【作者】 刘伟；

【导师】 祖小涛；

【作者基本信息】 电子科技大学 ， 物理学， 2022， 硕士

【摘要】 随着化石燃料的逐渐枯竭和环境污染问题的日益加重,电动汽车市场得到爆发式发展。此外,当今人们的生活已经跟便携式电子产品密不可分。这些都为目前的电池技术带来了新的挑战。电动汽车和便携式电子产品的电池主要都是锂离子电池（Li-ion batteries,LIBs）,同时钠离子电池（Na-ion batteries,NIBs）作为替代者也受到广泛关注。目前商业上使用的LIBs/NIBs存在的主要问题为低能量密度、低功率密度、低循环能力以及低安全性。而这些问题的主要原因是电池的电极材料性能不足。目前的研究普遍认为二维（Two dimensional,2D）材料在电极材料应用上具有极大的潜力,因为2D材料具有极大的比表面积。因此在本工作中我们主要进行2D电极材料方面的研究。本文的主要研究内容如下:近年来,2D五边型（penta）结构在离子电池电极材料的应用中受到了越来越多的关注。在这项工作中,我们建立了60种2D penta材料的模型,基于密度泛函理论计算了它们的电子特征和稳定性,最终筛选出penta-PC₂作为研究对象。研究结果表明,penta-PC₂是一种有潜力的LIBs/NIBs电极材料。理由如下:1、不同于绝大多数半导体penta电极材料,penta-PC₂表现出金属性,来自C-2pz轨道的金属态电荷密度在整个penta-PC₂中均匀而统一地分布,导致penta-PC₂具有优异的导电能力。2、除动力学稳定性外,我们发现2D penta-PC₂还具有热稳定性和机械稳定性。特别是,它可以承受高达1500K的温度。3、penta-PC₂具有超高的理论存储容量,Li/Na理论存储容量为1462/1949 m Ah·g^-1,约为石墨的3和4倍。4、对于Li/Na吸附,penta-PC₂在高浓度和低浓度下都表现出相当负的吸附能（<-0.8e V）以及微小的晶格常数变化（<2%）。5、Li/Na在penta-PC₂上具有低的各向同性迁移势垒（0.21/0.28e V）。6、对于Li/Na吸附,penta-PC₂表现出适当的平均开路电压（0.75/0.63V）。综合以上因素,用penta-PC₂制作的电极将会表现出优良的导电能力、出色的循环能力、超高的离子容量、快速的充放电速率以及良好的安全性能,说明了它用作LIBs/NIBs电极材料的潜力。更多还原

【Abstract】 With the gradual depletion of fossil fuels and the aggravation of environmental pollution,the electric vehicle market has developed explosively.In addition,people’s life today has been inseparable from portable electronic products.All these have brought new challenges to the current battery technology.Batteries of electric vehicles and portable electronic products mainly are Li-ion batteries（LIBs）.At the same time,Na-ion batteries（NIBs）have also attracted extensive attention as a substitute.At present,the main problems of LIBs/NIBs used commercially are low energy density,low power density,low cycle capacity and low safety.The main reason for these problems is the insufficient performance of battery electrode materials.Current researches generally believe that two-dimensional（2D）materials have great potential in the application of electrode materials,because 2D materials have great specific surface area.Therefore,we mainly study the 2D electrode materials in this work.The main research contents of this paper are as follows:In recent years,2D pentagonal（penta）structures have attracted more and more attention in the application of ion battery electrode materials.In this work,we established the models of 60 kinds of 2D penta materials,calculated their electronic characteristics and stability based on density functional theory,and finally selected penta-PC₂as the research object.The results show that penta-PC₂is a potential LIBs/NIBs electrode material.The reasons are as follows:1.Different from most semiconductor penta electrode materials,penta-PC₂shows metallicity.The metal state charge density from C-2pz orbit is evenly and uniformly distributed in the whole penta-PC₂,resulting in excellent conductivity of penta-PC₂.2.In addition to the dynamic stability,we found that 2D penta-PC₂also has thermal and mechanical stability.In particular,it can withstand temperatures up to 1500K.3.Penta-PC₂has ultra-high theoretical storage capacity.The theoretical storage capacity of Li/Na are 1462/1949mahg^-1,which is about 3 and 4 times of graphite.4.For Li/Na adsorption,penta-PC₂shows quite negative adsorption energy（<-0.8ev）and small change of lattice constant（<2%）at both high and low concentrations.5.Li/Na have low and isotropic migration potential barriers（0.21e V/0.28e V）on penta-PC₂.6.For Li/Na adsorption,penta-PC₂shows an appropriate average open circuit voltage（0.75/0.63V）.Based on the above factors,the electrode made of penta-PC₂will show excellent conductivity,outstanding circulation ability,ultra-high ion capacity,fast charge/discharge rate and good safety performance,indicating its potential as LIBs/NIBs electrode material.更多还原