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1.
Current paper comprises the electrodeposition of nanostructured porous Co1−xNix layered double hydroxide (Co1−xNix LDHs) thin films on to stainless steel substrate by a potentiodynamic mode. The compositional impacts on the various properties of Co1−xNix LDHs are examined via structural, morphological, surface wettability and electrochemical studies. The nanocrystalline Co1−xNix LDHs thin films possess varying porous, nanoflake like morphology and superhydrophilic behavior by the composition influence. Electrochemical studies demonstrate the supercapacitive performance of Co1−xNix LDHs thin film electrodes. The maximal specific capacitance for Co1−xNix LDHs electrode is found to be ∼1213 F g−1 for composition Co0.66Ni0.34 LDH in 2 M KOH electrolyte at 5 mV s−1 scan rate owing specific energy of 104 Whkg−1, specific power of 1.44 kW kg−1 with ∼94% of coulomb efficiency and stability of electrode retained to 77% after 10,000th cycle. The high capacitance retention proposes the deposited Co1−xNix LDHs thin film as promising contender for supercapacitor applications.  相似文献   

2.
A network of CoxNiyAlz layered triple hydroxides (LTHs) nanosheets was prepared by the potentiostatic deposition process at −1.0 V (vs. Ag/AgCl) onto stainless steel electrodes. X-ray diffraction patterns show that the CoxNiyAlzLTHs belong to the hexagonal system with layered structure. Cyclic voltammetry and charge discharge measurements in the potential range of −0.1 to 0.5 V and 0.0–0.4 V, respectively, vs. Ag/AgCl in 1 M KOH electrolyte indicate that CoxNiyAlzLTHs have excellent supercapacitive characteristics. The maximum specific capacitance of ∼1263 F g−1 was obtained for Co0.59Ni0.21Al0.20LTH. The impedance studies indicated highly conducting nature of the CoxNiyAlzLTHs.  相似文献   

3.
LiNi0.6CoxMn0.4−xO2 (x = 0.05, 0.10, 0.15, 0.2) cathode materials are prepared, and their structural and electrochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetric (DSC) and charge–discharge test. The results show that well-ordering layered LiNi0.6CoxMn0.4−xO2 (x = 0.05, 0.10, 0.15, 0.2) cathode materials are successfully prepared in air at 850 °C. The increase of the Co content in LiNi0.6Mn0.4−xCoxO2 leads to the acceleration of the grain growth, the increase of the initial discharge capacity and the deterioration of the cycling performance of LiNi0.6Mn0.4−xCoxO2. It also leads to the enhancement of the ratio Ni3+/Ni2+ in LiNi0.6CoxMn0.4−xO2, which is approved by the XPS analysis, resulting in the increase of the phase transition during cycling. This is speculated to be main reason for the deteriotion of the cycling performance. All synthesized LiNi0.6CoxMn0.4−xO2 samples charged at 4.3 V show exothermic peaks with an onset temperature of larger than 255 °C, and give out less than 400 J g−1 of total heat flow associated with the peaks in DSC analysis profile, exhibiting better thermal stability. LiNi0.6Co0.05Mn0.35O2 with low Co content and good thermal stability presents a capacity of 156.6 mAh g−1 and 98.5% of initial capacity retention after 50 cycles, showing to be a promising cathode materials for Li-ion batteries.  相似文献   

4.
A new type of Li1−xFe0.8Ni0.2O2–LixMnO2 (Mn/(Fe + Ni + Mn) = 0.8) material was synthesized at 350 °C in air atmosphere using a solid-state reaction. The material had an XRD pattern that closely resembled that of the original Li1−xFeO2–LixMnO2 (Mn/(Fe + Mn) = 0.8) with much reduced impurity peaks. The Li/Li1−xFe0.8Ni0.2O2–LixMnO2 cell showed a high initial discharge capacity above 192 mAh g−1, which was higher than that of the parent Li/Li1−xFeO2–LixMnO2 (186 mAh g−1). We expected that the increase of initial discharge capacity and the change of shape of discharge curve for the Li/Li1−xFe0.8Ni0.2O2–LixMnO2 cell is the result from the redox reaction from Ni2+ to Ni3+ during charge/discharge process. This cell exhibited not only a typical voltage plateau in the 2.8 V region, but also an excellent cycle retention rate (96%) up to 45 cycles.  相似文献   

