Study On The Preparation And Electrochemical Performance Of Water Chestnut Shell-based Carbon Materials

With the advantages of abundant sources,low cost,easy availability,renewability,environment benign and facile preparation,the biomass-derived carbons are the first choice of anode materials for lithium/sodium-ion batteries(LIBs/SIBs)and supercapacitors(SCs).In this paper,the water caltrop shell,a kind of biomass waste,was used to prepare the electrode materials for the first time.The water caltrop shell-derived hard carbons were synthesized through the direct carbonization and hydrothermal synthesis respectively.It was investigated that the effects of the morphology and microstructure of the materials on electrochemical performance in detail and explored the energy storage mechanisms of LIBs/SIBs.Porous carbon was fabricated by activation of the water caltrop shell with KOH.The relationships among the specific surface area,pore size distribution and capacitance characteristics were systematically discussed.The water caltrop shell derived-hard carbons prepared by the direct carbonization possess low specific surface area,high heteroatom content and dense structure.The performance of lithium/sodium storage are significantly influenced by the carbonization temperature because of the difference in their microstructure.The water caltrop shell derived-hard carbons pyrolyzed at 900?(LJ-900)displays a highest reversible specific capacity of 347.5 mAh g-1 with an initial Coulombic efficiency(ICE)of 65.02%at 0.1C(1C=250 mA g-1)and an excellent cycling stability in LIBs.LJ-1300 electrode delivers a reversible specific capacity of 394.0 mAh g-1 with an ICE up to 84.3 1%at 0.1C,and a prominent cycling stability with 91.78%capacity retention after 200 cycles at 0.4C in SIBs.Via hydrothermal synthesis,the water caltrop shell derived-hard carbons inherit a large specific area and low heteroatom content.As the anode materials for LIBs,HT-1100 electrode delivers the best performance,including a highest reversible specific capacity of 405 mAh g-1 with an ICE of 57.32%at 0.1C.HT-1300 electrode shows the reversible specific capacity of 253.8 mAh g-1 as well as an ICE of 59.87%at 0.1C,and a superior cycling performance with the reversible specific capacity of 182.0 mAh g-1 only degraded by 8%after 200 cycles at 0.4C.Porous carbon(ALJ-x)was synthesized by chemical activation of water caltrop shell with KOH.The effects of different impregnation on the structure and electrochemical properties of the ALJ-x were systematically investigated.The results show that the specific surface area of samples increases as the carbonization temperature rises.Surprisingly,ALJ-4 manifests a specific surface area up to 2046.74 m2 g-1 when the impregnation ratio is 4:1.As the electrode materials in SCs,ALJ-4 exhibits a maximum specific capacitance of 126.1 F g-1 at the current density of 0.1 A g-1 and retains a specific capacitance of 112.3 F g-1 even at 0.5 A g-1.