Structure And Electrochemical Performance Of Pilot-Scale Super Activated Carbon

Super activated carbon has great potential in the electrochemical energy storage due to its very large specific surface area,relatively narrow pore size distribution,low ash content and good electrical conductivity,etc.Alkaline activation method,especially the KOH activation of petroleum coke is the common method to prepare super activated carbon,but its industrial preparation still faces many challenges both in technique and product quality.Recently,we overcame some major technical difficulties including the optimized design of reactor mass transfer,the metal potassium processing technique,the ash control technique,the particle size control technique,and the surface treatment technique,thus offering the stable pilot-scale production of super activated carbon products.In this thesis,we systematically analyzed the physical structure of this pilot-scale super activated carbon?SAC?,and compared its performance with the commercially available activated carbons.Then,we explored the electorchemical performace of SAC for the electrode materials of supercapacitor and the materials for Li-S cathode.The major concluions are summaried as follows.?1?Using petroleum coke as raw material and KOH as activator,the SAC has been sucessfully prepared in a pilot scale?30 tone/year?.Its main performance indexes are as follows:the average particle size of?i ?m,tap density>0.35 g/cm3,conductivity>4 S/cm,the surface area>2000 m2/g,the average pore size 1-3 nm,ash<0.07 wt%,oxygen content<2 wt%.Compared with commercially aviable activated carbons,the SAC has higher specific surface area,lower ash content and oxygen content,and narrower particle size distribution.?2?When used as EDLCs' electrode material in Et₄NBF₄/PC electrolyte,SAC could deliver a specific capacitance of 122 F/g at 0.5A/g,and 104.6 F/g at 10 A/g,and a good capacitance retention of 94.5%after 5000 cycles.Due to the more symmetric structure and smaller ionic radius of SBP+,SAC in SBPBF4/PC electrolyte has a high capacitance of 134.6 F/g,which is amost 10%higher than that in the Et4NBF4/PC.In addition,the capacitance retention in SBPBF4/PC is 96.2%after 5000 cycles.?3?The potential application of SAC in the high-performance Li-S battery was also explored.Firstly,using SAC as conductive support material,SAC/S composite could be easily prepared by a melt-diffusion method.Due to the rich microporous structure and strong confined effect,SAC/S delivered a specific capacitance of 870 mAh g^-1 at 0.5 C and a capacitance retention of 67%after 300 cycles.Secondly,SAC could be served as a f'unctional coating which could be coated on the external surface of sulfur cathode or separator.It was found that the SAC coated on the separator performed better than that coated on the sulfur cathode.The pure sulfur cathode with the assistance of SAC coated separator could deliver an initial capacitance of 1320 mAh g^-1 at 0.5 C and a reversible capacitance of 997 mAh g^-1 with a capacitance remaining of 76%after 100 cycles.