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1.
A LiFePO4 material with ordered olivine structure is synthesized from amorphous FePO4 · 4H2O through a solid–liquid phase reaction using (NH4)2SO3 as the reducing agent, followed by thermal conversion of the intermediate NH4FePO4 in the presence of LiCOOCH3 · 2H2O. Simultaneous thermogravimetric–differential thermal analysis indicates that the crystallization temperature of LiFePO4 is about 437 °C. Ellipsoidal particle morphology of the resulting LiFePO4 powder with a particle size mainly in the range 100–300 nm is observed by using scanning electron microscopy and transmission electron microscopy. As an electrode material for rechargeable lithium batteries, the LiFePO4 sample delivers a discharge capacity of 167 mA h g–1 at a constant current of 17 mA g–1 (0.1 C rate; throughout this study n C rate means that rated capacity of LiFePO4 (170 mA h g–1) is charged or discharged completely in 1/n hours), approaching the theoretical value of 170 mA h g–1. Moreover, the electrode shows excellent high‐rate charge and discharge capability and high electrochemical reversibility. No capacity loss can be observed up to 50 cycles under 5 C and 10 C rate conditions. With a conventional charge mode, that is, 5 C rate charging to 4.2 V and then keeping this voltage until the charge current is decreased to 0.1 C rate, a discharge capacity of ca. 134 mA h g–1 and cycling efficiency of 99.2–99.6 % can be obtained at 5 C rate. 相似文献
2.
Interest in binary oxides has been renewed because of their novel reactivity towards Li at low potential, which leads to large capacity gains. Here, the structural, morphological, and electrochemical properties of copper‐supported Fe3O4 deposits prepared by cathodic reduction of a FeIII chelate in alkaline solution are reported. By tuning the deposit growth parameters, namely the deposition time and the temperature of the electrolytic bath, it is possible to prepare deposits with various morphologies. Thick deposits with well‐faceted particles of Fe3O4 are produced when long deposition times are used; thin and shapeless deposits are formed after shorter electrolysis times. A screening study shows Fe3O4 films prepared at 50 °C under –5 mA cm–2 for 40 s give the best electrochemical performance towards Li, namely with a sustained reversible capacity for over 50 cycles and outstanding rate capability even after 50 repeated charge–discharge sequences. Electrodeposition techniques provide an alternative efficient way to configure high‐performance conversion electrodes based on carbon‐free binary oxides. 相似文献
3.
J.&#x;C. Arrebola A. Caballero M. Cruz L. Hernn J. Morales E.&#x;R. Castelln 《Advanced functional materials》2006,16(14):1904-1912
Li–Ni–Mn spinels of nominal composition LiNi0.5Mn1.5O4, which are functional materials for electrodes in high‐voltage lithium batteries, are prepared by thermal decomposition of mixed nanocrystalline oxalates obtained by grinding hydrated salts and oxalic acid in the presence of polyethyleneglycol 400. Their structure, microstructure, and texture are established from combined X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction, transmission electron microscopy (TEM), IR spectroscopy, and N2 absorption measurements. The polymer tailors the shape of particles, which adopt a nanorodlike morphology at low temperatures (400 °C). In fact, the nanorods consist of highly distorted oriented nanocrystals connected by a polymer‐based film as inferred from IR and XPS spectra. The electrochemical properties of spinels in this peculiar form are quite poor, mainly as a result of the high microstrain content of their nanocrystals. Raising the temperature up to 800 °C partially destroys the nanorods, which become highly crystalline nanoparticles approximately 80 nm in size. At this temperature, the polymer facilitates crystal growth; this leads to highly crystalline polyhedral nanoparticles as revealed from TEM images and microstrain data. Following functionalization as a cathode in lithium cells, this material exhibits a very good rate capability, coulombic efficiency, and capacity retention even upon cycling at voltages as high as 5 V. Moreover, it withstands fast‐charge–slow‐discharge processes, which is an important cycle‐life‐related property for commercial batteries. 相似文献
4.
