MOF-Derived Molybdenum Disulfide And Its Heterostructures For High-Performance Sodium-Ion Batteries

The rapid development of modern industry leads to the increasing depletion of energy resource.It is urgent to develop clean energy and large-scale energy storage system.Due to the high cost caused by the shortage and uneven distribution of lithium resources,traditional lithium-ion batteries are not suitable for large-scale energy storage systems.Benefit from the abundant natural reserves and similar chemical properties of Na⁺to Li⁺,sodium-ion batteries are expected to replace lithium-ion batteries to make up the shortfall in the demand for large-scale energy storage systems.However,the larger radius of Na⁺leads to the sluggish ion transmission and structural collapse of electrode during the repeated charge-discharge process,resulting in poor rate performance and rapid capacity attenuation.In this dissertation,in view of the above problems,the advantages of MOF materials and transition metal sulfide is utilized to prepare transition metal sulfide using MOFs as precursor,then through the carbon recombination and the construction of heterostructure to improve the properties.The electrochemical performance,reaction mechanism and performance in full-cell of the modified transition metal sulfide composite anode were investigated in the sodium-ion battery,and the electrochemical performance was further tested in the potassium-ion battery.The main contents and research results are as follows:1.MoS₂@C anode for sodium ion batteryThe rod-like MoS₂ derived from Mo-MOF was covered by polydopamine coating layer.After carbonization,MoS₂@C multiple carbon composite with core-shell structure was obtained.MoS₂@C anode shows improved electrochemical performance in sodium ion batteries.A high specific capacity of 450 m Ah g^-1 is maintained after 200 cycles at the current density of 1 A g^-1.At the current density of5 A g^-1,the specific capacity reaches 274 m Ah g^-1,and when the current density reduces to 0.1 A g^-1,the specific capacity recovers to 475 m Ah g^-1,showing good rate capacity.In addition,on the basis of exploring the size control factors of MOFs and the influence of electrolyte on the performance of the metal sulfide electrode,the appropriate size of MOF and electrolyte were determined.However,the enhanced performance brought by the simple carbon recombination strategy is limited.2.MoS₂-Zn S@C heterostructure anode for sodium-ion batteryCarbon-coated MoS₂-Zn S heterostructures（MoS₂-Zn S@C）were constructed by treating the MOF precursor with a one-step sulfurization/carbonization strategy.The heterostructures not only introduce abundant C-S-C and C-N bonds which contribute to ion storage with enhancive active sites,but also effectively accelerate the ion diffusion and the reaction rate.Corresponding reaction mechanism was revealed via XRD and HR-TEM tests.Compared with pure MoS₂ and Zn S,the sodium-ion batteries with MoS₂-Zn S@C heterostructures anode show outstanding rate capability and long cycle stability.The specific capacity is about 309 m Ah g^-1 at 10 A g^-1and343 m Ah g^-1 after 1200 cycles at 5 A g^-1.In addition,a high specific capacity of 270m Ah g^-1 is achieved at 1 A g^-1 in a full-cell made up of MoS₂-Zn S@C/ether-based electrolyte/Na₃V₂（PO₄）₃,showing sufficient application potential.Extended the application to potassium-ion batteries,the MoS₂-Zn S heterostructures also shows enhanced K⁺storage capacity.