Controlled Nanoarchitecture of Aligned Electrospinning Fiber Composite Electrolyte Based on Plant and Animal Biopolymers for Safe Na‐Ion Batteries

The resurgence of solid‐state Na + battery, sustained through lithium deficiency and mounting costs, offers an auspicious alternative to solid‐state Li + battery. This study introduces a nanoarchitectural approach that integrates electrospinning with a simple solution casting technique to develop a mechanically robust (21.8 MPa), thin film (~76 μm), flexible, wearable, and free‐standing nanoporous aligned electrospun composite electrolyte membrane for solid‐state Na + batteries. The aligned electrospun composite electrolyte membrane combines fully biodegradable, biocompatible biopolymers: cellulose acetate—a cellulose derivative and chitosan—obtained from crustaceans' shells. Nanoporous electrospun cellulose acetate fiber mats were fabricated by optimizing electrospinning parameters, then coated with a chitosan and NaPF 6 solution. The high nanoporosity and aligned microstructure of the cellulose acetate fibers, along with the chitosan matrix, created uniform Na + transfer channels, leading to a promising room temperature (RT = 23 °C) Na + conductivity of 4.12 × 10 −4 S cm −1 and ion transference number ( = 0.58). At 0.1 mA cm −2 , a uniform sodium plating–stripping was observed for over 600 h at RT. In an application of a full hybrid battery set up, comprising a Na 3 V 2 (PO 4 ) 3 cathode, developed aligned electrospun composite electrolyte, and Na anode, 93.2 mA h g −1 discharge capacity was achieved at 0.1 C. After 100 cycles, the cell demonstrated a Coulombic efficiency exceeding 88% with 86% capacity retention. This engineered nanoarchitectural design of plant and animal resource‐based composite electrolyte, along with promising material and electrochemical performance, lays a foundation for the development of green electrolyte systems for SIB application.