共查询到20条相似文献,搜索用时 15 毫秒
1.
《Electrochemistry communications》2003,5(2):146-148
The thermal instability of the LiCoO2 cathode material was greatly improved by the nanoparticle AlPO4 coating. The AlPO4 coating appears to minimize the violent exothermic reaction of the cathode with the flammable electrolytes, resulting in excellent thermal stability even at the overcharged state. Moreover, the results of the overcharge and elevated temperature cycling tests show that, when compared with the spinel Li1.05Mn1.95O4, the AlPO4 nanoparticle coating results not only in enhanced thermal stability of the cathodes but also in reduced Co dissolution in the electrolytes. 相似文献
2.
《Journal of solid state chemistry》1987,67(2):316-323
The crystal structures of the lithium-rich and lithium-deficient spinel phases Li2[Mn2]O4 and Li0.2[Mn2]O4 have been determined by neutron-diffraction techniques. Structure refinements confirm earlier reports that the [Mn2]O4 framework of the Li[Mn2]O4 spinel remains intact during both lithium insertion and extraction, but demonstrate unequivocally that in Li2[Mn2]O4 the Li+ ions reside in face-shared tetrahedra and octahedra of the cubic-close-packed oxygen-anion array; in Li0.2[Mn2]O4 the Li+ ions are located randomly on only the tetrahedral sites of the spinel structure. 相似文献
3.
The potentiometric response of PLD-made LiFePO(4) thin films versus Li(+) ions in aqueous solutions has been investigated, and a sensitivity of 54 mV dec(-1) has been observed in a Li(+) concentration range of 1-10(-4) M. Physical and electrochemical measurements of electrodes aged in aqueous medium show a slight surface oxidation with formation of heterosite-FePO(4) that we show to be responsible for the stable potential response measured. Cyclic voltamperometry measurements operated in different Li(+) concentration clearly highlight the key relation between the material lithium ion insertion/de-insertion capability and its potentiometric sensing response implying a faradaic-governed sensing mechanism. Based on such a finding, selection criteria (enlisting among others the potential of the redox couple, the nature of the insertion process) are herein underlined in the search for new sensitive materials. 相似文献
4.
K. C. Mahesh G. S. Suresh T. V. Venkatesha 《Journal of Solid State Electrochemistry》2012,16(11):3559-3571
Layered, lithium-rich Li[Li0.2Co0.3Mn0.5]O2 cathode material is synthesized by reactions under autogenic pressure at elevated temperature (RAPET) method, and its electrochemical behavior is studied in 2?M Li2SO4 aqueous solution and compared with that in a non-aqueous electrolyte. In cyclic voltammetry (CV), Li[Li0.2Co0.3Mn0.5]O2 electrode exhibits a pair of reversible redox peaks corresponding to lithium ion intercalation and deintercalation at the safe potential window without causing the electrolysis of water. CV experiments at various scan rates revealed a linear relationship between the peak current and the square root of scan rate for all peak pairs, indicating that the lithium ion intercalation–deintercalation processes are diffusion controlled. The corresponding diffusion coefficients are found to be in the order of 10?8?cm2?s?1. A typical cell employing Li[Li0.2Co0.3Mn0.5]O2 as cathode and LiTi2(PO4)3 as anode in 2?M Li2SO4 solution delivers a discharge capacity of 90?mA?h g?1. Electrochemical impedance spectral data measured at various discharge potentials are analyzed to determine the kinetic parameters which characterize intercalation–deintercalation of lithium ions in Li[Li0.2Co0.3Mn0.5]O2 from 2?M Li2SO4 aqueous electrolyte. 相似文献
5.
Developing an efficient in situ electrochemical cell for neutron diffraction of electrode materials for Li-ion batteries remains a major technical challenge. We recently published the results of the first experiment carried out with such a cell developed by our group. In order to improve the quality of data we optimized the preparation of the electrode, introduced a gradient in the carbon content, and controlled the porosity. Li4Ti5O12 was used as a model material to demonstrate the advantages of the new approach. 10 diffractograms were recorded in situ during the first electrochemical cycle and then refined to obtain the evolution of unit cell parameters, oxygen position, and of the quantitative ratio between Li4Ti5O12 and Li7Ti5O12. 相似文献
6.
