Preparation And Properties Of Flax Cellulose-based Carbon Materials For Supercapacitor Electrode

Owing to many excellent characteristics,such as rich sources,environmental friendliness,large pore network,high specific surface area,tunable porosities and relatively low density,porous carbon materials show great potential in energy storage and energy conversion applications.Supercapacitors are considered as the most promising energy storage device due to excellent cycling stability,long service life,high power density and green environmental protection.In this paper,the renewable,biodegradable and abundant cellulose materials in nature are reasonably utilized.Porous carbon materials with rich pore structure were prepared by using non-wood flax fiber as raw material,and the possibility of applying porous carbon to the electrode of supercapacitor was explored.This paper mainly conducts research from the following three aspects:1.Beating is one of the most important processes in papermaking,proper beating can make pulp fiber into fibrillation and improve their swellability.The 40,60,80°SR bleached flax pulp were used as the carbon precursor,KOH and urea in the form of mixed aqueous solution absorbed by flax pulp fiber were used as activators and dopants.It is then freeze-dried and activated at high temperature to obtain activated porous carbons(APCs).The results showed that with the increase of the degree of beating,the specific area and pore volume of carbon materials increased gradually,and the content of doped elements also increased,which APC-60 had the best electrochemical performance.2.Cellulose solution was obtained by dissolving bleached flax pulp with NaOH/urea aqueous solution,followed by gelation and freeze-drying to obtain a cellulose aerogel.Cellulose-based N-doped porous carbon aerogels(CCA)were prepared by self-activating cellulose aerogel containing NaOH and urea,which adjust the pore distribution,surface doping elements and electrochemical performance of CCA by changing the activation temperature(600,700,800?,respectively).As a result,CCA-700 had a maximum specific surface area and pore volume and exhibited excellent electrochemical performance.3.Graphene oxide(GO)not only has good electrical conductivity,but also can accelerate the gelation of cellulose solution.Cellulose solution was obtained by dissolving bleached flax pulp with NaOH/urea aqueous solution,and then mixing the GO solution prepared by the modified Hummer method into cellulose solution to obtain flax cellulose/GO hydrogel,and freeze-drying to obtain flax cellulose/GO aerogel.Then Flax cellulose/GO carbon aerogels(CGOCA)were obtained by activating flax cellulose/GO aerogel under the synergistic activation between sodium hydroxide and urea at 600,700 and 800?,respectively.The results showed that CGOCA-700 not only had the highest specific surface area and pore volume,but also had the best capacitance characteristics and lower equivalent series impedance.