Hierarchical FexBi2−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 FexBi2−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 FexBi2−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.