Beyond Li metal batteries

This study -Influence of Potassium Metal-Support Interactions on Dendrite Growth - combines synchrotron X‑ray nanotomography, cryogenic electron microscopy (cryo‑EM), and modeling to reveal how interactions between potassium metal and different current collector supports determine the morphology of electrodeposited potassium. On potassiophobic supports (e.g., bare copper foil), deposits form a triphasic, fibrous, porous structure with large cracks and voids, indicative of unstable growth, whereas on potassiophilic supports (e.g., oxygen‑functionalized carbon cloth), potassium deposits are dense, pore‑free, and uniformly covered by solid electrolyte interphase, showing much greater morphological stability. These results directly link the energetics of metal‑support wettability to dendrite suppression and points toward tailored support surface chemistry as a pathway to safer, higher‑performance potassium metal anodes 

In this work, researchers engineered an artificial solid‑electrolyte interphase (SEI) and cathode electrolyte interface (CEI) for potassium metal batteries by spin‑coating aluminum oxide (Al₂O₃) nanopowder onto both sides of a commercial polypropylene separator. The Al₂O₃‑modified separator dramatically improves electrolyte wetting, boosts ionic conductivity and potassium‑ion transference number, and enables symmetric potassium cells to cycle stably over 1,000 cycles at practical current densities. Cryogenic FIB analysis shows that potassium deposits on the modified separator form dense, planar morphology rather than dendritic filaments, while the engineered CEI reduces cathode cracking and suppresses Fe crossover; multiscale modeling underscores how these interfaces influence current distribution and morphological stability to deliver significantly enhanced cycling performance in potassium metal cells. 

In article “Stable Potassium Metal Anodes with an All-Aluminum Current Collector through Improved Electrolyte Wetting“, dendrite-free plating/stripping is achieved through improved electrolyte wetting, employing an aluminum-powder-coated aluminum foil “Al@Al,” without any modification of the support surface chemistry or electrolyte additives. The reservoir-free Al@Al half-cell is stable at 1000 cycles (1950 h) at 0.5 mA/cm2, with 98.9% cycling Coulombic efficiency and 85 mV overpotential. The pre-potassiated cell is stable through a wide current range, including 130 cycles (2600 min) at 3.0 mA/cm2, with 178  mV overpotential. Al@Al is fully wetted by a 4 M KFSI/DME electrolyte (θCA = 0°), producing a uniform solid electrolyte interphase (SEI) during the initial galvanostatic formation cycles. On planar aluminum foil with a nearly identical surface oxide, the electrolyte wets poorly (θCA = 52°). This correlates with coarse irregular SEI clumps at formation, 3D potassium islands with further SEI coarsening during plating/stripping, possibly dead potassium metal on stripped surfaces, and rapid failure. The electrochemical stability of Al@Al versus planar Al is not related to differences in potassiophilicity (nearly identical) as obtained from thermal wetting experiments. The key fundamental takeaway is that the incomplete electrolyte wetting of collectors results in early onset of SEI instability and dendrites. 

In article “Dendrite-Free Potassium Metal Anodes in a Carbonate Electrolyte“, 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 den-sity and geometrically frustrates dendrites. The rGO@3D-Cu symmetric cells and half-cells achieve state-of-the-art plating and stripping performance. The half-cells cells of rGO@3D-Cu (no K reservoir) are stable at 0.5 mA/cm2 for 10,000 min, and at 1 mA/cm−2 for 5000 min.