Young‐Uk Park Dong‐Hwa Seo Hyungsub Kim Jongsoon Kim Seongsu Lee Byoungkook Kim Kisuk Kang 《Advanced functional materials》2014,24(29):4603-4614
Room‐temperature Na‐ion batteries (NIBs) have recently attracted attention as potential alternatives to current Li‐ion batteries (LIBs). The natural abundance of sodium and the similarity between the electrochemical properties of NIBs and LIBs make NIBs well suited for applications requiring low cost and long‐term reliability. Here, the first successful synthesis of a series of Na3(VO1?x PO4)2F1+2x (0 ≤ x ≤ 1) compounds as a new family of high‐performance cathode materials for NIBs is reported. The Na3(VO1?x PO4)2F1+2x series can function as high‐performance cathodes for NIBs with high energy density and good cycle life, although the redox mechanism varies depending on the composition. The combined first‐principles calculations and experimental analysis reveal the detailed structural and electrochemical mechanisms of the various compositions in solid solutions of Na3(VOPO4)2F and Na3V2(PO4)2F3. The comparative data for the Na y (VO1?x PO4)2F1+2x electrodes show a clear relationship among V3+/V4+/V5+ redox reactions, Na+?Na+ interactions, and Na+ intercalation mechanisms in NIBs. The new family of high‐energy cathode materials reported here is expected to spur the development of low‐cost, high‐performance NIBs. 相似文献
5.
Y. Sharma N. Sharma G. V. Subba Rao B. V. R. Chowdari 《Advanced functional materials》2007,17(15):2855-2861
ZnCo2O4 has been synthesized by the low‐temperature and cost‐effective urea combustion method. X‐ray diffraction (XRD), HR‐TEM and selected area electron diffraction (SAED) studies confirmed its formation in pure and nano‐phase form with particle size ～ 15–20 nm. Galvanostatic cycling of nano‐ZnCo2O4 in the voltage range 0.005–3.0 V versus Li at 60 mA g–1 gave reversible capacities of 900 and 960 mA h g–1, when cycled at 25 °C and 55 °C, respectively. These values correspond to ～ 8.3 and ～ 8.8 mol of recyclable Li per mole of ZnCo2O4. Almost stable cycling performance was exhibited in the range 5–60 cycles at 60 mA g–1 and at 25 °C with ～ 98 % coulombic efficiency. A similar cycling stability at 55 °C, and good rate‐capability both at 25 and 55 °C were found. The average discharge‐ and charge‐potentials were ～ 1.2 V and ～ 1.9 V, respectively. The ex‐situ‐XRD, ‐HRTEM, ‐SAED and galvanostatic cycling data are consistent with a reaction mechanism for Li‐recyclability involving both de‐alloying‐alloying of Zn and displacement reactions, viz., LiZn ? Zn ? ZnO and Co ? CoO ? Co3O4. For the first time we have shown that both Zn‐ and Co‐ions act as mutual beneficial matrices and reversible capacity contribution of Zn through both alloy formation and displacement reaction takes place to yield stable and high capacities. Thus, nano‐ZnCo2O4 ranks among the best oxide materials with regard to Li‐recyclability. 相似文献
6.
Oxides with the nominal chemical formula Li6ALa2Ta2O12 (A = Sr, Ba) have been prepared via a solid‐state reaction in air using high purity La2O3, LiOH·H2O, Sr(NO3)2, Ba(NO3)2, and Ta2O5 and are characterized by powder X‐ray diffraction (XRD) in order to identify the phase formation and AC impedance to determine the lithium ion conductivity. The powder XRD data of Li6ALa2Ta2O12 show that they are isostructural with the parent garnet‐like compound Li5La3Ta2O12. The cubic lattice parameter was found to increase with increasing ionic size of the alkaline earth ions (Li6SrLa2Ta2O12: 12.808(2) Å; Li6BaLa2Ta2O12: 12.946(3) Å). AC impedance results show that both the strontium and barium members exhibit mainly a bulk contribution with a rather small grain‐boundary contribution. The ionic conductivity increases with increasing ionic radius of the alkaline earth elements. The barium compound, Li6BaLa2Ta2O12, shows the highest ionic conductivity, 4.0×10–5 S cm–1 at 22 °C with an activation energy of 0.40 eV, which is comparable to other lithium ion conductors, especially with the presently employed solid electrolyte lithium phosphorus oxynitride (Lipon) for all‐solid‐state lithium ion batteries. DC electrical measurements using lithium‐ion‐blocking and reversible electrodes revealed that the electronic conductivity is very small, and a high electrochemical stability (> 6 V/Li) was exhibited at room temperature. Interestingly, Li6ALa2Ta2O12 was found to be chemically stable with molten metallic lithium. 相似文献
7.
