共查询到19条相似文献,搜索用时 125 毫秒
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商业化LiFePO_4(LFP)正极材料的导电性一直是制约其性能提高的关键。为了提高LFP的性能,利用沸石咪唑酯骨架-8(ZIF-8)制备多孔碳材料(CZIF-8)改善商业化LFP正极材料的导电性,对比了两种改性LFP的方法:1)将退火的ZIF-8以物理混合的方法与LFP混合制得LFP/CZIF-8正极材料;2)ZIF-8在LFP表面原位生长后退火制得LFP@CZIF-8正极材料。X射线粉末衍射(XRD)、氮气吸脱附(BET)和拉曼光谱等测试证明,改性后的LFP仍具有橄榄石型结构,同时出现了具有介孔结构的石墨化碳材料的特征。扫描电子显微镜(SEM)和透射电子显微镜(TEM)测试证明LFP/CZIF-8样品中LFP与CZIF-8之间未形成链接结构,而在LFP@CZIF-8样品中二者形成了核壳结构。电化学阻抗测试(EIS)表明,改性后样品的离子传输阻抗明显减小,说明两种方法均提高了LFP的导电性。充放电循环测试表明,两种改性方法均能提高LFP的循环性能和库伦效率。不同的是,倍率性能测试表明,LFP/CZIF-8样品的高倍率性能比LFP@CZIF-8样品更有优势,在10.0 C电流倍率下能够达到57.8 m A·h/g。这一研究为商业化锂离子电池电极材料的改性提供了新的思路,并且通过方法优化为产业化做了铺垫。 相似文献
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采用湿法球磨法制备了锂离子电池混合正极材料LiNi 0.5Co 0.2Mn 0.3O2/LiFePO4 (NMC532/LFP). 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试和电化学阻抗谱测试(EIS)等方法研究对比了LiNi 0.5Co 0.2Mn 0.3O2(NMC532)和LiNi 0.5Co 0.2Mn 0.3O2/LiFePO4 (NMC532/LFP)的容量衰减机理,结果表明:循环50次和60℃高温存储后,NMC532/LFP的容量保持率分别为97.80%、86.48%,其循环和高温存储性能较好. 循环和高温存储后NMC532和NMC532/LFP的电荷传递阻抗Rct明显增大,但NMC532/LFP的Rct较小. NMC532和NMC532/LFP的I(003)/I(104)值都有所减小,但NMC532/LFP的I(003)/I(104)值比NMC532的大,即NMC532/LFP材料的阳离子混排现象有所改善. 循环后NMC532、NMC532/LFP颗粒没有出现明显的表面开裂和链接断裂现象,但NMC532颗粒有部分发生粉化. 高温储存后NMC532颗粒表面出现裂纹,且颗粒之间的链接断裂,NMC532/LFP颗粒表面出现轻微粉化. 材料结构规整度下降,阳离子混排程度加剧,电荷传递阻抗增大是NMC532和NMC532/LFP容量衰减的主要原因. 相似文献
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金属锂负极由于比容量高(3860 mAh·g-1)及氧化还原电位极低(-3.04 V vs.标准氢气电极(SHE)),被认为是实现高能量密度锂电池的理想负极。然而,金属锂电极与电解液反应剧烈,且锂离子在电极表面沉积不均匀容易产生枝晶,导致其循环稳定性和安全性都较差,限制了其应用推广。我们前期通过构建金属锂-碳纳米管(Li-CNT)复合结构,极大的提高了金属锂的比表面积,降低了电极电流密度,从而有效地抑制了锂枝晶的生长,提高了金属锂电极的循环稳定性和安全性能。本工作在前期工作基础上,采用简单的液相反应,利用4-氟苯乙烯(FPS)对Li-CNT进行表面修饰并进行原位聚合,得到了表面富含氟化锂(Li F)保护层的Li-CNT(FPS-Li-CNT)。该表面修饰层能够有效抑制电解液和空气对Li-CNT的侵蚀,显著的提高了LiCNT电极的界面稳定性。FPS-Li-CNT与磷酸铁锂正极(LFP)组成的LFP||FPS-Li-CNT全电池,在正负极容量配比为1:6条件下,能够稳定循环280圈,库伦效率达到97.7%。 相似文献
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LiFePO_4的制备及其充放电过程中的结构演变和性能研究 总被引:2,自引:0,他引:2
分别以FeC2O4·2H2O(a), Fe2O3(b)和Fe3O4(c)为铁源,采用高温固相法制备了3种LiFePO4(LFP)(简称LFPa, LFPb和LFPc).采用碳包覆法制备了LFPa~LFPc的锂离子电池正极片(LFPA~LFPC).用X-射线衍射仪(XRD)分析了铁源对其结构的影响和充放电过程中的结构演变;用循环伏安法(CV)和交流阻抗法(EIS)对锂离子脱嵌动力学作了初步探讨.XRD分析结果表明,LFPa~LFPc均具有单一的橄榄石结构.LFP在循环过程中结构基本稳定,结晶度有所降低.充放电测试表明,LFPA~LFPC在0.2C倍率下首次放电比容量分别为130 mA·h·g-1, 147 mA·h·g-1和152 mA·h·g-1.其中LFPA拥有较好的倍率性能;CV和EIS研究发现,LFPA在充放电过程中极化小,可逆性好. 相似文献
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常压敞开式离子化质谱(Ambient ionization mass spectrometry,AIMS)是指无需复杂样品前处理,并且可在开放环境下对样品进行解吸和离子化的质谱技术。随着该技术的逐渐成熟,其在临床医学诊断中的应用越来越广泛。该文综述了AIMS领域的各种技术在肿瘤组织诊断中的应用,并对未来进行了展望。 相似文献
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通过牺牲模板法制备了一种三维框架Li6.28La3Zr2Al0.24O12(3D-LLZAO)无机电解质,并将其用于构建聚氧化乙烯(PEO)基复合固态电解质膜.通过扫描电子显微镜(SEM)、X射线衍射(XRD)等物理表征及电化学阻抗谱(EIS)、线性扫描伏安(LSV)和充放电循环等电化学测试方法研究了PEO基固态电解质的性能.结果表明加入10%(w) 3D-LLZAO的PEO基复合固态电解质CPE-10具有较小的体电阻、较宽的电化学稳定窗口.复合电解质CPE-10室温下离子电导率为1.58×10-4 S·cm-1,锂离子迁移数为0.26.利用复合固态电解质组装的锂锂对称电池可在室温下0.05 mA·cm-2的电流密度条件下稳定循环1600 h.以磷酸铁锂(LFP)为正极组装的LFP/CPE-10/Li电池在0.5 C倍率下初始放电比容量为155.6m Ah·g-1,循环100次后容量保持率为86%. 相似文献
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原子力显微镜在蛋白单分子结构与功能研究中的应用 总被引:7,自引:0,他引:7
原子力显微镜(AFM)以其超常的信噪比、空间分辨率和灵活的探测环境使得单个蛋白分子能在生理条件下成像,在蛋白单分子结构与功能研究中得到广泛地应用。论文介绍了AFM在分子马达、光合蛋白、分子伴侣等蛋白表面结构表征中的应用;AFM在蛋白单分子表面的粘弹性、电荷分布、分子间相互作用等物理属性研究中的进展;总结了AFM在蛋白分子功能研究和单分子操纵中的应用。 相似文献
