Lithium Extraction Properties in Anode Material Li_2MgSi for Lithium Ion Batteries

使用基于平面波展开的第一原理赝势法,研究了锂离子电池负极材料Li2MgSi在各种脱锂量下的锂脱嵌形成能、相应的体积变化、能带结构、电子态密度以及电荷密度分布.计算结果表明:脱锂量越大需要的能量越大,随脱锂量的变化,平均一个锂的脱嵌形成能在-1.21--1.61 eV之间.脱锂过程中,体积先膨胀后收缩,整个过程中体积变化很大,是导致材料循环性能较差的重要原因.在脱锂过程中材料显示了由半导体性到金属性又到半导体性的特征.The ab initio pseudopotential method with the plane wave expansion of the crystal wavefunction is employed to study the anode material Li2MgSi for lithium ion batteries.The lithium deintercalation formation energies and the corresponding changes of crystal volumes under various amounts of lithium deintercalations are presented.The energy band structures and the electronic density of states and the charge densities for the lithium extractions in Li2MgSi are also discussed.The calculation results show that the more extractions of Li the more energies it needs.The deintercalation formation energies per lithium are between-1.21 eV to-1.61 eV for different amount of lithium extractions.The volume first expands then shrinks and the changes of volume are very big during the whole process.That is the important cause of bad cycle performance.And the material changes from semiconducting to metallic then to semiconducting crystal.福建省自然科学基金资助项目(E0410025

An explorative longitudinal study of disordered eating attitudes and behaviors among pregnant women in Hong Kong

abstractpublished_or_final_versiontocClinical PsychologyMasterMaster of Social Science

Smoking and its relations with eating attitudes, body satisfaction andmood among female adolescents in Hong Kong

published_or_final_versionClinical PsychologyDoctoralDoctor of Psycholog

The reaction sequence of lithiation in Mg_2Ge and the changes of its electronic structure

Mg2Ge有望成为新的锂离子电池负极材料.使用基于平面波展开的第一性原理赝势法,计算并得到了Li嵌入Mg2Ge负极材料时的反应次序.Li首先占据其中的间隙位置,占满间隙位置后随着嵌Li量的进一步增加,Li将逐步替位Mg2Ge中一半的Mg位置,直到生成Li2MgGe.计算结果表明,在整个嵌Li过程中主体材料的体积先膨胀后收缩,体积胀缩量很大,这是导致Mg2Ge作为锂离子电池电极材料循环性能较差的重要原因.对材料电子结构的分析表明,随着Li嵌入量的增加,主体材料发生了从半导体性到金属性、又到半金属性的转化.Mg_2Ge is a promising new anode material for lithium ion batteries.The ab initio pseudopotential method with the plane wave expansion of the crystal wave function was employed to study the lithiation properties of anode material Mg_2Ge.The reaction sequence of lithiation in Mg_2Ge have been calculated.It was found that Li ions firstly occupy the interstitial sites until the interstitial sites are full,and then substitute the Mg sites until half of the Mg sites are replaced to form the phase of Li_2MgGe.The calculation results also show that the crystal volume firstly expands and then shrinks as the number of Li ions increases.The changes of crystal volume are very big during the whole process which is the cause of bad cycle performance of the material.The electronic structures are also analyzed,which indicates that the host material changes from semiconducting to metallic then to semiconducting with the increase of Li intercalations.国家自然科学基金(批准号:10774124);; 国家重点基础研究发展规划(批准号:2007CB209702);; 福建省自然科学基金(批准号:E0410025)资助的课题~

Computer Simulation on Li-Insertion Routes Based on First-Principles

为了研究锂离子电池负极材料InSb的L i嵌入过程,使用基于密度泛函理论的第一原理赝势法,计算了L i离子电池非碳类负极材料InSb在L i嵌入时的125相不同情况下的总能、平衡体积和各相间转换的L i嵌入形成能及相对体积变化等,进而参考电压轮廓实验曲线,筛选出了中间经历两相的最可能的反应路径为L i+In4Sb4→L i1In4Sb4,2L i+L i1In4Sb4→L i3In4Sb4,9L i+L i3In4Sb4→L i12Sb4+4 In;中间经历三相的最可能的反应路径为L i+In4Sb4→L i1In4Sb4,2L i+L i1In4Sb4→L i3In4Sb4,4L i+L i3In4Sb4→L i7In3Sb4+In,5L i+L i7In3Sb4→L i12Sb4+3 In。计算了L i3Sb的晶格常数、总能等,讨论了其能带结构和电子态密度等性质。结果表明:随着L i嵌入到InSb中并生成L i3Sb,其体积略有膨胀,材料发生了由半导体性到金属性又到半导体性的转变。In order to study the process of Li intercalations in InSb,an Ab initio method with the first-principles pseudo potentials based on the density functional theory was used to calculate the total energies,the equilibrium volumes of Li intercalations in InSb in 125 possible cases,the formation energies and the relative volume changes during the material changed from one phase to another.Comparing with the experimental voltage profile curve,we show that the most favored intercalation route for undergoing two intermediate phase is Li+In_4Sb_4 →Li_1In_4Sb_4,2Li+Li_1In_4Sb_4 →Li_3In_4Sb_4,9Li+Li_3In_4Sb_4 →Li_(12) Sb_4+4In,and the most favored route for undergoing three intermediate is Li+In_4Sb_4 →Li_1In_4Sb_4,2Li+Li_1In_4Sb_4 →Li_3In_4Sb_4,4Li+Li_3In_4Sb_4 →Li_7In_3Sb_4+In,5Li+Li_7In_3Sb_4 →Li_(12)Sb_4+3In.The lattice constant and total energy of Li_3Sb was also calculated.The band structures,electronic density of states for Li_3Sb were also discussed.The result shows that the volume slightly expands from InSb to Li_3Sb.The material changed from semiconducting to metallic then again to semiconducting.福建省自然科学基金计划资助项目(E0410025

