Enthalpy-Driven Room-Temperature Superwetting of Liquid Na-K Alloy as Flexible and Dendrite-Free Anodes

Sodium (Na) metal anodes are promising candidates for various batteries with high energy density and high-power density, however, the dendrite growth of Na metal is impeding their practical applications. The binary alloy Na-K is in the liquid state at room temperature with a wide composition range, which renders it inherently free from solid dendrite growth. Whereas the application of Na-K alloy is plagued by the lack of a wettable matrix to immobilize the liquid metal. Herein, a facile method is reported to introduce oxygen-rich functional groups into carbon fiber cloth (O-CFC), which is initially Na-K phobic yet turns into superwetting after the treatment. The superwetting behavior of the O-CFC can be attributed to the favorable enthalpy changes as a result of the introduction of O-rich functional groups. The superwetting property of the O-CFC exhibits good universality, which can be extended to melting Na and K metals. By adopting the superwetting O-CFC as a host for liquid Na-K alloy, the liquid metal can be well retained in the matrix and deliver a stable cycling for >1600 h. The concept of enthalpy-driven wettability regulation can be enlightening for the host material design of other liquid metals and alloys.