Modulating ion transport via a Cu-MOF@Zein nanofiber-tailored separator for ultrastable and dendrite-free sodium-metal batteries

Sodium metal, featuring low redox potential (−2.714 V vs SHE), high theoretical capacity (1166 mAh g−1), and natural feasibility, is recognized as the ideal anode for sodium-metal batteries (SMBs). Nevertheless, detrimental sodium dendrite and unstable solid electrolyte interphase (SEI) still fetter the practical applications of SMBs. Herein, Cu-MOF (HUKST-1)@Zein nanofiber-modified polypropylene (PZH) separators are developed to tackle these problems. The rich sodiophilic functional groups and intrinsic nanochannels within Zein and MOF frameworks expectedly enable a remarkable Na ion transference number of 0.78, a robust SEI, and dendrite-free SMBs as verified by in situ characterizations and theoretical simulations. Consequently, NaǁNa cells with the PZH separator could stably cycle over 2000 h at 4 mA cm−2/20 mAh cm−2. Moreover, Na3V2(PO4)3@CǁNa full cells with the PZH separator retain a high capacity of 83.1 mAh g−1 over 1500 cycles with a low fading rate of ∼0.0089% per cycle, confirming the practical employment of PZH separators in SMBs.