Lithium Extraction Properties in Anode Material Li_(2.5)Cu_(0.5)N for Lithium Ion Batteries

使用基于平面波展开的第一原理赝势法,计算了锂离子电池非碳基负极材料Li2.5Cu0.5N在各种脱锂量下的Li脱嵌形成能以及相应的体积变化,讨论了脱锂前后材料的电荷密度,电子状态密度等电子性质.计算表明,Li2.5Cu0.5N晶体中LiN层的锂的脱出能要比LiCu层的锂小得多,即LiN层中的锂更容易脱嵌.结果还表明,各种脱锂量的Li脱嵌能大致在-2.72~-4.08 eV/Li之间.当脱锂量小于30%,材料的体积变化较小,随着脱锂量的增大,材料的体积变化较大.The ab initio pseudopotential method with the plane wave expansion of the crystal wavefunction was employed to study the non-carbon-basing anode material Li_(2.5)Cu_(0.5)N for lithium ion batteries.The lithium deintercalation formation energies and the corresponding changes of crystal volumes under various amounts of lithium deintercalations are presented.The charge densities and the electronic density of states for the lithium extraction in Li_(2.5)Cu_(0.5)N are also discussed.The calculation results show that the Li extraction in the LiN layer is much easier than that in the LiCu layer.The deintercalation formation energies per lithium are around-2.72 eV to-4.08 eV for different amount of lithium extracted.The changes of volume are small for lithium extraction at <30%,however,the changes are large when the extractions are further increased.国家自然科学基金(10374076);; 福建省自然科学基金(E0410025)资

Structural and electronic properties of T-graphene and its derivatives

采用基于密度泛函理论的第一原理方法研究了T型石墨烯及其衍生物-n(n=1-5)的结构稳定性和电子结构性质.T型石墨烯是一种拥有四角形环的二维碳材; 料同素异构体,通过改变连接四角形环的碳链上的碳原子个数n,可以得到一系列的sp-sp~2杂化结构,称其为T型石墨烯衍生物-n.计算结果表明:这些; 材料的结构稳定性、化学键类型和电子结构性质都依存于n的奇偶性.其中T型石墨烯(n=0)的结构最稳定,并形成一个由8个碳原子构成的大环.声子谱计算; 的结果表明,n为偶数时的体系具有动力学稳定性,而n为奇数时的体系则是不稳定的.n为偶数时体系四角形环之间的碳链上的化学键呈单、三键交叉排列,体系; 显示为金属性特征,且随着n的增大,体系的金属性加强.n为奇数时体系四角形环之间的碳链上的化学键则为双键连续排列,体系呈金属性且具有磁性(n=1除; 外).研究表明该系列材料作为一种新的二维碳材料同素异构体,具有独特的结构和丰富的电子结构特性,很可能在纳米器件中得到广泛应用.Recent years there has been aroused a growing interest in designing two-dimensional (2D) structures of carbon allotropes, owing to the great success in graphene. The T-graphene is a newly proposed 2D carbon allotrope possessing tetragonal symmetry other than hexagonal symmetry of graphene. Also, the energetic and dynamical stabilities of T-graphene have been revealed. So motivated, we investigate the structural stabilities and electronic properties of T-graphene and especially its derivatives-n (n = 1-5) by using the first-principle calculation based on the density function theory. By changing the atomic number (n) of the linear carbon chains connecting the two tetragon rings of T-graphene, a series of sp-sp 2 hybrid structures can be formed, which is named T-graphene derivatives-n. The calculation results show that the structural stabilities, chemical bond types and electronic structures of these materials depend greatly on the parity of n. Owing to a strong pi-bond formed by eight carbon atoms in T-graphene, it becomes the one with the lowest energy in all these materials studied in this work. An interesting phenomenon is found that the T-graphene derivatives-n with even n are dynamically stable as witnessed by the calculated phonon spectra without imaginary modes, while those with odd n are dynamically unstable. The metallic behaviors are present in the T-graphene derivatives-n with even carbon atoms in the linear carbon chains, showing an alternating single and triple C-C bonds. Besides, we observe that the metallicity of the T-graphene derivatives-n with even n becomes stronger as n increases. On the other hand, the linear carbon chains with odd carbon atoms are comprised of continuous C=C double bonds. These T-graphene derivatives-n with odd n also show metallic behaviors, but turn into magnetic materials (except for n = 1), the magnetic moments are about 0.961 mu B (n = 3) and 0.863 mu B (n = 5) respectively, and ferromagnetic ordering is the only possibility for the magnetism, which rarely occurs in carbon material. Our first-principle studies indicate that the introducing carbon chains between the tetragonal carbon rings of T-graphene constitute an efficient method to obtain new two-dimensional carbon allotrope. With different numbers (even or odd) of carbon atoms on the chains, the constructed 2D carbon allotropes could show contrasting dynamical and magnetic properties. These findings provide a theoretical basis for designing two-dimensional carbon materials and carbon-based nanoelectronic devices.National key Research and Development Program, China [2016YFA0202601];; Young Scientists Fund of the National Natural Science Foundation of; China [11605073]; Scientific Research Foundation of the Education; Department of Fujian Province, China [JAT160690

