| Lithium-sulfur battery is one of the most promising lithium secondary battery.However,the electrical conductivity of the elemental sulfur and its discharge end products are bad,in the process of charging and discharging,polysulfide dissolve in the electrolyte,then shuttling back and forth between the cathode and anode,which causing the deterioration of cell cycle stability and lower the utilization of active material,greatly hindered the development of lithium-sulfur battery in the actual application.In this paper,the preparation of the deoxidized carbon coated CNT-S composite were achieved,then the use of synthetic LATP solid electrolyte assembled new semi-solid lithium-sulfur battery for use as a solution,so as to improve the specific capacity and cyclic stability.This subject adopts two steps to synthetic the deoxidized carbon coated CNT-S composite.First the method of ball mill and heating is used for physical mixing,Then hydrazine hydrate was used to deoxidizing the carbon precursor for the preparation of the deoxidized carbon in the aqueous solution.By using the method of ultrasonic stirring,the carbon layer was coated on the surface of CNT-S,which forming a three-dimensional structure of cladding.XRD,SEM and TGA tests showed that elemental sulfur and carbon nanotube have good crystal type and degree of crystallinity;Sulfur fully spread into the holes or gaps of carbon nanotubes,this carbon layer coated on the surface of the CNT-S material showed characteristic peak bulge,exquisite deoxidized carbon layer evenly coated on the outer surface of CNT-S,sulfur content was 64%,meet the requirement of the use of lithium-sulfur battery.Through a variety of preparation technology of exploration,best ratio of material components for(CNT: S=2:7 deoxidized carbon: CNT-S=1:4);Temperature conditions for room temperature,using ethanol as dispersant,hydrazine hydrate and deoxidized carbon mass ratio as 9:10,reduction for 12 hours,under the condition of alkaline(PH=8),and then the composites assembled into liquid lithium-sulfur battery which have higher discharge specific capacity and greater cycle performance.By comparing the deoxidized carbon coated CNT-S composite and CNT-S composite which assembled into liquid battery:CV and EIS test showed that the utilization rate of material and good electrical conductivity,At the small discharge current density of 100mA/g,the deoxidized carbon coated CNT-S composite showed higher first discharge capacity which is 1221mAh/g,the utilization rate of sulfur is 72.9%;After 200 cycles,the specific capacity still remained at around 810mAh/g,the capacity retention rate is 66.3%,equivalent to only a 0.17% reduction in each cycle,at the same time its overall coulomb efficiency is about 98%.In order to finally solve the problem of the dissolving of polysulfide,this experiment using deoxidized carbon coated CNT-S composite as anode,then add the synthetic LATP block as solid electrolyte to assemble new semi-solid cell.Electrochemical tests showed that: At the current density of 100mA/g,given by the start of the 1022mAh/g fell to 890mAh/g after 50 cycles,capacity remained at a rate of 87%.At the same time the semi-solid cell also showed a better robustness under different charge and discharge current density.Not only verify the advantages of deoxidized carbon coated CNT-S composite relative to the CNT-S,but also verify the feasibility of whole semi-solid cell structure design,provided the practical application of lithium-sulfur battery with new solution. |
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