Synthesis And Performances Of Cathode Materials With Layered Structure For Electrochemical Energy Storage Devices

In recent years,the environmental and energy problems have become serious with the impact of human activities on the nature gradually.In order to solve these problems,renewable energy sources have attracted the worldwide attention.An efficient,safe and cheap energy storage is essential for largescale use of renewable energy sources,such as wind power and photovoltaic.Ion batteries and electrochemical capacitors,as two primary forms of electrochemical energy storage devices,have become the focus of current researches.The charge storage of ion batteries relies on the intercalation and deintercalation of ions between positive and negative electrodes.Therefore,this kind of device has the characteristics of high specific energy and low specific power.Differently,electrochemical capacitors store charge on the surface of electrode/electrolyte though fast ions adsorption.Hence,the characteristics of electrochemical capacitors are low specific energy and high specific power.Limited by the energy storage mechanism,it is difficult for a single electrochemical energy device to realize high specific energy and high specific power simultaneously.Therefore,in this work,the specific energy and specific power of electrochemical energy storage devices will be balanced through design of electrode material structure which is taken as the topic to be investigated and discussed.The typical two-dimensional layered tungstic acid linked pernigraniline(TALP)materials was studied as the main research object.The structure,performances,charge storage mechanism,kinetic behavior and electrode preparations of TALP were investigated in the main research topic.Then,the layered V2O5 materials taken as the research comparison object was modified by high-gravity technology and metal elements doping and the influence on the kinetic properties of modified V2O5 materials as cathode materials of lithium ion batteries were also studied.The main contents and progress of this work are as follows:1.Two-dimensional layered TALP materials were successfully prepared by a simple precipitation method.The structural and electrochemical properties of TALP were studied compared with polyaniline(PANI),.The results showed that TALP have a typical two-dimensional layered structure and the layer spacing is 11.8 A.Compared to PANI,the CV curve of TALP electrode is similar to that of PANI.Besides,TALP electrode has the rapid charge/discharge capability at high current densities,as well as excellent cyclic stability.The capacity retention of TALP electrode is 63.3%after 2000 cycles at a current density of 200 mA g-1 which is much higher than that of PANI electrode.2.Two-dimensional layered TALP materials were successfully prepared by a simple precipitation method.The structural and electrochemical properties of TALP were studied compared with polyaniline(PANI),.The results showed that TALP have a typical two-dimensional layered structure and the layer spacing is 11.8 A.Compared to PANI,the CV curve of TALP electrode is similar to that of PANI.Besides,TALP electrode has the rapid charge/discharge capability at high current densities,as well as excellent cyclic stability.The capacity retention of TALP electrode is 63.3%after 2000 cycles at a current density of 200 mA g-1 which is much higher than that of PANI electrode.3.The influences of binders and press pressures on electrochemical kinetics of TALP electrode were studied.The results showed that CMC&SBR binder was more easily dispersed among TALP particles which promoted TALP(CMC&SBR)electrode had smaller resistance and rate properties.On this basis,with the increase of press pressures,the density of TALP electrode increases gradually and tends to be stable at 6.0t,while the rate performance of TALP electrode is also improved significantly.4.The electrochemical kinetics of asymmetric lithium ion capacitors based on TALP in different anionic electrolytes was preliminarily studied.The results showed that the whole device based on TALP(ClO4-)has fast charge/discharge capacity and good cycling stability.In addition,the capacity retention of the device after 1000 cycles can reach 90.9%at a current density of 100 mA g-1,and the device can deliver a pair of higher energy density and power density compared to another two devices.5.It is the first time to synthesize V2O5 samples by using high-gravity technology to pretreat the raw materials.The influence of this technology on the growth of V2O5 particles was investigated and the dynamic behavior of V2O5 electrode was analyzed.The effects of iron and different concentrations of copper on the structure of V2O5 samples were also investigated.The results showed that the micro-spherical particles of samples were self-assembled by nanosheets with 'pore structures inside particles which was related to the intervention of high-gravity technology,and the V2O5 samples have a rapid charge/discharge ability at high current densities(>5C).In addition,the particle morphologies of V2O5 samples with iron and copper doped are more uniform.Among them,the cyclic stability of V2O5 electrode could be significantly improve with the doping of iron,while the capacity of V2O5 electrode could be enhanced by copper doping to some extent.In this work,the two-dimensional layered TALP material not only has a typical layered structure,but also shows excellent dynamic behavior owing to its structural characteristics.In comparison,the dynamic performance of layered V2O5 electrode could be improved by two kinds of optimization methods to some extent which is limited by its inherent characterizations and not able to surpass the dynamic properties of TALP material.Therefore,TALP material initially achieves the purpose of balancing the specific power and specific energy of electrochemical energy storage devices from the perspective of electrode material structure design in a long-term perspective.