5.
We investigated the effect of CO2 on layered Li1+zNi1−xyCoxMyO2 (M = Al, Mn) cathode materials for lithium ion batteries which were prepared by solid-state reactions. Li1+zNi(1−x)/2CoxMn(1−x)/2O2 (Ni/Mn mole ratio = 1) singularly exhibited high storage stability. On the other hand, Li1+zNi0.80Co0.15Al0.05O2 samples were very unstable due to CO2 absorption. XPS and XRD measurements showed the reduction of Ni3+ to Ni2+ and the formation of Li2CO3 for Li1+zNi0.80Co0.15Al0.05O2 samples after CO2 exposure. SEM images also indicated that the surfaces of CO2-treated samples were covered with passivation films, which may contain Li2CO3. The relationship between CO2-exposure time and CO32− content suggests that there are two steps in the carbonation reactions; the first step occurs with the excess Li components, Li2O for example, and the second with LiNi0.80Co0.15Al0.05O2 itself. It is well consistent with the fact that the discharge capacity was not decreased and the capacity retention was improved until the excess lithium is consumed and then fast deterioration occurred.  相似文献   

6.
A series of cathode materials with molecular notation of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li1/3Mn2/3]O2·0.4Li[Ni1/3Mn1/3Co1/3]O2 (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g−1 between 2.0 and 4.8 V at 18 mA g−1.  相似文献   

7.
In this work structural and transport properties of layered Li1+x(Mn1/3Co1/3Ni1/3)1−xO2 oxides (x = 0; 0.03; 0.06) prepared by a “soft chemistry” method are presented. The excessive lithium was found to significantly improve transport properties of the materials, a corresponding linear decrease of the unit cell parameters was observed. The electrical conductivity of Li1.03(Mn1/3Co1/3Ni1/3)0.97O2 composition was high enough to use this material in a form of a pellet, without any additives, in lithium batteries and characterize structural and transport properties of deintercalated Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 compounds. For deintercalated samples a linear increase of the lattice parameter c together with a linear decrease of the parameter a with the increasing deintercalation degree occurred, but only up to 0.4-0.5 mol of extracted lithium. Further deintercalation showed a reversal of the trend. Electrical conductivity measurements performed of Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 samples (y = 0.1; 0.3; 0.5; 0.6) showed an ongoing improvement, almost two orders of magnitude, in relation to the starting composition. Additionally, OCV measurements, discharge characteristics and lithium diffusion coefficient measurements were performed for Li/Li+/Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 cells.  相似文献   

8.
Li1+x(Ni1/3Mn1/3Co1/3)1−xO2 layered materials were synthesized by the co-precipitation method with different Li/M molar ratios (M = Ni + Mn + Co). Elemental titration evaluated by inductively coupled plasma spectrometry (ICP), structural properties studied by X-ray diffraction (XRD), Rietveld analysis of XRD data, scanning electron microscopy (SEM) and magnetic measurements carried out by superconducting quantum interference devices (SQUID) showed the well-defined α-NaFeO2 structure with cationic distribution close to the nominal formula. The Li/Ni cation mixing on the 3b Wyckoff site of the interlayer space was consistent with the structural model [Li1−yNiy]3b[Lix+yNi(1−x)/3−yMn(1−x)/3Co(1−x)/3]3aO2 (x = 0.02, 0.04) and was very small. Both Rietveld refinements and magnetic measurements revealed a concentration of Ni2+-3b ions lower than 2%; moreover, for the optimized sample synthesized at Li/M = 1.10, only 1.43% of nickel ions were located into the Li sublattice. Electrochemical properties were investigated by galvanostatic charge-discharge cycling. Data obtained with Li1+x(Ni1/3Mn1/3Co1/3)1−xO2 reflected the high degree of sample optimization. An initial discharge capacity of 150 mAh g−1 was delivered at 1 C-rate in the cut-off voltage of 3.0-4.3 V. More than 95% of its initial capacity was retained after 30 cycles at 1 C-rate. Finally, it is demonstrated that a cation mixing below 2% is considered as the threshold for which the electrochemical performance does not change for Li1+x(Ni1/3Mn1/3Co1/3)1−xO2.  相似文献   

