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1.
Li[Ni(1/3−z)Co(1/3−z)Mn(1/3−z)Mgz]O2 (z = 0, 0.04) positive electrode materials were synthesized via a co-precipitation method. These materials have α-NaFeO2 () structure, as confirmed by X-ray diffraction (XRD) studies. Cation mixing in Li layer seemed to be decreased by Mg substitution as examined by Rietveld refinements of XRD data. Spherical morphologies were observed for the as-synthesized final products by scanning electron microscopy. Their electrochemical properties during charge and discharge were discussed. When magnesium ions are substituted, the initial reversible capacity reduced. However, the substitution for Mn sites in Li[Ni1/3Co1/3Mn1/3]O2 did not decrease the capacity because Mn sites substitution did not result in loss of electroactive elements in the compound. Differential scanning calorimetric studies showed the exothermic peaks of the charged electrode Li[Ni(1/3−z)Co(1/3−z)Mn(1/3−z)Mgz]O2 (z = 0.04) were significantly smaller than that of Li[Ni1/3Co1/3Mn1/3]O2, which means that thermal stability was greatly improved by Mg substitution even at highly delithiated state. 相似文献
2.
Layered metastable lithium manganese oxides, Li2/3[Ni1/3−xMn2/3−yMx+y]O2 (x = y = 1/36 for M = Al, Co, and Fe and x = 2/36, y = 0 for M = Mg) were prepared by the ion exchange of Li for Na in P2-Na2/3[Ni1/3−xMn2/3−yMx+y]O2 precursors. The Al and Co doping produced the T#2 structure with the space group Cmca. On the other hand, the Fe and Mg doped samples had the O6 structure with space group R-3m. Electron diffraction revealed the 1:2 type ordering within the Ni1/3−xMn2/3−yMx+yO2 slab. It was found that the stacking sequence and electrochemical performance of the Li cells containing T#2-Li2/3[Ni1/3Mn2/3]O2 were affected by the doping with small amounts of Al, Co, Fe, and Mg. The discharge capacity of the Al doped sample was around 200 mAh g−1 in the voltage range between 2.0 and 4.7 V at the current density of 14.4 mA g−1 along with a good capacity retention. Moreover, for the Al and Co doped and undoped oxides, the irreversible phase transition of the T#2 into the O2 structure was observed during the initial lithium deintercalation. 相似文献
3.
Ismael Saadoune Mohamed Labrini Mustapha Yahya Abdelmajid Almaggoussi 《Electrochimica acta》2010,55(18):5180-4086
We reported here on the synthesis, the crystal structure and the study of the structural changes during the electrochemical cycling of layered LiNi0.1Mn0.1Co0.8O2 positive electrode material. Rietveld refinement analysis shows that this material exhibits almost an ideal α-NaFeO2 structure with practically no lithium-nickel disorder. The SQUID measurements confirm this structural result and evidenced that this material consists of Ni2+, Mn4+ and Co3+ ions.Unlike LiNiO2 and LiCoO2 conventional electrode materials, there was no structural modification upon lithium removal in the whole 0.42 ≤ x ≤1.0 studied composition range. The peaks revealed in the incremental capacity curve were attributed to the successive oxidation of Ni2+ and Co3+ while Mn4+ remains electrochemically inactive. 相似文献
4.
Spherical Li[Ni0.4Co0.2Mn(0.4−x)Mgx]O2−yFy (x = 0, 0.04, y = 0, 0.08) with phase-pure and well-ordered layered structure have been synthesized by heat-treatment of spherical [Ni0.4Co0.2Mn0.4−xMgx]3O4 precursors with LiOH·H2O and LiF salts. The average particle size of the powders was about 10-15 μm and the size distribution was quite narrow due to the homogeneity of the metal carbonate, [Ni0.4Co0.2Mn(0.4−x)Mgx]CO3 (x = 0, 0.04) precursors. Although the Li[Ni0.4Co0.2Mn0.36Mg0.04]O1.92F0.08 delivered somewhat slightly lower initial discharge capacity, however, the capacity retention, interfacial resistance, and thermal stability were greatly enhanced comparing to the Li[Ni0.4Co0.2Mn0.4]O2 and Li[Ni0.4Co0.2Mn0.36Mg0.04]O2. 相似文献
5.
