Pore Structure Design Of Electrospun Carbon Fiber And Its Energy Storage Application

As a new type of energy storage device that has begun to be widely used in practical applications,supercapacitors stand out by virtue of their unique advantages in the competition with traditional capacitors and secondary ion batteries.The hybrid ion capacitor gradually developed from its foundation not only inherits the high power density and long cycle life of supercapacitors to a certain extent,but also has an energy density higher than that of supercapacitors.Regardless of the former or the latter,electrode materials play an extremely important role.The main work of this paper is to use the combination of electrospinning technology and pore-making method to prepare electrode materials with excellent electrochemical performance.The specific work content is as follows:1.The development of flexible supercapacitors is highly desired for electrode materials with good flexibility and a high specific surface area.The electrospun carbon fiber membranes(CFMs)have the possibility of being used as flexible electrodes due to their one-dimensional fiber structure.However,the porosity of the original PAN-based fibers is generally not high,and it is necessary to use appropriate methods to make holes and design the pore distribution.Herein,by treating the electrospun CFMs with KOH impregnation activation process,we have succeeded in making the activation of CFMs more uniform and avoiding the occurrence of local over-activation.On the premise of ensuring that the fiber structure of CFMs is not damaged,the specific surface area of activated CFMs(ACFMs)was increased to2408 m²g^-1,and the mechanical flexibility of CFMs was well maintained.As a result,the optimal ACFMs delivers a specific capacitance of 289.2 F g^-1at a current density of 0.5 A g^-1in aqueous electrolyte and an energy density of 14.8 Wh kg^-1in neutral electrolyte.In addition,the flexible solid-state symmetric supercapacitor also shows excellent electrochemical performance,making it have great potential in energy storage applications for wearable,foldable and portable electronic devices.2.Potassium ion hybrid capacitors are becoming an important development direction of capacitor systems due to the abundant potassium resources and low cost.However,the development of high-performance anode potassium storage materials is still an urgent problem to be solved.In this part,we designed a hollow MoS₂spherical shell structure(H-MoS₂@CNFs)wrapped in carbon fibers(CNFs).The hollow structure of MoS₂shortens the potassium ion transmission path and optimizes the contact between the electrode and the electrolyte.CNFs coating alleviates the volume expansion of MoS₂and provides a fast path for electrons.As the anode of a potassium-ion batteries(PIB),H-MoS₂@CNFs maintains a reversible capacity of366.1 mAh g^-1after 100 cycles at 0.1 A g^-1,and it possess a reversible capacity of184.7 mA g^-1even at 10 A g^-1,showing the the performance of high capacity and high rate.In addition,due to its excellent flexibility,the influence of binder and conductive agent on the quality of the electrode is avoided when preparing the independent electrode.As a result,the assembled H-MoS₂@CNFs//ACFMs potassium-ion hybrid capacitor(PIHC)exhibits a high energy density of 180.6 Wh kg^-1at a power density of 398 W kg^-1,which furnishes a reliable basis for the development of two-dimensional materials in PIHC.