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1.
F. Lian P. Axmann C. Stinner Q. G. Liu M. Wohlfahrt-Mehrens 《Journal of Applied Electrochemistry》2008,38(5):613-617
Positive electrode material LiNi1/2Mn1/2O2 was synthesized via the carbonate co-precipitation method and the hydroxide precipitation route to study the effects of the
precursor on its structural and electrochemical properties. The results of X-ray diffraction and Rietveld refinement show
that the carbonate precursor of Ni2+ and Mn2+ exhibits one phase at a pH of 8.5, while the hydroxide deposit separates into Ni(OH)2 and Mn(OH)2 phases under the same experimental conditions. LiNi1/2Mn1/2O2 material prepared from the hydroxide precursor shows 8.9% Li/Ni exchange and a large capacity loss of 11.3% in the first
10 cycles. By contrast, more uniform distribution of transition metal ions and stable Mn2+ in the carbonate precursor contribute to only 7.8% Li/Ni disorder in the obtained LiNi1/2Mn1/2O2, which delivers a reversible capacity of about 182 mAh g−1 at a current rate of 14 mA g−1 between 2.5 and 4.8 V. 相似文献
2.
Dae Geun Lee Ravindra K. Gupta Yong Soo Cho Kwang Taek Hwang 《Journal of Applied Electrochemistry》2009,39(5):671-679
Improved electrochemical properties of Li(Ni0.7Co0.3)O2 cathode material are reported. Samples were synthesized by the co-precipitation method with various sintering conditions,
namely temperature, time and atmosphere. Li(Ni0.7Co0.3)O2 sintered at 850 °C for 14 h in air exhibited the lowest unit cell volume accompanied with relatively higher values of c/a and I
103/I
104 reflection peaks ratios. This also exhibited superior electrochemical properties, such as high charge–discharge capacity,
high Coulombic efficiency, and low irreversible capacity loss. This can be attributed to improved hexagonal ordering, crystallinity
and morphology. The electrochemical cell parameters were better than the reported ones, probably due to controlled sintering
conditions. 相似文献
3.
Cobalt oxide [Co3O4] anode materials were synthesized by a simple hydrothermal process, and the reaction conditions were optimized to provide
good electrochemical properties. The effect of various synthetic reaction and heat treatment conditions on the structure and
electrochemical properties of Co3O4 powder was also studied. Physical characterizations of Co3O4 are investigated by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller [BET] method. The BET surface
area decreased with values at 131.8 m2/g, 76.1 m2/g, and 55.2 m2/g with the increasing calcination temperature at 200°C, 300°C, and 400°C, respectively. The Co3O4 particle calcinated at 200°C for 3 h has a higher surface area and uniform particle size distribution which may result in
better sites to accommodate Li+ and electrical contact and to give a good electrochemical property. The cell composed of Super P as a carbon conductor shows
better electrochemical properties than that composed of acetylene black. Among the samples prepared under different reaction
conditions, Co3O4 prepared at 200°C for 10 h showed a better cycling performance than the other samples. It gave an initial discharge capacity
of 1,330 mAh/g, decreased to 779 mAh/g after 10 cycles, and then showed a steady discharge capacity of 606 mAh/g after 60
cycles. 相似文献
4.
《Carbon》2015
High energy light-ion (3.8 MeV He) bombardment is used to introduce lattice defects in a 3-dimensional (3D) interconnected network of graphene aerogels (GAs). When these materials are used as anodes for lithium ion batteries, we observe improved percentage reversible capacity and cycle stability compared to those without ion-beam treatment. Furthermore, all ion-beam treated 3D graphene samples exhibit substantially higher Coulombic efficiencies, suggesting at beneficial role of vacancy-type defects in stabilizing solid-electrolyte interphases. Although 3D graphene exhibits initial reversible capacities that are 2–3 times higher than that of graphite (∼372 mAh/g), fast capacity fading is observed but becomes more stable after ion-beam treatment. Our experimental results demonstrate that ion-beam treatment is an effective route to tune and produce good-performance graphene electrodes, and that vacancy-type defects help to promote reversible lithium storage capacity in graphene. We further observe that 3D GAs irradiated to the highest dose studied (1016 cm−2) fail rapidly upon electrochemical cycling, likely caused by the excessive ion-beam damage and graphene restacking. Raman I(D)/I(D′) signature is considered linked to defect type in graphene and thus is proposed, for the first time, as an indicator of the reversible capacity for GAs. 相似文献
5.
