Construction And Properties Of MXene/Cellulose Flexible Conductive Composite Film

With the development of science and technology and the increasing demand for flexible electronic products,the wearable supercapacitors have attracted much attention.However,the extensive use of electronic products generates much electromagnetic interference(EMI),which seriously affects human health.Therefore,it is necessary to develop multi-functional flexible electronic products with energy storage and electromagnetic shielding.Transition metal carbide/nitride(Ti3C2Tx MXene)is a new type of two-dimensional conductive material.Whereas,the flexibility and mechanical strength of MXene based films are poor due to their size and disordered arrangement.The self stacking of MXene nanosheets affects the electrical properties of MXene based films and limits its application in flexible functional materials.Therefore,the article is dedicated to increasing the mechanical properties without damaging the good electrical conductivity of MXene based films and improving the stacking problem between MXene nanosheets.In this study,bacterial cellulose(BC)with a 3D network structure was used as a flexible intercalating agent for highly conductive MXene nanosheets,crosslinking agents(tannic acid,organic boron)and aramid nanocellulose(ANFs)were introduced to strengthen cellulose/MXene composite film,respectively.In addition,the production of high-performance MXene based special functional paper was expanded through the papermaking process.The mechanical properties,electrical conductivity,electromagnetic shielding and other properties of cellulose/MXene composite films and MXene based composite paper were further studied.The main research work in this thesis is as following:(1)A series of functionalized crosslinked nanocellulose/MXene flexible conductive composite films were prepared by combining BC with MXene using tannic acid and organic boron ester(organic boron)as crosslinking agents,which can be excellent electrode materials for supercapacitors.The effects of tannic acid and organic boron crosslinking agents on the various properties of cellulose/MXene composite electrodes were investigated.The electrodes were further assembled into symmetrical flexible supercapacitors and the electrochemical properties were investigated.The results showed that:(Ⅰ)the tensile strength of BC-B-MXene3(B,organic boron as crosslinking agent)and BC-TA-MXene2(TA,tannic acid as crosslinking agent)composite films were increased by 4.9 and 1.8 times compared with BC-MXene.The specific capacities of BC-B-MXene3 and BC-TA-MXene2 electrodes were 598 and 573 F/g at 1 A/g,respectively.The capacitance retention rates were 83.3%and 84.6%after 10000 cycles at 5 A/g.(Ⅱ)the mass specific capacities of BC-B-MXene3 and BC-TA-MXene2 flexible devices at 1 A/g were 410 and 350 F/g,respectively.The capacitance retention rates were 97%and 96%after 1000 folds,respectively.When the power density was 800 W/kg,the corresponding energy densities were 36.1 and 31.1 Wh/kg,respectively.(2)The ANFs/BC composite fibers with aramid nanocellulose(ANFs)as a reinforcement system for BC can be intercalating agent of MXene nanosheets.Subsequently,the prepared ANFs/BC composite fibers were used as intercalation agents for MXene nanosheets with high conductivity,which leveraged the synergistic effect of the three factors.Therefore,MXene nanosheets can evenly distribute in the ANFs/BC system and improve the mechanical properties of MXene/cellulose composite films.The effects of ANFs/BC content on the electrochemical,conductivity,mechanical properties and electromagnetic shielding properties of the ANFs/BC-MXene electrodes were studied.The electrode material was assembled into a symmetrical flexible supercapacitor to explore its electrochemical performance.The results show that:(I)when the addition amount of ANFs/BC was 20%,the tensile strength of ANFs/BC-MXene2 composite film reached the maximum value(33.5 MPa),which was 2.7 times higher than that of BC-MXene composite film.The specific capacity of ANFs/BC-MXene2 electrode was 580 F/g at 1 A/g.The capacitance retention rate was 83%after 10000 cycles at 5 A/g.The electromagnetic shielding effectiveness of the ANFs/BC-MXene2 composite film reached 44.2 dB.(Ⅱ)the mass specific capacity of ANFs/BC-MXene2 flexible devices was 370 F/g at 1 A/g.After bending for 180°,the specific capacity can still remain 99%of the initial value.The power density of the ANFs/BC-MXene2 flexible device was 800 W/kg,the corresponding energy density was 33.4 Wh/kg.(3)MXene based special paper can be prepared through the papermaking process.The surface sizing technology commonly used in papermaking processes is mainly to treat paper through cross-linking agents.Therefore,the cellulose/MXene composite film was treated firstly with crosslinking agents through the immersion method similar to the surface sizing process to explore the effects of the crosslinking agent on the conductivity properties,electromagnetic shielding and mechanical properties of the cellulose/MXene composite film.The results show that:the tensile strength of NCO-BC-MXene4 and BGT-BC-MXene4 composite films reached 64 and 52 MPa,which was 1.9 and 1.57 times higher than that of BC-MXene4 composite films,respectively.Moreover,NCO-BC-MXene4 and BGT-BC-MXene4 composite films still maintained excellent electrical conductivity and electromagnetic shielding performance.(4)Based on the previous three chapters,BC/MXene4 with excellent electromagnetic shielding performance,mechanical properties and conductivity was selected as the conductive filler,the green and low-carbon paper fibers were used as the matrix.MXene based conductive composite paper with excellent performance was prepared using wet papermaking and surface sizing processes.The effects of different processes and BC-MXene content on the comprehensive properties of MXene based conductive composite paper were explored,such as conductivity,electromagnetic shielding performance and mechanical properties.The results showed that:(I)the conductivity of MXene based composite paper(C-M)prepared by surface sizing process alone was 0,and the EMI SE value was only 1 dB.Therefore,the conductive filler MXene cannot be successfully inserted into the paper fibers through surface sizing process alone.(Ⅱ)the electrical conductivity and electromagnetic shielding effectiveness of MXene based composite paper through a combination of wet papermaking and surface sizing process(Mx/C)increased with increasing the BC-MXene content,but the mechanical properties decreased gradually.The combination of electrical conductivity and mechanical property testing results proved that M40/C composite paper had excellent performance(electrical conductivity:330 S/m;SE value:32 dB;tensile strength:23.6 MPa).The electromagnetic shielding effectiveness and electrical conductivity didn’t change after 2000 bends.It also had good photothermal conversion ability and thermal conductivity of 1.398 W/(m·K).