Electronic structural changes in LiTi(2)O(4) spinel compounds upon electrochemical lithium insertions were investigated by X-ray absorption spectroscopy (XAS) measurements and first principles calculations based on spin-polarized density functional theory. Ti K-edge, O K-edge XAS spectra and theoretical calculations indicate that oxide ions as well as titanium ions are involved in electronic structural changes caused by electrochemical lithium ion insertions. The considerable effect of the oxide ions in the early 3d transition metal (titanium) oxide system is discussed in this article. 相似文献
7.
A series of Sc3+-doped spinel lithium manganese oxides Li1+xScyMn2-yO4(y=0.01, 0.02, 0.06, and 0.10)were synthesized by solid state reaction using LiOH·H2O, MnO2, and Sc2O3 as starting materials. The results of powder X-ray diffraction indicated that the doped Li1+xScyMn2-yO4 maintain the cubic structure of spinel phase Fd3m. The electrochemical properties were characterized by electrochemical methods. The initial discharge capacity reached 135 mAh/g and the capacity fading rate was less than 2% after 40 cycles. The spinel phase was well preserved after 40 cycles. The doping of Sc3+ effectively improved the cycleability of spinels, and was a promising way for the improvement of spinel LiMn2O4 cathode materials. 相似文献
8.
Mircea Dan Valerie Pralong Nicolae Vaszilcsin Andrea Kellenberger Narcis Duteanu 《Journal of Solid State Electrochemistry》2011,15(6):1227-1233
The paper presents the electrochemical investigation of mixed oxide YBaCo4O7 in alkaline aqueous solution during oxygen insertion/release. The electrochemical behaviour of YBaCo4O7 has been studied by cyclic voltammetry and electrochemical impedance spectroscopy. In correlation with these techniques,
the compound morphology was determined by scanning electron microscopy. Based on the results obtained, the electrochemical
processes occurring at the interface mixed oxide (YBaCo4O7)/electrolyte solution have been identified, and furthermore a mechanism of YBaCo4O7 oxidation/reduction in alkaline aqueous solutions has been proposed. 相似文献
9.
Shirakawa J Nakayama M Wakihara M Uchimoto Y 《The journal of physical chemistry. B》2006,110(36):17743-17750
The electrochemical lithium insertion reaction of monoclinic Li(3)Fe(2)(PO(4))(3) as cathode materials of lithium-ion batteries was investigated from the viewpoint of the electronic structure around Fe and the polyanion unit (PO(4)). Fe K-edge and L(III,II)-edge XAS measurements revealed that Fe(3+) was reduced to Fe(2+) upon Li insertion. In addition, O K-edge and P K-edge XAS also showed spectral changes upon Li insertion, which corresponded to changes in the electronic structure of the PO(4) polyanion unit. The ab initio density functional calculation was performed within the GGA and LDA+U methods. The LDA+U method reproduced well the cell potential upon lithium intercalation into Li(3)Fe(2)(PO(4))(3), whereas the GGA method underestimated the intercalation. The calculated electronic structure of Li(3)Fe(2)(PO(4))(3) described strong P 3p-O 2p covalent bonding, while weak hybridization was indicated in Fe 3d-O 2p. Moreover, the difference in electronic density between Li(3)Fe(2)(PO(4))(3) and the lithiated model indicated that the polarization effect between inserted Li and oxygen induced the changes in the electronic structure around the polyanion unit. 相似文献
10.
A simple model for the phase behaviour of a globular protein and a flexible polymer in an aqueous medium is described, in which both the compact feature of the protein and the flexble feature of the polymer have been included. The phase diagrams calculated by using the model suggest that for a given protein, the behaviour depends strongly on the polymer molecular weight. Fluid-fluid-solid three-phase and fluid-fluid two-phase equilibria can be found only when the polymer molecular weight is sufficiently high; otherwise, the only two-phase region in the phase diagram is a fluid-solid two-phase region. 相似文献
11.
