荷电状态对锂离子电池电化学性能的影响研究

以LiNi0.6Co0.2Mn0.2O为主要正极材料制备锂离子电池,通过循环伏安法、电化学阻抗谱和恒电流间歇滴定技术研究了过充状态、过放状态和正常使用条件下锂离子电池电化学参数变化规律。结果表明,锂离子电池在过充、过放时,固体电解质界面(SEI)膜遭到破坏,电荷转移和离子扩散难度增加,电池整体电阻增大,安全性降低;然而,以恒电流间歇滴定方式将电池过充到4.5 V时,电池正、负极材料结构的改变具有可逆性,电池可以恢复到正常状态;将电池过放至2.5 V后,正极或负极材料的结构遭到严重破坏,该破坏过程不可逆。该项研究结果对于明确荷电状态对电池整体性能的影响、开发新型电池检测技术并进行电池安全设计具有重要意义。     

LR6型碱锰电池150mA恒流连放过程的研究

采用恒流放电和交流阻抗技术研究碱锰电池150 mA连续放电过程中正负极电化学行为的变化。结果表明:在LR6型碱锰电池150 mA连续放电过程中,电压的变化主要由正极极化引起的;而在放电末期,电压的下降主要是由负极区碱浓度的降低以及负极阻抗的升高所引起的。     

LiCoO2-SiO/石墨锂离子电池循环衰减机理研究

研究了LiCoO₂正极和氧化亚硅/石墨复合负极（LiCoO₂-SiO/石墨）软包锂离子电池体系（LIBs）循环衰减机理,通过循环过程中电化学阻抗（EIS）、增量容量分析（ICA）、正负极形貌等分析了循环的影响因素。结果表明,硅基负极材料在完全嵌锂状态下的体积膨胀不仅会导致SiO负极的颗粒破碎,与电解液的副反应加剧,其膨胀应力还会造成电极的导电网络和粘结剂网络的破损,从而导致正负极活性物质利用率降低,降低SiO负极材料的循环性能。此外,SiO负极的充放电电压平台较高,与石墨材料复合使用时,容易造成电池正极的过充和放电容量损失,正极过充会加剧正极材料结构破裂。而随着循环的进行,过充程度和放电容量损失会愈发严重,加速电池循环性能衰减。     

Direct observation of time-dependent space charge profiles in XLPEcable under high electric fields

Space charge distribution was measured, applying an electric field of >1 MV/cm to 3 mm thick XLPE cable insulation. Improving the conventional pulse electro-acoustic method, a new method was developed to measure space charge when applying HV to cables. Under high field, hetero charges were formed soon after voltage application, followed by an injection from the cathode. Then intermittent injections of charge packets from the anode took place. The space charge distribution kept changing without becoming stabilized. A simulation was done assuming hysteresis of the injection characteristics. The observed intermittent injection near the anode was qualitatively reproduced using computer simulation     

AA 型 TAG-LiMn_2O_4 锂离子蓄电池

用Ｌｉ２ＣＯ３和ＥＭＤ高温合成得到的尖晶石（ＬｉＭｎ２Ｏ４）作阴极活性材料,与Ｌｉ配对做成试验电池,充电容量达１３０ｍＡｈ／ｇ,放电容量为１１０ｍＡｈ／ｇ,显示ＬｉＭｎ２Ｏ４有较好的充放电性能。对热解苯碳（ＰｙＣ）、处理的人造石墨（ＴＡＧ）、天然石墨（ＮＧ）和玻璃碳（ＧＣ）进行研究,发现ＴＡＧ有较好的充放电性能。用ＬｉＭｎ２Ｏ４做阴极活性材料,ＴＡＧ做阳极活性材料,组装成ＡＡ型锂离子蓄电池,初始放电容量为５４０ｍＡｈ,以０．２Ｃ（１００ｍＡ）恒流放电,６０ｍＡ恒流充电,电池循环寿命已达２００次。     

过放电对MCMB-LiCoO2电池性能的影响

通过对MCMB为负极、LiCoO2为正极、金属锂为参比电极的AA型三电极锂离子电池的性能测试及正负极对锂参比电极的电位测试,并结合X R D和SEM实验,研究了过放电对MCMB-LiCoO2锂离子电池性能的影响。结果表明:当M CMB-LiCoO2电池过放至0.0伏时,负极MCMB表面上的SEI膜被损坏,集流体铜箔的腐蚀溶解较严重,再次形成的SEI膜的性能可能较差,这使负极阻抗增大,极化增强,相应地使电池在过放电以后的循环过程中的放电容量、放电电压和充放电效率大为降低。但过放电对MCMB的结构和正极性能没有影响。     

宽脉冲300W功率放大器的研制

重点讨论了VHF频段推挽式功率放大器BLF278在脉冲工作状态下,输出峰值功率达到300 W的电路结构.在明确BLF278性能的基础上,重点分析了功放电路中阻抗匹配用传输线变压器的磁芯材料设计和电路结构设计两个方面.根据理论指导,选择Ni-Zn软磁铁氧体以及25 Ω、16.7 Ω的同轴电缆,成功制作了能够用于1∶4和1...     

