Electrochemical performance of methyl methacrylate graft-copolymerized composite separator based on radiation polymerization technique

The pre-irradiation method is introduced to prepare methyl methacrylate graft-copolymerized composite separators. The morphologies of the grafted membranes (GMs) were observed under a scanning electron microscope. The cyclic voltammetry and electrochemical impedance spectra results indicated that the obtained polymer electrolytes (PEs) based on GMs could hold the excellent performance of Li⁺ transportation and possess good affinity with Li metal electrode. The Li/PEs/LiCoO₂ cells demonstrated excellent cycling performance with little capacity loss after 80 cycles. These cells also showed a good rate property and could retain 70.2% (25 °C) and 81% (75 °C) of discharge capacity at 2C rate as compared to that at C/5 rate. The results of this paper suggest that the high-quality composite separators can be obtained by pre-irradiation technique, and this also offered a new and convenient way for the large-scale manufacture of Li-ion polymer battery.     

锂-亚硫酰氯电池储存寿命研究

锂-亚硫酰氯电池作为一种免维护、高比能、长储存寿命电池,目前已经在以国防领域为代表的国民经济中得到了广泛应用;其储存寿命的考核在行业内尚属难题;通过广泛、深入地调研和对前期锂-亚硫酰氯电池储存数据的收集整理,研究了锂-亚硫酰氯电池的储存寿命影响因素及其试验评估方法;通过研究得知,锂-亚硫酰氯电池的储存寿命试验应尽早备样,若时间紧迫可通过加速试验方法;提出了通过等效储存试验时间来评估电池储存寿命及其可靠度的方法,指出当等效储存试验时间不足时,应安排样本进行容量回归分析,得出其退化规律;此外,还要对电池储存末期热性能进行分析;在以上工作基础上对电池储存寿命进行综合评估;最后,通过案例分析,进行了工程演算;为后续锂-亚硫酰氯电池储存寿命评估提供了参考。     

First-Principles Study of Li Doping in a Double-Wall Carbon Nanotube

By performing first-principles calculations, we study Li doping in a double-wall carbon nanotube where a （5,0） tube is confined inside a （14,0） tube. There are three possible sites for Li doping and two of them are energetically favorable. The change of energy band structure is closely related to the doping sites and the charge transfer is investigated. Bader charge analysis indicates that Li prefers to donate its electron to the inner （5,0） tube. Moreover, the Li capacity of the system can reach LIC4.75 which makes it a promising candidate for Li-ion battery materials.     

Electronic properties of Li-doped zigzag graphene nanoribbons

Zigzag graphene nanoribbons (ZGNRs) are known to exhibit metallic behavior. Depending on structural properties such as edge status, doping and width of nanoribbons, the electronic properties of these structures may vary. In this study, changes in electronic properties of crystal by doping Lithium (Li) atom to ZGNR structure are analyzed. In spin polarized calculations are made using Density Functional Theory (DFT) with generalized gradient approximation (GGA) as exchange correlation. As a result of calculations, it has been determined that Li atom affects electronic properties of ZGNR structure significantly. It is observed that ZGNR structure exhibiting metallic behavior in pure state shows half-metal and semiconductor behavior with Li atom.     

Numerical modeling of lithium ion battery for predicting thermal behavior in a cylindrical cell

The thermal behavior of lithium ion battery during charge and discharge is investigated by a numerical simulation. The commercially available cylindrical 18650 battery is modeled in this study. Two different models are used. The porous electrode model is simulated to obtain the Li content inside the particles. The transient thermo-electric model is used to predict the temperature distribution inside the cell. The results suggest that the increase in temperature during discharge is higher than that during charge. The temperature difference between charge and discharge is decreased with increasing C-rates. At a rate of 1C, the discharge temperature increases with a waving region at the beginning, whereas the charge temperature increases until certain point and then decreases. The thermal behavior is closely related to the change in entropy and applied current.     