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Fenghua Zheng Chenghao Yang Xunhui Xiong Jiawen Xiong Renzong Hu Yu Chen Meilin Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(44):13250-13254
Lithium‐rich layered oxides are promising cathode materials for lithium‐ion batteries and exhibit a high reversible capacity exceeding 250 mAh g−1. However, voltage fade is the major problem that needs to be overcome before they can find practical applications. Here, Li1.2Mn0.54Ni0.13Co0.13O2 (LLMO) oxides are subjected to nanoscale LiFePO4 (LFP) surface modification. The resulting materials combine the advantages of both bulk doping and surface coating as the LLMO crystal structure is stabilized through cationic doping, and the LLMO cathode materials are protected from corrosion induced by organic electrolytes. An LLMO cathode modified with 5 wt % LFP (LLMO–LFP5) demonstrated suppressed voltage fade and a discharge capacity of 282.8 mAh g−1 at 0.1 C with a capacity retention of 98.1 % after 120 cycles. Moreover, the nanoscale LFP layers incorporated into the LLMO surfaces can effectively maintain the lithium‐ion and charge transport channels, and the LLMO–LFP5 cathode demonstrated an excellent rate capacity. 相似文献
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Saji VS Kim YS Kim TH Cho J Song HK 《Physical chemistry chemical physics : PCCP》2011,13(43):19226-19237
Nanostructured materials have attracted recent research interest as battery materials due to their expected enhancement of properties. The characteristic nanoscale dimension and its structuring guarantees improved charge and mass transfer during charge/discharge processes. Among the potential cathode materials investigated as a substitute to LiCoO(2), one of the most promising materials is LiFePO(4) with olivine structure (LFP). In this perspective article, the current research and development in the synthesis and electrochemical studies of nanostructured LFP are reviewed with a special emphasis on one-dimensional (1D) nanostructures and nanocompositing with 1D conductive materials. In addition to various examples of 1D LFP with detailed synthetic methods, why 1D nanostructures could be meaningful is discussed in terms of a geometric point of view and the anisotropic lithiation/de-lithiation mechanism of LFP. 相似文献
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The current status of the isolation, identification, biological activity, utilization and development prospects of flavonoids found in litchi fruit pericarp (LFP) tissues is reviewed. LFP tissues account for approximately 15% by weight of the whole fresh fruit and are comprised of significant amount of flavonoids. The major flavonoids in ripe LFP include flavonols and anthocyanins. The major flavanols in the LFP are reported to be procyanidin B4, procyanidin B2 and epicatechin, while cyanindin-3-rutinside, cyanidin-3-glucoside, quercetin-3-rutinosde and quercetin-3-glucoside are identified as the important anthocyanins. Litchi flavanols and anthocyanins exhibit good potential antioxidant activity. The hydroxyl radical and superoxide anion scavenging activities of procyanidin B2 are greater than those of procyanidin B4 and epicatechin, while epicatechin has the highest alpha,alpha-diphenyl-beta-picrylhydrazyl radical (DPPH*) scavenging activity. In addition to the antioxidant activity, LFP extract displays a dose- and time-dependent