development of advanced low-temperature potassium metal batteries.