Application Research Of Ti₃C₂T_x/Biomass Composite Films On Flexible Supercapacitors

The development and popularization of portable and wearable devices put forward higher requirements for energy supply devices.Compared with batteries,supercapacitors have been widely concerned and studied for its high-power density and excellent cycling performance.From the perspective of practical application,flexible supercapacitors,as the power supply components of wearable devices,have become one of the focuses of research because of their flexibility and foldability.Ti₃C₂T_x,a kind of 2D material,is widely used as electrode material for supercapacitors because of its great potential in energy storage.However,when used as flexible supercapacitor electrode material,the inherent stacking defects of 2D Ti₃C₂T_x nanosheets lead to a decrease in the utilization rate of the active site,and the weak force between the sheets leads to its lack of necessary mechanical properties,which makes it difficult to meet the practical application,thus restricting the further development of Ti₃C₂T_x in production and life.In view of the above defects Ti₃C₂T_x materials,the biomass materials(nanocellulose,tannin acid and sodium lignosulfonate)are used to composite with Ti₃C₂T_x.The mechanical properties of Ti₃C₂T_x/biomass composite film,benefited from these hydrogen bonds activity sites on the surface of the biomass and the interaction with Ti₃C₂T_x with termination group of O and OH on the surface,can be increased obviously.In addition,the biomass can be inserted into Ti₃C₂T_x nanosheets of interlayer to prevent its stack and expand layer spacing to expose more active sites and increase capacitance.Morever,using electroactive biomass tannic acid and sodium lignosulfonate can provide additional capacitance.The specific research work is as follows:1.A Ti₃C₂T_x/cellulose/tannic(Ti₃C₂T_x/CNF/TA)acid composite film was successfully prepared by vacuum-assistant filtration and used as flexible solid-state super capacitor electrode materials.The obtained Ti₃C₂T_x/CNF/TA_2.5 composite film has a specific capacitance of 240 F g^-1,increased by about 20%compared with Ti₃C₂T_xfilm,this is the result of insert of cellulose and tannins and expand the layer spacing.Furthermore,tannins provide excess capacitance.The rete performance was improved by 12%at the current density from 0.5 to 20 A g^-1 for the samples.In addition,the mechanical performance of the composite films was increased by 62.5%compared with the tensile strength of 12.5 MPa Ti₃C₂T_x film.The flexible solid-state supercapacitor assembled by this material reached a capacitance of 724.8 F cm^-3,and an energy density of 14.2 Wh L^-1 with a high-power density of 566.4 W L^-1,even a maximum power density of 22677.8 W L^-1.Due to the excellent mechanical properties of the electrode materials,the device assembled from the electrode materials has no damage under different bending angles,and its electrochemical capacitance has no loss,showing its great potential in the field of energy storage.2.Additionally,nacre-like Ti₃C₂T_x/HCNF@Lig composite films constructed with Ti₃C₂T_x and cellulose nanofiber(CNF)@sodium lignosulphonate(Lig)obtained through hydrothermal process have been successfully synthesized.Wood-inspired structure electroactive HCNF@Lig composite films present enhanced mechanical tensile strength of up to 132.8 MPa.The self-enhancing of HCNF obtained by hydrothermal treatment of CNF to associate HCNF films shows high tensile strength of up to 114 MPa.Nacre-like deformable Ti₃C₂T_x/HCNF@Lig(3@1)composite films exhibit high electrical conductivity(up to 1.75×10⁵ S m^-1)and mechanical properties(up to 256 MPa).The electrodes of Ti₃C₂T_x/HCNF@Lig(3@1)_97/3 composite films assembled flexible solid-state supercapacitors possess excellent volumetric specific capacitance of 748.96 F cm^-3.The corresponding arbitrary deformable flexible supercapacitor shows superior energy density of 16.2 Wh L^-1 and outstanding electrochemical cycle stability.The as-prepared self-enhancing HCNF and wood-inspired HCNF@Lig composite films and biomimetic nacre-like Ti₃C₂T_x/HCNF@Lig composite films with controllable conductivity,mechanical properties and excellent electrochemical performance are expected to be practically applied in the flexible/wearable energy storage devices and other fields.