Study On Synthesis And Electrochemical Behavior Of Ti₄O₇/S Composite Electrode Mateirals

With the continuous development of the material civilization,human being's demand for energy is increasing rapidly.Lithium–sulfur batteries,as a new kind of energy storage system,have a promising application prospect for a multitude of emerging applications,ranging from stationary grid storage to mobile electric vehicles and have attracted considerable attention due to their high energy density and low material cost.Compared with traditional lithium ion batteries,lithium sulfur battery possesses more advantages for its mechanism of energy storage.However until now,the lithium sulfur battery was still at the laboratory research stage and hardly achieved large-scale industrial production due to a series of problems such as low specific capacity and short cycle life.As analysed from the structure and operational principle of lithium sulfur battery,these problems were mainly attributed to low electronic conductivity of active sulfur and the dissolution of intermediates polysulfide ions in liquid electrolytes,which triggered a shuttling effect.In order to solve these crucial problems,this paper carried out research on the modified sulfur-based cathode aiming at research on the modification of polar materials of lithium-sulfur batteries.Ti₄O₇ particles was prepared to modify the positive electrode on the basis of P25 powder,and explored differences of the performance;Different morphology Ti₄O₇/sulfur composite positive electrodes were prepared and their electrochemical differences of performance were studied;Ti₄O₇rods/multilayer graphene/sulfur composite cathode was prepared by compounding Ti₄O₇ rods with multilayer graphite.The main research contents are displayed as follows:On the basis of the P25 powder,through the hydrothermal method and hydrogen reduction at a high temperature,Ti₄O₇ particles was prepared with the size of 300 nm.And the Ti₄O₇ particles/sulfur composite cathode materials were successfully prepared.As a cathode material,compared with P25 powder,Ti₄O₇ particles enhanced the interaction of the chemical bond,reduced the shuttle effect of polysulfides,enhanced the electronic conductance of the composite positive electrode.The capacity of this cell retained a reversible capacity of 467 mAh g^-11 after 300 cycles at 1 C.Even at a 2C rate,the average reversible capacity reached 514 mAh g^-1.The effect of different morphological Ti₄O₇ on the cathode modification of lithium-sulfur battery was studied.When the Ethanol/glycerin was added as a solvent respectively,pure morphology of Ti₄O₇ rods/Ti₄O₇ particles was successfully prepared by the solvent method at a high temperature.The Ti₄O₇ rods was prepared with the diameter of 130-150 nm and the length of several tens of micrometers.Thereby we prepare Ti₄O₇ rods/sulfur and Ti₄O₇ particles/sulfur composite cathode materials.Through the CV and EIS analyses,one-dimensional Ti₄O₇ rods could reduce the charge transfer resistance of the batteries,promote the electrochemical reaction and improve the electrochemical performance of the battery.Ti₄O₇ rods/sulfur composite exhibited high reversible capacity of 580 mAh g^-1 at 1 C after 300 cycles.On the basis of pure phase Ti₄O₇ rods,the composites of Ti₄O₇ rods and multilayer graphene were prepared by the method of high-temperature hydrogen reduction.Compared with the batteries with a positive electrode material of pure Ti₄O₇ rods,the composites of Ti₄O₇ rods and multilayer graphene greatly improved the cycle and rate performance of the battery,the capacity of this cell retained as high as 621 mAh g^-1 after 300 cycles at 1 C.