SE991: Intermetallic current collectors for reversible sodium and potassium metal batteries

Sodium and potassium metal batteries are promising alternatives to lithium-ion batteries because of the greater natural abundance and lower cost of Na and K resources. However, their practical development is limited by unstable metal electrodeposition, dendrite growth, continuous solid-electrolyte interphase formation, and low Coulombic efficiency. Here, we present an interfacial materials design strategy based on thermodynamically stable ternary intermetallic current collectors to regulate alkali-metal plating and stripping. For sodium metal batteries, repeated rolling and folding of Sb2Te3 with Na metal forms a self-standing Na-Sb-Te/Na metallurgical composite containing a vacancy-rich Na2(Sb2/6Te3/6Vac1/6) intermetallic scaffold. This sodiophilic framework enables dense and planar Na deposition, supports 100% depth-of-discharge cycling, and improves the performance of anode-free sodium metal batteries.[1] This concept is further extended to potassium metal batteries using an accumulative roll-bonding process to form a K-Bi-Te/K metallurgical composite. The resulting K2(Bi2/6Te3/6Vac1/6) intermetallic scaffold is potassiophilic and electrochemically stable, enabling improved K plating/stripping in both carbonate and ether electrolytes. Symmetric cells show extended cycling stability, and full potassium metal batteries paired with Prussian blue or organic cathodes exhibit improved capacity retention.[2]Across both systems, cryogenic electron microscopy, synchrotron X-ray nano-tomography, and multiscale simulations reveal that the intermetallic scaffolds promote uniform metal wetting, suppress filamentary growth, reduce porous/dead-metal formation, and stabilize the metal/electrolyte interface. These results demonstrate that rational current-collector and interphase design can provide a general pathway toward safer and more reversible beyond-lithium metal batteries.