9.
A kind of cathode material of Pr1−xSrx FeO3 (x = 0–0.5) for intermediate temperature solid oxide fuel cells (IT-SOFCs) was prepared by the coprecipitation method. Crystal structure, thermal expansion, electrical conductivity and electrochemical performance of the Pr1−xSrxFeO3 perovskite oxide cathodes were studied by different methods. The results revealed that Prl−xSrxFeO3 exhibited similar orthorhombic structure from x = 0.1 to 0.3 and took cubic structure when x = 0.4–0.5. The unit cell volume decreased and the thermal expansion coefficient (TEC) of the materials increased as the strontium content increased. When 0 < x ≤ 0.3, the samples exhibited good thermal expansion compatibility with YSZ electrolyte. The electrical conductivity increased with the increasing of doped strontium content. When x = 0.3–0.5, the electrical conductivities were higher than 100 S cm−1. The conductivity of Pr0.8Sr0.2FeO3 was 78 S cm−1 at 800 °C. Compared with the La0.8Sr0.2MnO3 cathode, Pr0.8Sr0.2FeO3 showed higher polarization current density and lower polarization resistance (0.2038 Ω cm2). The value of I0 for Pr0.8Sr0.2FeO3 at 800 °C is 123.6 mA cm−2. It is higher than that of La0.8Sr0.2MnO3. Therefore, Pr1−xSrxFeO3 can be considered as a candidate cathode material for IT-SOFCs.  相似文献   

10.
In this work structural and transport properties of layered LiNi1−yzCoyMnzO2 (y = 0.25, 0.35, 0.5 and z = 0.1) cathode materials are presented. In the considered group of oxides, LiNi1−yzCoyMnzO2, there is no clear correlation between electrical conductivity and the a parameter (M-M distance in the octahedra layers). A non-monotonic modification of electrical properties of LixNi0.65Co0.25Mn0.1O2 cathode materials is observed upon lithium deintercalation.  相似文献   

11.
Cathode materials prepared by a co-precipitation are 0.3Li2MnO3·0.7LiMn1−xNiyCo0.1O2 (0.2 ≤ x ≤ 0.4) cathode materials with a layered-spinel structure. In the voltage range of 2.0-4.6 V, the cathodes show more than one redox reaction peak during its cyclic voltammogram. The Li/0.3Li2MnO3·0.7LiMn1−xNiyCo0.1O2 (x = 0.3, y = 0.2) cell shows the initial discharge capacity of about 200 mAh g−1. However, when x = 0.2 and y = 0.1, the cell exhibits a rapid decrease in discharge capacity and poor cycle life.  相似文献   

12.
A simple method has been employed to prepare pillared layered Li1−2xCaxCoO2 cathode materials by cationic exchange under hydrothermal conditions. The synthesized materials were characterized by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), field emission scanning electron microscope (FE-SEM) and galvanostatic charge–discharge cycling. The XRD data of the products show that they are single phases and retain the layered α-NaFeO2 type structure. The FE-SEM images of the materials prepared by hydrothermal method show uniform small particles, and the particle size of the materials is about 200 nm. The initial discharge specific capacities of layered LiCoO2 and pillared layered Li0.946Ca0.027CoO2 cathode materials calcined at 800 °C for 5 h within the potential range of 3.0–4.3 V (vs. Li+/Li) are 144.6 and 142.3 mAh g−1, respectively, and both materials retain good charge–discharge cycling performance. However, with increasing upper cutoff voltage, the pillar effect of Ca2+ in Li1−2xCaxCoO2 becomes more significant. The pillared layered Li0.946Ca0.027CoO2 has a higher capacity with an initial discharge specific capacity of 177.9 and 215.8 mAh g−1 within the potential range of 3.0–4.5 and 4.7 V (vs. Li+/Li), respectively, and retains good charge–discharge cycling performance.  相似文献   

