A "two-pronged" strategy towards dendrite-free potassium metal anodes: Potassiophilic zinc modification synergized with in-situ red phosphorus-derived protective layer

Potassium metal batteries (PMBs) have been considered as a promising energy storage devices benefiting from abundant reserves, low prices, and modest standard electrode potential of potassium (K) metal. However, the commercial development of PMBs has been severely prevented by uncontrolled dendrite growth and low Coulombic efficiency (CE) of K metal anode. Herein, a "two-pronged" strategy of zinc-modified copper matrix (denote as Cu@Zn) coupled with a red phosphorus derived solid electrolyte interface (SEI) layer (denote as RPCu@Zn) is proposed to realize a dendrite-free K metal anode with high CE. Zinc acts as an active site to induce homogeneous nucleation and dendrite-free deposition of K metal, while red phosphorus film can in situ derive a stable SEI layer in situ to inhibit side reactions and dendrite growth. Benefiting from this "two-pronged" strategy, the Cu@Zn-K anode exhibits outstanding reversibility with an average CE as high as 99.23% after 1000 cycles. The RP-Cu@Zn-K anode represents an excellent cycling lifespan over 660 h at a current density of 1.0 mA cm-2 and an area capacity of 1.0 mAh cm-2. The capacity of the full cell matched with RP-Cu@Zn-K as the anode and perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) as the cathode is maintained at 72.6 mAh g-1 after 300 cycles. This work provides a brief strategy that endows the dual properties of dendrite-free and stable SEI layer to K metal anode.