Oxygen‐Deficient Bismuth Oxide/Graphene of Ultrahigh Capacitance as Advanced Flexible Anode for Asymmetric Supercapacitors

Abstract

Oxygen‐deficient bismuth oxide (r‐Bi2O3)/graphene (GN) is designed, fabricated, and demonstrated via a facile solvothermal and subsequent solution reduction method. The ultrafine network bacterial cellulose (BC) as substrate for r‐Bi2O3/GN exhibits high flexibility, remarkable tensile strength (55.1 MPa), and large mass loading of 9.8 mg cm−2. The flexible r‐Bi2O3/GN/BC anode delivers appreciable areal capacitance (6675 mF cm−2 at 1 mA cm−2) coupled with good rate capability (3750 mF cm−2 at 50 mA cm−2). In addition, oxygen vacancies have great influence on the capacitive performance of Bi2O3, delivering significantly improved capacitive values than the untreated Bi2O3 flexible electrode, and ultrahigh gravimetric capacitance of 1137 F g−1 (based on the mass of r‐Bi2O3) can be obtained, achieving 83% of the theoretical value (1370 F g−1). Flexible asymmetric supercapacitor is fabricated with r‐Bi2O3/GN/BC and Co3O4/GN/BC paper as the negative and positive electrodes, respectively. The operation voltage is expanded to 1.6 V, revealing a maximum areal energy density of 0.449 mWh cm−2 (7.74 mWh cm−3) and an areal power density of 40 mW cm−2 (690 mW cm−3). Therefore, this flexible anode with excellent electrochemical performance and high mechanical properties shows great potential in the field of flexible energy storage devices.