Applications Of Nanocellulose Based Composite Carbon Aerogel In Flexible Electron Devices

In recent years,the rapid development of flexible wearable electronic devices has expanded the versatility of human-computer interaction and changed the traditional health diagnosis model.The key technologies for the development of flexible wearable electronic devices mainly focus on flexible sensor technology,integrated technology of sensor devices and wearable substrates,and flexible portable energy storage technology.In different application scenarios,along with the mechanical motion of external forces and changes in ambient temperature/humidity,electronic devices are required to meet good flexibility and stable sensing and energy storage performance.3D porous carbon materials have unique advantages over metals and conductive polymers,including their hierarchical pore structure,high specific surface area and high pore volume,good thermal/chemical stability,light weight,high conductivity,and strong plasticity.Based on the above characteristics,the 3D porous carbon shows a specific structure-response capability through the micro-nano-level structural design,which is of great significance for the development and application of flexible sensor devices.On the other hand,3D porous carbon materials are easy to be modified and regulated,which are ideal electrocatalyst carrier.At the same time,based on the structural considerations of the energy storage electrode system,3D porous carbon can be developed as a three-dimensional self-supporting air electrode material to meet the requirements of new generation of high energy density metal-air batteries for flexible energy storage.In this paper,renewable cellulose nanofiber?CNF?is used as the basic component of flexible 3D porous carbon.In respect of the application of 3D porous carbon in flexible electronic devices,including flexible pressure sensing and flexible zinc-air batteries?ZAB?,a series of studies have been carried out,including the construction strategy,the structural mechanism and the control mechanism of material mechanical properties,the control of electrocatalytic performance and the design of three-dimensional self-supporting air electrodes,etc.The specific contents are as follows:1.Through the strategy of directional freezing casting,1D nanocellulose and carbon nanotubes?CNT?and 2D graphene are used to build a 3D continuous wave layered network structure.Based on the synergy of multi-scale nanostructures,the prepared CNT/r GO-CNF carbon aerogel has excellent structural stability,outstanding compressibility and mechanical stability under high strain compression at ultra-low density(?4.3 mg cm^-3).And the 50%strain/50,000 cycles of cyclic compression test,showed excellent fatigue resistance,and energy dissipation ability to resist mechanical deformation.2.The compressible elastic CNT/r GO-CNF carbon aerogel was used as the piezoresistive sensing element to further explore the mechanical-electrical response performance of 3D layered porous carbon aerogel.The test results show that the CNT/r GO-CNF sensing element has good electromechanical response capability,high signal-to-noise ratio,and excellent pressure/strain response stability and sensitivity.It has different sensitivities in a wide stress range(0-100 Pa is 22.05 k Pa^-1,0-1 k Pa is 11.82 k Pa^-1),especially has a high sensitivity coefficient?GF=15.07?under small strain.The micro water drop test shows that the material has an ultra-low detection limit of 0.875 Pa for micro pressure.The component is further used in wearable sensing applications,which can realize human pulse monitoring and motion signal output.These functions make CNT/r GO-CNF carbon aerogels expected to be widely used in flexible wearable electronic derivative products for biological signal monitoring.3.By building synergistically with nanocellulose and graphene,and introducing Fe-PA/GA@GO/CNFs doping system,Fe P/Fe₂O₃ loaded and N,P-doped carbon aerogel?Fe P/Fe₂O₃@NPCA?with 3D honeycomb structure was in-situ synthesized.Fe P/Fe₂O₃@NPCA have good conductivity,mechanical stability,vertical channels and rich pore structure to provide effective transmission channels for gas diffusion and electrolyte infiltration.Thanks to its high specific surface area and pore structure,and the synergy between Fe P/Fe₂O₃ and N,P-doped carbon nanosheets,3D carbon aerogels exhibit excellent ORR/OER electrocatalytic activity(E_gap=0.79 V),which can be used as a three-dimensional self-supporting air electrode.The result not only show excellent battery performance through the conventional aqueous ZAB system,including high energy density(130 m W cm^-2),high specific capacity(5 m A cm^-2/767 m Ah g^-1)and excellent charge and discharge stability(5 m A cm^-2/160 h),the flow type ZAB device and the flexible solid-state ZAB have also been used to expand the application of three-dimensional self-supporting air electrodes,with good charge and discharge stability.In particular,the assembled solid ZAB shows good flexibility,bendability and relatively stable battery performance under bending/compression mechanical external forces.