大气压液体阴极等离子体的电学特性

大气压液体电极放电是近年来兴起的一种产生大气压等离子体的新方法,此方法因为结构简单、成本低廉、操作方便等优点而具有广泛的应用前景。为此,采用水平面为放电阴极、金属棒为放电阳极,产生了大气压辉光放电等离子体;试验测量了放电等离子体的伏安特性,表明放电发生在反常辉光放电模式,在40～100mA范围内,随着放电电流的增加,放...     

大气压氦气介质阻挡放电的二维演化过程

为了研究大气压氦气的介质阻挡放电机理,利用像增强高速相机(ICCD),以20ns曝光时间,拍摄了多组时序发展的时空分辨放电图像,揭示了放电形式由汤森放电向辉光放电的演化。所测阴极位降区厚度0.4mm,应属亚辉光放电类型,而底面拍摄的图像则揭示了放电径向发展的过程。将放电图像转化为可视性更强的三维图像后,发现放电由覆盖整个电极的微弱汤森放电起始,在场强略高的中心处率先发展,并迅速向外扩散。     

Ozone production using pulsed dielectric barrier discharge inoxygen

The production of ozone was investigated using a dielectric barrier discharge in oxygen, and employing short-duration pulsed power. The dependence of the ozone concentration (parts per million, ppm) and ozone production yield (g(O₃)/kWh) on the peak pulsed voltage (17.5 to 57.9 kV) and the pulse repetition rate (25 to 400 pulses/s, pps) were investigated. In the present study, the following parameters were kept constant: a pressure of 1.01×10⁵ Pa, a temperature of 26±4°C a gas flow rate of 3.0 1/min and a gaseous gap length of 11 mm. A concentric coaxial cylindrical reactor was used. A spiral copper wire (1 mm in diameter) was wound on a polyvinylchloride (PVC) cylindrical configuration (26 mm in diameter) and placed centrally in a concentric coaxial electrode system with 4 mm thick PVC dielectric layer adjacent to a copper outer electrode of 58 mm in internal diameter. HV and current pulses were provided by a magnetic pulse compressor power source     

直流刻蚀铝集流体对LiCoO2正极性能的影响

利用扫描电子显微镜、恒流充放电、循环伏安及交流阻抗等方法,研究了直流刻蚀铝集流体及对锂离子电池LiCoO2正极性能的影响。经直流刻蚀后的铝集流体表面形成均匀的蜂窝状结构,使活性材料与之相互"啮合",正极首次放电比容量由138.1 mAh/g升高到146.2 mAh/g,循环稳定性、电化学阻抗等性能得到了改善。     

移动通信设备氢镍电池的制备及性能研究

采用烧结镍为正极,添加氧化亚钴和羰基镍粉的储氢材料为负极,聚乙烯(PE)/聚丙烯(PP)的复合物为隔膜,制备得到通信设备用富液式QNG90方形氢镍电池,对所得电池充放电时的温度变化及电化学性能进行测试,并与贫液式QNF90方形氢镍电池进行比较。当富液式电池以0.2 C充电6 h,温升为5.0℃;以1.0 C放电,温升为9.5℃。20℃下对电池进行倍率放电与低温放电测试结果表明,当富液式电池以10.0 C放电至0.8 V的放电容量为室温0.2 C放电容量的73.4%,-40℃下以0.2 C放电时容量为常温0.2 C放电容量的75.2%,50℃下满容量电池以1.436 V恒压浮充50 h,未出现热失控和电流失控,0.2 C充放电的循环次数超过1 100次。     

Creepage discharge propagation in air and SF6 gasinfluenced by surface charge on solid dielectrics

Influence of surface charging on creepage discharge propagation in air and SF₆ gas was investigated. The authors have employed a surface charging system using corona discharges, which permitted the deposition of surface charge on solid dielectrics with a given density distribution. By applying a lightning impulse across the charged surface of polyester film, they measured the discharge extension length as a function of surface potential generated by the surface charge. It was found that the impulse creepage discharges along the charged surface under a potential of 2 to 3 kV, extended a distance which was maximum 6× longer than the case of the uncharged surface both in air and SF₆ gas. Experimental results were also discussed from the viewpoint of the specific capacitance, permitting their application to actual HV apparatus such as GIS     

EMP作用下的电缆耦合及屏蔽效能试验分析

介绍了三同轴法、线注入法、功率吸收钳法、混波室法等电缆屏蔽效能测试方法.进行了电磁脉冲作用下的同轴电缆和裸线耦合试验,探讨了该环境下同轴电缆屏蔽效能的测试方法.试验分析表明,电缆耦合后的波形为衰减振荡波,振荡周期正比于电缆的电长度,频谱与照射场的频谱不一致,裸线的耦合输出衰减较快.根据试验数据,采用峰值场强法计算的电缆屏蔽效能与峰值电压法的结果吻合,所以可采用峰值场强法对电缆进行电磁脉冲的屏蔽效能测试.电磁脉冲作用下的同轴电缆屏蔽效能较相当频段连续波作用下的略低.     

