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1.
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   

2.
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   

3.
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   

4.
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   

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.
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   

7.
Amorphous LiCo1/3Mn1/3Ni1/3O2 thin films were deposited on the NASICON-type Li-ion conducting glass ceramics, Li1+x+yAlxTi2−xSiyP3−yO12 (LATSP), by radio frequency (RF) magnetron sputtering below 130 °C. The amorphous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Li/PEO18-Li(CF3SO2)2N/LATSP/LiCo1/3Mn1/3Ni1/3O2/Au all-solid-state cells were fabricated to investigate the electrochemical performance of the amorphous films. It was found that the low-temperature deposited amorphous cathode film shows a high discharge voltage and a high discharge capacity of around 130 mAh g−1.  相似文献   

8.
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   

9.
The spherical Li[Ni1/3Co1/3Mn1/3]O2 powders with appropriate porosity, small particle size and good particle size distribution were successfully prepared by a slurry spray drying method. The Li[Ni1/3Co1/3Mn1/3]O2 powders were characterized by XRD, SEM, ICP, BET, EIS and galvanostatic charge/discharge testing. The material calcined at 950 °C had the best electrochemical performance. Its initial discharge capacity was 188.9 mAh g−1 at the discharge rate of 0.2 C (32 mA g−1), and retained 91.4% of the capacity on going from 0.2 to 4 C rate. From the EIS result, it was found that the favorable electrochemical performance of the Li[Ni1/3Co1/3Mn1/3]O2 cathode material was primarily attributed to the particular morphology formed by the spray drying process which was favorable for the charge transfer during the deintercalation and intercalation cycling.  相似文献   

10.
Layer-structured Zr doped Li[Ni1/3Co1/3Mn1−x/3Zrx/3]O2 (0 ≤ x ≤ 0.05) were synthesized via slurry spray drying method. The powders were characterized by XRD, SEM and galvanostatic charge/discharge tests. The products remained single-phase within the range of 0 ≤ x ≤ 0.03. The charge and discharge cycling of the cells showed that Zr doping enhanced cycle life compared to the bare one, while did not cause the reduction of the discharge capacity of Li[Ni1/3Co1/3Mn1/3]O2. The unchanged peak shape in the differential capacity versus voltage curve suggested that the Zr had the effect to stabilize the structure during cycling. More interestingly, the rate capability was greatly improved. The sample with x = 0.01 presented a capacity of 160.2 mAh g−1 at current density of 640 mA g−1(4 C), corresponding to 92.4% of its capacity at 32 mA g−1(0.2 C). The favorable performance of the doped sample could be attributed to its increased lattice parameter.  相似文献   

11.
A modified Zr-coating process was introduced to improve the electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O2. The ZrO2-coating was carried out on an intermediate, (Ni1/3Co1/3Mn1/3)(OH)2, rather than on Li(Ni1/3Co1/3Mn1/3)O2. After a heat treatment process, one part of the Zr covered the surface of Li(Ni1/3Co1/3Mn1/3)O2 in the form of a Li2ZrO3 coating layer, and the other part diffused into the crystal lattice of Li(Ni1/3Co1/3Mn1/3)O2. A decreasing gradient distribution in the concentration of Zr was detected from the surface to the bulk of Li(Ni1/3Co1/3Mn1/3)O2 by X-ray photoelectron spectra (XPS). Electrochemical tests indicated that the 1% (Zr/Ni + Co + Mn) ZrO2-modified Li(Ni1/3Co1/3Mn1/3)O2 prepared by this process showed better cyclability and rate capability than bare Li(Ni1/3Co1/3Mn1/3)O2. The result can be ascribed to the special effect of Zr in ZrO2-modified Li(Ni1/3Co1/3Mn1/3)O2. The surface coating layer of Li2ZrO3 improved the cycle performance, while the incorporation of Zr in the crystal lattice of Li(Ni1/3Co1/3Mn1/3)O2 modified the rate capability by increasing the lattice parameters. Electrochemical impedance spectra (EIS) results showed that the increase of charge transfer resistance during cycling was suppressed significantly by ZrO2 modification.  相似文献   

12.
Structural changes and their relationship with thermal stability of charged Li0.33Ni1/3Co1/3Mn1/3O2 cathode samples have been studied using time-resolved X-ray diffraction (TR-XRD) in a wide temperature from 25 to 600 °C with and without the presence of electrolyte in comparison with Li0.27Ni0.8Co0.15Al0.05O2 cathodes. Unique phase transition behavior during heating is found for the Li0.33Ni1/3Co1/3Mn1/3O2 cathode samples: when no electrolyte is present, the initial layered structure changes first to a LiM2O4-type spinel, and then to a M3O4-type spinel and remains in this structure up to 600 °C. For the Li0.33Ni1/3Co1/3Mn1/3O2 cathode sample with electrolyte, additional phase transition from the M3O4-type spinel to the MO-type rock salt phase takes place from about 400 to 441 °C together with the formation of metallic phase at about 460 °C. The major difference between this type of phase transitions and that for Li0.27Ni0.8Co0.15Al0.05O2 in the presence of electrolyte is the delayed phase transition from the spinel-type to the rock salt-type phase by stretching the temperature range of spinel phases from about 20 to 140 °C. This unique behavior is considered as the key factor of the better thermal stability of the Li1−xNi1/3Co1/3Mn1/3O2 cathode materials.  相似文献   

