Design Of Molybdenum Disulfide/Carbon Composites And Its Applications In Lithium-ion Batteries

The choice of anode material is critical to improving the performance of lithium-ion batteries.The graphite anode popular on the market today has the disadvantage of low energy density and cannot meet the requirements of large energy density.To this end,it is particularly urgent to explore new,high-energy-density lithium-ion battery anode materials.Among the many materials,transition metal sulfides have the advantages of high theoretical capacity and good electrical conductivity,and are considered to be lithium-ion battery anode materials with great application potential.However,transition metal-sulfur compounds have the disadvantages of low conductivity,cycling performance and poor rate performance,which hinder their application in lithium-ion batteries.In order to solve the above problems,molybdenum disulfide/carbon composites with different morphologies and structures were designed and synthesized to study their electrochemical properties,The specific contents are as follows:1.By hydrothermal method,sodium molybdate dihydrate was used as molybdenum source,thiourea as sulfur source,and treated fungus as carbon source to synthesize molybdenum disulfide/carbon composite precursors of different morphology,and rose-like,chrysanthemum-like and broccoli-like molybdenum disulfide/carbon complexes were obtained after annealing treatment.The experimental results show that the rose-like molybdenum disulfide/carbon composite has excellent electrochemical performance,and the Mo S₂/FC-2 electrode can still release the high discharge capacity of 885.1 m Ah g^-1 at a high current density of 2.0 A g^-1,and the reversible capacity can also be restored when the current density recovers to 0.1 A g^-1.2.On the basis of the aforementioned work,the electrospinning strategy is used to confine the rose-like molybdenum disulfide/carbon complex to the spinning fiber to form a 3D network structure.This structure is beneficial to improve the interfacial conversion reaction kinetics,increase ion channels,shorten the lithium ion intercalation and removal paths,and alleviate the volume effect of the electrode during the charge-discharge reaction.At the same time,electrospinning produces a large number of fiber structures,which increases the specific surface area of the material and is conducive to improving the surface capacitance.The electrochemical performance test results show that the discharge capacity at the current density of 5.0 A g^-1 is 387.4 m Ah g^-1.The discharge specific capacity after 200 cycles at current density 1.0 A g^-1 is 495.0 m Ah g^-1.3.Using the in-situ synthesis route,the molybdenum source and sulfur source were directly added to the spinning liquid for spinning,and then the multi-level layered structure of molybdenum disulfide nanosheets grown on carbon nanofibers in situ was constructed by hydrothermal and annealing treatment.Carbon nanofibers generated by electrospinning can provide a large number of electron/ion transport channels,improving the diffusion efficiency of ions in electrochemical reactions.The multi-stage hierarchical structure can increase the reactive site of molybdenum disulfide nanosheets,and the in-situ growth of molybdenum disulfide nanosheets has strong interaction with carbon fibers,which improves the stability of the structure.The electrochemical test results show that the discharge capacity of the composite can be maintained at 495.6 m Ah g^-1 at the current density of 5.0 A g^-1.After 200 cycles of discharge cycle at 1.0 A g^-1 current density,the discharge capacity remained at 641.2m A h g^-1,which proved that the obtained material had good cycle stability.