13.
ZrCo1−xNix (x = 0, 0.1, 0.2 and 0.3) alloys were prepared and their hydrogen storage behavior were studied. ZrCo1−xNix alloys of compositions with x = 0, 0.1, 0.2 and 0.3 prepared by arc-melting method and characterized by X-ray diffraction analysis. XRD analysis showed that the alloys of composition with x = 0, 0.1, 0.2 and 0.3 forms cubic phase similar to ZrCo with traces of ZrCo2 phase. A trace amount of an additional phase similar to ZrNi was found for the alloy with composition x = 0.3. Hydrogen desorption pressure–composition–temperature (PCT) measurements were carried out using Sievert's type volumetric apparatus and the hydrogen desorption pressure–composition isotherms (PCIs) were generated for all the alloys in the temperature range of 523–603 K. A single sloping plateau was observed for each isotherm and the plateau pressure was found to increase with increasing Ni content in ZrCo1−xNix alloys at the same experimental temperature. A van't Hoff plot was constructed using plateau pressure data of each pressure–composition isotherm and the thermodynamic parameters were calculated for desorption of hydrogen in the ZrCo1−xNix–H2 systems. The enthalpy and entropy change for desorption of hydrogen were calculated. In addition, the hydrogen absorption–desorption cyclic life studies were performed on ZrCo1−xNix alloys at 583 K up to 50 cycles. It was observed that with increasing Ni content the durability against disproportionation of alloys increases.  相似文献   

14.
Prospective positive-electrode (cathode) materials for a lithium secondary battery, viz., Li[Li0.2Ni0.2−x/2Mn0.6−x/2Crx]O2 (x = 0, 0.02, 0.04, 0.06, 0.08), were synthesized using a solid-state pyrolysis method. The structural and electrochemical properties were examined by means of X-ray diffraction, cyclic voltammetry, SEM and charge–discharge tests. The results demonstrated that the powders maintain the α-NaFeO2-type layered structure regardless of the chromium content in the range x ≤ 0.08. The Cr doping of x = 0.04 showed improved capacity and rate capability comparing to undoped Li[Li0.2Ni0.2Mn0.6]O2. ac impedance measurement showed that Cr-doped electrode has the lower impedance value during cycling. It is considered that the higher capacity and superior rate capability of Cr-doping samples would be ascribed to the reduced resistance of the electrode during cycling.  相似文献   

15.
A (Ni1/3Co1/3Mn1/3)CO3 precursor with an uniform, spherical morphology was prepared by coprecipitation using a continuously stirred tank reactor method. The as-prepared spherical (Ni1/3Co1/3Mn1/3)CO3 precursor served to produce dense, spherical Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 (0 ≤ x ≤ 0.15) cathode materials. These Li-rich cathodes were also prepared by a second synthesis route that involved the use of an M3O4 (M = Ni1/3Co1/3Mn1/3) spinel compound, itself obtained from the carbonate (Ni1/3Co1/3Mn1/3)CO3 precursor. In both cases, the final Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 products were highly uniform, having a narrow particle size distribution (10-μm average particle size) as a result of the homogeneity and spherical morphology of the starting mixed-metal carbonate precursor. The rate capability of the Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 electrode materials, which was significantly improved with increased lithium content, was found to be better in the case of the denser materials made from the spinel precursor compound. This result suggests that spherical morphology, high density, and increased lithium content were key factors in enabling the high rate capabilities, and hence the power performances, of the Li-rich Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 cathodes.  相似文献   

16.
Sub-micro spinel LiNi0.5−xMn1.5+xO4 (x < 0.1) cathode materials powder was successfully synthesized by the ultrasonic-assisted co-precipitation (UACP) method. The structure and electrochemical performance of this as-prepared powder were characterized by powder XRD, SEM, XPS, CV and the galvanostatic charge–discharge test in detail. XRD shows that there is a small LiyNi1−yO impurity peak placed close to the (4 0 0) line of the spinel LiNi0.5−xMn1.5+xO4, and the powders are well crystallized. XPS exhibits that the Mn oxidation state is between +3 and +4, and Ni oxidation state is +2 in LiNi0.5−xMn1.5+xO4. SEM shows that the prepared powders (UACP) have the uniform and narrow size distribution which is less than 200 nm. Galvanostatic charge–discharge test indicates that the initial discharge capacities for the LiNi0.5−xMn1.5+xO4 (UACP) at C/3, 1C and 2C, are 130.2, 119.0 and 110.0 mAh g−1, respectively. After 100 cycles, their capacity retentions are 99.8%, 88.2%, and 73.5%, respectively. LiNi0.5−xMn1.5+xO4 (UACP) at C/3 discharge rate exhibits superior capacity retention upon cycling, and it also shows well high current discharge performance. CV curve implies that LiNi0.5−xMn1.5+xO4 (x < 0.1) spinel synthesized by ultrasonic-assisted co-precipitation method has both reversibility and cycle capability because of the ultrasonic-catalysis.  相似文献   

