Preparation Of Selenides And Its Application In Asymmetrical Supercapacitors

Recently,supercapacitors?also referred to electrochemical capacitors?have received intense attention as new generation of energy storage devices,mainly due to their rapid charge and discharge,high power density,and excellent cycle performance.There is a very low energy density of Supercapacitors,though the power density is higher than conventional secondary capacitors and lithium-ion batteries.According to the energy density formula E=1/2 CV²,the energy density is related to the specific capacitance and the potential window.Therefore,the following work is carried out in this paper to increase the energy density:?1?MoSe₂ nanosheets were grown on a nickel foam substrate by electrodeposition with SeO₂ as selenide source and NaMoO₄·2H₂O as molybdenum source.Then assembled with activated carbon?AC?into asymmetric supercapacitor?ASC?.The results shows that the as-synthesized MoSe₂ electrode possesses a high specifc capacitance of 2192.4 F g^-1 at 1 A g^-1.When use 3 M KOH as electrolytes,ASC can operate stably at a high voltage of 1.6 V,with amaximum energy density of18.0 W h kg^-1.In addition,the MoSe₂//AC ASC maintains 90.59%of the specific capacitance after 5000 charge-discharge cycles.?2?In situ growth nickel selenide?Ni₃Se₂?nanosheets on nickel?Ni?foam by a facile one-step hydrothermal method with Ni foam as nickel source,SeO₂ as selenide source,and NaBH₄ as reducing agent.The optimal amount of substance ratio of NaBH₄/SeO₂ is 4:1.Ni₃Se₂ and AC were assembled into ASC under optimal conditions.Ni₃Se₂ electrode possesses a high specifc capacitance of 854 F g^-1 at a current density of 1 A g^-1 through characterization and testing.When use 3 M KOH as electrolytes,ASC can operate stably at a high voltage of 1.6 V,with amaximum energy density of 18.0 W h kg^-1.In addition,the MoSe₂//AC ASC maintains 91.11%of the specific capacitance after 5000 charge-discharge cycles.The excellent performance of Ni₃Se₂ electrode is mainly due to the pseudo-capacitive by Ni₃Se₂and the 3D structure of Ni foam.?3?Using a simple one-step hydrothermal method to in situ synthesis Ni₃Se₂,NiTe and NiTe/Ni₃Se₂ on nickel?Ni?foam by using SeO₂ as selenide source,Te O₂ as tellurium source,nickel foam as substrate and nickel source,and hydrazine hydrate as reducing agent.NiTe/Ni₃Se₂ has a high mass specific capacitance of 2176.5 F g^-1at 1 A g^-1,exhibits that the electrode material has excellent electrochemical performance.NiTe/Ni₃Se₂//AC ASC assembled with AC can operate stably at a high voltage of 1.6 V in 3 M KOH electrolytes,and the energy density and power density reached 46.6 W h kg^-1 and 799.8 W kg^-1,respectively.Futhermore,NiTe/Ni₃Se₂//AC ASC exerts prominent charge-discharge stability?specific capacitance maintained96.3%after 5000 cycles?.