Mesoporous Germanium Anode Materials for Lithium‐Ion Battery with Exceptional Cycling Stability in Wide Temperature Range

Porous structured materials have unique architectures and are promising for lithium‐ion batteries to enhance performances. In particular, mesoporous materials have many advantages including a high surface area and large void spaces which can increase reactivity and accessibility of lithium ions. This study reports a synthesis of newly developed mesoporous germanium (Ge) particles prepared by a zincothermic reduction at a mild temperature for high performance lithium‐ion batteries which can operate in a wide temperature range. The optimized Ge battery anodes with the mesoporous structure exhibit outstanding electrochemical properties in a wide temperature ranging from ?20 to 60 °C. Ge anodes exhibit a stable cycling retention at various temperatures (capacity retention of 99% after 100 cycles at 25 °C, 84% after 300 cycles at 60 °C, and 50% after 50 cycles at ?20 °C). Furthermore, full cells consisting of the mesoporous Ge anode and an LiFePO₄ cathode show an excellent cyclability at ?20 and 25 °C. Mesoporous Ge materials synthesized by the zincothermic reduction can be potentially applied as high performance anode materials for practical lithium‐ion batteries.     

In‐situ Observations of Nanoscale Effects in Germanium Nanowire Growth with Ternary Eutectic Alloys

Vapour‐liquid‐solid (VLS) techniques are popular routes for the scalable synthesis of semiconductor nanowires. In this article, in‐situ electron microscopy is used to correlate the equilibrium content of ternary (Au_0.75Ag_0.25–Ge and Au_0.65Ag_0.35–Ge) metastable alloys with the kinetics, thermodynamics and diameter of Ge nanowires grown via a VLS mechanism. The shape and geometry of the heterogeneous interfaces between the liquid eutectic and solid Ge nanowires varies as a function of nanowire diameter and eutectic alloy composition. The behaviour of the faceted heterogeneous liquid–solid interface correlates with the growth kinetics of the nanowires, where the main growth facet at the solid nanowire–liquid catalyst drop contact line lengthens for faster nanowire growth kinetics. Pronounced diameter dependent growth kinetics, as inferred from liquid–solid interfacial behaviour, is apparent for the synthesised nanowires. Direct in‐situ microscopy observations facilitates the comparison between the nanowire growth behaviour from ternary (Au–Ag–Ge) and binary (Au–Ge) eutectic systems.     

Determination of various constituent elements of polyethylene terephthalate bottles used for beverages in Japan

Polyethylene terephthalate (PET) bottles are some of the most commonly used containers for beverages. During the manufacturing process of PET resin in Japan, metallic catalysts such as Sb and Ge are widely used, with other metals or metallic compounds also being employed to improve the quality of PET bottles. However, few reports into the contents of such elements exist. Thus, we herein report the concentrations of 34 elements (ie, Li, B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Zr, Mo, Ag, Cd, Sn, Sb, Cs, Ba, W, Pb, and U) in 16 samples of unused virgin PET bottles for beverages. The measurement was performed by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS), and these bottles were found to contain five main elements (ie, <0.5- to 50-mg/kg Ge, <1- to 26-mg/kg Ti, <0.1- to 279-mg/kg Sb, <10- to 48-mg/kg P, and <0.5- to 53-mg/kg Co) that were used as polymerisation catalysts, stabilisers, oxidation catalysts, and bluing agents. Furthermore, when these residual element concentrations in 21 commercial mineral-water PET bottles were determined, there was no significant difference from unused bottles.     

Thermal Evolution of Solid Products Derived from Germanium-Containing Preceramic Polymer

The products formed during thermolysis of poly(germasilethyne) have been studied within temperature range 20–1600°C by means of Raman spectroscopy, XRD and EDS analysis, and SEM analysis. The evolution of solid products derived from poly(germasilethyne) as a function of heat-treatment temperature passes through several stages. At earlier stages the cross-linking of polymer molecules and the formation of rigid three-dimensional network occur. The particularity of the first stage of thermal transformation of poly(germasilethyne) in comparison with silicon analogue is not only the formation of the skeleton in the solid phase but also the release of disordered carbon phase. The stage of intensive thermal decomposition of germanium-containing polymer includes the escape of gaseous products, the formation of strongly disordered carbon, amorphous covalent silicon–germanium-carbon network and germanium as inorganic phase (most likely Si_1–x–yGe_xC_y). High-temperature treatment results in the evaporation of germanium, the formation and ordering of carbon and -SiC phases. The presence of germanium in the products of thermolysis of polymer leads to a faster growth of the oxides during exposition of thermolyzed polymer to air at high temperatures.     