17.
Several substituted titanates of formula Li4−xMgxTi5−xVxO12 (0 ≤ x ≤ 1) were synthesized (and investigated) as anode materials in rechargeable lithium batteries. Five samples labeled as S1–S5 were calcined (fired) at 900 °C for 10 h in air, and slowly cooled to room temperature in a tube furnace. The structural properties of the synthesized products have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transmission infrared (FTIR). XRD explained that the crystal structures of all samples were monoclinic while S1 and S3 were hexagonal. The morphology of the crystal of S1 was spherical while the other samples were prismatic in shape. SEM investigations explained that S4 had larger grain size diameter of 15–16 μm in comparison with the other samples. S4 sample had the highest conductivity 2.452 × 10−4 S cm−1. At a voltage plateau located at about 1.55 V (vs. Li +), S4 cell exhibited an initial specific discharge capacity of 198 mAh g−1. The results of cyclic voltammetry for Li4−xMgxTi5−xVxO12 showed that the electrochemical reaction was based on Ti4+/Ti3+ redox couple at potential range from 1.5 to 1.7 V. There is a pair of reversible redox peaks corresponding to the process of Li+ intercalation and de-intercalation in the Li–Ti–O oxides.  相似文献   

18.
Lithium non-stoichiometric Li[Lix(Ni1/3Co1/3Mn1/3)1−x]O2 materials (0 ≤ x ≤ 0.17) were synthesized using a spray drying method. The electrochemical properties and structural stabilities of the synthesized materials were investigated. The synthesized materials exhibited a hexagonal structure in all the x-value and the lattice parameters of the materials were gradually decreased with increasing x-value due to an increasing amount of Ni3+ ions for charge compensation. The capacity retention ability and rate capability of the stoichiometric Li(Ni1/3Co1/3Mn1/3)O2 material were improved by increasing x-value, the so-called overlithiation. We found that the overlithiated materials could keep more structural integrity than the stoichiometric one during electrochemical cyclings, which could be one of reasons for a better electrochemical properties of the overlithiated materials.  相似文献   

19.
Direct borohydride fuel cells (DBFCs), with a series of perovskite-type oxides La1−xSrxCoO3 (x = 0.1-0.5) as the cathode catalysts and a hydrogen storage alloy as the anode catalyst, are studied in this paper. The structures of the perovskite-type catalysts are mainly La1−xSrxCoO3 (x = 0.1-0.5) oxides phases. However, with the increase of strontium content, the intensities of the X-ray diffraction peaks of the impure phases La2Sr2O5 and SrLaCoO4 are gradually enhanced. Without using any precious metals or expensive ion exchange membranes, a maximum current density of 275 mA cm−2 and a power density of 109 mW cm−2 are obtained with the Sr content of x = 0.2 at 60 °C for this novel type of fuel cell.  相似文献   

20.
The present work focused on the investigation of the hydrogen generation through the ethanol steam reforming over the core–shell structured NixOy–, FexOy–, and CoxOy–Pd loaded Zeolite Y catalysts. The transmission electron microscopy (TEM) image of NixOy–Pd represented a very clear core–shell structure, but the other two catalysts, CoxOy– and FexOy–Pd, were irregular and non-uniform. The catalytic performances differed according to the added core metal and the support. The core–shell structured CoxOy–Pd/Zeolite Y provided a significantly higher reforming reactivity compared to the other catalysts. The H2 production was maximized to 98% over CoxOy–Pd(50.0 wt%)/Zeolite Y at the conditions of reaction temperature 600 °C, CH3CH2OH:H2O = 1:3, and GHSV (gas hourly space velocity) 8400 h−1. In the mechanism that was suggested in this work, the cobalt component played an important role in the partial oxidation and the CO activation for acetaldehyde and CO2 respectively, and eventually, cobalt increased the hydrogen yield and suppressed the CO generation.  相似文献   

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