Fabrication of α-Bi2O3, β-Bi2O3, and β-Bi2O3/SGO composite: correlation between structure and electrochemical performance

Abstract

In this work, α-Bi₂O₃ and β-Bi₂O₃ were successfully synthesized via a hydrothermal calcination route, and their electrochemical properties were systematically studied. The results demonstrate that the low-temperature stable α-phase Bi₂O₃ presents superior electrochemical performance. This can be ascribed to its stable structure, which not only effectively suppresses surface side reactions but also preserves structural integrity during repeated charge–discharge cycling. To further enhance the electrochemical performance of Bi₂O₃, the Bi₂O₃–SGO composite was rationally designed and successfully synthesized via a composite strategy combining β-Bi₂O₃ and sulfonated graphene oxide (SGO). Analysis of the charge storage mechanism reveals that the addition of a small amount of SGO does not introduce surface-controlled capacitance into the material. The incorporation of SGO can enhance the electrical conductivity and optimize the microscopic morphology of the composite, as well as alleviate the volume expansion during the charge–discharge process. This effectively improves the intrinsic structural instability of β-Bi₂O₃, thereby synergistically boosting the electrochemical performance of the electrode material. The as-fabricated β-Bi₂O₃/SGO composite delivers a high specific capacitance of 1105 F g⁻¹ at 1 A g⁻¹. It also possesses superior rate capability with 758 F g⁻¹ maintained at 50 A g⁻¹ and exhibits satisfactory cycling durability, achieving 88% capacitance retention over 2000 consecutive cycles. As-obtained asymmetric supercapacitors with NiCoO₂ as the positive electrode and β-Bi₂O₃/SGO as the negative electrode possess a superior energy density of up to 38.5 Wh kg⁻¹.