N. Meethong H.‐Y. S. Huang S. A. Speakman W. C. Carter Y.‐M. Chiang 《Advanced functional materials》2007,17(7):1115-1123
High energy lithium‐ion batteries have improved performance in a wide variety of mobile electronic devices. A new goal in portable power is the achievement of safe and durable high‐power batteries for applications such as power tools and electric vehicles. Towards this end, olivine‐based positive electrodes are amongst the most important and technologically enabling materials. While certain lithium metal phosphate olivines have been shown to be promising, not all olivines demonstrate beneficial properties. The mechanisms allowing high power in these compounds have been extensively debated. Here we show that certain high rate capability olivines are distinguished by having extended lithium nonstoichiometry (up to ca. 20 %), with which is correlated a reduced lattice misfit as the material undergoes an electrochemically driven, reversible, first‐order phase transformation. The rate capability in several other intercalation oxides can also be correlated with lattice strain, and suggests that nanomechanics plays an important and previously unrecognized role in determining battery performance. 相似文献
8.
9.
Xi Wang Xing‐Long Wu Yu‐Guo Guo Yeteng Zhong Xinqiang Cao Ying Ma Jiannian Yao 《Advanced functional materials》2010,20(10):1680-1686
Single‐, double‐, and triple‐shelled hollow spheres assembled by Co3O4 nanosheets are successfully synthesized through a novel method. The possible formation mechanism of these novel structures was investigated using powder X‐ray diffraction, scanning and transmission electron microscopies, Fourier transform IR, X‐ray photoelectron spectroscopy, and thermogravimetric analysis. Both poly(vinylpyrrolidone) (PVP) soft templates and the formation of cobalt glycolate play key roles in the formation of these novel multishelled hollow structures. When tested as the anode material in lithium‐ion batteries (LIBs), these multishelled microspheres exhibit excellent cycling performance, good rate capacity, and enhanced lithium storage capacity. This superior cyclic stability and capacity result from the synergetic effect of small diffusion lengths in the nanosheet building blocks and sufficient void space to buffer the volume expansion. This facile strategy may be extended to synthesize other transition metal oxide materials with hollow multishelled micro‐/nanostrucutures, which may find application in sensors and catalysts due to their unique structural features. 相似文献
10.
Hollow tin dioxide (SnO2) microspheres were synthesized by the simple heat treatment of a mixture composed of tin(IV ) tetrachloride pentahydrate (SnCl4·5H2O) and resorcinol–formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre‐formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field‐emission scanning electron microscopy (FE‐SEM) images showed 1.7–2.5 μm sized hollow spherical particles. Transmission electron microscopy (TEM) images showed that the produced spherical particles are composed of a hollow inner cavity and thin outer shell. When the hollow SnO2 microspheres were used as a lithium‐battery anode, they exhibited extraordinarily high discharge capacities and coulombic efficiency. The reported synthetic procedure is straightforward and inexpensive, and consequently can be readily adopted to produce large quantities of hollow SnO2 microspheres. This straightforward approach can be extended for the synthesis of other hollow microspheres including those obtained from ZrO2 and ZrO2/CeO2 solid solutions. 相似文献
11.
C. Kim K.&#x;S. Yang M. Kojima K. Yoshida Y.&#x;J. Kim Y.&#x;A. Kim M. Endo 《Advanced functional materials》2006,16(18):2393-2397
A carbon nanofiber‐based electrode, exhibiting a large accessible surface area (derived from the nanometer‐sized fiber diameter), high carbon purity (without binder), relatively high electrical conductivity, structural integrity, thin web macromorphology, a large reversible capacity (ca. 450 mA h g–1), and a relatively linearly inclined voltage profile, is fabricated by nanofiber formation via electrospinning of a polymer solution and its subsequent thermal treatment. It is envisaged that these characteristics of this novel carbon material will make it an ideal candidate for the anode material of high‐power lithium‐ion batteries (where a high current is critically needed), owing to the highly reduced lithium‐ion diffusion path within the active material. 相似文献
12.
A new approach is developed for cutting conventional micrometer‐long entangled carbon nanotubes (CNTs) to short ca. 200 nm long segments with excellent dispersion. CNTs with different lengths are used as anode materials in Li‐ion batteries. The reversible capacity of the Li‐ion batteries is increased and the irreversible capacity is decreased upon shortening the length of the CNTs. The reason for this is that the insertion/extraction of Li ions is easier into/from short CNTs as compared to long CNTs because of the shortened length and the presence of lateral defects. Moreover, short CNTs have a lower electrical resistance and Warburg prefactor, resulting in better rate performance at high current densities. The present study suggests that short segments of CNTs obtained by cutting long CNTs may possess novel properties that may be useful for a wide variety of applications. 相似文献
13.
