Preparation Of SnS₂ Based Composites And Their Application In Electrochemical Energy Storage

With the increase of productivity and the continuous development of green and clean energy sources,there is a growing demand for energy storage devices.At present,the shortage of lithium resources and higher costs have limited the further application of lithium-ion batteries in large-scale energy storage systems,which has led to more attention to the lower-cost sodium-ion batteries.However,due to the large ionic radius and mass of Na⁺,anode materials with high theoretical capacity and large layer spacing need to be found to match it.SnS₂material,with its typical two-dimensional layer structure and high theoretical capacity,is a highly promising anode material for sodium ion batteries.However,the poor ionic and electronic conductivity of SnS₂materials,large volume changes,and the growth of sodium dendrites during cycling lead to problems such as slow reaction kinetics and severe capacity decay.To address this series of problems,this paper will improve the sodium storage performance of SnS₂materials in terms of improving the interface stability and optimizing the geometric structure and material components,as follows.First,a hollow Co-SnS₂@CuS@C heterojunction composite was designed.By compounding SnS₂with the highly conductive and stable CuS@C framework,heterojunctions are constructed to induce electron leaving domains and form internal electric fields,which accelerate the electron migration rate while lowering the migration energy barrier of Na⁺,effectively improving the electron conductivity and ionic conductivity of the material and enhancing the reaction kinetics.The three-dimensional hollow structure formed by the tight bond between SnS₂and hollow CuS@C can effectively buffer the volume deformation generated during cycling and improve the cycling stability.the introduction of Co²⁺into the material can further improve the reaction kinetics of Na⁺.The battery performance of Co-SnS₂@CuS@C material was tested and it exhibited good sodium storage performance.Under the current density of 0.2 A g^-1,the discharge capacity after 100 cycles was 492.6 m Ah g^-1,and the average capacity attenuation of each cycle was only 0.09%.After the current density increases to 2.0 A g^-1,Co-SnS₂@CuS@C can still provide 344.8 m Ah g^-1discharge capacity after repeated charging and discharging for 500 cycles.The superiority of the composite material for energy storage is explored in conjunction with DFT calculations.Then,to improve the stability of the solid electrolyte interface(SEI)and further improve the Na⁺migration kinetics,a Sb-SnSSe@MHCS 3D cluster material was prepared,which consists of Sb/Se double-doped SnS₂nanosheets with porous hollow carbon spheres.Among them,high conductivity carbon spheres can improve the electron transfer ability at the core lamellae stacking of Sb-SnSSe@MHCS materials,while the introduction of Sb³⁺and Se^2-enhances the ionic and electronic conductivity of SnS₂nanosheet layers.The three-dimensional structure as well as the cavities and pores inside the carbon spheres can effectively buffer the mechanical stress caused by the volume deformation during the cycling process while shortening the Na⁺diffusion path.The directionally aligned Sb-SnSSe nanosheet layers can reduce the diffusion resistance of Na⁺and enable more uniform deposition of Na⁺,effectively improving the problem of sodium dendrite growth.The 1:1 S/Se element doping can broaden the layer spacing of SnS₂and relieve the interlayer stress during Na⁺intercalation.The introduction of Sb³⁺can induce the generation of off-domain electrons and form a synergy with Se^2-to provide more active sites and improve the reaction kinetics of the material.With 100 cycles at 0.1 A g^-1current density,the discharge capacity can still reach 668.8 m Ah g^-1,with a capacity retention rate of 94.4%.when the current density is increased to 1.0 A g^-1,500 cycles can still provide a discharge capacity of 448.8m Ah g^-1.Further,Sb-SnSSe@MHCS was applied to the sodium ion hybrid capacitor and was able to achieve a capacity retention of 90.1%at a long cycle of 5000 turns at a current density of 1.6 A g^-1.The excellent sodium storage properties of the material were investigated in depth by combining DFT calculations with COMSOL simulations.