Anatase phase nanocrystalline TiO2 powders were prepared by hydrothermal method with the TTIP (titanium tetra isopropoxide) at 200 oC in a stirred autoclave
system. The effects of synthesis conditions on the physical properties of catalyst were investigated by using XRD, SEM, DLS,
DSC and BET. The TiO2 powders obtained from the optimum condition showed uniform spherical shape, crystalline structure, submicron size with a
sharp size distribution and few agglomerates. The optimum synthesis conditions were obtained within the covered experimental
ranges. The photocatalytic activity of TiO2 powders prepared by the hydrothermal method was tested for photooxidation of methyl orange. 相似文献
6.
7.
The spherical LiFePO4/C and LiFe0.9Mg0.1PO4/C powders were successfully prepared from spherical FePO4 via a simple uniform-phase precipitation method at normal pressure, using FeCl3 and H3PO4 as the reactants. The FePO4, LiFePO4/C, and LiFe0.9Mg0.1PO4/C powders were characterized by scanning electron microscopies (SEM), powder X-ray diffraction (XRD), X-ray photoelectron
spectrometer (XPS), and tap-density testing. The uniform spherical particles produced are amorphous, but they were crystallized
to FePO4 after calcining above 400 °C. Due to the homogeneity of the basic FePO4, the final products, LiFePO4/C and LiFe0.9Mg0.1PO4/C, are also significantly uniform and the particle size is of about 1 μm in diameter. The tap-density of the spherical LiFePO4/C and LiFe0.9Mg0.1PO4/C are 1.75 and 1.77 g cm−3, respectively, which are remarkably higher than the non-spherical LiFePO4 powders (the tap-density is 1.0–1.3 g cm−3). The excellent specific capacities of 148 and 157 mAh g−1 with a rate of 0.1 C are achieved for the LiFePO4/C and LiFe0.9Mg0.1PO4/C, respectively. Comparison of the cyclic voltammograms of LiFePO4/C and LiFe0.9Mg0.1PO4/C shows enhanced redox current and reversibility for the sample substituting Mg on the Fe site. LiFe0.9Mg0.1PO4/C exhibits better high-rate and cycle performances than the un-substituted LiFePO4/C. 相似文献
8.
Various vanadium oxide nanostructures are currently drawn interest for the potential applications of Li batteries, super capacitors,
and electrochromic display devices. In this article, the synthesis of V2O5 nanotubes by hydrothermal method using 1-hexadecylamine (HDA) and PEO as a template and surface reactant were reported, respectively.
The structural properties and electrochemical performances of these nanostructures were investigated for the application of
Li batteries. Structure and morphology of the samples were investigated by XRD, FTIR, SEM, and TEM analysis. The battery with
V2O5 nanotubes electrode showed initial specific capacity of 185 mAhg−1, whereas the PEO surfactant V2O5 nanotubes exhibited 142 mAhg−1. It was found that PEO surfactant V2O5 nanotubes material showed less specific capacity at initial stages but better stability was exhibited at higher cycle numbers
when compared to that of V2O5 nanotubes. The cyclic performance of the PEO surfactant material seems to be improved with the role of polymeric component
due to its surface reaction with V2O5 nanotubes during the hydrothermal process. 相似文献
9.