G. Yang W. Hou X. Feng L. Xu Y. Liu G. Wang W. Ding 《Advanced functional materials》2007,17(3):401-412
A detailed study on the intercalative polymerization of aniline within different layered inorganic acid hosts (HNb3O8, HTiNbO5, and HSr2Nb3O10) and the conformation and electrochemical properties of the resulting nanocomposites is presented. Two different mechanisms are proposed for the polymerization of monomers within the confined intralamella, initiated by chemical oxidants or microwave irradiation. The orientation of the aromatic rings and the extent of oxidation and protonation of the interlayered polyaniline (PANI) is closely related to the different layer properties. To emphasize the controlled structure–property relationship, the nanocomposites are modeled as “porous electrolytes” and analyzed by equivalent circuit, cyclic voltammetry (CV), and charge–discharge measurements. Compared with the nanocomposites in which the aromatic rings are parallel with the inorganic slabs, the nanocomposites in which the aromatic rings are perpendicular to the slabs demonstrate higher conductivity, electroactivity, and discharge capacity. In the latter, a good 2D channel for the insertion/desertion of ions was provided and simultaneously more ions could be reserved within a relatively wider space. A charge–discharge mechanism is suggested for the chemical reaction in the Li/PANI nanocomposite battery and is in good agreement with the experimental facts. 相似文献
14.
Dawei Liu Betzaida Battalla Garcia Qifeng Zhang Qing Guo Yunhuai Zhang Saghar Sepehri Guozhong Cao 《Advanced functional materials》2009,19(7):1015-1023
Novel nanowall arrays of hydrous manganese dioxide MnO2 · 0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1 M solution possess a surface area of ～96 m2 g?1 and exhibit a stable high intercalation capacity of 256 mA hg?1 with a film of 0.5 µm in thickness, far exceeding the theoretical limit of 150 mA hg?1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ～230 mA hg?1 for films of ～2.5 µm) than that of anodic deposited films of the same thickness (～80 mA hg?1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro‐ and mesoporosity of the MnO2 · 0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid‐state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de‐intercalation. 相似文献
15.
To replace Pb with a less toxic metal is a key scientific challenge because of the toxicity of Pb and the most viable replacement are Sn and Ge. In this study, we propose Sn-Pb-Ge ternary-metal perovskites CH3NH3SnxPbyGe1-x-yI3 (0 < x, y < 1) for the first time. For the identification of new families, the features were verified by fist principle calculations from a theoretical perspective, especially the structural and electric performance, optical property and crystal structure. The Sn-Pb-Ge ternary-metal perovskites are prepared for from the aqueous HI/H3PO2 solvent mixture the first time, For CH3NH3Sn0.25Pb0.5Ge0.25I3, the computed results are in good agreement with the experimental data, which provide a clear-sighted insight into the design of environmentally friendly perovskites for potential electrical and tunable optical application. 相似文献
16.
SnSx (x = 1, 2) compounds are composed of earth‐abundant elements and are nontoxic and low‐cost materials that have received increasing attention as energy materials over the past decades, owing to their huge potential in batteries. Generally, SnSx materials have excellent chemical stability and high theoretical capacity and reversibility due to their unique 2D‐layered structure and semiconductor properties. As a promising matrix material for storing different alkali metal ions through alloying/dealloying reactions, SnSx compounds have broad electrochemical prospects in batteries. Herein, the structural properties of SnSx materials and their advantages as electrode materials are discussed. Furthermore, detailed accounts of various synthesis methods and applications of SnSx materials in lithium‐ion batteries, sodium‐ion batteries, and other new rechargeable batteries are emphasized. Ultimately, the challenges and opportunities for future research on SnSx compounds are discussed based on the available academic knowledge, including recent scientific advances. 相似文献
17.
