Preparation Of Carbon Nanocomposite Based On Potassium Citrate And Its Application In Flexible Supercapacitors

Flexible electrochemical energy storage devices are the core technology that supports the development of flexible electronic devices and are the most important development direction in the field of energy storage.Among many energy storage methods,supercapacitors have become a research focus in recent years due to their fast charge and discharge rate,excellent cycle stability and specific capacitance.Electrode materials are the heart of supercapacitors,so a lot of research is devoted to the development of new electrode materials.Electrode materials mainly include carbon-based materials,metal oxides/hydroxides,and conductive polymers.Because carbon-based materials have the characteristics of high specific surface area,low cost,high physical and chemical stability,and easy synthesis and improvement,they are widely used as electrode materials for electric double layer capacitors and have become the focus of attention in the current material field.Based on the characteristics of the above-mentioned carbon-based materials,this article uses electrospinning technology and high-temperature calcination to prepare flexible carbon nanofibers;prepares silver nanowires/porous carbon composites by solvothermal method;prepares silver nanowires/porous by vacuum filtration method carbon composite conductive film material.And use a variety of analysis methods and characterization techniques to explore the structure and electrochemical properties of the materials.Specifically,it includes the following three parts:(1)The first part uses electrospinning technology to prepare potassium citrate/polyacrylonitrile electrospun membrane,and prepare composite nano-carbon fiber after high temperature calcination.Based on the characteristics of multi-stage decomposition of potassium citrate,carbon nanofibers have the advantages of novel microporous structure and good conductivity,which help to improve the capacitance performance of carbon materials.Specifically,the product prepared when the potassium citrate addition amount in the spinning precursor solution is 1 mg/ml has a specific capacitance value of as high as 404 F/g at a current density of 1 A/g.Compared with polyacrylonitrile fiber,its Cs has increased by 100%,and its specific capacity can still reach 270 F/g even at a high current density of 10 A/g.In the two-electrode symmetrical capacitor(SC)system test,the specific capacitance reached 93.20 F/g at a voltage range of 0-1.4 V and a high current density of 10 A/g.The capacitance retention rate of the SC system can still reach 99.3%after 5000 cycles at a current density of 5 A/g.This provides a guarantee for the long-term stable operation of the supercapacitor.(2)In the second part,silver nanowires(Ag Nanowires,Ag NW)with uniform morphology and size were synthesized by solvothermal method,using ethylene glycol to reduce silver.One-step calcination of potassium citrate was used to prepare 3D porous carbon nanosheets(Porous Carbon,PC),which were introduced into the Ag NW preparation process to synthesize Ag NW/PC composites.The Ag NW/PC composite material has a novel structure and excellent performance.The experiment found that when the PC doping amount is 1.5 mg/mL,the diameter of Ag NW is about 200 nm and the length is about 25?m.The Ag NW/PC composite prepared under this ratio was tested for its electrochemical performance using a three-electrode test system.The specific capacitance value of the composite material can reach 64 F/g at a current density of 0.1 A/g.(3)The third part is the use of vacuum filtration to prepare Ag NW/PC composites dispersed in 70%ethanol/water solution into a film?The film was peeled off and transferred,and a polyvinyl alcohol/phosphoric acid(PVA/H3PO4)hydrogel was coated on one side to obtain a flexible Ag NW/PC composite film.The R/R0 of the Ag NW/PC composite film is only 1.3 after being bent 1000 times with a bending radius of 2 mm,showing good conductivity stability.When the Ag NW/PC composite film is placed at an extreme temperature of 90? for 60 minutes,the R/R0 is only 1.54,showing good oxidation resistance.The resulting Ag NW/PC composite film is assembled into a symmetrical capacitor(SC).Through calculation,we find that the specific capacity is 23.1 F/cm2 in the straight state,and the specific capacity is 23.3 F/cm2 in the twisted state.The lower specific capacity is 20 F/cm2.This result shows that the assembled symmetrical supercapacitor has high flexibility and has good application prospects in portable electronic equipment and wearable devices.