Facile synthesis of ultrathin Bi(OH)SO₄·H₂O nanosheets and battery-like electrode for symmetric supercapacitors

The phase engineering of Bi(OH)SO₄·H₂O nanosheets is proposed as a simple, adaptable, and cost-effective solution for the combustion of Bi₂O₃ using H₂SO₄. This study revealed that the formation of Bi(OH)SO₄·H₂O with a nanosheet-like morphology. The synthesized nanosheets were employed as electrode materials for electrochemical storage devices. The estimated capacity of the Bi(OH)SO₄·H₂O electrode is 327.69 mAh g^–1 at 1 A g^–1. Solid-state coin-cell-type symmetric supercapacitor devices (CSSDs) were developed. The fabricated CSSDs exhibit a high specific capacity (33 mAh g^–1 at 1.1 A g^–1), energy density (62.23 Wh kg^–1), and power density (2074.11 W kg^–1) with a significant retained energy density of up to 32.98 Wh kg^–1 at 10794.51 W kg^–1. Furthermore, they exhibited cycling stability at 5.5 A g^–1, maintaining 76.65% of its initial capacity after 10,000 cycles. In addition, to investigate the device performance in real time, two CSSDs were connected in series to power a red LED. The obtained results provide insights into bismuth-based electrodes for energy storage applications.