Enhanced ionic conductivity and electrochemical performance of environmental friendly guar gum-based bio polymer gel electrolytes doped with Al2O3 nanofibers for Li-ion batteries.

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Recently, biopolymers made from natural resources are gaining popularity as polymer electrolytes (PEs) in electrochemical devices. In the present work, a series of guar gum (GG)-based biopolymer gel electrolytes (BGEs) filled with different amounts of Al2O3 nanofibers are synthesized and tested. The BGEs containing 7.5 wt% Al2O3 nanofibers show the maximum room temperature ionic conductivity of 2.37 × 10-3 S/cm at an uptake ratio of 120 %. Given the high conductivity, this uptake ratio is low, demonstrating that Al2O3 nanofibers affect GG's ion transport characteristics. XRD reveals that the Al2O3 in GG can create conducive environment for ion conduction. FTIR and XPS analyses demonstrate that nanofibers have the ability to generate supplementary routes for ion conduction in GG. Electrochemical investigations show that BGEs with 7.5 wt% nanofibers have a broad electrochemical potential range of 4.6 V. BGEs are stable at metallic electrodes and have a cationic transference number of 0.59. The initial discharge capacity at 0.5C has been measured to be 127 mAh g-1 for Li|BGE|LiFePO4 cell in the first cycle and 116 mAh g-1 with coulombic efficiency of over 94 % after 100 cycles. Nanofiber-dispersed BGEs have high thermal and mechanical stabilities, according to TGA, DSC, and UTM tests.