高容量正极材料0.08LiCo0.75Al0.25O2-0.92LiNiO2的合成与电化学性能研究

在恒定pH值下将层状钴铝双羟基复合金属氧化物(CoAl-LDH)均匀包覆在球状Ni(OH)2表面,与LiOH.H2O混合均匀后,经高温煅烧制得钴铝酸锂包覆镍酸锂0.08LiCo0.75Al0.25O2-0.92LiNiO2正极材料.电化学测试表明,0.08LiCo0.75Al0.25O2-0.92LiNiO2正极比容量高,具有良好的倍率性能和循环寿命,其0.1C放电比容量为211 mAh·g-1,0.5C放电比容量为195.6 mAh·g-1,3C放电比容量为161 mAh·g-1,0.5C 30周期循环后容量保持率为93.2%,明显优于LiNiO2和钴酸锂包覆镍酸锂0.08LiCoO2-0.92LiNiO2正极.     

LiCoO2梯度包覆LiNi0.96Co0.04O2电极材料的电化学性能

镍钴酸锂(LiNi0.8Co0.2O2)与目前商业用锂离子电池正极材料钴酸锂(LiCoO2)相比,具有成本低、实际比容量高和环境友好等优势。但LiNi0.8Co0.2O2的充放循环性能还有待提高,对其进行阳离子掺杂或表面修饰可以改善其电化学性能,这方面的研究已经成为热点。Fey等人[1]用溶胶凝胶法制     

泡沫塑料包覆SrAl2O4:Eu2+, Dy3+长余辉材料的耐水性能

利用废弃聚苯乙烯泡沫塑料作为包覆材料,采用简单的物理包覆技术对SrAl2O4∶Eu2+,Dy3+长余辉发光材料进行表面包覆。 X射线粉末衍射、傅里叶红外光谱、激发发射光谱、热重分析、透射电子显微镜观察和耐水性能测试等实验结果表明,包覆层薄,厚度为5~10 nm,聚苯乙烯泡沫塑料的包覆质量分数为4.9%,包覆没有改变材料的内部结构,对材料的发光性能影响较小。 包覆能有效改善材料的防水性能,经过15 h浸水后,材料初始发光强度依然达到5.02 cd/m2,余辉时间达到10 h以上。     

XANES研究Al2O3包覆LiNi0.4Co0.2Mn0.4O2材料的稳定性

采用溶胶凝胶水解法在LiNi0.4Co0.2Mn0.4O2(NCM)表面包覆了0.5 wt%Al2O3.透射电镜(TEM)表明在NCM表面形成了均匀的Al2O3包覆层;分别采用恒电位极化及热重分析(TG)研究了包覆前后NCM的析氧特性;采用X射线吸收近边结构谱(XANES)研究了包覆前后O的电子结构.结果表明,包覆后的NCM析氧量更少;Al2O3包覆使得NCM表面层中与金属3d轨道杂化的O比例减少,而更稳定的、与金属4sp轨道杂化的O比例增加.这些因素导致Al2O3包覆后的NCM更加稳定、安全性更高.     

ZrO2包覆高镍LiNi0.8Co0.1Mn0.1O2正极材料提高其循环稳定性的作用机理

高镍三元材料作为一种锂离子电池正极材料,因其较高的放电比容量而得到科学界和工业界的广泛关注。研究表明,高镍三元材料的比容量与材料中的Ni含量呈正相关,但Ni含量的增加也会加剧循环过程中的界面副反应,材料表面释氧以及结构转变等问题。本文采用ZrO₂包覆LiNi_0.8Co_0.1Mn_0.1O₂材料,利用X射线衍射证明,在高温处理下ZrO₂包覆物中的Zr⁴⁺会掺杂进LiNi_0.8Co_0.1Mn_0.1O₂材料表面晶格中,使得X射线衍射谱中的(003)衍射峰左移。电化学测试证明在4.3和4.5 V的截止电压下,改性最优的材料在1C循环100周后容量保持率分别从84.89%和75.60%提高到97.61%和81.37%,同时发现循环稳定性的提升主要来自材料表面的Zr⁴⁺掺杂。X射线光电子能谱证明Zr⁴⁺表层掺杂后材料的Ni化合价由Ni3+向Ni²⁺转变,透射电子显微镜观察到Zr⁴⁺的表层掺杂使得材料表面的层状结构发生重构,从而稳定了材料体相结构,提高了材料整体的循环稳定性。     

