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<正>Properties of two LiFePO_4/C composites with low carbon content synthesized from precursors dried by spray drying and blast drying are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and electrochemical measurements. The two samples have a different morphology and particle size, while the structure of LiFePO_4 is unaffected. The LiFePO_4/C composite prepared from the precursor dried by blast drying has a much lower surface resistance and a much better rate capability because the deposited carbon is more graphite-like and more conductive. The cycling performance is also much better for the LiFePO_4/C composite prepared from the precursor dried by blast drying because only a slight impedance growth is involved upon cycling. These results suggest that the precursor drying process has a significant impact on the properties of LiFePO_4/C composite, and its effect is highly dependent on the carbon content. 相似文献
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前驱体配料温度对水热法制备LiFePO4的影响 总被引:1,自引:0,他引:1
研究了配料温度对水热法制备磷酸铁锂的影响.通过X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)以及元素分析等手段分析了不同温度下制备的前驱体和最终的LiFePO4样品,其结果表明配料温度对磷酸铁锂前驱体颜色和特性有明显影响.通过仔细控制该温度可以制得高纯Li3PO4中间体并抑制前驱体中Fe(OH)3的形成.有利于进一步获得结晶良好不含Fe3+的LiFePO4样品,显著提高了LiFePO4材料的放电比容量.当配料温度为30℃时获得的样品,0.1C倍率下放电比容量达到156 mAh·g-1,0.5C倍率下放电比容量为151 mAh·g-1,10C倍率下放电比容量为127 mAh·g-1,循环20次容量保持率达99%. 相似文献
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Xu Guang Gao Guo Rong Hu Zhong Dong Peng Ke Du Xin Rong Deng 《中国化学快报》2007,18(10):1256-1260
A compound"vacuum firing and water quenching"technique was presented in the synthesis of LiFePO_4 cathode powder.The sample was prepared by heating the pre-decomposed precursor mixtures sealed in vacuum quartz-tube,followed by water quenching at the sintering temperature.The results indicate that using the"fast quenching"treatment can succeed in controlling overgrowth of the grain size of final product and improving its utilization ratio of active material.The sample synthesized by this technique has the high reversible discharge specific capacity and good cyclic electrochemical performance. 相似文献
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优化碳包覆对正极材料LiFePO4/C高倍率性能的影响 总被引:2,自引:0,他引:2
碳包覆层的结构和形态对LiFePO4正极材料的电子电导率影响很大. 本文以聚丙烯和葡萄糖为碳源, 二茂铁为催化剂前驱体, 采用原位固相法合成LiFePO4/C复合材料, 并对其微观结构和形貌, 碳的结构与含量, 电化学性能进行分析. 结果表明, 聚丙烯热解形成的碳包覆层石墨化程度高, 可提高材料的高倍率放电性能. 二茂铁的加入有助于优化包覆层的碳结构. 制备的LiFePO4/C复合材料具有优异的高倍率电化学性能, 10C (1C=170 mA·g-1)放电比容量达到145 mAh·g-1. 相似文献
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Synthetic LiFePO4/C without using inert gas 总被引:2,自引:0,他引:2
Guo Rong Hu Xu Guang Gao Zhong Dong Peng Ke Du Yan Jun Liu 《中国化学快报》2007,18(3):337-340
LiFePO_4/C was synthesized by high temperature solid-state method with cheap Fe2O3, LiH2PO4 and glucose as raw materials in absence of inert gas. The sample had ordered olivine-type structure other impurities characterized by the test of X-ray diffraction (XRD). The charge-discharge test showed the sample could demonstrate 120.5 mAh/g at 0.2C rate with good cyclic capability. The powder microelectrode cyclic voltammetry test indicated that the redox process of the sample had good reversibility. 相似文献
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A rapid method has been described for the quantitative extraction of milligram amounts of Mn/II/ with 2-PRONAPOX into CHCl3. The extraction coefficient /E/ of Mn/II/ between CHCl3 and aqueous solution containing 0.2M NH4Cl shows a maximum value of E=143 at pH 10.5. The percentage extraction is better than 98% in the pH range from 9 to 11 and an equilibration time of 6 min. The effects of anions and cations have been studied. The stoichiometry of metal: reagent determined by substoichiometric extraction and slope ratio method is found to be 12. The decontamination factors for most of the elements are better than 104 in the substoichiometric extraction of Mn/II/. 相似文献
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Chenyang Zhao Xiaoju Yin Zhikun Guo Dan Zhao Guiye Yang Aosai Chen Lishuang Fan Yu Zhang Naiqing Zhang 《中国化学快报》2021,32(7):2254-2258
Lithium metal has a very outstanding theoretical capacity(3860 mAh/g) and is one of the most superior anode materials for high energy density batteries.However,the uncontrollable dendrite growth and the fo rmation of "dead lithium" are the important hidden dangers of short cycle life and low safety.However,the uncontrollable dendrite growth and the fo rmation of dead lithium leads to short cycle life and hidden dange r,which hinder its practical application.Controlling the nucleation and growth process of lithium is an effective strategy to inhibit lithium dendrite.Herein,a simple in situ self-catalytic method is used to construct nitrogen doped carbon nanotube arrays on stainless steel mesh(N-CNT@SS) as a lithium composite anode.The N-doped CNTs provide a great number of N-functional groups,which enhance the lithiophilic of anode and provide a large number of uniform nucleation sites,hence it has excellent structural stability for cycles.The arrays provide neat lithium-ion transport channels to uniform lithiumion flux and inhibits dendrite generation,revealed by the COMSOL multi-physics concentration field simulation.The N-CNT@SS composite anode sustain stable at 98.9% over 300 cycles at 1 mA/cm2.NCNT@SS as the anode is coupled LiFePO_4(LFP) as the cathode construct a full battery,demonstrating excellent cycling stability with a capacity of 152.33 mAh/g and capacity retaining ratio of 95.4% after 100 cycles at 0.5 C. 相似文献
