Modulating the coexistence of - and -phase MnS in bird's nest-like carbonaceous frameworks for achieved high energy density in hybrid supercapacitors

MnS has great potential for development in supercapacitor applications due to its superior theoretical specific capacity and polycrystalline properties. Nevertheless, the application of MnS is inhibited by the poor electronic conductivity and unavoidable volume expansion. Designing the morphology and crystal structure for improving the performance of supercapacitors deserves extensive interest. Herein, the bird's nest-like carbonaceous frameworks with alpha-MnS and gamma-MnS hybrid phases (alpha/gamma-MnS@CFs) for supercapacitors is designed by the tem-plate and phase-controlled strategies. Benefiting from the hybrid phases of MnS and structural superiorities, the alpha/gamma-MnS with the bird's nest-like structure mitigates volume variation, improves electrical conductivity, and exhibits superior stability and high specific capacity. As a result, the alpha/gamma-MnS@CFs electrode shows an excellent specific capacity of 1059.2 C g- 1 at 1 A g(-1) and 84.1% capacity retention after 5000 cycles at 10 A g(-1). Additionally, the hybrid supercapacitor (HSC) device achieves a striking energy density of 65.2 Wh kg(-1) at 953.5 W kg(- 1) and remarkable cycling stability of 69.8% after 5000 cycles at 10 A g(-1). This work supplies a good idea for the preparation of transition metal sulfides with a polycrystalline characteristic for application in energy storage systems.