Multifunctional Nanofibers Enable Dual-Network Polymer Electrolytes for High-Performance Lithium Metal Batteries

Solid-state polymer-based lithium metal batteries (LMBs) have emerged as a core development direction for next-generation high-energy-density energy storage devices. However, their practical application is hindered by the fragile solid electrolyte interphase (SEI) and limited oxidation stability of polymer electrolytes (PEs). Herein, a rational "physical-chemical" dual-network design coupled with heteroatom incorporation is proposed to construct high-performance polymer electrolytes. In this dual-network structure, nanofibers of poly(vinyl alcohol) (PVA) and Hexakis (1,2,4-triazol-3-ylamino) cyclotriphosphazene (HATA) form a physical cross-linked network rich in phosphorus (P) and nitrogen (N) elements through hydrogen bonding. This physical network is further integrated with a chemically cross-linked network in situ formed by 2-(((3-(aziridin-1-yl)propionyl)oxy)methyl)-2-ethylpropylene-1,3-diol bis(3-(aziridin-1-yl)propionate) (TTMAP) and 1,3-dioxolane (DOL) monomers, realizing the hydrogen bond interaction between the double networks and the synergistic regulation of multiple heteroatoms. This dual-network synergistic architecture expands the electrochemical stability window to 5.8 V, enabling compatibility with high-voltage cathodes. Benefiting from the protective effect of hydrogen bonds on the cathode material and the improvement of ion conduction, the assembled Li||LiFePO₄ battery and Li||LiNi_0.8Co_0.1Mn_0.1O₂ battery exhibit capacity retention rates of 87.1% (after 400 cycles at 5C) and 77.9% (after 100 cycles at 0.2C), respectively. Furthermore, heteroatoms facilitate the formation of a robust organic-inorganic hybrid SEI layer rich in N and P elements on the Li anode surface, endowing the symmetric Li||Li battery with stable plating/stripping behavior for over 1000 h at a current density of 0.5 mA cm^-2 without discernible dendrite formation. Overall, this meticulously engineered polymer electrolyte presents a viable and promising pathway for the advancement of safe, high-performance LMBs.