Flexible Design Of Carbon Fiber Electrode And Potassium Storage Research

With the change of people’s lifestyle,the development trend of electronic products has gradually shifted from bulky and large electronic products to small,portable,customizable/wearable flexible electronic devices.Flexible electrochemical energy storage devices,considered as the pioneer of flexible electronic products,are extremely important.As the core of EES devi ce,the flexibility of electrode is indispensable.However,most of the previous reports focused on the optimization of the electrochemical properties of electrode materials,ignoring the flexible design of electrode materials.Using intrinsic flexibility as an independent electrode,compared with the electrode attached to the flexible substrate/collector,it will avoid the challenges of low energy density caused by the self weight of the inactive substrate and poor stability or even deactivation caused by the falling off of the active material during bending.Therefore,the research and development of intrinsic flexible electrode materials with significant flexibility,excellent electrochemical performance and environmental friendliness and suitable energy storage devices are the top priority.According to the above problems,carbon nanofibers（CNF）with high aspect ratio,large specific surface area and high conductivity are used as intrinsic flexible electrode materials.CNF as flexible electrodes on both sides can consider Faraday/capacitive hybrid capacitors with high energy/power density.As a potential substitute for lithium,potassium ion hybrid capacitor（PIHC）has also attracted much attention because of its high abundance,closer to the standard po tential of lithium battery and safer potassium potential.The specific research is as follows:（1）In Chapter 2,from the perspective of flexibility theory and simulation,nanofibers are analyzed and designed based on micro,meso and macro levels.Based on this model,CNF flexible anode with high electrochemical activity is successfully prepared and applied to PIB and PIHC.Finite element analysis and theory show that the triple structure of porous,kink and winding network can give nanofibers excellent flexibility.The nitrogen sulfur Co doped kinked carbon nanofibers（S/N-KCNF）have been proved to have excellent flexibility and electrochemical activity.In addition,the electrochemical analysis results show that the S/N-KCNF half cell has high specific capacity(410 m Ah g^-1 at 50 m A g^-1),high rate performance(2410 m Ah g^-1 at 50 m A g^-1)and long cycle stability（93.3%capacity retention after 2000 cycles）.In addition,the soft package PIHC assembled by S/N-KCNF//TAC（activated carbon）can supply power under bending.（2）In Chapter 3,activated porous carbon nanofibers（APCNF）with large specific surface area,significant electrical conductivity and excellent flexibility were prepared by sacrificial template and chemical activation,and used as flexible ca thode materials in PIB and PIHC.The test and analysis results show that APCNF contains the mixed energy storage mechanism of pseudocapacitance and electric double layer at the same time,so it has considerable energy density(105.1 Wh kg^-1)and power density(8091W kg^-1).In addition,the soft pack PIHC using APCNF and S/N-KCNF as flexible positive and negative electrodes can cycle stably at different bending angles.The above results show that the CNF after structural optimization and heteroatom modifica tion has the potential to be the flexible anode and cathode of PIHC at the same time.