Poly (3, 4-ethylenedioxythiophene) engineered hollow Bi₂O₃ core-shell architectures for long cycle performance of flexible supercapacitors

The booming development of electronic devices has promoted the in-depth research on flexible supercapacitors. The structural design of core@shell can be regarded as an effective method of achieving excellent electrochemical performance and outstanding flexibility of electrode materials. Herein, a special structure of core@shell hybrid Bi₂O₃-x@carbon fiber@poly (3, 4-ethylenedioxythiophene) (Bi₂O₃-x@CF@PEDOT) electrode derived from a Bi-metal-organic framework (Bi-MOF) is fabricated by using the electrospinning technique, and using the stabilization, pyrolyzation and polymerization procedures. The amount of Bi-MOF is regulated to obtain an optimized flexible substrate (Bi₂O₃-x@CF). The free space of the hollow Bi₂O₃ microrod can effectively alleviate the volume expansion during long cycling processes and further promote ion diffusion. The effective optimizations for the structure and content could significantly improve the conductivity and electrochemical performance of the constructed electrode. The prepared Bi₂O₃–0.5@CF@PEDOT electrode exhibits a satisfied specific capacitance of 460 F g⁻¹ (1 A g⁻¹) and great cycling stability. The assembled symmetric supercapacitor yields a desired energy density (i.e., 16.4 Wh kg⁻¹) and power density (i.e., 500.34 W kg⁻¹), and remarkable cycling performance (i.e., 99 % capacitance retention after 8500 cycles). Moreover, the excellent flexibility of the device is demonstrated by folding the supercapacitor into different angles and without obvious capacitance loss. This work provides a special structural design method of constructing high-performance flexible electrodes.