添加剂LiBOB在LiCoO2体系中的性能研究

采用恒流充放电法研究了LiBOB对LiCoO2作正极体系高温循环性能的影响。使用DSC法分析了LiBOB对负极SEI膜热稳定性的影响。初步探讨了LiBOB对PC基电解质与MAG相容性的影响机理。交流阻抗法测试结果表明,LiBOB的添加使MAG电极表面形成一层稳定的固体电解液相界面膜(SEI),抑制了PC共嵌,并使循环性能得到改善。DSC结果分析表明,LiBOB使负极SEI膜的热稳定性得到了改善。     

The effect of electrode contamination, cleaning and conditioning onhigh-energy pulsed-power device performance

High-energy pulsed-power devices routinely use field strengths above those at which broad-area, cathode-initiated, HV vacuum-breakdown occur (>10⁷ to 3×10⁷ V/m). Examples include magnetically-insulated transmission lines and current convolutes, high-current-density electron and ion diodes, high-power microwave devices and cavities and other structures for electrostatic and RF accelerators. Energy deposited in anode surfaces may exceed anode plasma thermal-desorption creation thresholds on the time scale of the pulse. Stimulated desorption by electron or photon bombardment also can lead to plasma formation on electrode or insulator surfaces. Device performance is limited above these thresholds, particularly in pulse length and energy, by the formation and expansion of neutral and plasma layers formed primarily from electrode contaminants. In-situ conditioning techniques to modify and eliminate the contaminants through multiple HV pulses, low base pressures, RF discharge cleaning, heating, surface coatings and ion- and electron-beam surface treatment allow access to new regimes of performance through control of plasma formation and modification of the plasma properties. Experimental and theoretical progress from a variety of devices and small scale experiments with a variety of treatment methods are reviewed and recommendations given for future work     

Relationship between electrode surface roughness and impulse breakdown voltage in vacuum gap of Cu and Cu-Cr electrodes

The relationship between the impulse breakdown voltage of vacuum gaps and electrode surface roughness was investigated for the purpose of controlling the surface roughness on HV conductors. The roughness of mechanically polished Cu and Cu-Cr electrodes was measured with a roughness meter, and the relationship between the breakdown voltage and surface roughness was obtained for plate-to-plate gaps. The discharge-conditioning effect increased with reduction in the surface roughness. The breakdown voltage depended not only on the roughness of the cathode but also on the anode surfaces. Reducing the surface roughness was found not to be an effective way to increase the breakdown voltage for non-uniform field gaps after discharge conditioning.     

聚合物锂离子电池的高倍率放电性能研究

研究了正极厚度、正极导电剂含量、负极材料、电池尺寸以及电解液对聚合物锂离子电池高倍率放电性能的影响,结果表明:提高正极导电剂的含量能提高电池10.0 C倍率的放电性能;采用薄正极、中间相碳微球(MCMB)负极材料扣大电池尺寸设计,也能提高电池的高倍率放电性能;在高于10.0 C倍率放电时,功能电解液对高倍率放电性能有较大影响.通过各种影响因素的优化组合,得到了一种聚合物锂离子电池.该电池的最大放电倍率可达20.0 C;300次循环后,10.0 C放电容量仍保持初始容量的84%.     

高压电缆状态检测技术有效性研究

目前各种高压电缆状态检测技术的有效性、经济性和可操作性一直困扰着高压电缆状态检修策略的制定。对近10年来高压电缆运行故障进行统计,在此基础上分析了各种状态检测技术的有效性;然后分析了各种局放在线监测技术的特点,并在实验室模拟试验的基础上,比较了不同局放在线监测方法的有效性和灵敏度;最后提出了电缆状态检测技术的应用建议。     

高压XLPE电力电缆缓冲层放电问题分析

高压与超高压交联电缆金属护套与电缆线芯之间的缓冲层是电缆的重要组成部分。近年,国内交联聚乙烯(XLPE)高压电缆线路故障中多次出现缓冲层放电现象。文中总结国内电缆缓冲层设计经验,分析不同类型高压电力电缆缓冲层作用,总结缓冲层半导电材料、长期进水运行、缓冲层设计缺陷等可能放电原因,通过分析三起高压电缆缓冲层放电典型案例,说明缓冲层设计的缺陷隐患及缓冲层放电问题原因,对电缆设计及电缆故障分析提供有效参考。