Inorganic-Directed Charge Delocalization Channels: Boosting Uniform Charge Distribution and Rapid Na plus Transport for Solid-State Sodium Metal Batteries

초록

Composite polymer electrolytes (CPEs) are promising for all-solid-state sodium metal batteries but suffer from low ionic conductivity, which stems from limited Na-salt dissociation and narrow polymer amorphous domains, as well as sluggish ion transport caused by discontinuous composite interfacial charge-transfer paths, and poor electrode/electrolyte interfacial stability. This study proposes an original molecular interface engineering strategy: inorganic Zr4+ induces organic phase reconstruction to build continuous high-speed ion channels, simultaneously accelerating Na-salt dissociation and reducing ion migration energy barriers. Zr4+ directs the oriented reorganization of polar groups (& horbar;C equivalent to N) to alleviate Na-metal anode interfacial passivation, facilitate NaF/Na3N-rich stable solid electrolyte interphase formation, and enable uniform Na deposition. Moreover, Zr & horbar;N & boxH;C metal-ligand coordination at the organic/inorganic interface induces interfacial electronic coupling and charge redistribution, promoting fast Na+ migration along continuous coordination pathways. The developed CPEs, denoted as polyacrylonitrile-metal organic framework@polyethylene oxide-Na[N(SO2CF3)2] (PM@PN), show a synergistic interface-bulk effect that significantly enhances electrolyte performance, as evidenced by a reduced apparent activation energy of 0.027 eV (derived from Vogel-Tammann-Fulcher, VTF fitting above T m), an enhanced ionic conductivity of 3.52 & times; 10-4 S cm-1, and a Na+ transference number of 0.67 at 60 degrees C, along with an expanded electrochemical window of 5.06 V. The Na|PM@PN|Na symmetric cell demonstrates 0.56 mA cm-2 critical current density and stable Na deposition/stripping over 700 h at 0.4 mA cm-2. Additionally, the assembled Na3V2(PO4)3|PM@PN|Na full cell maintains 93.99% capacity retention after 200 cycles at 0.1 C, confirming PM@PN's applicability in advanced all-solid-state sodium metal batteries.

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