Woven fabric-based separators with low tortuosity for sodium-ion batteries

In order to achieve high-performance and stable sodium-ion batteries, numerous attempts have been made to construct continuous ion transport pathways, in which a separator is one of the key components that affects the battery performance. In this study, a novel low-tortuosity woven fabric separator is fabricated by combining a weaving technique with a cellulose-solution method, followed by an infusion of a TEMPO-oxidized bacterial cellulose slurry into woven fabric substrates. The macropores in the fabric combine with the micropores in the oxidized bacterial cellulose to form a separator with a suitable pore structure and low tortuosity, forming a continuous sodium ion transport channel within the sodium-ion battery and effectively enhancing ion transport dynamics. The results show that, compared with a commercial polypropylene separator, the TEMPO-oxidized bacterial cellulose-woven fabric separator has a special weaving structure and lower tortuosity (0.77), as well as significant advantages in tensile strength (3.07 MPa), ionic conductivity (1.15 mS c), ionic transfer number (0.75), thermal stability, and electrochemical stability. This novel and simple preparation method provides new possibilities for achieving high-performance separators of sodium-ion batteries through rational structural design by textile technology. A textile-assisted yarn-alignment method is developed to design separators with low tortuosity, concentrated pore size distribution, and excellent mechanical properties for sodium-ion batteries to achieve fast ion transport.