Controllable Synthesis Of SnS₂ Electrode Materials And Their Electrochemical Performance In Supercapacitors

The limited resources and serious environmental pollution have restricted the development of our modern society,so it is urgent to explore the new green energy.As an energy storage device,supercapacitor can achieve the mutual conversion between chemical energy and electric energy.Although supercapacitors had lower energy density,they have advantages in power density.The performance of supercapacitors fills the gap between traditional capacitors and batteries,and their progress and update have great significance to the healthy development of energy conservation and environmental protection industry.Electrode materials play the most significant role in supercapacitors,which can seriously affect their overall performance.SnS₂can be used as a battery-type electrode material for supercapacitors due to its abundant supply,low cost and layered structure which is convenient for the diffusion of electrolyte ions.At present,the biggest defects of SnS₂ are low conductivity and unstable structure.In order to alleviate these problems and obtain better electrochemical performance,people choose to regulate the morphology and structure of SnS₂ or prepare SnS₂-based composite electrode materials.In this paper,SnS₂ electrodes with remarkable electrochemical properties were synthesized through simple methods,the primary works are shown as follows:（1）SnS₂ nanoflowers（SnS₂ NFs）and SnS₂ nanoplates（SnS₂ NPs）were prepared via convenient solvo/hydro-thermal routes using ethanol and De-ioned（DI）water as solvents,and their electrochemical properties were compared.At 1 A g^-1,SnS₂ NFs possessed a specific capacity of 264.4 C g^-1,which was higher than that of SnS₂ NPs(201.6 C g^-1).Besides,SnS₂NFs possessed excellent rate capability,when the current density was increased to 10 A g^-1,its specific capacity could reach 202.7 C g^-1,while it was 151.0 C g^-1 for SnS₂ NPs.The hybrid supercapacitors（HSCs）were assembled using SnS₂ NFs（SnS₂ NPs）as cathode,and activated carbon（AC）as anode,respectively,both of the HSCs had a voltage window of 0～1.7 V.The specific capacity of SnS₂ NFs//AC HSC was calculated to be 112.0 C g^-1 at 1 A g^-1,which was higher than that of SnS₂ NPs//AC HSC(103.3 C g^-1).At 904.3 W kg^-1,SnS₂ NFs//AC HSC had an energy density of 28.1 W h kg^-1,while SnS₂ NPs//AC HSC showed an energy density of 24.2W h kg^-1 at 844.3 W kg^-1.After 5000 cycles at 5 A g^-1,the SnS₂ NFs//AC HSC showed a higher capacity retention of 95.5%.As for SnS₂ NPs//AC HSC,it was 87.1%.（2）Using a simple hydrothermal method,SnS₂/SnO₂ nanoflowers（SnS₂/SnO₂ NFs）composite electrode was successfully prepared,and the influences of thiourea on the morphology and structure of samples were explored by changing its dosage.With the increase of thiourea dosage,the products had turned into pure SnS₂ nanosheets（SnS₂ NSs）.Both of SnS₂/SnO₂ NFs and SnS₂ NSs were belonged to battery-type electrode materials,their electrochemical properties were compared through three-electrode and two-electrode tests.SnS₂/SnO₂ NFs had a larger specific surface area(52.5 m² g^-1),which was conducive to the rapid transfer of electrolyte ions.Thus at 1 A g^-1,they delivered a higher specific capacity up to304.6 C g^-1.Its rate performance was 72.5%at 10 A g^-1.As for SnS₂ NSs,under the same conditions,they delivered a specific capacity of 244.1 C g^-1 with 70.9%capacity retained.The SnS₂/SnO₂ NFs（SnS₂ NSs）was employed as cathode,and AC was employed as anode to assemble two HSCs:SnS₂/SnO₂ NFs//AC HSC and SnS₂ NSs//AC HSC,and their highest voltage window were determined to be 1.6 V.The two HSCs showed excellent cycling stability.The capacity retention were namely 100.5%and 101.2%after 5000 continuous GCD loops at6 A g^-1.At the power density of 993.2 W kg^-1,the SnS₂/SnO₂ NFs//AC HSC showed an energy density of 33.4 W h kg^-1.While SnS₂ NSs//AC HSC possessed a lower energy density of 27.4W h kg^-1 at 929.9 W kg^-1.