第一性原理计算：锰酸锂掺杂Fe和Co的性质研究

文章基于密度泛函理论的第一性原理计算,研究了LiMn2O4电池材料在掺杂Fe和Co离子时的电子结构和电化学性能。发现Fe\Co取代Mn3+在热力学上是会更加稳定,提升电化学性能。掺杂Fe后,LiMn2O4电池材料晶格参数减小(约0.3%);掺杂Co后,LiMn2O4电池材料晶格参数减小(约0.5%)。这两种掺杂方式让与之相邻的Mn3+被氧化成Mn4+,从而降低了Jahn-Teller畸变情况产生可能性。对于掺Fe尖晶石型锰酸锂(Li8Mn15FeO32),Mn环境中的Li离子会更容易被提取,第一次放电电压从原来的3.7V增加至4.623V;对于掺Co尖晶石型锰酸锂(Li8Mn15CoO32),第一次放电电压从原来的3.7V增加至4.101V。研究为锂电池电容量研究提供理论数据的参考。     

加载角度和线型缺口对锂离子电池隔膜拉伸性能的影响

锂离子电池隔膜作为防止正负极接触的物理屏障,其结构完整性对于电池安全至关重要。进行了4种商业隔膜单轴拉伸实验,分析加载角度和线型缺口对隔膜材料拉伸强度、弹性模量、断裂模式的影响。结果表明:无缺口试样在0°方向上的拉伸强度最大,90°方向上拉伸强度最小;当两个无缺口试样的加载角度互为补角时,它们的拉伸强度接近。对于缺口试样而言,缺口方向沿着90°的试样有最大破坏载荷;线型缺口试样有更高的弹性模量,但是塑性变形大幅减少。无缺口试样和缺口试样在拉伸过程中的断裂模式相同,即除0°试样沿横向断裂外,其他加载角度的试样均沿着纵向断裂。     

Analysis of Li distribution in ultrathin all-solid-state Li-ion battery (ASSLiB) by neutron depth profiling (NDP)

Lithium-ion batteries are promising energy storage technology devices. They possess many advantages, including high energy density, flexible and lightweight construction and considerable durability. The rapid development of nanotechnologies can further improve their capacity, cycle life and safety. In this experiment, Li-ion diffusion in an all-solid lithium-ion battery (ASSLiB) was studied using the Neutron Depth Profiling (NDP) nuclear analytical technique. The thin ASSLiB system was synthesised by RF magnetron sputtering. The experiment showed that NDP is a very efficient experimental tool for direct analysis of Li distribution in Li batteries. It has been found that the depth profile of Li strongly depends on the state of charge of the battery. About one-third of the total number of Li in ASSLiB can move between the electrodes during charging / discharging. It has been also shown, using the multipixel detectors, that the lateral distribution of Li in ASSLiB is not homogeneous. This can mean, for example, that the position of Li is affected by structural defects that may arise due to variation of the volume or stress of the battery during charging or discharging. In the work are presented first results of measurements performed on ASSLiB of a 1?µm thickness.     

4A碳纳米管及相关结构的嵌锂特性(英文)

碳纳米管独特的一维结构和强烈的卷曲效应为外来原子提供了理想的嵌入通道。本文全面总结了近年来我们对直径仅为4A的三种单壁碳纳米管嵌锂特性的密度泛函研究工作。我们具体讨论了体系嵌锂后的结构、能量、电子、电化学等特性。由于这些超小直径的碳纳米管最初合成于沸石晶体的纳米管道,我们也讨论了碳纳米管?沸石晶体复合体系的嵌锂特性。另外,我们还研究了由(5,0)和(14,0)碳纳米管组成的双壁碳纳米管体系的嵌锂特性。我们的理论计算表明,超小直径碳纳米管及相关结构作为锂离子电池负极材料具有很好的应用前景。     

减反膜对单晶硅太阳能电池性能的影响分析

在太阳能电池效率的评价中,电池材料、掺杂浓度、扩散长度等都是比较重要的参数,合理地改变相关参数可以优化太阳能电池的性能,提高电池效率。此外,在太阳能电池表面镀一层具有减反作用的光学薄膜（简称减反膜）也是提高电池效率的重要手段。以提高电池效率为目标,对单晶硅太阳能电池的掺杂浓度和扩散长度等微观参数进行计算优化,分析了掺杂浓度和扩散长度变化对电池效率的影响。并在此基础上分析了不同类型的减反膜对于电池效率的影响,给出了最佳减反膜材料及其膜系厚度,并且结合镀膜后电池量子效率的变化验证了其准确性。结果表明,在优化电池掺杂浓度和扩散长度的基础上,选择合适的减反膜,电池效率最高可达20.35%,相比于优化前提高了8.25%。     

