A study on capacity fading of lithium-ion battery with manganese spinel positive electrode during cycling

The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge-discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn₂O₄ spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu₂O and MnO or MnO₂, respectively. These depositions of Cu and Mn oxides did not uniformly deposited on the anode side, and most of them were detected on the carbon surface nearby to the separator side. The SEI layer is hard and about 0.3 μm in thickness. Furthermore, the cycling performance of the cells can be improved by adding 1,2,3-benzotrazole (a corrosion inhibitor of Cu) before assembling the cell, it then coordinates strongly with Cu ions into the electrolyte. From the results, it is obvious that the existing of Cu oxide as well as Mn oxide in the SEI layer, which blocks the normal intercalation of the lithium ions, is one of the factors for the capacity fading of the cells.     

砼双向楼板在均布荷载作用下板角抗裂承载力探究

推导出现浇双向板在均布荷载作用下，板角不先出现裂缝的抗弯、抗剪承载力计算公式。     

Statische und dynamische Axialdruckversuche an vergrouteten Rohr‐in‐Rohr‐Verbindungen mit verschiedenen Füllmaterialien

In diesem Beitrag wird über Ergebnisse von experimentellen und numerischen Untersuchungen an vergrouteten Rohr‐in‐Rohr‐Verbindungen berichtet, die am Institut für Stahlbau der Leibniz Universität Hannover durchgeführt wurden. Diese sogenannten “Grouted Joints” kommen z. B. als Verbindungselemente zwischen dem im Boden eingerammten Pfahl und dem Turm einer Offshore‐Windenergieanlage zum Einsatz. An deutlich kleineren Prüfkörpern wurden Axialdruckversuche im Labor durchgeführt, um den Unterschied zwischen glatten und gerippten Stahlrohrmantelflächen im Grenzzustand der Tragfähigkeit und Ermüdung aufzuzeigen. Dabei kamen auch verschiedene Füllmaterialien für den Ringspalt zum Einsatz. Die Tragfähigkeit bei den Prüfkörpern mit glatten Rohrmantelflächen ist hauptsächlich von der Haftfestigkeit des Füllmaterials auf den Stahloberflächen und deren Beschaffenheit abhängig. Durch die Anordnung von Schubrippen kann die Trag‐ und Ermüdungslast um ein Vielfaches gegenüber der glatten Variante gesteigert werden. Dies ist hauptsächlich auf die Wirkung von Druckstreben zwischen den Schubrippen zurückzuführen, deren Tragfähigkeit sich mit zunehmender Druckfestigkeit des Füllmaterials erhöht. Mit einem Bemessungsmodell kann unter Berücksichtigung der Druckstrebentragfähigkeit und Anzahl der Schubrippen die Traglast von Grouted Joints abgeschätzt werden. Static and dynamic axial compression tests on grouted tube‐in‐tube connections with various grout materials. This paper summarises static and dynamic axial compression tests on small scale grouted joints for offshore wind energy converters. The connection is mostly used between driven monopiles and tower sections as tube‐in‐tube connection. The gap between the tubes is filled with grout materials. The test series comprises grouted joints with smooth and ribbed surfaces of the tubes which are loaded by axial compression. The ultimate and fatigue limit state of the connection can be increased with shear keys along the overlapped length of the tubes to get a ribbed contact surface to the grout. In this case the axial load is transferred by compression struts between the shear keys. The bearing capacity depends mainly on the compressive strength of the grout and the geometry of the shear keys. In addition to the experimental results an analytical design concept is presented within this paper for grouted joints with shear keys. With the analytical model the axial load capacity of the grouted joint can be determined under consideration of the compression struts and number of shear keys.     

蓄电池生极板固化对产品质量的影响

本文为提高蓄电池的容量和寿命,对铅蓄电池制造过程的生极板涂填后固化等进行了讨论。     

氢镍电池负极放电储备容量的调节

研究了封口化成条件下金属氢化物镍电池负极放电储备容量的调节方法。研究表明 ,加入铝合金或金属锌均可以有效提高氢电极的放电储备容量 ,而且对电池的性能无影响。同时确定了铝合金和锌的加入方式     

交流电机调速在煤矿机械上的应用

对近年交流电机调速中的变频调速、开关磁阻调速在煤矿的情况进行分析和介绍。     

浅谈低压配电网的无功补偿

介绍了低压配电网无功补偿的补偿原则、补偿方式和补偿容量的确定方法,结合实际分析了采取无功补偿的效果和意义。     

多微电网互联系统的储能容量配置

随着微电网的发展,微电网之间互联的研究逐渐兴起。为了满足多微电网系统的电能质量和运行稳定性等要求,储能系统发挥着重要作用。同时,为了实现微电网互联运行的经济性最优,需要对多微电网的储能系统进行协调容量配置。建立了层级式微电网互联模型,以传输功率损耗最低作为互联微电网之间以及微电网与大电网之间的功率交换原则,基于多微电网互联系统功率交换和分时售/购电价,建立以多微电网系统经济性最优为目标的目标函数,采用改进的粒子群算法对该模型进行优化求解,最终获得储能系统的容量配置参数。实验结果表明,在满足系统稳定性的前提下,文中提出储能系统容量配置方法使得多微电网系统的经济性更优。     

Cost reduction of a hybrid energy storage system considering correlation between wind and PV power

A hybrid energy storage system (HESS) plays an important role in balancing the cost with the performance in terms of stabilizing the fluctuant power of wind farms and photovoltaic (PV) stations. This paper first discusses hybrid energy storage systems, as well as chemical properties in different medium, deeming the ramp rate as one of the determinants that must be observed in the cost calculation. Then, a mathematical tool, Copula, is explained in details for the purpose of unscrambling the dependences between the power of wind and PV plants. To lower the cost, the basic rule for allocation of buffered power is also put forward, with the minimum energy capacities of the battery ESS(BESS) and the supercapacitor ESS(SC-ESS) simultaneously determined by integration. And the paper introduces the probability method to analyze how power and energy is compensated in certain confidence level. After that, two definitions of coefficients are set up, separately describing energy storage status and wind curtailment level. Finally, the paper gives a numerical example stemmed from real data acquired in wind farms and PV stations in Belgium. The conclusion presents the fact that the cost of a HESS varies not only with the ramp rate of its BESS, but also inevitably with the dependences between the power of wind and PV plants, which means both are indispensable considerations.     

变电站供电负荷与变压器的容量选择

针对变电站供电区域内负荷情况,对变压器容量选择和经济运行的条件及要求进行了分析.结合实例,介绍了变压器实施经济运行与容量选择之间的安全和经济效益关系,提出了相关注意事项.