The electrochemical properties of fluoride-coated lithium cobalt oxide [LiCoO2] thin films were characterized. Aluminum fluoride [AlF3] and lanthanum fluoride [LaF3] coating layers were fabricated on a pristine LiCoO2 thin film by using a spin-coating process. The AlF3- and LaF3-coated films exhibited a higher rate capability, cyclic performance, and stability at high temperature than the pristine
film. This indicates that the AlF3 and LaF3 layers effectively protected the surface of the pristine LiCoO2 film from the reactive electrolyte. 相似文献
10.
N. Santhosh R. Govindaraj M. Senthil Pandian P. Ramasamy S. Mukhopadhyay 《Journal of Porous Materials》2016,23(6):1483-1487
Mesoporous TiO2 microspheres were successfully synthesized by a facile hydrothermal process and the obtained product was sintered at 450 °C. The sintered TiO2 powder was characterised by powder X-ray diffraction pattern and the result shows pure anatase phase with good crystalline nature. The morphological image of field emission scanning electron microscopy and high resolution transmission electron microscopy shows spherical shape and size of the particles is around 100 to 300 nm. The Brunauer–Emmett–Teller surface area of synthesized TiO2 material was 56.32 m2 g?1 and average pore width of synthesized materials was 7.1 and 9.3 nm. Bimodal pore structure of TiO2 microspheres has been very effective for electrolyte diffusion into photoanode in dye sensitized solar cells. The synthesized anatase TiO2 microsphere based dye sensitized solar cells have high surface area with light scattering effect to enhance the photocurrent and conversion efficiency than the commercial P25 photoanode material. The power conversion efficiency of synthesized mesoporous TiO2 microspheres and commercial P25 material is 4.2 and 2.7 % respectively. Therefore bimodal mesoporous anatase TiO2 microsphere appears to be a promising and potential candidate for dye sensitized solar cells (DSSC) application. 相似文献
11.
Amorphous La2O-TiO2 powders were synthesized by the polymerized complex (PC) method. The activation energies for crystallization and grain growth
of La2Ti2O7 from these precursors were determined from results of XRD and DTA and compared with those for La2Ti2O7 precursors by the conventional solid-state reaction (SSR). Activation energy of grain growth of La2Ti2O7 in PC-sample was determined to be 7.1 kJ/mol while that of SSR sample was 14.8 kJ/mol. The energy required for the phase
transformation from amorphous PC sample to layered perovskite was 432 kJ/mol, while the SSR sample did not show this transition
below 900‡C. It was clearly demonstrated that the La2Ti2O7 crystals were formed at a lower temperature and they grew in size faster in the sample prepared by the PC method relative
to the sample prepared by the SSR method. Mixing of elements in molecular level in PC preparation appeared responsible for
these differences. 相似文献
12.
Shengyao Chen Changhuan Mi Linghao Su Bo Gao Qingbin Fu Xiaogang Zhang 《Journal of Applied Electrochemistry》2009,39(10):1943-1948
LiMn2O4/multi-walled carbon nanotubes (MWNTs) composite was synthesized by mechanical activation reaction followed by a heat-treatment
(500 °C). The LiMn2O4 and LiMn2O4/MWNTs as cathodes were investigated in 1 M Li2SO4 by cyclic voltammetry (CV), galvanostatic charge/discharge (GC), and electrochemical impedance spectroscopy (EIS). The LiMn2O4/MWNTs cathode delivered higher discharge capacity (117 mAh g−1) than LiMn2O4 (84.6 mAh g−1). Furthermore, the results from EIS showed that LiMn2O4/MWNTs had a faster kinetic process for lithium ion intercalation/de-intercalation than LiMn2O4. Besides, LiMn2O4/MWNTs had better cycling stability and rate capability than LiMn2O4, which was confirmed by GC testing. SEM images showed that a three-dimensional network structure was formed during the mechanical
activation, giving a decrease of particle size. 相似文献
13.