SiO2/TiH2包覆粉体的制备及其释氢特性

熔体发泡法因可通过其简单的工艺制备高强度的泡沫铝而受到广泛的关注．TiH2颗粒可以作为泡沫铝的发泡剂，但其仍存在分解温度与铝熔点的温度失配问题．这种温度失配是导致泡沫铝制品孔洞结构难以控制的最大障碍，解决办法之一是延迟TiH2的分解过程．     

碳包覆Na2Ti6O13纳米管的电化学性能研究

以金红石型TiO2和NaOH为原料,由水热反应制备Na2Ti6O13纳米管.然后,在含有0.1 mol.L-1NaOH的葡萄糖水溶液中反应4 h制得碳包覆的Na2Ti6O13纳米管.X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析表明,该碳包覆Na2Ti6O13纳米管外径约14～19 nm,内径约2～5 nm,长度为数百纳米,有一层厚度约为2 nm的碳层包覆在纳米管外壁.以其作为锂离子电池负极材料,恒电流充放电测试表明,在50 mA.g-1电流密度下首周可逆容量达到161 mAh.g-1,循环100周后容量保持在147 mAh.g-1.相比于Na2Ti6O13纳米管,提高了20%以上.电流密度升至1600 mA.g-1充放电,碳包覆Na2Ti6O13纳米管可逆容量仍有70 mAh.g-1左右,远高于Na2Ti6O13纳米管,表现出良好的倍率性能.     

AlF3包覆对Li1.2Mn0.534Ni0.133Co0.133O2正极材料电化学性能的影响

通过共沉淀法制备锂离子电池富锂锰基正极材料Li1.2Mn0.534Ni0.133Co0.133O2,并对其进行AlF3包覆。实验结果表明,通过AlF3包覆,材料的电化学性能得到明显提高。在0.2C下,包覆前材料的首次放电比容量为253 mAh.g-1,首次充放电效率仅为88.8%。经过AlF3包覆,材料的首次放电比容量提高到294 mAh.g-1,首次充放电效率高达96.4%。同样,在1.0C下循环50次,未包覆材料的放电比容量由225 mAh.g-1降到185 mAh.g-1,容量保持率仅为82.2%。经过AlF3包覆,材料的放电比容量由230mAh.g-1仅降为222 mAh.g-1,容量保持率高达96.5%。     

微量Mg/F表面梯度渗透改善高电压LiCoO2界面脆弱

采用高温固相法在1 050℃下烧结,制备了LiCoO₂低浓度梯度改性样品,分别为LiF掺杂包覆(LCOLF、LCO@LF)和MgF₂掺杂包覆(LCOMF、LCO@MF)。通过光电子能谱、透射电子显微镜和电化学技术等表征方法,对比分析材料形貌及电化学性能。结果表明,体相掺杂复合电极中,LCOLF热重测试显示出最优热稳定性,LCOMF晶体中(003)和(104)晶面间距收缩;45℃下1C倍率循环70圈后,LCOLF和LCOMF比容量分别为141.45和166.98 mAh·g^-1,循环性能优于LiCoO₂。表面包覆复合电极中,LCO@LF和LCO@MF晶粒表面光洁且晶格氧键价都向更高结合能方向增强;LCO@MF构建了坚实且紧密的包覆层,循环70圈后,放电比容量和容量保持率分别为183 mAh·g-1和91.26%(LCO@LF分别为154.38 mAh·g^-1和77.54%),循环性能显著优于体相掺杂。     

KCl-KBO2-K2CO3, K2MoO4-KBO2-K2CO3, and K2WO4-KBO2-K2CO3 ternary systems

phase diagrams of KCl-KBO₂-K₂CO₃, K₂MoO₄-KBO₂-K₂CO₃, and K₂WO₄-KBO₂-K₂CO₃ ternary systems were studied by a calculation-experimental method and differential thermal analysis (DTA). The coordinates of ternary eutectics were determined to be E ₁: 622°C, 8.5 mol % KBO₂, 56.5 mol % KCl, and 35 mol % K₂CO₃; E ₂: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂MoO₄; E ₃: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂WO₄. The specific heats of melting of the eutectics were determined.     

Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O system

Solubility in the Na₂Cr₂O₇-(NH₄)₂Cr₂O₇-K₂Cr₂O₇-H₂O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.     

The preparation of NbH5(Me2PCH2CH2Me2)2 and NbHL2(Me2PCH2CH2PMe2)2 (L = CO or C2H4)

MMe₅(dmpe) (M = Nb or Ta, dmpe = Me₂PCH₂CH₂PMe₂) reacts with H₂ (500 atm) and dmpe in THF at 60°C to give MH₅(dmpe)_2? NbH₅(dmpe)₂ readily reacts with two mol of CO or ethylene (L) to give NbHL₂(dmpe)₂. The exchange of the hydride ligand with the ethylene protons in NbH(C₂H₄)₂(dmpe)₂ is not rapid on the ¹H NMR time scale (60 MHz) at 95°C.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

NaBO2-NaCl-Na2CO3, NaBO2- Na2CO3-NaMoO4, NaBO2- Na2CO3-NaWO4, and NaBO2-NaCl-Na2WO4 ternary systems

The phase diagrams of the NaBO₂-NaCl-Na₂CO₃, NaBO₂-Na₂CO₃-Na₂MoO₄, NaBO₂- Na₂CO₃-Na₂WO₄, and NaBO₂-NaCl-Na₂WO₄ ternary systems were studied by a calculation-experimental method and differential thermal analysis. The coordinates of ternary eutectics were determined: E ₁: 612°C, 16 mol % NaBO₂, 42 mol % NaCl, and 42 mol % Na₂CO₃; E ₂: 568°C, 12 mol % NaBO₂, 28 mol % Na₂CO₃, and 60 mol % Na₂MoO₄; E ₃: 575°C, 12 mol % NaBO₂, 32 mol % Na₂CO₃, and 56 mol % Na₂WO₄; E ₄: 628°C, 8 mol % NaBO₂, 20 mol % NaCl, and 72 mol % Na₂WO₄; and E ₅: 655°C, 9 mol % NaBO₂, 53 mol % NaCl, and 38 mol % Na₂WO₄.     

Li2SO4-Na2SO4-H2O和Li2SO4- K2SO4-H2O溶液的体积性质

本文用高精度数字式振荡管密度计测定了288K至318K温度范围内Li₂SO₄ + Na₂SO₄ + H₂O和 Li₂SO₄ + K₂SO₄ + H₂O三元体系的密度。混合溶液的离子强度范围从0.1到4.5 mol.kg_–1,混合溶液中Na₂SO₄和K₂SO₄的离子强度分数为0.2,0.4,0.6和0.8。用密度实验值拟合得到了不同温度下Pitzer离子相互作用模型混合参数θ_V和 ψ_V,模型的计算值与实验值的偏差在±0.002 g.cm_–3以内。用Pitzer模型计算了不同离子强度下三元体系的混合体积。     

(H2NC4H8NCH2CH2NH2)(HNCH2CH2NH2)3Zn2Ge2Se8: A new,templated one-dimensional ternary semiconductor stabilized by mixed organic cations

The novel, 1D semiconductor (H₂NC₄H₈NCH₂CH₂NH₂)(HNCH₂CH₂NH₂)₃Zn₂Ge₂Se₈ has been synthesized under solvothermal conditions using N-(2-aminoethyl)piperazine as solvent and templating agent at 200 °C. The material was characterized by single crystal and powder X-ray diffraction, IR and Raman spectroscopy and thermogravimetric analysis. The compound consists of 1D anionic [Zn₂Ge₂Se₈]⁴⁻ chains made of alternating edge-shared [ZnSe₄] and [GeSe₄] tetrahedra that charged balanced by one N-(2-aminoethyl)piperazinium and three piperazinium cations. The optical properties were investigated with solid state UV–Vis/near IR spectroscopy and the results show that the solid is a medium gap semiconductor with an absorption edge at 1.8 eV.     

