| In recent years,under the fast development of industrialization,the demand for available energy has increased day by day.However,the long-term development of energy system is impeded by the energy crisis and serious environmental pollution,which are caused by the continuous exploitation and consumption of limited traditional fossil energy.Therefore,it is necessary to explore more suitable energy storage systems.In the continuous research process,lithium-ion batteries(LIBs)have received extensive attention and gradually incorporated into the commercial application map,and finally achieved the relevant development and application in different fields.Nevertheless,in view of the inherent problems of limited lithium resource reserves and uneven distribution,lithium-ion batteries are difficult to meet the development needs of large-scale energy equipment in the future.Based on this,a series of electrochemical energy storage devices such as sodium/potassium ion batteries(SIBs/KIBs)and corresponding hybrid ion capacitors(SIHCs/KIHCs)are widely regarded as promising energy storage devices to replace the traditional lithium ion batteries due to their advantages of abundant crustal resources and low raw material prices.Nevertheless,the large radius of Na/K ions makes it difficult for these energy storage devices to obtain satisfactory electrochemical performance during cycling process.Therefore,it is necessary to explore more suitable electrode materials to promote its development.Among various electrode materials,transition metal compounds materials(TMDs)have been widely investigated due to their abundant reserves,low cost,good ionic conductivity and electrochemical stability.Based on this,this paper intends to prepare a variety of transition metal compound composite electrode materials with different morphological and structural characteristics through nanostructure design and composite structure engineering,and then apply them as anode materials in sodium/potassium ion batteries and corresponding hybrid ion capacitors.At the same time,the reaction mechanism and kinetic process of the materials were systematically analyzed through a series of electrochemical tests,and the relevant contents are as follows:1.The MoSe2-C one-dimensional hollow nanotube(MoSe2-G-CNTs)composite is synthesized by using manganese dioxide(MnO2)nanowires as bifunctional template through subsequent catalytic polymerization and high-temperature calcination process.Then,the MoSe2-G-CNTs are employed as anode material for sodium/potassium ion storage,denmostrating high electrochemical storage capacity and long cycle stability.As the anode material in KIBs,it still has a specific capacity of 188 mAh g-1 after 2000 cycles at a current density of 1.0 A g-1,and 236 mAh g-1 after 5000 cycles under a current density of 5.0 A g-1 for Na+storage.Besides,the electrochemical reaction process and kinetic characteristics of MoSe2-G-CNTs are further revealed by in situ Raman and Galvanostatic intermittent titration technique(GITT)measurements.Furthermore,the material is successfully applied in potassium ion hybrid capacitors(KIHCs)through reasonable matching with activated carbon(AC)cathode,which could present a high energy density of 109.8 Wh kg-1 and a stable cycling life over 6000 cycles at a current density of 2.0 A g-1,denmonstrating the huge development prospect.2.The unique MoSe2-carbon three-dimensional hollow nano-bowl(MoSe2(?)CNB)nanocomposite is successfully prepared by using the silicon dioxide(SiO2)nanospheres as the hard template through hydrothermal reaction and subsequent high-temperature calcination.The obtained MoSe2(?)CNB occupies a variety of excellent structural properties including hollow nanobowls construction,heteroatomic nitrogen doping and carbon coating.When used as anode materials,the MoSe2(?)CNB exhibits excellent electrochemical sodium/potassium ion storage properties,including a high reversible capacity(405 mAh g-1/0.2 A g-1,337.4 mAh g-1/0.1 A g-1)and long cyclic stability(7500 cycles/10 A g-1,550 cycles/2.0 A g-1).The relevant in situ and ex situ tests reveal the electrochemical reaction mechanism during the cycling process and the possible reasons for its excellent electrochemical performance.Furthermore,the KIHCs are successfully assembled with MoSe2(?)CNB anode and AC cathode,exhibiting a high energy density of 130.7 Wh kg-1 and a power density of 13607 W kg-1.The above work could provide enlightenment for the exploration and application of various energy storage devices in the future.3.The uniform WSe2 nanoparticles-carbon two-dimensional nanosheets(WSe2/PNCNS)composite is prepared by using MnO2 nanosheets as the reaction template through subsequent template removal and high-temperature calcination process.Profiting from the strong synergistic effect between WSe2 and carbon,the WSe2/PNCNS anode materials can show excellent electrochemical sodium/potassium ion storage performance.When used as an anode in sodium ion battery,it can display a high reversible capacity(382.7 mAh g-1,0.2 A g-1)and a long cycle life of over 7500 cycles under a high current density of 10.0 A g-1.Besides,when employed as anode in potassium ion battery,it has a long cycle life of over 2500 cycles with a capacity of 112.2 mAh g-1 at the current density of 2.0 A g-1,showing the good multifunctional application characteristics.Furthermore,the potassium ion storage mechanism of WSe2/PNCNS electrode and the reason for its excellent electrochemical performance were also investigated through a series of measurements(in situ Raman,ex situ XRD,ex situ HRTEM)and theoretical calculation results,which provides more enlightenment for future large-scale development.More importantly,the successful assembly of Na/K hybrid ion capacitors provides more possibilities for the commercial development of energy storage devices in the future. |
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