inhibitory effect on human breast cancer, which could be attributed, in part, to its inhibition of proliferation and induction of apoptosis in cancer cells through upregulation and down-regulation of multiple genes. Furthermore, various anticancer activities are observed for epicatechin, procyanidin B2, procyanidin B4 and the ethyl acetate fraction of LFP tissue extracts. Procyanidin B4 and the ethyl acetate fraction show a stronger inhibitory effect on HELF than MCF-7 proliferation, while epicatechin and procyanidin B2 have lower cytotoxicities towards MCF-7 and HELF than paclitaxel. It is therefore suggested that flavonoids from LFP might be potentially useful components for functional foods and/or anti-breast cancer drugs. 相似文献
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Pipette-friendly laminar flow patterning for cell-based assays 总被引:1,自引:0,他引:1
Laminar flow patterning (LFP) is a characteristic method of microfluidic systems that allows two (or more) different solutions to flow side-by-side in a channel without convective mixing. This fluid behavior can be used to pattern cell suspensions, particles, and treatments as well as to create chemical gradients. LFP is typically implemented using syringe pumps and, for this reason, is most effective in constant flow scenarios such as long-term gradient generation. However, the complexity of using syringe pumps for patterning cell suspensions typically makes it a less attractive option than other standard patterning methods. We present a passive microfluidic method that enables short-term LFP of multiple fluids using a single pipette and allows each sample to be loaded in any sequence, at any point in time relative to one another. The proposed method is well-suited for cell-based assays, reduces the complexity of LFP to be on a similar level as other cell patterning methods, can be scaled to include more than two streams of fluid, and enables arrays of individually addressable devices for LFP on a single chip. 相似文献
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Phenyl azide, 2,6-diethylphenyl azide, 2,6-diisopropylphenyl azide, and 2,4,6-tri-tert-butylphenyl azide were studied by laser flash photolysis (LFP) methods. LFP (266 nm) of the azides in glassy 3-methylpentane at 77 K produces the transient UV-vis absorption spectra of the corresponding singlet nitrenes. At 77 K, the singlet nitrenes relax to the corresponding triplet nitrenes. The triplet nitrenes are persistent at 77 K and their spectra were recorded. The rate constants of singlet to triplet intersystem crossing were determined at this temperature. LFP of 2,4,6-tri-tert-butyl phenyl azide in pentane at ambient temperature again produces a singlet nitrene, which is too short-lived to detect by nanosecond spectroscopy under these conditions. Unlike the other azides, the first detectable intermediate produced upon LFP of 2,4,6-tri-tert-butyl phenyl azide at ambient temperature is the benzazirine (285 nm) which has a lifetime of 62 ns controlled by ring opening to a didehydroazepine. The results are interpreted with the aid of Density Functional Theoretical and Molecular Orbital Calculations. 相似文献
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Mao-xiang Jing Hong-ai Zhai Zhi-chao Pi Jing-quan Li Li-li Chen Xiang-qian Shen Xiao-ming Xi Ke-song Xiao 《Russian Journal of Applied Chemistry》2016,89(7):1183-1188