Feng Wu Huaquan Lu Yuefeng Su Ning Li Liying Bao Shi Chen 《Journal of Applied Electrochemistry》2010,40(4):783-789
The Li-rich layered cathode material, Li[Ni0.2Li0.2Mn0.6]O2, was synthesized via a “mixed oxalate” method, and its structural and electrochemical properties were compared with the same
material synthesized by the sol–gel method. X-ray diffraction (XRD) shows that the synthesized powders have a layered O3–LiCoO2-type structure with the R-3m symmetry. X-ray photoelectron spectroscopy (XPS) indicates that in the above material, Ni and Mn exist in the oxidation states
of +2 and +4, respectively. The layered material exhibits an excellent electrochemical performance. Its discharge capacity
increases gradually from the initial value of 228 mA hg−1 to a stable capacity of over 260 mA hg−1 after the 10th cycle. It delivers a larger capacity of 258 mA hg−1 at the 30th cycle. The dQ/dV curves suggest that the increasing capacity results from the redox-reaction of Mn4+/Mn3+. 相似文献
14.
A lithium insertion material having the composition LiNi0.3Co0.3Mn0.3Fe0.1O2 was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO2 structure type (R3m; a=2.8689(5) Å and 14.296(5) Å in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi0.3Co0.3Mn0.3Fe0.1O2 when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi0.3Co0.3Mn0.3Fe0.1O2 in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity. 相似文献
15.
《Ceramics International》2017,43(2):2320-2324
Li-rich Mn-based cathode materials (Li1.2Ni0.2Mn0.6O2) have been synthesized by a polyvinyl alcohol (PVA)-assisted sol-gel method. The influence of PVA content on the structure and electrochemical performance of Li1.2Ni0.2Mn0.6O2 has been investigated respectively. XRD results of the Li1.2Ni0.2Mn0.6O2 powders show that they exhibit similar XRD patterns as those of Li-rich Mn-based cathode materials, and the crystalline nature of the layered compound are improved by the presence of PVA. Physical characterizations indicate that the as-synthesized oxide is composed of uniform and separated particles compared to the larged aggregated ones of the product synthesized under the same condition but without PVA. As cathode for lithium ion battery, the material synthesized with 10% PVA exhibits not only a relatively high discharge capacity of 254.2 mA h g−1, but also excellent rate performance and good cycling performance. EIS results show that the material synthesized with PVA decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance. 相似文献
16.
Dong Young Kim Sujung Kim Min-Kyeong Yeo In-Gyung Jung Misook Kang 《Korean Journal of Chemical Engineering》2009,26(1):261-264
Nanometer-sized bismuth tungsten oxides, Bi2WO6s, were successfully synthesized by hydrothermal treatment at 200 °C for 24 hr, and their morphologies and crystallite sizes
were influenced by adjusting the conditions to pH 4, 7, and 9. TEM images revealed that the particles were sheet-shaped and
the crystallite sizes ranged from 7–120 nm. The samples absorbed in the visible range at about 380–400 nm. The lowest conductivity,
1.0×106 ohm/square, was observed for Bi2WO6 prepared at pH 4 with a 150 nm film thickness. As the annealing temperature for Bi2WO6 prepared at pH 7 was increased, the conductivity decreased due of formation of larger particles by coagulation and sintering
at high temperatures. Conductivity appears to improve with increasing film thickness up to 1,500 nm. 相似文献
17.