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Zhixian Zhou Yanjun Xing Yangjie Wu 《Journal of inclusion phenomena and macrocyclic chemistry》1999,34(2):221-233
The extraction of perrhenate with 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcali x[4]arene ( L) into 1,2-dichloroethane was investigated. The presence of Na+ in the aqueous phase is necessary for the extraction. The extraction equilibrium has been established and the thermodynamic quantities H°, TS° and log Kex are -61.3 kJ/mol, -41.4 kJ/mol and 3.69, respectively. The effect of diverse ions on the extraction of ReO4- was studied. The corresponding extracted complex [Na L]ReO4...H2O was prepared and characterized by EA, IR and X-ray structure analysis. The complex crystallizes in the tetragonal space group P4ncc with a = b = 14.735(3), c = 29.094(3) Å, V = 6316(2) Å3, Z = 4. 相似文献
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The effects of neutral organophosphorous compounds on the extraction of thorium by -hydroxy naphthaldoxime in xylene are reported. Enhancement of the extraction is explained by a complex adduct formation in the organic phase. Synergistic coefficients and apparent formation constant of complex adducts are calculated. 相似文献
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Summary The comparative effects of the distribution of 4-heptanone, 2–, and 4-methylcyclohexanone oximes between water and chloroform, the hydrolysis of the oximes and the solubilities of the corresponding palladium (II) chloride complexes in chloroform on the palladium extraction efficiency of the oximes are discussed. Steric effects were found to influence the relative extraction efficiency order to the greatest extent.The relative extraction efficiency order found using the outlined conditions was: 4-methylcyclohexanone oxime4-heptanone oxime 2-methylcyclohexanone oxime.
Zusammenfassung Die Verteilung von 4-Heptanon-, 2- und 4-Methylcyklohexanonoxim zwischen Wasser und Chloroform, die Hydrolyse der Oxime und die Löslichkeit der entsprechenden Palladium(II)chloridkomplexe in Chloroform wurden hinsichtlich ihres Einflusses auf die Palladiumextraktion vergleichend diskutiert. Sterische Umstände beeinflussen die Extraktion in größtem Ausmaß. Unter den angeführten Bedingungen ergab sich folgende Reihenfolge der relativen Extraktionswirksamkeit: 4-Methylcyklohexanonoxim 4-Heptanonoxim 2-Methylcyklohexanonoxim.相似文献
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A method has been developed for rapid and selective extraction of Au/III/ with ethyl thioacetoacetate /HETAcAc/ into chloroform at pH 4. The effect of various parameters on the extraction coefficient values have been studied. The stoichiometry of the extracted species 13 was obtained by the slope ratio method and by the method of substoichiometric extraction. 相似文献
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LiFePO4的制备、结构与电性能研究 总被引:1,自引:1,他引:0
应用高速球磨-高温固相反应法于不同煅烧温度(400~700℃)下合成L iFePO4锂离子电池正极材料,X-射线衍射、扫描电镜和恒电流充放电等测试表明,煅烧温度对合成的L iFePO4晶体结构、表观形貌以及电化学性能均有很大影响;经600℃煅烧得到的L iFePO4样品具有良好的充放电性能,以0.1C倍率充放电,首次放电比容量为128.8 mAh/g,第15次放电比容量为129.1 mAh/g,充放电效率在99.7%以上;其高温充放电性能亦佳. 相似文献
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A new method for on-line solvent extraction covalent hydride generation in a non-aqueous extraction phase is proposed. Both liquid–liquid extraction and gas–liquid separation steps are accomplished in an online mode and with AFS as detector. Hydride generation is carried out in an aliquot of metal-complex extraction solution by sodium tetrahydroborate in N,N-dimethylformamide solution and anhydrous acetic acid. An improved U-type gas–liquid separator was used. The working conditions and manifolds scheme of flow injection were optimized. The detection limit attained for mercury was 20ngL–1. The precision of the determination at a concentration level of around 20 times the detection limit was 5.6%. The proposed method gives improved sensitivity and eliminates interference. The method has been applied to the determination of mercury in certified reference materials with good accuracy and precision. 相似文献
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T. Omori M. Tadokodo Y. Suzuki H. Suganuma K. Yoshihara 《Journal of Radioanalytical and Nuclear Chemistry》1994,181(1):71-76
Solvent extraction mechanism of pertechnetic acid with TBP from perchloric acid solutions is discussed. When cyclohexane is used as a diluent of TBP, perchloric acid can be extracted in the form of HClO4(TBP)2 into the organic phase. The TBP extraction of pertechnetic acid competes with perchloric acid and its equilibria are expressed as follows: HTcO4+3TBPHTcO4(TBP)3 and HTcO4(TBP)3+TBPHTcO4(TBP)4. 相似文献