Research Of Synthesis And Electrochemical Performance Of Zinc/Carbon Based Nanostructured Materials

In order to meet the increasing energy demand brought by the development of society,the development of new kind of energy storage devices with high energy density,high power density,high cyclic life and high safety insurance has become the main research direction.The commercial energy storage devices at present have many defects,such as low energy density,low power density,slow charging speed and poor security.In order to solve these problems,we need to start with electrode materials,especially the development of new high-performance anode materials applied to energy storage devices,to meet the urgent energy demands of people.This dissertation focuses on the study of the negative electrode materials of new electrochemical energy storage devices with high energy density,high power density,high cyclic stability and high safety.In this dissertation,the controllable synthesis and electrochemical analysis of water-based zinc electrode and water-based carbon electrode are studied.In the research of water-based zinc electrode materials,principle of promoting uniform deposition of zinc electrode in the charging and discharging process is adhered to,and the corresponding electrochemical performance of water-based zinc electrode materials is improved.In the research of water-based carbon electrode materials,the electrochemical performance is improved by three-dimensional structure and surface doping.In terms of high-performance zinc materials,this dissertation mainly studies ZnO/GN composite materials,Zn-Al-CO₃ LDHs,Zn-Al-F LDHs and flower-like Zn-Al-CO₃ LDHs.In the aspect of high-performance carbon materials,this dissertation mainly studies nitrogen-enriched hollow carbon spheres.The main research findings are as fellows.?1?Study on the controllable synthesis and electrochemical properties of ZnO/graphene?ZnO/GN?composite.ZnO/GN composite with ZnO nanoplates in-situ grown on the surface of graphene was prepared,and the mechanism of vertical in-situ growth was studied by adjusting the first step reaction time.The mechanism of increasing the hydrogen evolution potential of graphene composite due to the in-situ growth of zinc oxide was studied,and the improved working stability of the zinc anode material was verified by the scanning electron microscopy of the negative electrodes.After 400 cycles at current density of 1 A/g,the flexible quasi-solid-state energy storage device based on the ZnO/GN composite still has a very high capacity retention of 86.69%of the initial capacity.The highest energy density of the device is 526.19 Wh/kg at the current density of 1 A/g based on the total mass of the active material,and it still has 377.03 Wh/kg at the maximum power density of 85.69 kW/kg.?2?Study on the controllable synthesis and electrochemical properties of Zn-Al-CO₃layered double hydroxides?LDHs?.Zn-Al-CO₃ LDHs nanoplates were prepared and their synthesis mechanism was studied.The electrochemical performance of this material was optimized by studying the difference of the morphology and electrochemical performance of the materials with different zinc aluminum ratios.The highest discharging specific capacity is 303.5 mAh/g at 1 A/g,and when the current density is increased to 30 A/g,this material still has 81.9%of the capacity at current density of 1 A/g.?3?On the basis of the prepared Zn-Al-CO₃ LDHs,the fluorine ion intercalated Zn-Al-F LDHs were prepared by self-assembly ion-exchange method,and their electrochemical properties as the negative electrode materials of energy storage devices were studied.Zn-Al-F LDHs have many advantages,such as high crystallinity,less impurities and more uniform size distribution,which is conducive to the maintenance of electrochemical performance during charging and discharging process.The energy storage device based on Zn-Al-F LDHs has very slow capacity attenuation and good cyclic stability during 600 charging and discharging tests.At the same time,at the current density of 1 A/g,the highest specific capacity of 383.08 mAh/g is obtained,and at the current density of 100 A/g,it can still maintain 72.03%of the specific capacity at the current density of 1 A/g.?4?On the basis of the prepared Zn-Al-CO₃ LDHs,the three-dimensional flower-like Zn-Al-CO₃ LDHs were prepared by one-step self-assembly hydrothermal method,and their electrochemical performance as negative materials of energy storage devices was studied.The influence of PSS concentration on the morphology and electrochemical performance of flower-like Zn-Al-CO₃ LDHs was studied,and the electrochemical properties of the material were optimized.At the current density of 1 A/g,the highest discharge capacity is 310.55 mAh/g.When the current density is increased to 50 A/g,this assembled device still has 75.8%of the capacity at the current density of 1 A/g.This material can maintain high specific capacity and have excellent cyclic stability during 200cycles,and still maintain 89.7%of the initial capacity after 200 cycles.?5?Study on the controllable synthesis and electrochemical properties of nitrogen-doped hollow carbon spheres.Through the process of coating,nitrogen enrichment,carbonization and template removal,the nitrogen-doped hollow carbon spheres were successfully prepared by multi-step method.The surface heteroatom doping and structural framework modification of carbon materials were studied.The effects of calcination temperature on the morphology and electrochemical performance of the final product were studied,and the electrochemical performance of the materials was optimized.During 2000 cycles,the specific capacity of the material keep constant,and the remaining capacity is close to 100%.In addition,when the current density is 1 A/g,the material has the highest discharge capacity of 285 F/g;and when the current density is increased to 20 A/g,the material still has 77.2%of the capacity at the current density of 1 A/g.