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The rational design and optimization of solid polymer electrolytes (SPEs) are critical for the application of safety and high efficiency lithium ion batteries (LIBs). Herein, we synthesized a novel poly(ethylene oxide) (PEO)-based SPE (PEO@AF SPE) with a crosslinking network by the introduction of alginate fiber (AF) membranes. Depending on the high-strength supporting AF skeleton and the crosslinking network formed by hydrogen bonds between the PEO matrix and AF skeleton, the obtained PEO@AF SPE exhibits an excellent tensile strength of 3.71 MPa, favorable heat resistance (close to 120 °C), and wide electrochemical stability window (5.2 V vs Li/Li + ). Meanwhile, the abundant oxygen-containing groups in alginate macromolecular and the three-dimensional (3D) porous structure of the AF membrane can greatly increase Li + anchor points and provide more Li + migration pathways, leading to the enhancement of Li + conduction and interfacial stability between the SPE and Li anode. Furthermore, the assembled LiFePO 4 /PEO@AF SPE/Li cells also exhibit satisfactory electrochemical performance. These results reveal that PEO incorporating with AFs can boost the mechanical strength, thermostability, and electrochemical properties of the SPE simultaneously. Furthermore, one will expect that the newly designed PEO@AF SPE with cross-linked networks thus provides the possibility for future applications of safety and high-performance LIBs.

Keywords: Co 6 Ni 3 S 8 , carbon aerogel, nitrogen and sulfur vacancies, sodium-ion storage, long cycle performance Recently, the metal sulfide-carbon nanocomposites hold the promise of being low cost alternative to lithium ion batteries, but the commercial application is seriously hindered by its relatively inferior cyclic performance. Herein, we introduced N and S vacancies in N,S co-doped carbon (NSC) shell for anchoring a new bimetallic sulphides core of Co 6 Ni 3 S 8 using Co-Ni-alginate biomass. The obtained Co 6 Ni 3 S 8 /carbon aerogels (Co 6 Ni 3 S 8 @NSCA) exhibit remarkable excellent sodium-ion storage property: a high reversible capacity (568.1 mAh g -1 at 1 A g -1 ) and an excellent cycle stability (94.4% after 300 cycles). Density functional theory (DFT) calculation results disclose nitrogen and sulfur vacancies in carbon shell can enhance the binding between Co 6 Ni 3 S 8 core and NSC shell, ensuring an improved structural and electrochemical stability. In addition, an increased adsorption energy of Na + (-1.88 eV) and a decreased barrier energy of Na + diffusion (0.46 eV) were observed indicating a fast Na + diffusion process. The Powder X-ray diffraction (XRD) refinement confirms that the lattice parameters of Co 6 Ni 3 S 8 extend to 0.9972 nm compared with Co 9 S 8 (0.9928 nm), suppressing the volume expansion in Na + diffusion processes.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

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