Structural Regulation And Performance Study Of Carbon Based Materials For Zinc Ion Capacitor Cathode

The massive use of fossil fuels not only causes serious environmental pollution,but also puts great pressure on the energy demand of society,so it is especially important to research and develop new energy storage materials and devices.In recent years,a new low-cost zinc ion hybrid capacitor,which consists of a capacitive positive electrode and a battery negative electrode,has gained much attention since its inception because of its excellent energy storage performance.The zinc ion hybrid capacitor is based on the repeated stripping-deposition（oxidation-reduction）of the negative electrode of zinc metal and the continuous adsorption-desorption process of the positive electrode in the zinc ion energy storage system for electrochemical energy storage.This hybrid energy storage mechanism allows the device to have high specific capacity output while maintaining excellent safety and cycling stability,presenting a novel solution for future high-performance energy storage technologies.However,zinc ion capacitors still suffer from low energy density and mismatch between positive and negative electrochemical reactions.Therefore,there is an urgent need to study the electrode materials for zinc ion capacitors with matched positive and negative electrodes.In this thesis,we design and construct a new carbon material as the positive electrode material for zinc ion capacitors,assemble it with zinc negative electrode to construct zinc ion capacitors,and investigate the relationship between its structure and performance.The main research results are as follows:（1）Nitrogen-doped metal organic framework-derived porous carbon（NMDPC）cathode materials were constructed by in situ growth of metal organic framework（MOF）materials on carbon nanorods.A zinc-ion hybrid capacitor（ZHC）was assembled from NMDPC cathode and zinc metal cathode.It was found that due to the nitrogen doping,excellent pore structure and high specific surface area,the NMDPC-700 material exhibited excellent electrochemical properties such as high specific capacitance,high energy density and good cycling stability.Specifically,the ZHC exhibited high specific capacitance of 255.6 F g^-1 and high energy density of 90.88 Wh kg^-1 at a current density of 0.5 A g^-1,and high capacity retention of 97.8%after 10,000 cycles at a current density of 10 A g^-1.This study not only prepares porous carbon cathode materials with excellent performance and improves the electrochemical performance of zinc ion hybrid capacitors,but also provides theoretical guidance for the design and construction of carbon-based nanomaterials for ZHC.（2）A novel nitrogen-phosphorus co-doped Ti₃C₂ nanosheet（Ti₃C₂-N,P）was synthesized conveniently and efficiently by hydrothermal method using Ti₃C₂ as raw material and diammonium hydrogen phosphate as nitrogen and phosphorus sources.A zinc-ion hybrid capacitor（ZHC）was assembled from Ti₃C₂-N,P positive electrode and zinc metal negative electrode.It was found that the Ti₃C₂-N,P material exhibited excellent energy storage performance such as high specific capacitance,high energy density and good cycling stability due to the larger layer spacing and more lattice defects of MXene material by nitrogen and phosphorus atom doping.Specifically,the ZHC has a high specific capacitance of 238.95 F g^-1 at a current density of 0.5 A g^-1(much higher than that of undoped MXene at 62.68 F g^-1)and a high energy density of 43.89 Wh kg^-1,and the energy density of the device can still reach 29.87 Wh kg^-1 at a high power density of 5.75 k W kg^-1.At a current density of10 A g^-1,the ZHC exhibited an excellent capacitance retention rate of 95.2%after 10,000 times of continuous charging and discharging.This study not only prepared a nitrogen-phosphorus co-doped Ti₃C₂ cathode material with excellent performance to improve the energy storage performance of ZHCs,but also provided an effective strategy for the design and construction of cathode carbon materials for ZHCs.