锂离子电池硅基负极材料的研究进展

电动汽车和先进电子设备对锂离子电池的能量密度提出了更高的要求.硅的理论比容量能够达到4 200 mAh/g,被认为是一种很有前景的锂离子电池负极材料.但是,硅在充放电过程中巨大的体积变化(＞300％)导致容量迅速衰减.近年来,研究者们采用不同方法改善了其循环性能,主要有:制备硅基复合材料;制备特殊形貌的硅基材料;选用更加合适的粘结剂、电解液、集流体和控制电压窗口.对这些方法进行了概述,并展望了硅作为高能量密度锂离子电池负极材料的应用前景.     

Preparation of ferroelectric thin films for Si-based devices

Abstract

Lead titanate (PbTiO₃) thin films have been prepared on titanium dioxide coated silicon wafers by chemical vapor deposition (CVD). The pure PbTiO₃ thin films were deposited by controlling the experimental conditions. The gas phase reaction of TiO₂ occurred by exceeding the critical value of titanium input fraction at constant oxygen partial pressure. Strontium titanate (SrTiO₃) thin films have been prepared on p-type silicon wafers by radio frequency (RF) magnetron sputtering. The SrTiO₃ thin film was polycrystalline and the Sr/Ti ratio of this film was 0.91. The SrTiO₃ thin films contain three regions, an external surface layer, a main layer and an interfacial layer. The stoichiometric SrTiO₃ thin film was obtained by using the SrO excess target. The SrTiO₃ film annealed at 600[ddot]C has an ideal capacitance-voltage (C-V) curve and maximum effective dielectric constant.     

Accelerated stressing and degradation mechanisms for Si-based photoemitters

A silicon p-n junction biased in avalanche breakdown mode emits visible light. Such a diode offers the potential for very large scale integration (VLSI)-compatible light emitters for on/off chip signal transmission and contactless functional testing of wafers. The reliability of such emitters must be evaluated before widespread use is possible. Si light emitters were stressed with ac excitation, dc excitation, and increased temperature to accelerate the aging. The results clearly show that the effects of ac and temperature stressing are negligible on light emission. DC stressing results in light coalescence for low values of current (less than 25 mA) with total light emission coming out of the junction remaining constant. However, dc stressing with large current values (larger than 40 mA) does not show light coalescence. The light coalescence phenomenon can be reversed when emitters are subjected to higher levels of currents. The difference in light coalescence behavior for large and small values of dc excitation and the reversibility of the phenomenon is consistent with the hydrogen migration model.     

锂离子电池硅基负极材料改性研究进展

锂离子电池硅基负极材料由于理论容量较高(4200 mAh/g),成为最具吸引力的新一代负极材料.然而,硅在充放电过程中体积变化较大,引起电池容量的快速衰减,从而导致电池的循环性能变差.为解决此问题,表面处理、多相掺杂、形成硅化物等方法被用来改善硅基负极材料的电化学性能.综述了以上方法对硅基负极材料改性研究的最新进展,并对各种改性方法进行了简单的评述.     

硅基磷灰石电解质材料的研究进展

介绍了硅基磷灰石电解质材料的结构和电荷传导机理;综述了材料的制备方法以及改性的研究进展,主要包括纳米粉体的制备、先进烧结技术的使用和通过掺杂提高氧离子电导率等;对研究的方向提出了建议.     

锂离子蓄电池硅基负极材料的研究

综述了锂离子蓄电池硅基负极材料的制备、特性以及电化学性能的研究概况。分析了常温下锂与晶体硅以及无定形材料的电化学合金化机理,介绍了硅材料在充放电过程中的失效机制。重点探讨了单质硅、硅-金属复合材料、硅-碳材料作为锂离子蓄电池阳极材料的发展过程、反应机理以及充放电特性,并对其存在的问题进行了分析。对未来硅基材料的研究和应用作了探讨及预测,认为无定形合金薄膜材料以及纳米复合材料将是硅基材料的研究重点,硅基材料作为锂离子蓄电池商业化负极材料指日可待。     

小型化微带环行器的设计与仿真

为了降低微带环行器的平面尺寸,满足器件小型化需求,采用三维电磁仿真软件HFSS设计了不同结构(单Y结、双Y结和鱼刺结)的微带环行器.仿真结果表明:与单Y结和双Y结微带环行器相比,鱼刺结微带环行器可以显著减小器件的平面尺寸,提高铁氧体基片的有效使用面积.在中心频率处,鱼刺结微带环行器的反射、隔离度和插入损耗分别为33.8、48.6和0.17 dB,电压驻波比为1.05,带宽高于300 MHz,满足器件的性能要求.     

