Preparation Of Selenium Nanowires And Selenium/graphene And Their Lithium Battery Properties

Due to the lithium-ion battery good reversibility and long cycle life, Li-ion battery has been extensively used in portable electronic devices. However, the energy density of the Li-ion battery is not able to meet the growing energy storage needs, because of the rise of electric vehicles and the use of large-scale grid energy storage. Therefore, developing a high energy density, low high-power, high efficiency and low cost, safety Li-ion battery is urgently needed. In this thesis, we synthesized a dimensional amorphous, crystalline,crystalline/amorphous selenium nanowires and selenium/graphene composites by high energy ball milling and high temperature tube furnace calcination. We analyzed the morphology and composition of the sample by X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (SEM), transmission electron microscopy (TEM, high resolution transmission electron microscopy HRTEM, selected area electron diffraction SAED), X-ray photoelectron spectroscopy (XPS), N2 specific surface area measurements (BET), ultraviolet-visible absorption spectrum (UV-vis) and other analytical techniques and by Land battery test system and electrochemical workstation we test the storage capacity of the material. To analyze of the charge and discharge process we made clear explanation to the Li-ion battery reaction mechanism.Applying the high-energy ball milling and high-temperature tube furnace calcination,we prepared a dimensional amorphous, crystalline, crystalline/amorphous selenium nanowires material. Firstly, by adjusting the rotational high-energy ball milling speed, time and controlling the quality of the sample, we obtained the optimal experimental conditions for the formation of the amorphous selenium nanowires. By controlling the temperature of the tube furnace, we successfully synthesized the partially crystalline and completely crystalline selenium nanowires. Analyzing the different ball milling time of the samples, we made a reasonable explanation for the growth process of the selenium nanowires. Finally,we studied the storage capacity of three samples (a-Se 755mAh·g-1, c/a-Se 705mAh·g-1,c-Se 250mAh·g-1) and the reaction mechanism during charging and discharging.Applying the high-energy ball milling prepared selenium/graphene composites, we selected the most appropriate condition to form it by XRD, SEM and BET. Then by TEM,XPS, Raman, we analyzed the state of selenium and the combination with graphene. Finally,by charge-discharge curves of the lithium selenium/graphene battery, cyclic voltammetry,cyclic stability and high-rate discharge curve curves, we gained a high energy density(705mAh·g-1), good cyclic stability and high-current discharge stability electrode material.