Bismuth compounds are of interest because of abundant reserves and high theoretical capacity for use as anodes in supercapacitors. In this work, bismuth oxycarbonate is synthesized by a hydrothermal method, and bismuth oxide is obtained by the subsequent calcination process, both of which possess high specific capacity. In particular, Bi₂O₃ possesses a specific capacity of 1178 F g⁻¹ (1178 C g⁻¹, 327 mA h g⁻¹) at a current density of 1 A g⁻¹, and still retains 94.9% capacity at 20 A g⁻¹, indicating excellent rate capability. Furthermore, Ni(OH)₂ is prepared with a specific capacity of 2447 F g⁻¹ at 1 A g⁻¹. Using Bi₂O₃ as the anode and Ni(OH)₂ as the cathode, respectively, the soft-packed supercapacitors are assembled with a large voltage window of 1.75 V. The energy density is as high as 139.7 W h kg⁻¹ at a power density of 874.8 W kg⁻¹. Even at 18 000 W kg⁻¹, the device retains an energy density of 94 W h kg⁻¹. Connecting two devices in series as a power source can light up 88 light emitting diodes (LEDs) for 2 hours, and drive a tiny fan to run for 18 seconds. The work provides new ways for the practical application of supercapacitors.