Ra W Nakayama M Cho W Wakihara M Uchimoto Y 《Physical chemistry chemical physics : PCCP》2006,8(7):882-889
Electronic and local structural changes in ramsdellite-type Li(2+x)Ti3O7 compound were investigated by X-ray absorption spectroscopy (XAS) measurements. Upon electrochemical Li-ion insertions, the host lattice with ramsdellite structure is retained, indicated by X-ray powder diffraction. Ti K-edge extended X-ray absorption fine structure (EXAFS) analysis shows, however, slight local structural distortions around Ti ions. The energy shifts and the changes in the peak intensity of Ti K-edge and Ti L-edge XAS reveal the reducing oxidation states of Ti ions as the amount of electrochemically-inserted Li-ion increases. Equally important, oxide ions have a significant effect on the electronic transfer process, suggested by O K-edge XAS. These results on electronic structural changes were interpreted using the Zaanen-Sawatzky-Allen scheme. 相似文献
12.
Zhang Xinghan Ma Fei Wei Guangye Lei Ze Qu Jingkui 《Journal of Solid State Electrochemistry》2020,24(10):2301-2313
Journal of Solid State Electrochemistry - Recently, niobium tungsten oxide has garnered considerable attention owing to its excellent Li-ion diffusion rate and prominent structural stability during... 相似文献
13.
The mechanism of Li-ion transport in the garnet Li5La3Nb2O12 总被引:2,自引:0,他引:2
van Wüllen L Echelmeyer T Meyer HW Wilmer D 《Physical chemistry chemical physics : PCCP》2007,9(25):3298-3303
We present a detailed study on the exact location and dynamics of Li ions in the garnet-type material Li(5)La(3)Nb(2)O(12) employing advanced solid state NMR strategies. Applying temperature-dependent (7)Li-NMR, (6)Li-MAS-NMR, (6)Li-{(7)Li}-CPMAS-NMR, (6)Li-{(7)Li}-CPMAS-REDOR-NMR as well as 2D-(6)Li-{(7)Li}-CPMAS-Exchange-NMR spectroscopy, we were able to quantify the distribution of the Li cations among the various possible sites within the garnet-type structure and to identify intrinsic details of Li migration. The results indicate a sensitive dependence of the distribution of Li cations among the tetrahedral and octahedral sites on the temperature of the final annealing process. This distribution profoundly affects the mobility of the Li cations within the garnet-type framework structure. Extended Li mobility at ambient temperature is only possible if the majority of the Li cations is accommodated in the octahedral sites, as observed for the sample annealed at 900 degrees C. Octahedrally-coordinated Li cations could be identified as the mobile Li species, whereas the tetrahedral sites seem to act as a trap for the Li cations, rendering the tetrahedrally-coordinated Li cations immobile on the time scale of the NMR experiments. 相似文献
14.
Summary Shear and concentration dependent flow studies on solutions of a narrow molecular weight fraction of 90.3 % hydrolysed polyvinylalcohol are reported, together with precise density measurements on these same solutions. From the derived flowing volume and partial molar volume values it is concluded that two association processes occur; the first appears similar to micellization of surfactants, the second is association of micellar spheres.
Zusammenfassung Es wurde die Scher- und Konzentrationsabhängigkeit des Fließverhaltens von Polyvinylalkohollösungen (90,3 % hydrolysiert) mit niedriger Polydispersität untersucht. An den gleichen Lösungen wurden auch Präzisionsdichtemessungen ausgeführt. Aus dem berechneten Fließvolumen und dem partiellen Molvolumen kann gefolgert werden, daß zwei Assoziationsprozesse vorliegen. Der erste davon gleicht der Mizellbildung von Tensiden, der zweite entspricht der Assoziation kugelförmiger Mizellen.相似文献
15.
Chun-Yang Wu Yu-Xiang Wang Jian Xie Gao-Shao Cao Tie-Jie Zhu Xin-Bing Zhao 《Journal of Solid State Electrochemistry》2012,16(12):3915-3921
A Li4Ti5O12/carbon nanofibers (LTO/CNFs) composite has been synthesized by solid-state reaction with the in situ growth of CNFs using the chemical vapor deposition method in N2/C2H2. The nanocomposite is characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, Raman spectrum, and nitrogen adsorption/desorption isotherms, and is investigated as an anode material for lithium-ion (Li-ion) batteries. The underlying mechanism for the improvement is analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The in situ synthesized composite shows better electrochemical performance than the bare LTO. The in situ formation of CNFs not only supply an efficient electronic conductive network but also reduce the particle size of LTO and increase in specific surface area, leading to increased electrical conductivity and rapider Li-ion diffusion in electrode/electrolyte interface and bulk electrode. 相似文献
16.
