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(cathode+anode)(-1). This work highlights the prospect of scalable KC8 foil anodes to achieve practical PIBs.