多层多孔锂离子电池结构的导波频散特征及其应用EI北大核心CSCD

采用状态矩阵与勒让德级数联合法,同步联立Biot理论,构建多层多孔锂离子电池声传播特性理论模型,以厚1.9 mm软包钴酸锂电池为例,数值分析了荷电状态(State of Charge,SOC)对多模态频散曲线的影响规律。同时,建立了电池中的声传播特性频域仿真模型,提取频域仿真中的超声导波频散曲线。此外,以体积小、柔性强的压电纤维复合材料(Macro Fiber Composite,MFC)为基础,实验探究了不同SOC对锂离子电池中声学行为的影响。采用互相关分析获取电池放电过程中声波渡越时间的偏移规律,建立了1.9 mm软包钴酸锂电池的声学波动行为与电池SOC间的映射关系。     

Doping-enhanced lithium diffusion in lithium-ion batteries

We disclose a distortion-assisted diffusion mechanism in Li3N and Li2.5Co0.5N by first-principles simulations. A B(2g) soft mode at the Γ point is found in α-Li3N, and a more stable α'-Li3N (P3m1) structure, which is 0.71 meV lower in energy, is further derived. The same soft mode is inherited into Li2.5Co0.5N and is enhanced due to Co doping. Consequently, unlike the usual Peierls spin instability along Co-N chains, large lithium-ion displacements on the Li-N plane are induced by a set of soft modes. Such a distortion is expected to offer Li atoms a route to bypass the high diffusion barrier and promote Li-ion conductivity. In addition, we further illustrate abnormal Born effective charges along Co-N chains which result from the competition between the motions of electrons and ion cores. Our results provide future opportunities in both fundamental understanding and structural modifications of Li-ion battery materials.     

利用重离子辐照技术制备锂离子电池隔膜

用能量11.4MeV/u和注量1×108ions/cm2的197Au离子垂直辐照聚丙烯薄膜,通过电导测量法监测温度、硫酸浓度和重铬酸钾浓度对径迹蚀刻速率的影响,得到合适的蚀刻条件;成功制备出孔径范围在600—1000nm的重离子径迹聚丙烯孔膜,并用场发射扫描电镜对孔的形状及孔径大小进行了表征,对孔洞锥角的形成进行了分析,为重离子辐照技术制备锂离子电池隔膜提供了实验数据。     

Luminescence properties of MgO produced by solution combustion synthesis and doped with lanthanides and Li

The objective of this study is to explore the possibility of synthesizing MgO with controlled luminescence and thermoluminescence (TL) properties using the Solution Combustion Synthesis (SCS) method by doping with different lanthanides (Ln) and co-doping with lithium (Li). The goal is to further establish the SCS technique as a new route for developing new TL and optically stimulated luminescence (OSL) dosimetric materials. Undoped and doped MgO samples were synthesized by SCS and characterized using radioluminescence (RL) and TL. The data obtained showed that Li doping can increase considerably the intensity of the RL and TL from Ln-doped MgO produced by SCS. In MgO:Ln,Li the introduced lanthanides are responsible for the emission during both RL and TL processes, although other emission bands are also observed (e.g., ∼700-750 nm). The incorporation of lanthanides also introduces trapping centers as indicated by different peaks in the TL curves. The results in this study show that the SCS technique can potentially produce materials with TL intensity comparable to commercial dosimetric materials, although further optimizations are still required.     

掺质KCl晶体F_A色心电子能级

在计算KCl晶体中的F_A心电子能级时,本文认为是基质和掺质对色心电子云束缚的松紧程度之差确定了电子云分布,据此对三种典型的掺质:Li:KCl:F_A(II);Cu:KCl:F_A(III);Ti:KCl:F_A(III),采用不同的出发点进行计算,结果和实验值比较,误差在5%以内.     

