Preparation Of Transition Metal Sulfide Nanomaterials And Properties For Supercapacitors

With environmental pollution continuing around the world and non-renewable resources like oil and coal becoming less and less available,it becomes more and more urgent to develop a new energy storage device with remarkable performance.Supercapacitors are green,pollution-free,long service life,fast charging and discharging speed and so on.They can be widely used in the fields of national defense industry,mobile communications,electric vehicles and so on.However,the low energy density of the SCs limits their use.Therefore,it is urgent to design a kind of electrode material for supercapacitor with higher energy density.Transition metal sulfides have higher conductivity and electrochemical activity than transition metal oxides and hydroxides,that have good stability.So,they are very suitable to be used as electrode materials for supercapacitors.In binary transition metal sulfides,the synergistic effect of bimetallic ions could provide richer REDOX reactions,exhibit better electrical conductivity,and produce better electrochemical energy storage performance.Therefore,a variety of high performance transition metal sulfide composites are synthesized in this thesis to promote the property of supercapacitors.The major researches are as follows:1.Herein,a non-polluting and simple electrodeposition strategy is presented by us for fabricating ternary iron cobalt transition metal sulfide(FeCoS)on Ni foam with nanosheet arrays,which are used as cathode materials for asymmetric supercapacitors.The FeCoS-15nanosheet arrays reveal an admirable specific capacitance of 3741.03 F g^-1when the current density is 1 A g_-1 and also exhibit a fantastic cycling performance with 92.84%capacitance retention at 20 A g^-1 up to 10,000 cycles.Furthermore,the asymmetric supercapacitors using the FeCoS-15 nanosheet arrays as the positive electrode and the activated carbon(AC)as the negative electrodes demonstrate remarkable electrochemical performance.Our device exhibits an energy density of 54.08 Wh kg^-1 with the power density of 800 W kg^-1,achieving an impressive cycling retention of 85.64%over 10,000 cycles.The excellent results show that FeCoS nanosheet array materials have a roomy application prospect for high-performance asymmetric supercapacitors2.The design and development of composite materials with novel structures is one of the effective ways to enhance the electrochemical properties of supercapacitors.In this paper,a one-step electrodeposition method is used to adjust the morphology and structure of CoMnS nanomaterials by changing the amount of CS₂.CoMnS nanomaterials with unique flower-like structures are reasonably prepared,which promotes the flow of electron transfer and improves the electrochemical behavior.It is worth noting that when the amount of CS₂ is 4 mmol,the specific capacitance of CoMnS-4 reaches 3469.5 F g^-1 at 1 A g^-1,and the specific capacitance is still 2830.5 F g^-1(maintaining 81.56%)until the high current density reaches 20 A g^-1.After10 000 cycles,it shows excellent cycle stability(maintaining 95.78%at 20 A g^-1).The CoMnS-4//AC asymmetric supercapacitor device has an excellent energy density of 85.91 W h kg^-1when the power density is 800 W kg^-1.3.Reasonable design of composite materials with unique core-shell nanoflower structures is an important strategy to improve the electrochemical properties of supercapacitors such as capacitance and cycle stability.Herein,a two-step electrodeposition technique is used to orderly synthesize CuCo₂O₄ and CoS on Ni foam coated with Cu/Cobimetal metal organic framework(Cu/Co-MOF)to fabricate a hierarchical core-shell nanoflower material(CuCo₂O₄@CoS-Cu/Co-MOF).This unique structure can increase the electrochemically active site of the composite,promoting the Faradaic redox reaction and enhancing its electrochemical properties.The CuCo₂O₄@CoS-Cu/Co-MOF shows a prominent specific capacitance of 3150 F g^-1 at 1 A g^-1,marvelous rate performance of 81.82%(2577.3 F g^-1 at 30 A g^-1)and long cycle life(maintaining 96.74%after 10,000 cycles).what's more,the assembled CuCo₂O₄@CoS-Cu/Co-MOF//CNTs device shows an energy density of 73.19 Wh kg^-1 at the power density is 849.94W kg^–1,which has unexpected application prospects.