锂离子电池硅基薄膜负极材料的研究进展

作为锂离子电池材料,硅基材料有优于碳材料、钛酸锂材料以及锡基材料的理论比容量,成为锂离子电池负极材料研究的一大热点。由于硅基材料存在较大的体积效应,阻碍了硅基材料的商业化。综述了近几年来锂离子电池硅基薄膜材料的研究进展,分析了此类材料的优缺点,展望了硅基薄膜材料的发展方向。     

锂离子电池硅基负极材料粘结剂的研究进展

综述了硅基负极材料粘结剂的研究进展。重点论述了羧甲基纤维素钠(CMC)、聚丙烯酸(PAA)、海藻酸钠和导电聚合物等粘结剂在硅基负极材料中的应用。比较了不同类型粘结剂的优缺点,展望了硅基负极材料粘结剂的发展方向。     

基于DGS的小型化UWB-MIMO天线的设计

根据目前无线通信系统发展趋势,设计了一款具有高隔离度的小型化双单元超宽带(UWB)多输入多输出(MIMO)天线,整体尺寸仅为18 mm×22 mm×1 mm。该天线贴片采用刻蚀六角星的矩形结构,并在其右侧上下位置分别挖去“w”形及小矩形,实现了天线的宽带化;采用缺陷地(DGS)结构,在接地板顶端刻蚀两个半径相等的半圆形槽,实现了天线的高隔离度。仿真与实测结果基本吻合,天线最终的工作带宽为2.75～10.64 GHz(相对带宽达到117.85%),且在带宽范围内隔离度均大于22 dB,包络相关系数(ECC)小于0.015。由此,所设计的天线不仅尺寸极小、结构简单,且性能方面良好,可广泛应用于无线通信系统中。     

小型蓝牙标签天线的仿真设计

小型标签 RFID芯片的工作频率为13.56 MHz,本文主要设计了小型蓝牙标签的天线,该天线采用电感耦合的形式。用 ANSYS公司的电磁仿真软件 HFSS对小型标签天线的各种形状,厚度,层数,圈数的场强进行仿真分析和比较,做好线圈的电感匹配,并查看天线的 S参数使其频率在13.56 MHz时有较好的谐振,设计出了满足在小型标签中尺寸小,抗干扰性能强的天线,使其在13.56 MHz 时具有最好的传输性能。最后将天线安装在 RFID 芯片上后进行封装,得到成本低,实用性强,应用广泛的小型标签。结果测得标签的最远读取距离为35 cm。     

超宽带小型化微带环行器的设计与仿真

设计了一种超宽带小型化双Y结微带环行器,阐述了微带环行器的工作原理、设计理论和方法。在理论分析的基础上,结合计算机辅助软件AppCAD,分别计算出了大小Y结的尺寸,利用HFSS软件进一步对环行器进行建模、仿真,并且根据小Y结尺寸对于环行器带宽的影响,对其进行了优化处理。结果表明,该环行器在7.5～12.5GHz范围内,插入损耗小于0.1dB,隔离度大于20dB,电压驻波比小于1.22,相对带宽大于50%,仿真数据均满足设计要求和性能指标,也满足了环行器小型化的设计要求。     

小型化磁保持式射频同轴开关设计

针对目前微波系统多通道微波通路切换以及星载微波器件小型化的需求,提出了小型化射频同轴开关的设计需求.通过原理分析,结合HFSS电场仿真软件和Maxwell低频电磁仿真软件,设计制作了一种具有磁保持功能、低耗能、体积小、可靠性高等优点的射频同轴开关.所研制的开关在DC～19 GHz频段内工作性能良好,工作频率f:DC～8...     

A new, easily miniaturized steerable endoscope

This article describes a new steerable endoscope for laparoscopic surgery. The steerable mechanism was inspired by the tentacles of squid and consists only of standard parts such as cables, coil springs, rings, and tubes. Laparoscopic surgery is carried out using an endoscope and long and slender instruments that are inserted through small incisions in the abdominal wall. The endoscope contains a light source and a camera that displays a picture of the abdominal cavity on a monitor in the operation room. The surgeon uses the instruments to carry out the operation while estimating the spatial position of the instruments and the organs from the camera picture. The mechanism can be easily miniaturized to a very small diameter, making it suitable for low-cost mass production of steerable endoscopes, instruments, and catheters. A patent for the mechanism has been applied for, and it is currently being commercialized.     

