Electro‐Chemo‐Mechanically Stable and Sodiophilic Interface for Na Metal Anode in Liquid‐based and Solid‐State Batteries

Abstract Na metal batteries (NMBs) are attracting increasing attention because of their high energy density. However, the widespread application of NMBs is hindered by the growth of Na dendrites and interface instability. The design of artificial solid electrolyte interphase (SEI) with tuned chemical/electrochemical/mechanical properties is the key to achieving high‐performance NMBs. This work develops a metal‐doped nanoscale polymeric film with tunable composition, sodiophilic sites and improved stiffness. The incorporation of metal crosslinkers in the polymer chains results in exceptional electrochemical stability for Na metal anodes, leading to a significantly prolonged lifespan even at high current densities, which is at the top of the reported literature. The mechanical properties measurements and electro‐chemo‐mechanical phase‐field model are performed to interpret the impact of the ionic transportation capability (decoupled mechanical) and mechanic property in the metal‐doped polymer interface. In addition, this approach provides a promising strategy for the rational design of electrode interfaces, providing enhanced mechanical stability and improved sodiophilicity, which can open up opportunities for the fabrication of next‐generation energy storage.