Preparation And Electrochemical Performance Of Molybdenum Disulfide/Carbon Composites

Substantial attention has been given to clean and efficient energy storage devices due to environmental pollution and energy crisis.Sodium-ion batteries（SIBs）have become a promising energy storage device,with low cost,high safety and abundant sodium resources.At present,the key to sodium-ion batteries is the development of suitable electrode materials.Molybdenum disulfide（MoS₂）,a typical two-dimensional layered material with unique structure and property,has received wide attention in energy storage and transformation field.However,the inherent defects of MoS₂（low conductivity,easy agglomeration,low specific surface area,poor stability,etc.）inhabit its further application.Therefore,we designed MoS₂composites with variable structures and compositions.The main content of this thesis is as follows:（1）3D molybdenum sulfide/Graphene（3D MoS₂/G）composites were prepared by solvothermal method with Graphene oxide as carbon source,ammonium molybdate as molybdenum source,carbon disulfide as sulfur source and reducing agent,silicon dioxide nanospheres as template.HRSEM,HRTEM,Raman,XPS,XRD etc.were used to analyze the composition and morphology of these samples.The electrochemical performance of 3D MoS₂/G composites as anode electrodes in sodium-ion batteries was tested through the galvanostatic discharge/charge voltage,CV,cycling stability and rate performance.The results show that 3D MoS₂/G has the best performance in cycling stability and rate performance(525m A h g^-1 after 100 cycles at the current density of 500 m A g^-1).This mainly dues to the addition of Graphene,which improves the conductivity of MoS₂and inhibites the volume expansion of MoS₂during charge/discharge,thus enhancing the structural stability of the composites.In addition,the Si O₂ templates constructed macroporous structure which brought abundant specific surface area,active sites that are conducive to sodium-ion adsorption,electrolyte infiltration and sodium-ion diffusion.（2）Using sodium molybdate as molybdenum source,thiourea as sulfur source,commercial carbon paper as substrate and silicon dioxide nanospheres as template,3D F-MoS₂/CP,2D MoS₂/CP,3D foam MoS₂ electrodes were prepared by simple high-temperature reduction and etching methods.The obtained materials were tested as sodium-ion batteries’anodes.The effects of morphology,structure and specific surface area of MoS₂ on electrochemical performance were investigated,and compared our self-supported electrode with traditional electrode.The results show that Si O₂ nanospheres templates provided more sodium-ion transport channels,increased the specific surface area of MoS₂ and exposed more active sites,which are beneficial to the storage of sodium-ions.In addition,carbon paper has excellent conductivity which increases the conductivity of MoS₂,facilitating the charge transportation and ion diffusion.The 3D F-MoS₂/CP free-standing electrode showed the best rate performance and cycle stability.In the rate performance test,3D F-MoS₂/CP showed a high capacity(225m A h g^-1 at 2000 m A g^-1)and good capacity recovery.In the cycling test,at 2000 m A g^-1,after1000 cycles,the capacity retention rate was 67%with an extra-low per cycle decay（0.033%）and high Coulombic efficiency（99.8%）.