Synthesis and electrochemical performance of micro-mesoporous carbon-sulfur composite cathode for Li–S batteries

Even though significant improvement has been made in the Li–S battery technology, the poor cycling and rate performance have always limited the further growth. Thus, the development of cost-effective and high performing electrodes is considered to be an important technology for the practical aspect. It is quite logical that the porous electrode systems can improve the electrochemical performance of a given battery system. Here, this study benchmarks a new class of electrodes based on double (micro and meso)porous carbon spheres (MMPCs) prepared by a facile soft template method followed by wet chemical etching. The particle size analysis, performed by scanning electron microscopy, shows that the templating agents, such as sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide(CTAB), have a distinct effect on the size distribution of carbon particles. Different electrochemical characterizations have been carried out to understand the effect of SDS and CTAB on the electrochemical performance of carbon-sulfur nanocomposite electrode. BET analysis shows that the pore size distribution of the carbon spheres prepared by only the soft template method (MPCs) is mainly in the micropore range, which limits the storage and the dispersive capacity. However, the etched samples (MMPCs) showed better electrochemical performance, such as high initial discharge capacity of 921 mAh g^?1(sulfur loading ～77.2%) with 82.7% capacity retention at the end of 150 cycles at 200 mA g^?1 and an impressive rate capability of 1086 mAh g^?1 at a current density of 100 mA g^?1.This improved performance could be attributed to the double porous structure of MMPCs. Such a feasible and facile architecture provides a good strategy to prepare other different materials that require better material dispersion and electrode/electrolyte interactions.     

Photothermal investigation study of porous silicon layer doped lithium

This paper presents a series of experimental photothermal deflection technique (PTD) spectra of porous silicon layers doped with lithium on crystalline silicon backing (PS/Li) and their numerical analysis. The aim of this work is to investigate the influence of Li doping on the opto-thermal properties (optical absorption, band-gap energy, thermal diffusivity and thermal conductivity). Also, we correlate these results with other evaluation studies such as I–V measurements and atomic force microscope analysis performed on the material. We observe a red shift of the gap, which can be related to the reduction of crystallite size. Moreover, we notice a decrease of thermal properties with the same behavior as electrical conductivity.     

锂离子对稀土掺杂氧化物的红外激光诱导热辐射的影响

由于具有较高的可见波段荧光效率,基于稀土掺杂氧化物的红外激光诱导热辐射具有重大的应用潜力。进一步提高红外诱导热辐射效率具有重大的实用价值。设计了一种改善稀土掺杂氧化物材料中红外诱导热辐射效率的方案,即通过掺杂改性杂质,既可以改变稀土离子周围局域晶场的对称性;同时又引入了晶格缺陷。对应的效果包括：一方面,可以通过增强稀土离子周围的晶场强度来提高稀土元素对于入射光子的吸收能力;另一方面,可以利用晶格缺陷作为猝灭中心来增加材料的热转化能力,最终将显著提高杂质改性材料的光热转化效率,即获得更加高效的红外诱导热辐射材料。为了验证设计方案的可行性,利用溶胶-凝胶方法合成了不同浓度的镱离子和锂离子的共掺杂样品,通过XRD及TEM测试分析了杂质对样品结构的影响,并且基于荧光发射光谱具体研究了杂质掺杂浓度对热辐射效率的影响。该工作为高效稀土掺杂热辐射材料的制备提供一定的参考。     

The morphological evolution, mechanical properties and ionic conductivities of electrospinning P(VDF-HFP) membranes at various temperatures

Poly(vinylidene difluoride-co-hexafluoropropylene) [P(VDF-HFP)] membranes as separators for lithium-ion batteries were prepared from electrospinning. The morphological evolution of the separators at various temperatures were characterized by atomic force microscopy (AFM) equipped with a hot stage. We found the swollen effect of electrolytes on the P(VDF-HFP) phase through in situ observation. The electrochemical measurements results showed the ionic conductivity increased gradually with the increase of temperature. To evaluate the mechanical properties of the P(VDF-HFP) membranes at various temperatures, the tensile curves of the separators were also investigated.     

一种采用Li3N掺杂电子注入层的底发射倒置结构OLED的制备

采用Li3N掺杂电子注入层Alq3∶Li3N,制作了一种结构为ITO/Alq3 Alq3∶Li3N/Alq3/NPB/MoO3/Al的倒置底发射有机发光器件.其中ITO玻璃作为透明阴极,金属Al作为顶部阳极,在ITO阴极与电子传输层之间加入Li3N n型掺杂层,改善了该器件的电子注入和传输能力|在Al阳极与空穴传输层之间加入MoO3缓冲层,降低了Al阳极与NPB之间较大的空穴注入势垒,改善了空穴注入能力.实验表明:此结构的倒置底发射有机发光器件性能可达到传统结构的常用有机发光器件如ITO/NPB/Alq3/LiF/Al的性能,完全可以满足非晶硅薄膜晶体管有源有机发光器件中驱动电路的匹配及性能要求.