Structure Regulation And Lithium-ion Energy Storage Property Of Polyacrylonitrile-based Nano-carbon

Today’s environmental pollution and energy shortage problems are gradually emerging,and the demand for green,economical,and high-storage-density electronic devices is increasing.Lithium-ion batteries based on long life have been widely used in energy storage equipment.The energy storage capacity of lithium-ion batteries has been greatly limited by the performance of anode materials.The development of anode materials with excellent performance and complete functions has become the research focuses.As a kind of anode electrode material with wide distribution,controllable cost,diverse structure,and environmental protection,carbon materials have become the focus of researchers.However,the application of carbon materials in lithium-ion batteries is greatly restricted by its low specific capacity and poor multiplier performance.Therefore,it is necessary to modify carbon materials through structural design and component modification to prepare practical and functional anode electrode materials.This thesis mainly focuses on acrylonitrile as raw material,through adopting the chemical structure doping of hetero-elements and physical structure design to regulate carbon materials,to prepare the structure and element controllable carbon materials,and study its electrochemical energy storage performance.The specific work content includes the following two parts:（1）Iodine and nitrogen double-doped carbon flowers were prepared through self-polymerization and high-temperature calcination of acrylonitrile with potassium iodide as a chemical etcher.The flower-like structure ensures the rapid diffusion of lithium ions.The iodine element improves the pore size distribution of the carbon material while the synergistic effect of iodine and nitrogen realizes high ion storage of the carbon material.In addition,the iodine atom also enhances the electrical conductivity of the carbon material and promotes the transfer ability of electrons.As an anode material of lithium-ion batteries,it has a reversible capacity of 410 m Ah g^-1after 150 cycles of 0.1 A g^-1.In addition,even if the current density was increased to2.0 A g^-1,the discharge-specific capacity can still be reached 181 m Ah g^-1after 1000discharge/charge cycles.The combination of electrochemical impedance spectroscopy,kinetics,and Galvanostatic Intermittent Titration Technique（GITT）shows that the material has fast charge transport kinetics and excellent rate performance.The iodine and nitrogen double--doped carbon flower material laid a certain foundation for the preparation and research of doped modified carbon anode materials.（2）Boron and nitrogen double-doped carbon flower was prepared by in-situ polymerization and high-temperature carbonization.The unique flower-like structure reduces the diffusion distance of lithium ions,and boron and nitrogen atoms provide more active sites,giving boron and nitrogen double-doped carbon flower excellent electrochemical properties.As an anode electrode material for lithium-ion batteries,the first discharge capacity is as high as 886 m Ah g^-1,and it still maintains 416 m Ah g^-1after 450 cycles.In addition,it exhibits excellent capacitance(182 m Ah g^-1)at high current density(2.0 A g^-1)even after 3000 cycles.The GITT test and the kinetic study showed that the material had excellent charge transport kinetics and contributed mainly to the capacitance characteristics in charge storage.In addition,the assembled full battery can still reach 104 Wh kg^-1 after 500 charge/discharge cycles at the current density of 0.1 A g^-1.These outstanding electrochemical energy storage performances prove that boron and nitrogen double-doped carbon flower materials have good charge transport,storage,and rapid charge and discharge capabilities.