13.
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   

14.
Structural, electrical and electrochemical properties of Mn-substituted phospho-olivines LiFe1−yMnyPO4 were investigated and compared to those of LiFePO4. Rietvield refined XRD patterns taken in the course of delithiation process showed apparent difference between phase compositions of these cathode materials upon lithium extraction. Contrary to the LiFePO4 and LiMnPO4 compositions for which a two-phase mechanism of electrochemical lithium extraction/insertion is observed, in case of Mn-substituted LiFe1−yMnyPO4 samples a single-phase mechanism of deintercalation was observed in the studied range of lithium concentration. Electrochemical characterization of the cathode materials were performed in Li/Li+/LixFe1−yMnyPO4-type cells for y = 0.0, 0.25, 0.55, 0.75 and 1.0 compositions. Voltammery studies showed low reversibility of the lithium extraction process in the high-voltage “manganese” range, while in the “iron” range the reversibility of lithium extraction is high. Impedance measurements of the LiFe1−yMnyPO4 cathode materials, which enabled separation of the ionic and electronic components of their entire electrical conductivity, showed distinct influence of Mn content on the electronic part of conductivity. EIS measurements performed at different states of cell charge revealed that the charge-transfer impedance in LixFe1−yMnyPO4 is much lower than that of LixFePO4.  相似文献   

15.
Cobalt–nickel layered double hydroxides (CoxNi1−x LDHs) were deposited onto stainless steel electrodes by the potentiostatic deposition method at −1.0 V vs. Ag/AgCl using various molar ratios of Co(NO3)2 and Ni(NO3)2 in distilled water. Their structure and surface morphology were studied by using X-ray diffraction analysis, energy dispersive X-ray spectroscopy and scanning electron microscopy. A network of CoxNi1−x LDH nanosheets was obtained. The nature of the cyclic voltammetry and charge–discharge curves suggested that the CoxNi1−x LDHs exist in the form of solid solutions. The capacitive characteristics of the CoxNi1−x LDHs in 1 M KOH electrolyte showed that Co0.72Ni0.28 LDHs had the highest specific capacitance value, 2104 F g−1, which is also the highest yet reported value for oxide materials in general.  相似文献   

16.
Combustion synthesized Li(Ni1/3Mn1/3Co1/3)O2 particles are coated with thin, conformal layers of Al2O3 by atomic layer deposition (ALD). XRD, Raman, and FTIR are used to confirm that no change to the bulk, local structure occurs after coating. Electrochemical impedance spectroscopy (EIS) results indicate that the surface of the Li(Ni1/3Mn1/3Co1/3)O2 are protected from dissolution and HF attack after only 4-layers, or ∼8.8 Å of alumina. Electrochemical performance at an upper cutoff of 4.5 V is greatly enhanced after the growth of Al2O3 surface film. Capacity retention is increased from 65% to 91% after 100 cycles at a rate of C/2 with the addition of only two atomic layers. Due to the conformal coating, the effects on Li(Ni1/3Mn1/3Co1/3)O2 overpotential and capacity are negligible below six ALD-layers. We propose that the use of ALD for coating on Li(Ni1/3Mn1/3Co1/3)O2 particles makes the material a stronger replacement candidate for LiCoO2 as a positive electrode in lithium ion batteries.  相似文献   

17.
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   

18.
The structural changes of the composite cathode made by mixing spinel LiMn2O4 and layered LiNi1/3Co1/3Mn1/3O2 in 1:1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ∼5.2 V vs. Li/Li+, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the LiNi1/3Co1/3Mn1/3O2 component only. When the cell voltage reaches at ∼4.0 V vs. Li/Li+, lithium extraction from the spinel LiMn2O4 component starts and becomes the major contributor for the cell capacity due to the higher rate capability of LiMn2O4. When the voltage passed 4.3 V, the major structural changes are from the LiNi1/3Co1/3Mn1/3O2 component, while the LiMn2O4 component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel LiMn2O4 component, with much less changes in the layered LiNi1/3Co1/3Mn1/3O2 component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research.  相似文献   

19.
The layered LiNi1/3Mn1/3Co1/3O2 materials with good crystalline are synthesized by a novel method of hydrothermal method followed by a short calcination process. The crystalline structure and morphology of the synthesized materials are characterized by XRD, SEM. Their electrochemical performances are evaluated by CV, EIS and galvonostatic charge/discharge tests. The material synthesized at 850 °C for 6 h shows the highest initial discharge capacity of 187.7 mAh g−1 at 20 mA g−1. And the capacity retention of 97.9% is maintained at the end of 40 cycles at 1.0 C. CV test reveals almost no shift of anodic and cathodic peaks after first cycle, which indicates good reversible deintercalation and intercalation of Li+ ions.  相似文献   

20.
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   

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