Chemical Prepotassiation Realizes Scalable KC₈ Foil Anodes for Potassium-Ion Pouch Cells

Currently, graphite (Gr) and potassium metal are two typical and widely used anodes for potassium-ion batteries (PIBs). Unfortunately, the inevitable electrochemical prepotassiation of Gr anode and the unprocessable nature of K metal hinder the advancement of potassium-ion pouch cells. There is an urgent need to develop alternative anodes for promoting the practical applications of PIBs. Herein, KC₈ is proposed as a specialized anode for the research of PIBs. By taking a chemical prepotassiation strategy, a large-area KC₈ foil is successfully fabricated for the first time. Through molecularly tailoring K-arene complex, the Gibb's free energy of the Gr prepotassiation reaction can be changed, thus enabling accurate preparation of pure-phase KC₈.The size-controllable KC₈ anode exhibits a high areal capacity of 1.49 mAh cm⁻² comparable to the commercial Gr anode used in lithium-ion batteries. Based on this, a stackable pouch cell delivers an unprecedented high capacity of 106 mAh and high energy density >100 Wh kg⁻¹_{cathode+anode}. This work highlights the prospect of scalable KC₈ foil anodes to achieve practical PIBs.