Investigation of lithium insertion in anode material CuSn for lithium-ion batteries

【中文文摘】使用基于混合基表示的第一原理赝势法 ,研究了锂离子电池非碳类负极材料CuSn的Li嵌入时的形成能以及相应的电子结构 .还给出了Li嵌入时的体积变化 ,能带结构、电子态密度以及电荷密度分布等性质 ,并讨论了CuSn作为负极材料的特点 .计算发现 ,Cu Sn化合物在闪锌矿结构时 ,Li嵌入主体材料时的嵌入形成能大致在 3.5eV附近 【英文文摘】An ab initio method with mixed\|basis norm\|conserving non\|local pseudopotentials has been employed to investigate the non\|carbon\|baring anode material\|CuSn for lithium\|ion batteries. The lithium intercalation energies and their electronic structures have been calculated. The changes of volume, band structures, electronic density of states and charge density contour plots for lithium intercalation in CuSn are also presented. The characteristics of CuSn as an anode material for lithium ion batteries are al- so discussed. By calculation , we have found that the insertion formation energy of Li insertion CuSn electrode with zinc-blendetype structures as the host framework is about 3. 5eV.国家自然科学基金 (批准号 :10 1740 5 8)资助的课题~

Ab initio calculation of the voltage profile curve of Li insertions in InSb

【中文摘要】 InSb是很有应用前途的Li离子电池非碳类负极材料 .使用基于密度泛函理论的第一原理赝势法 ,计算了InSb在Li嵌入时的 12 5种不同情况下的总能、形成能以及平衡体积等 ,进而参考电压轮廓实验曲线 ,筛选出了若干条理论上可能的反应路径 ,得到了Li嵌入时的电压轮廓曲线 .结果表明 ,从体InSb相到Li3Sb相之间没有中间经历五个相及五个相以上的反应路径 ;中间经历一个相的最可能反应过程为Li+In4 Sb4 →Li1 In4 Sb4 ,11Li +Li1 In4 Sb4 →Li1 2 Sb4+4In ;中间经历四个相的仅有一条反应路径 :Li +In4 Sb4 →Li1 In4 Sb4 ,2Li +Li1 In4 Sb4 →Li3In4 Sb4 ,4Li +Li3In4 Sb4 →Li7In3Sb4 +In ,3Li+Li7In3Sb4 →Li1 0 In2 Sb4 +In ,2Li+Li1 0 In2 Sb4 →Li1 2 Sb4 +2In 【英文摘要】 InSb is an important non_carbon_bearing anode material for lithium (ion) batteries. An ab initio method with first_principles pseudopotentials based on the density functional theory has been used to calculate the total energies, formation energies and equilibrium volumes of Li intercalations in InSb in 125 possible cases. Comparing with the experimental voltage profile curve, we have picked out the possible reaction routes of Li insertions in InSb and a theoretical voltage profile curve is reached. Our resu...国家自然科学基金 (批准号 :10374076,10274064和 2 9925310 ); 福建省教育厅基金 (批准号 :ZA02242 )资助的课

First-principles calculation on the formation energies of lithium insertion in InSb

【中文文摘】InSb材料在近来的锂离子电池负极材料研究中受到了重视 .使用基于局域密度泛函理论的第一原理赝势法 ,计算了锂离子电池非碳类负极材料InSb各种锂嵌入情况时的形成能以及相应的电子结构 .讨论了锂嵌入时的体积变化、能带结构、电子态密度以及电荷分布等性质 .计算发现 ,闪锌矿结构的InSb材料 ,锂嵌入到主体材料的间隙位置时的形成能平均每个锂原子都在 2 2eV左右 【英文文摘】InSb as an anode material in lithium batteries has attracted considerable attention in recent investigations. An ab initio method with norm conserving non local pseudopotentials based on the local density functional theory has been used to investigate the non carbon bearing anode material InSb for lithium batteries. The formation energies of lithium intercalation and their electronic structures have been calculated. The changes of volume, band structures, electronic density of states and charge density contour plots for lithium intercalation in InSb are also discussed. We found that the formation energies of Li insertion in InSb are all about 212 eV per Li atom.国家自然科学基金 (批准号 :10 1740 5 8);; 福建省高等学校科技项目 (批准号 :ZA0 2 2 42 )资助的课