The Study Of Biopolymer/PPy And Nanosphere Composite Hydrogels

Supercapacitors,with superior characteristics of high power density,ultralong cycle life and fast charge and discharge rates,have become the hotspot of scientific fields both domestic and overseas.Electrode materials,as one of the key factors to determine the energy storage capacity of supercapacitors,have become the focus of the research of supercapacitors.Biopolymer materials(such as sodium lignosulfonate(Lig))have attracted wide attention of researchers both at home and abroad due to their abundance,low cost and no pollution.In addition,Lig,due to its large amount of electroactive groups(such as phenolic hydroxyl group and methoxyl group),can provide high specific capacitance during charging and discharging process.However,due to its poor electrical conductivity,the application of Lig in supercapacitor electrode materials is limited.Polypyrrole(PPy),as one of the most popular candidate of conductive polymer electrode materials,possesses the advantages,such as easy availability of raw materials,simple preparation,excellent electrochemical performance and high conductivity.Unfortunately,for the poor stability of PPy,it is not conducive to practical application.Therefore,Lig and pyrrole(Py)were used as the raw materials to prepare high electrochemical performance Lig/PPy composite materials(LP),high mechanical properties and electroactive Lig/PPy composite hydrogel(Lig/PPy hydrogel)and functionalized carbon nano sphere Lig/PPy composite hydrogel(FPNSLP).The specific research contents are as follows:(1)The composite of sodium lignosulfonate and polypyrrole(LP1)was successfully prepared via in situ polymerization using Lig and Py as the raw materials.LP1 has a specific capacitance value of 346 F/g at current density of 1 A/g.(2)The Lig/PPy hydrogel with electroactive three dimensional network structure was successfully prepared by polymerization of Py in Lig aqueous solution using FeCl3 as initiator.The excellent hydrogel(LP54)formed crosslinking short fiber and hierarchical porous structure.The hydrogel exhibited a maximum compressive strength of 6 KPa,showing a good mechanical performance.When used as the electrode of supercapacitors,LP54 showed outstanding electrochemical performance.As the current density is 0.5 A/g,the specific capacitance of the hydrogel LP54 displayed high specific capacitance of 409 F/g with good rate capability(62.3%)from 0.5 A/g to 10 A/g.Moreover,Under high current density of 10 A/g,the capacitance of the LP54 hydrogel can be maintained at 70.8%of the initial value after 1000 cycles.(3)The carbon nanospheres(PNS)with specific surface area of 2223 cm3/g were obtained by carbonization and KOH activation using PPy nanospheres as carbon precursors,which were synthesized by emulsion polymerization of Py.The functionalized carbon nanospheres(FPNS)were prepared through a hydrothermal process using PNS and Py,and then the functionalized carbon nanospheres Lig/PPy composite hydrogels(FPNSLP)were successfully prepared using FPNS,Lig and Py under low temperature in situ polymerization.At a current density of 0.5 A/g,the FPNSLP hydrogel has a specific capacitance of up to 538 F/g;the current density is from 0.5 A/g to 10 A/g,and its rate performance is as high as 68.4%.Additionally,FPNSLP hydrogel showed a superior mechanical property with the maximum compressive strength by up to 9.3 KPa.