熔融纺丝制备的PET/锗复合纤维:负离子释放性能、远红外辐射性能及抗菌性能

为了研究不同无机锗粉含量的PET/锗复合纤维的负离子发射、远红外辐射以及抗菌性能,采用熔融复合纺丝法制备了无机锗粉质量分数为1%—3%的PET/锗复合纤维。利用扫描电子显微镜(SEM)、XRD对纤维的表面和横截面形貌、物相结构进行了表征。结果表明,无机锗粉均匀地分散在纤维中,没有出现团聚现象。复合纤维的XRD图中在2θ=17.4°、24.1°、27°、33.5°、51.7°处出现了Ge-O的特征衍射峰,表明锗粉的晶格结构没有被纺丝的高温破坏。此外,负离子发射、远红外辐射以及抗菌性能测试表明,纤维的负离子发射量与纤维内部的锗含量成正比,当锗含量为3%时,达到1 470个/cm~3。在25~70℃范围内,纤维产生的负离子数量随温度的升高而增加,当温度超过70℃时,纤维产生的负离子数量基本达到饱和。当锗含量增加至3%时,PET/锗复合纤维的法向远红外发射率达到最大值0.9,12h内复合纤维对金黄色葡萄球菌的抑菌率达到97.8%。     

Improving narrow bandgap a-SiGe:H alloys grown by hot-wire chemical vapor deposition

We have improved the electronic properties of narrow-bandgap (Tauc gap below 1.5 eV) amorphous-silicon germanium alloys (a-SiGe:H) grown by hot-wire chemical vapor deposition (HWCVD) by lowering the substrate temperature and deposition rate. Prior to this work, we were unable to grow a-SiGe:H alloys with bandgaps below 1.5 eV that had photo-to-dark conductivity ratios comparable with our plasma-enhanced CVD (PECVD) grown materials [B.P. Nelson et al., Mater. Res. Soc. Symp. 507 (1998) 447]. Decreasing the filament diameter from our standard configuration of 0.5 mm to 0.38 or 0.25 mm provides first big improvements in the photoresponse of these alloys. Lowering the substrate temperature from our previous optimal temperatures (T_sub starting at 435 °C) to at 250 °C provides additional photo-to-dark conductivity ratio increasing by two orders of magnitude for growth conditions containing 20–30% GeH₄ in the gas phase (relative to the total GeH₄+SiH₄ flow).     

非对称面电极硅基锗金属-半导体-金属光电探测器的设计

针对金属-半导体-金属(MSM)光电探测器暗电流抑制的机理,本文提出了一种具有非对称面电极结构的硅基锗MSM光电探测器的设计方法,利用ATLAS仿真软件分析了电极结构参数对暗电流的影响,并通过实验得出样品器件的暗电流降低至微安量级。实验结果表明,采用非对称面电极结构设计可以有效抑制硅基锗MSM光电探测器的暗电流,提高器件性能。     

Si and Ge‐Based Anode Materials for Li‐, Na‐, and K‐Ion Batteries: A Perspective from Structure to Electrochemical Mechanism

Silicon and germanium are among the most promising candidates as anodes for Li‐ion batteries, meanwhile their potential application in sodium‐ and potassium‐ion batteries is emerging. The access of their entire potential requires a comprehensive understanding of their electrochemical mechanism. This Review highlights the processes taking place during the alloying reaction of Si and Ge with the alkali ions. Several associated challenges, including the volumetric expansion, particle pulverization, and uncontrolled formation of solid electrolyte interphase layer must be surmounted and different strategies, such as nanostructures and electrode formulation, have been implemented. Additionally, a new approach based on the use of layered Si and Ge‐based Zintl phases is presented. The versatility of this new family permits the tuning of their physical and chemical properties for specific applications. For batteries in particular, the layered structure buffers the volume expansion and exhibits an enhanced electronic conductivity, allowing high power applications.     

Relaxation of extrinsic and intrinsic stresses in germanium substrates with silicon films

Si films were deposited on Ge substrates at 400°C by two different Physical Vapor Deposition techniques: (A) ion beam sputtering and (B) magnetron sputtering. The intrinsic stresses in the as-deposited films were measured to be compressive and much greater in samples (A), about −1500 to −2000 MPa than in samples (B), about −300 to −500 MPa. The substrates were subsequently exposed to thermal treatments for varying times at 800°C. In the lower stressed (B) samples, the films had relaxed and reduced the overall curvature of the structure whereas in the high stresses (A) samples, an irreversible large increase in the substrate curvature was found to occur. This indicated that plastic deformation in the Ge substrates itself had occurred.     

含锗褐煤的利用现状

概述了我国含锗褐煤的资源状况，分析了我国从含锗褐煤中提取锗的方法和特点，对国外含锗煤的利用现状进行了评述，提出了含锗褐煤利用的发展方向。