Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

Abstract Potassium (K) metal anodes suffer from a challenging problem of dendrite growth. Here, it is demonstrated that a tailored current collector will stabilize the metal plating–stripping behavior even with a conventional KPF 6 ‐carbonate electrolyte. A 3D copper current collector is functionalized with partially reduced graphene oxide to create a potassiophilic surface, the electrode being denoted as rGO@3D‐Cu. Potassiophilic versus potassiophobic experiments demonstrate that molten K fully wets rGO@3D‐Cu after 6 s, but does not wet unfunctionalized 3D‐Cu. Electrochemically, a unique synergy is achieved that is driven by interfacial tension and geometry: the adherent rGO underlayer promotes 2D layer‐by‐layer (Frank–van der Merwe) metal film growth at early stages of plating, while the tortuous 3D‐Cu electrode reduces the current density and geometrically frustrates dendrites. The rGO@3D‐Cu symmetric cells and half‐cells achieve state‐of‐the‐art plating and stripping performance. The symmetric rGO@3D‐Cu cells exhibit stable cycling at 0.1–2 mA cm −2 , while baseline Cu prematurely fails when the current reaches 0.5 mA cm −2 . The half‐cells cells of rGO@3D‐Cu (no K reservoir) are stable at 0.5 mA cm −2 for 10 000 min (100 cycles), and at 1 mA cm −2 for 5000 min. The baseline 3D‐Cu, planar rGO@Cu, and planar Cu foil fails after 5110, 3012, and 1410 min, respectively.