Polymorphism in the Sc2Si2O7-Y2Si2O7 system

This paper examines the structural changes with temperature and composition in the Sc₂Si₂O₇-Y₂Si₂O₇ system; members of this system are expected to form in the intergranular region of Si₃N₄ and SiC structural ceramics when sintered with the aid of Y₂O₃ and Sc₂O₃ mixtures. A set of different compositions have been synthesized using the sol-gel method to obtain a xerogel, which has been calcined at temperatures between 1300 and 1750 °C during different times. The temperature-composition diagram of the system, obtained from powder XRD data, is dominated by the β-RE₂Si₂O₇ polymorph, with γ-RE₂Si₂O₇ and δ-RE₂Si₂O₇ showing very reduced stability fields. Isotherms at 1300 and 1600 °C have been analysed in detail to evaluate the solid solubility of the components. Although, the XRD data show a complete solid solubility of β-Sc₂Si₂O₇ in β-Y₂Si₂O₇ at 1300 °C, the ²⁹Si MAS-NMR spectra indicate a local structural change at x ca. 1.15 (Sc_2−xY_xSi₂O₇) related to the configuration of the Si tetrahedron, which does not affect the long-range order of the β-RE₂Si₂O₇ structure. Finally, it is interesting to note that, although Sc₂Si₂O₇ shows a unique stable polymorph (β), Sc³⁺ is able to replace Y³⁺ in γ-Y₂Si₂O₇ in the compositional range 1.86?x?2 (where x is Sc_2−xY_xSi₂O₇) as well as in δ-Y₂Si₂O₇ for compositions much closer to the pure Y₂Si₂O₇.     

Synthesis and characterization of inorganic solid electrolytes of Li2O-SiO2-P2O5 and Li2O-TiO2-SiO2-P2O5 systems

The lithium-ion-conducting inorganic solid electrolytes in the oxide systems Li₂O-SiO₂-P₂O₅ and Li₂O-TiO₂-SiO₂-P₂O₅ were prepared by the solid-state reaction, and the electrolyte pellet made by cold-pressing method had diameter of 13 mm and was about 1 mm thick. Phase identification and surface morphology of the products were carried out by X-ray diffraction and scanning electron microscopy. Ionic conductivity of the pellets was investigated through ac impedance. The results show that the adding of other cations can improve the ionic conductivity of the solid electrolyte, and the sintering temperature and duration can influence the ionic conductivity. The maximum ionic conductivity in the samples is 9.9 × 10⁻⁴ S/cm in the Li₂O-TiO₂-SiO₂-P₂O₅ system. Original Russian Text ? W. Li, M. Wang, Z.H. Li, X.F. Shang, H. Wang, Y.W. Wang, Y.B. Xu, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 11, pp. 1341–1345.     

Ag2Se-Tl2Se-Bi2Se3 quasi-ternary system

The Ag₂Se-Tl₂Se-Bi₂Se₃ quasi-ternary system (system A) was studied using DTA, X-ray powder diffraction, microstructure examination, and microhardness measurements. TlBiSe₂-AgBiSe₂, AgTlSe-AgBiSe₂, AgTlSe-Bi₂Se₃, and Tl₂Se-AgBiSe₂ polytherms, isothermal sections at 500 and 800 K, and liquidus surface projection of system A were constructed. System A is congruently triangulated into the following subordinate triangles: Tl₂Se-AgTlSe-Tl₉BiSe₆ (I), AgTlSe-Tl₉BiSe₆-TlBiSe₂ (II), Ag₂Se-AgTlSe-TlBiSe₂ (III), Ag₂Se-AgBiSe₂-TlBiSe₂ (IV), and AgBiSe₂-TlBiSe₂-Bi₂Se₃ (V). Subsystems I, III, and V are ternary systems with three-phase eutectic equilibrium; system II has a three-phase eutectic, and system IV is characterized by several invariant and monovariant peritectic and eutectic equilibria. Primary crystallization and homogeneity fields were outlined, and the types and coordinates of invariant and monovariant equilibria in system A were determined. A characteristic feature of the title system is an extensive field of solid solutions between high-temperature cubic AgBiSe₂ and TlBiSe₂ phases; this field lies as a continuous belt along the AgBiSe₂-TlBiSe₂ quasibinary section and covers about one-fourth of the surface area of the triangular diagram of system A.