The LiFePO4/carbon fiber (LFP/CF) cathodes were prepared by using activated carbon fiber cloth as current collector in place of conventional Al foil. The electrochemical properties of LFP/CF electrodes were analyzed by the cyclic voltammetry and galvanostatic charge/discharge tests. The results indicate that the activated carbon fiber cloth with high specific surface area and high porosity makes the LFP/CF electrode that possesses higher mass loading of 18–21 mg cm–2 and stronger redox reaction ability compared with Al foil-based electrode. The LFP/CF electrode shows excellent rate performance and cycle stability. At 0.1C, the discharge capacity is up to 190.1 mAh g–1 that exceeds the theoretical capacity due to the combination effect of battery and capacitor. Furthermore, the LFP/CF electrode shows an initial capacity of 150.4 mAh g–1 at 1C with a capacity retention of 74.7% after 425 cycles, which is higher than 62.4% for LFP/Al foil electrode, and an initial discharge capacity of 130 mAh g–1 at 5C with a capacity retention of 61.5% after 370 cycles. But this composite electrode is not suitable for charging/discharging at higher rate as 10C due to too much mass loading. 相似文献
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Guoqiang Cai Ka Y. Fung Ka M. Ng Ka L. Chu Kawai Hui Lixing Xue 《Journal of Solid State Electrochemistry》2016,20(2):379-387
LiFePO4 (LFP) is widely used as a cathode material for lithium-ion batteries (LIBs). While there exist many studies of the effect of particle size, purity, morphology, degree of agglomeration, and carbon coating on battery performance, it is not clear how these parameters are optimized in a commercial product. This paper aims at developing a causal table which relates the particle qualities to battery performance. A critical assessment of six commercial LFP products was performed in terms of material characteristics and the electrochemical performance of the corresponding button cells. One of the LFP samples with plate-like morphology, small particle size (0.15?×?0.4?×?0.6 μm), and around 2.5 wt% carbon coating had the highest specific capacity (164.9 mAh g?1 at 0.1 C) and rate capability (88.5 % at 1.5 C). The results are in general agreement with the relations captured in the causal table, verifying that it can be used to guide product development. 相似文献
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Lithium cation insertion/deinsertion reaction kinetics in a LiFePO4 (LFP)/graphitic carbon composite material were electrochemically studied with a cavity microelectrode (CME). The LFP/graphitic carbon composite has a core LFP (crystalline/amorphous)/graphitic carbon shell structure. In the crystalline and amorphous LFP phase, different reaction mechanisms were observed and characterized. While the reaction mechanism in the crystalline LFP phase is controlled by Li+ diffusion, the amorphous LFP phase shows a fast, surface-controlled, pseudocapacitive charge-storage mechanism. This pseudocapacitive behavior is extrinsic in origin since it comes from the presence of Fe3 + defects in the structure. These features explain the ultrafast performance of the material which offers interesting opportunities as a positive electrode for assembling high power and high energy hybrid supercapacitors. 相似文献