Electro-Spun Polymer Fibres Derived Carbon-Supported 1D Hierarchical WO₃/SnO₂ Nanocomposites with Enriched Surface Defects for High-Performance Supercapacitor Devices

Pseudocapacitive metal oxides are considered promising energy storage systems; however, their overall performance suffers from low intrinsic conductivity. [1] Herein, we report the design of 1D hierarchical architecture, carbon-supported WO₃/SnO₂nanocomposite-based fibers, via efficient and scalable strategies of single-spinneret electrospinning followed by controlled annealing for high-performance supercapacitor devices. As evident from the XPS and Raman analyses, the composite surface is enriched with surface defects such as oxygen vacancies (O_vac), which improves surface chemical structure, aids in efficient diffusion of the charge carriers, and enhances the conductivity.[2] The significant contribution of the two distinctive charge storage mechanisms accounts for the synergistic contribution of WO₃ and SnO₂ to the overall electrochemical behavior of the electrode.[3] Moreover, an interfacial charge build-up between WO₃ and SnO₂ due to nanoscale integration eradicates the charging and discharging processes, leading to better performance. Overall the unique combination of 1D hierarchical nanostructures, abundant electrochemically active sites (O_vac), and unique heterointerfacial properties have boosted the performance.[4] The half-cell measurements demonstrated a specific capacitance of 589 F g⁻¹ at 6 A g⁻¹ and enhanced columbic efficiency with a capacity retention of ~80% after 5000 charging-discharging cycles, indicating longer durability. Importantly, a flexible all-solid-state symmetric device (full-cell configuration) was assembled having energy density (E_d) of 2000 mW h kg^–1, power density (P_d) of 1200 W kg^–1, 100% durability (1,000 cycles), and the gravimetric capacitance of 10 F g^-1 at 0.5 A g^-1 for an extended working voltage window of 1.2 V. This work provides insight into the synthesis of hierarchical 1D nanocomposites of bimetallic metal oxides for high-performance, portable, and flexible supercapacitor device applications.<br/><br/>[1].Xiao, X.; Ding, T.; Yuan, L.; Shen, Y.; Zhong, Q.; Zhang, X.; Cao, Y.; Hu, B.; Zhai, T.; Gong, L.; Chen, J.; Tong, Y.; Zhou, J.; Wang, Z. L. <i>Adv. Energy Mater.</i> <b>2012</b>, <i>2</i> (11), 1328–1332.<br/>[2]. Huang, W.; Wang, J.; Bian, L.; Zhao, C.; Liu, D.; Guo, C.; Yang, B.; Cao, W. <i>Phys. Chem. Chem. Phys.</i> <b>2018</b>, <i>20</i> (25)17268–17278.<br/>[3]. Wu, Q. L.; Zhao, S. X.; Yu, L.; Zheng, X. X.; Wang, Y. F.; Yu, L. Q.; Nan, C. W.; Cao, G. <i>J. Mater. Chem. A</i> <b>2019</b>, <i>7</i> (21), 13205–13214.<br/>[4]. Gao, L.; Qu, F.; Wu, X., <i>J. Mater. </i><i>Chem. A</i>, <b>2014</b>, 2,7367