Study On Preparation And Plasma Modification Of Lithium Metal Anodes

Lithium metal is regarded as one of the most promising anode materials in the new generation of secondary batteries because of its high theoretical specific capacity(3860m Ah/g)and lowest redox potential(-3.04 V).However,the problems such as lithium dendrites,huge volume expansion and fragile Solid Electrolyte Interphase(SEI)of lithium metal anodes affect the practical application of lithium metal batteries.In order to solve these problems,strategies such as current collector and artificial solid electrolyte interphase are usually used to make up for the defects of lithium metal anodes themselves.In this thesis,combined with the unique advantages of plasma in material modification and preparation,a highly lithiophilic three-dimensional porous carbon foam was prepared as the current collector of lithium metal composite anodes.In addition,considering that the three-dimensional current collector will inevitably increase the overall quality and volume of the anodes,so from the aspect of preparing high-quality artificial SEI,a novel,convenient,accurate and pollution-free method for modifying lithium anodes by carbon tetrafluoride plasma was developed.The details are as follows.Initially,the micro-morphology and nitrogen chemical valence of three-dimensional carbon foam prepared by simple carbonization process were regulated by nitrogen and oxygen plasma to inhibit the growth of lithium dendrites.As a result,a three-dimensional carbon foam current collector with high lithiophilicity and good electrochemical performance was obtained(the Coulombic efficiency is still 99.3%after 100 cycles at the current density of 1 m A/cm~2).In addition,the equivalent models of the complexation of various nitrogen-containing functional groups with amorphous carbon representing three-dimensional carbon foam were constructed,and their binding energies with lithium ions were calculated by Density Functional Theory(DFT).The positive effect of plasma strategy on the regulation of lithiophilicity of three-dimensional carbon foam was explored from the aspects of electrochemical measurement and theoretical calculation.Furthermore,through the direct treatment of commercial lithium disks by carbon tetrafluoride plasma,a lithium fluoride-enriched artificial SEI was prepared,which greatly improved the electrochemical performance of lithium metal(stable cycle for 1700and 1400 hours under the current density of 1 and 2 m A/cm~2,respectively).In addition,a detailed comparative study of treated and untreated lithium disks with different cycles was carried out by Scanning Electron Microscope and X-ray Photoelectron Spectroscopy,in order to explore the contribution of this plasma strategy to the realization of high performance of lithium metal anodes.In summary,two plasma strategies with a certain innovative significance are proposed in this thesis,and the preparation and internal mechanism of high-performance lithium metal anodes are explored deeply.Therefore,this thesis has a certain significance to promote the application of plasma technology in the preparation and modification of lithium metal anodes materials.