Due to the minimal electrochemical oxidation-reduction potential, the potassium (K) metal anode has emerged as a focal in K-ion battery. However, the reactivity of K metal anode leads to significant side reactions, particularly gas evolution. Mitigating gas generation from K metal anodes has been a persistent challenge in the field. In this study, we propose a dual protective layer design through pre-treatment of the K metal anode, employing a Bi2O3 modification layer alongside a stable solid electrolyte interface (SEI) formed during the initial charge-discharge cycle, which significantly suppresses gas evolution. Furthermore, we observe that the Bi2O3 modification layer enhances K nucleation due to its strong potassiophilicity when incorporated into the substrate material. The resultant SEI, consisting of dual inorganic layers of Bi−F and K−F formed through the Bi2O3 modification, effectively mitigates side reactions and gas generation while inhibiting dendrite growth. Utilizing a Cu@BO@K host, we achieve a nucleation overpotential as low as 40 mV, with a stability of 1900 h in Cu@BO@K||Cu@BO@K cell and a high average Coulombic efficiency of 99.2% in Cu@BO@K||Cu cell at 0.5 mA cm−2/0.5 mAh cm−2. Additionally, the Cu@BO@K||PTCDA also presents a high reversible capacity of 114 mA g−1 at 100 mA g−1 after 200 cycles. We believe that this work presents a viable pathway for mitigating side reactions in K metal anodes.

This article is Open Access

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