Capturing polyselenides through MXene conductive additives for enhanced sodium ion storage

Transition metal selenides have been extensively investigated as anode materials for sodium-ion batteries (SIBs) owing to their high conversion reaction efficiency. However, they still suffer from the issue of polyselenide shuttling. Besides tailoring the intrinsic properties of the materials, rational design of the electrode structure plays a crucial role in addressing this challenge. Herein, we fabricated a composite electrode (CNF@ZIF-CoSe 2 /MXene) by immobilizing ZIF-derived CoSe 2 onto carbon fibers obtained from Aspergillus niger via biosorption, while incorporating MXene directly into the electrode slurry. In contrast to conventional methods that incorporate MXene during material synthesis, this approach simplifies the fabrication process, improves scalability, and exhibits enhanced compatibility with practical commercial applications. The Aspergillus niger -derived carbon fibers and MXene form a dual conductive network. Additionally, MXene effectively suppresses the shuttling of polyselenides by both chemical and physical interactions. As expected, compared to the electrode without MXene (CNF@ZIF-CoSe 2 ), the CNF@ZIF-CoSe 2 /MXene electrode demonstrates enhanced cycling stability and superior rate capability. Furthermore, the assembled full cell (Na 3 V 2 (PO 4 ) 3 //CNF@ZIF-CoSe 2 /MXene) delivers a high specific capacity of 395.8 mAh g −1 at 0.1 A g −1 . This work highlights the significance of electrode structure design and provides new insights into development of practically viable electrodes for SIBs.