利用共沉淀,固相反应热结晶法,合成具有尖晶石型的复合金属氧化物Mg1.5Mn0.5Ti0.75O4。具有尖晶石型结构的物质,可以插入大量的替代离子并且改变自身锂和氧的化学计量数,与此同时,还保持了结构的稳定。这种特性能够使得它们被用于离子交换研究,用来满足提取锂的需求。通过检测该复合氧化物的饱和交换能力值,分配系数值等,从而确定出该物质具体特性。实验表明,经过酸化的Mg1.5Mn0.5Ti0.75O4,其Mg2 的抽出比率能够达到72%,Mn4 和Ti4 的溶解比率低于8.2%。实验分析得出,Li 能够从无机离子交换剂Mg1.5Mn0.5Ti0.75O4中抽出以及插入,主要是归因于离子交换机理。被酸化的样品对Li 有一个10.6mmol?g-1的离子交换能力,并且对Li 还具有记忆性的离子筛性能。 相似文献
17.
Dr. Zhao‐Yang Fei Bo Sun Liang Zhao Prof. Wei‐Jie Ji Prof. Chak‐Tong Au 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(20):6480-6487
Gold nanoparticles (3–4 nm) were deposited on Mn3O4 nanocrystallites with three distinct morphologies (cubic, hexagonal, and octahedral). The resulting structures were characterized, and their activities for benzene combustion were evaluated. The dominant exposed facets for the three kinds of Mn3O4 polyhedrons show the activity order: (103)≈(200)>(101). A similar activity order was derived for the interfaces between the Au and the Mn3O4 facet: Au/(200)≈Au/(103)>Au/(101). The metal–support interactions between the Au nanoclusters and specific facets of the Mn3O4 polyhedrons lead to a unique interfacial synergism in which the electronic modification of the Au nanoparticles and the morphology of the Mn3O4 substrate have a joint effect that is responsible for a significant enhancement in the catalytic activity of the Au/Mn3O4 system. 相似文献
18.
He Jielong Bai Zhe Huang Xinping Zhang Zhengyu Lu Lu Li Jun 《Journal of Solid State Electrochemistry》2023,27(1):171-182
Journal of Solid State Electrochemistry - In this work, Li1.2Ni0.13Co0.13Mn0.54O2 was prepared by the sol–gel method and coated with FePO4. The experimental results show that the material... 相似文献
19.
Sulphur substitution of oxygen in LiMn2O4
spinel destroyed the ideal symmetry of MnO6 octahedrons.
In consequence, the phase change at about room temperature is strongly retarded,
manifested by lowering heat of the transition and hysteresis of the temperature
dependence of electrical conductivity. The optimal conditions for preparation
of sulphur substituted spinel LiMn2O4–ySy
have been determined. 相似文献
20.
Emo Chiellini Andrea Corti Salvatore D'Antone 《Polymer Degradation and Stability》2007,92(7):1378-1383
Several demonstrations of the effective biodegradation in soil of pro-oxidant activated polyethylene (PE) have been reported recently. Nevertheless a comprehensive understanding of the ultimate fate in the environment of the oxidized fragments of oxo-biodegradable polyethylene materials needs the extension of the studies to other natural environments and in particular to aqueous media (river, lake, brackish and marine waters) where accidental plastic littering and the resulting degraded fragments eventually may end up.In this respect, as part of our continuing activity in the area of oxo-biodegradable polymeric materials, in the present paper we wish to report on the results attained in an ongoing investigation on the biodegradation in a water medium of thermally pre-oxidized low density polyethylene (LDPE) film samples containing pro-oxidant additives.Thermally oxidized LDPE-film samples and corresponding acetone extractable fractions were submitted to the effect of microorganism flora present in river water. The effective biodegradation was assessed by monitoring the amount of CO2 developed over time in a respirometer apparatus. Levels of biodegradation up to 12 and 48% for the degraded fragments and corresponding fractions extracted with boiling acetone were detected on a 100-day time frame. 相似文献