Zhongdong Peng Kunchang Mu Yanbing Cao Lian Xu Ke Du Guorong Hu 《Ceramics International》2019,45(4):4184-4192
Lithium-rich layer oxides can possess satisfactory specific capacity but suffer from severe voltage attenuation and poor cycle stability. In this work, Al-B dual-doping technique is introduced to modify Li-rich layered oxide cathode materials. Cross-section scanning electron microscopy, Energy Disperse Spectroscopy and X-ray photoelectron spectroscopy results confirm that Al and B successfully doped into the interior of the bulk Li1.2Ni0.2MnO2 particles, and the High-resolution transmission electron microscopy and X-ray diffraction Rietveld refinement results reveal that the c-axis distance of LMR-AB increases. The Al-B co-doped sample shows greatly enhanced electrochemical performance. Specifically, it exhibits of a discharge capacity of 120?mAh?g?1 at 5?C and a capacity retention of 89.12% after 100 cycles at 1?C. The voltage decay is also greatly alleviated. The enhanced electrochemical performance of LMR-AB is due to the synergistic effects bought by the Al-B dual-doping, where increase of c-axis distance decreases Li+ intercalation/deintercalation barrier. B3+ doping into the tetrahedral site block the migration of TM ions and Al3+ act as pillars in the octahedral site, stabilizing the structure and suppressing the phase transition during cycling. 相似文献
18.
《Ceramics International》2017,43(17):15173-15178
LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode has been modified by incorporating ZrO2 nanoparticles to improve its electrochemical performance. Compared to the pristine electrode, the cycling stability and rate capability of 0.5 wt% ZrO2 modified-NCM622 have been improved significantly. The 0.5 wt% ZrO2 modified-NCM622 cathode shows a capacity retention of 83.8% after 100 cycles at 0.1 C between 2.8 and 4.3 V, while that of the pristine NCM622 electrode is only 75.6%. When the current rate is set as 5C, the capacity retention of the 0.5 wt% ZrO2-modified NCM622 is 10% higher than that of the pristine NCM622. Also, the rate capability of 0.5 wt% ZrO2-modified NCM622 is better than that of the pristine NCM622 at various C-rates in a voltage range of 2.8–4.3 V. The enhanced electrochemical performances of the ZrO2-modified NCM622 cathodes can be attributed to their high Li-ion conductivity and structural stability. 相似文献
19.
Core-shell nanostructures of Mn2O3@SiO2, Mn2O3@amino-functionalized silica, Mn2O3@vinyl-functionalized silica, and Mn2O3@allyl-functionalized silica were synthesized using the hydrolysis of the respective organosilane precursor over Mn2O3 nanoparticles dispersed using colloidal solutions of Tergitol and cyclohexane. The synthetic methodology used is an improvement
over the commonly used post-grafting or co-condensation method as it ensures a high density of functional groups over the
core-shell nanostructures. The high density of functional groups can be useful in immobilization of biomolecules and drugs
and thus can be used in targeted drug delivery. The high density of functional groups can be used for extraction of elements
present in trace amounts. These functionalized core-shell nanostructures were characterized using TEM, IR, and zeta potential
studies. The zeta potential study shows that the hydrolysis of organosilane to form the shell results in more number of functional
groups on it as compared to the shell formed using post-grafting method. The amino-functionalized core-shell nanostructures
were used for the immobilization of glucose and L -methionine and were characterized by zeta potential studies. 相似文献
20.
Pyonghun Kim Hongwei Xie Yuchun Zhai Xiangyu Zou Xiaochuan Lang 《Journal of Applied Electrochemistry》2012,42(4):257-262
The electrochemical reduction of Dy2O3 in CaCl2 melt was studied. The cyclic voltammetry, chronoamperometry, AC impedance and constant voltage electrolysis were employed.
A single cathodic current peak in the cyclic voltammogram and one response semicircle in the AC impedance spectrum were observed,
supporting a one-step electrochemical reduction mechanism of Dy2O3. No intermediates were observed by XRD, which confirmed the following electrochemical reduction sequence: Dy2O3 → Dy. The charge transfer resistances and the activation energies involved in the electrochemical reduction step of Dy2O3 were obtained by simulating the AC impedance spectra with equivalent circuits. The electrochemical reduction reaction of
Dy2O3 is controlled by the charge transfer process at a low voltage range and by the diffusion process at a high voltage range. 相似文献