Sanghyeon Kim Jaewon Choi Seong‐Min Bak Lingzi Sang Qun Li Arghya Patra Paul V. Braun 《Advanced functional materials》2019,29(27)
Solid‐state batteries can potentially enable new classes of electrode materials which are unstable against liquid electrolytes. Here, SnS nanocrystals, synthesized by a wet chemical method, are used to fabricate a Li‐ion electrode, and the electrochemical properties of this electrode are examined in both solid and liquid electrolyte designs. The SnS‐based solid‐state cell delivers a capacity of 629 mAh g?1 after 100 cycles and exhibits an unprecedentedly small irreversible capacity in the first cycle (8.2%), while the SnS‐based liquid cell shows a rapid capacity decay and large first cycle irreversible capacity (44.6%). Cyclic voltammetry (CV) experiments show significant solid electrolyte interphase (SEI) formation in the liquid cell during the first discharge while SEI formation by electrolyte reduction in the solid‐state cell appears negligible. Along with CV, X‐ray photoelectron spectroscopy and energy dispersive spectroscopy are used to investigate the differences between the solid‐state and liquid cells. The reaction chemistry of SnS in solid‐state cells is also studied in detail by ex situ X‐ray diffraction and X‐ray absorption spectroscopy. The overarching findings are that use of a solid electrolyte suppresses materials degradation and electrolyte reduction which leads to a small first cycle irreversible capacity and stable cycling. 相似文献
18.
This article summarizes our most recent studies on improved Li+‐intercalation properties in vanadium oxides by engineering the nanostructure and interlayer structure. The intercalation capacity and rate are enhanced by almost two orders of magnitude with appropriately fabricated nanostructures. Processing methods for single‐crystal V2O5 nanorod arrays, V2O5·n H2O nanotube arrays, and Ni/V2O5·n H2O core/shell nanocable arrays are presented; the morphologies, structures, and growth mechanisms of these nanostructures are discussed. Electrochemical analysis demonstrates that the intercalation properties of all three types of nanostructure exhibit significantly enhanced storage capacity and rate performance compared to the film electrode of vanadium pentoxide. Addition of TiO2 to orthorhombic V2O5 is found to affect the crystallinity, microstructure, and possible interaction force between adjacent layers in V2O5, and subsequently leads to enhanced Li+‐intercalation properties in V2O5. The amount of water intercalated in V2O5 is found to have a significant influence on the interlayer spacing and electrochemical performance of V2O5·n H2O. A systematic electrochemical study has demonstrated that the V2O5·0.3 H2O film has the optimal water content and exhibits the best Li+‐intercalation performance. 相似文献
19.
J. Saint M. Morcrette D. Larcher L. Laffont S. Beattie J.‐P. Pérès D. Talaga M. Couzi J.‐M. Tarascon 《Advanced functional materials》2007,17(11):1765-1774
Silicon–carbon composites consisting of Si particles embedded in a dense and non‐porous carbon matrix are prepared by the pyrolysis of intimate mixtures of poly(vinyl chloride) (PVC) and Si powder at 900 °C under a flow of N2. In contrast to bare micrometer‐sized (1–10 μm) and nanometer‐sized (10–100 nm) Si powders, which show poor cycling behavior with almost no capacity remaining after 15 cycles, the texture of the composite is seen to greatly enhance the reversibility of the alloying reaction of Si with Li. For instance, a capacity of ca. 1000 mA h g–1 is achieved for 20 cycles (0–2.0 V vs. Li+/Li) for a silicon–carbon composite containing nanometer‐sized Si particles. We also demonstrate that a mild manual grinding treatment degrades the cycling performance of the composites to levels as low as the parent Si, even though free Si is not released. The electrochemical measurements in conjunction with Raman spectroscopy data indicate that a huge stress is exerted on the Si domains by the in situ formed carbon. This carbon‐induced stress is found to disappear during the milling of the composites, indicating that the carbon‐induced pressure, along with the accompanying improvement in electrical connectivity, are the key parameters for the improved cycling behavior of Si versus Li. 相似文献
20.
Genki Kobayashi Shin‐ichi Nishimura Min‐Sik Park Ryoji Kanno Masatomo Yashima Takashi Ida Atsuo Yamada 《Advanced functional materials》2009,19(3):395-403
State‐of‐the‐art LiFePO4 technology has now opened the door for lithium ion batteries to take their place in large‐scale applications such as plug‐in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room‐temperature phase diagram is essential to understand the facile electrode reaction of LixFePO4 (0 < x < 1), but it has not been fully understood. Here, intermediate solid solution phases close to x = 0 and x = 1 have been isolated at room temperature. Size‐dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid‐solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two‐phase equilibrium potential is largely due to the bulk solid solution, and thus support the size‐dependent miscibility gap model. 相似文献