一种小型化SIR交指带通滤波器设计

本文基于阶跃阻抗谐振器（SIR）比同频率均匀阻抗（UIR）尺寸更小的原理,结合薄膜工艺设计加工了一款小型化的交指滤波器。设计的SIR谐振器长度比UIR谐振器长度缩短了24.8%。使用该小型化的谐振器设计了一款小型化的交指滤波器。使用薄膜工艺在0.254 mm厚的相对介电常数为98的陶瓷基板上对滤波器进行加工。经测试,滤波器的通带为355~435 GHz,带内中心插损为3 dB,带内平坦度为17 dB,带内回波损耗小于-186 dB,在带外28与51 GHz处的抑制度分别为-428与-661 dB。滤波器尺寸仅为640 m×479 mm（021λg×016λg）。     

光伏电站晶硅组件缺陷形成机理与检测技术

针对我国光伏电站在晶硅光伏组件运行维护过程中存在的实际情况,分析了晶硅光伏组件缺陷形成机理,提出了一种适用于现场应用的缺陷光伏组件检测方案。检测方案包括红外热成像排查、绝缘电阻测试、EL测试和光伏组件I-V特性测试四部分。通过该检测方案能够有效鉴别光伏组件缺陷的产生原因,及其对发电性能的影响程度。该方案对提高光伏电站运行维护效率、规范光伏电站施工安装操作和改进光伏组件生产厂家制造工艺具有重要意义。     

用微机电系统技术制作微质子交换膜燃料电池

采用微机电系统(MEMS)技术,在n型单晶硅片衬底上制作微型质子交换膜燃料电池(μPEMFC)的流场板,并用电子扫描电镜(SEM)观察其表面形貌。将它与用Nafion1135质子交换膜以传统热压方法制备的膜电极组装成H2/空气自呼吸式"PEMFC,该电池的体积为0.28mL,质量不足0.65g。用电化学阻抗谱(EIS)测量了电池装配压缩比与内阻的关系,结果表明:在常温常压下,当压缩比!2%时,随压缩比增加,电池内阻减小,功率性能提高显著;当压缩比为2%时,电池功率性能最好,其峰值比功率约为83mW/cm2;而当压缩比"2%时,这种变化不显著。     

A miniaturized slotted multiband antenna for wireless applications

A novel miniaturized slotted multiband antenna is presented in this article. The antenna consists of a kite-shaped slot in the radiating patch to obtain miniaturization, C- and G-shaped slots in the ground plane to incorporate multiband operation and a microstrip feedline to obtain an impedance matching. The aforementioned miniaturization method results in about 50% reduction in active patch area and about 36% reduction in volume of the proposed design, as compared to the conventional antenna. G-shaped slot is used to obtain operations at 3.6 and 5.8 GHz, while C-Shaped slot is used to obtain operations at 6.9 and 9.5 GHz. The antenna has an active patch area of only 384 \(\hbox {mm}^{2} (24\times 16\,\hbox {mm}^{2})\), and the entire performance analysis of the antenna are carried out using HFSS v.13.0 simulation software. The proposed design operates at about 3.58 (WiMAX), 5.9 (WLAN), 6.72 (Satellite TV), 8.51 and 9.76 GHz (X-band) with \({S}_{11}<-\,10\,\hbox {dB}\) bandwidth of about 1.95% (3.54–3.61 GHz), 3.5% (5.88–6.09 GHz), 1.7% (6.68–6.80 GHz), 4.4% (8.36–8.74 GHz) and 3.96% (9.4–9.78 GHz), respectively. The proposed structure is compact in size, simple in construction, low profile, easy to fabricate, exhibits good impedance matching, moderate gain and stable radiation characteristics across the operational bandwidths.     

用于硅基负极材料的新型PAA/PANi复合粘结剂的研究

开发了一种由聚丙烯酸和聚苯胺复合而成的新型硅基负极复合粘结剂,由于同时具备高粘结性和良好的导电性,不仅可以减少导电剂的用量,还可限制硅基负极材料循环过程中的体积膨胀。经过50次50 m A/g充放电循环后,用该新型复合粘结剂时纳米硅负极的比容量保持在250 m Ah/g左右。