Hierarchical Fe_xBi_2−xS₃ solid solutions for boosted supercapacitor performance

For the pursuit of high energy supercapacitors, the development of high performance pseudocapacitance or battery-type negative electrode material is urgently needed to make up for the capacity shortage of commercial electric double layer capacitor (EDLC) type materials. Herein, a porous and defect-rich Fe_xBi_2−xS₃ solid solution structure is firstly constructed by employing Fe-doped Bi₂O₂CO₃ porous nanosheets as a precursor, which presents dramatically increased energy storage performance than Bi₂S₃ and FeS₂ phase. For the optimized Fe_xBi_2−xS₃ solid solution (FeBiS-60%), the Fe solute is free and random dispersed in Bi₂S₃ framework, which can effectively modulate the electronic structure of Bi element and introduce rich-defect due to the existence of Fe(II). Meanwhile, the FeBiS-60%, constructed by pore nanosheets that are assembled by self-supported basic nanorod units, presents rich mesoporous channels for fast mass transfer and abundant active sites for promoting capacity performance. Therefore, a high capacitance of 832.8 F·g⁻¹ at a current density of 1 A·g⁻¹ is achieved by the FeBiS-60% electrode. Furthermore, a fabricated Ni₃S₂@Co₃S₄ (NCS)//FeBiS-60% hybrid supercapacitor device delivers an outstanding energy density of 85.33 Wh·kg⁻¹ at the power density of 0.799 kW·kg⁻¹, and ultra-long lifespan of remaining 86.7% initial capacitance after 8700 cycles.