Dendrite-Free Potassium Metal Anodes in a Carbonate Electrolyte.

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 KPF6 -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.