Li[Co1−zAlz]O2 (0 ≤ z ≤ 0.5) samples were prepared by co-precipitation and solid-state methods. The lattice constants varied smoothly with z for the co-precipitated samples but deviated for the solid-state samples above z = 0.2. The solid-state method may not produce materials with a uniform cation distribution when the aluminum content is large or when the duration of heating is too brief. Non-stoichiometric Lix[Co0.9Al0.1]O2 samples were synthesized by the co-precipitation method at various nominal compositions x = Li/(Co + Al) = 0.95, 1.0, 1.1, 1.2, 1.3. XRD patterns of the Lix[Co0.9Al0.1]O2 samples suggest the solid solution limit is between Li/(Co + Al) = 1.1 and 1.2. Electrochemical studies of the Li[Co1−zAlz]O2 samples were used to measure the rate of capacity reduction with Al content, found to be about −250 ± 30 (mAh/g)/(z = 1). Literature work on Li[Ni1/3Mn1/3Co1/3−zAlz]O2, Li[Ni1−zAlz]O2 and Li[Mn2−yAly]O4 demonstrates the same rate of capacity reduction with Al/(Al + M) ratio. These studies serve as baseline characterization of samples to be used to determine the impact of Al content on the thermal stability of delithiated Li[Co1−zAlz]O2 in electrolyte. 相似文献
6.
A novel Li[Ni0.67Co0.15Mn0.18]O2 cathode material encapsulated completely within a concentration-gradient shell was successfully synthesized via co-precipitation. The Li[Ni0.67Co0.15Mn0.18]O2 has a core of Li[Ni0.8Co0.15Mn0.05]O2 that is rich in Ni, a concentration-gradient shell having decreasing Ni concentration and increasing Mn concentration toward the particle surface, and a stable outer-layer of Li[Ni0.57Co0.15Mn0.28]O2. The electrochemical and thermal properties of the material were investigated and compared to those of the core Li[Ni0.8Co0.15Mn0.05]O2 material alone. The discharge capacity of the concentration-gradient Li[Ni0.67Co0.15Mn0.18]O2 electrode increased with increasing upper cutoff voltage to 4.5 V, and cells with this cathode material delivered a very high capacity, 213 mAh/g, with excellent cycling stability even at 55 °C. The enhanced thermal and lithium intercalation stability of the Li[Ni0.67Co0.15Mn0.18]O2 was attributed to the gradual increase in tetravalent Mn concentration and decrease in Ni concentration in the concentration-gradient shell layer. 相似文献
7.
Jung-Min Kim 《Electrochimica acta》2004,49(6):937-944
In this research, we studied the first cycle characteristics of Li[Ni1/3Co1/3Mn1/3]O2 charged up to 4.7 V. Properties, such as valence state of the transition metals and crystallographic features, were analyzed by X-ray absorption spectroscopy and X-ray and neutron diffractions. Especially, two plateaus observed around 3.75 and 4.54 V were investigated by ex situ X-ray absorption spectroscopy. XANES studies showed that the oxidation states of transition metals in Li[Ni1/3Co1/3Mn1/3]O2 are mostly Ni2+, Co3+ and Mn4+. Based on neutron diffraction Rietveld analysis, there is about 6% of all nickel divalent (Ni2+) ions mixed with lithium ions (cation mixing). Meanwhile, it was found that the oxidation reaction of Ni2+/Ni4+ is related to the lower plateau around 3.75 V, but that of Co3+/Co4+ seems to occur entire range of x in Li1−x[Ni1/3Co1/3Mn1/3]O2. Small volume change during cycling was attributed to the opposite variation of lattice parameter “c” and “a” with charging-discharging. 相似文献
8.
Cathode active materials with a composition of LiNi0.9Co0.1O2 were synthesized by a solid-state reaction method at 850 °C using Li2CO3, NiO or NiCO3, and CoCO3 or Co3O4, as the sources of Li, Ni, and Co, respectively. Electrochemical properties, structure, and microstructure of the synthesized LiNi0.9Co0.1O2 samples were analyzed. The curves of voltage vs. x in LixNi0.9Co0.1O2 for the first charge–discharge and the intercalated and deintercalated Li quantity Δx were studied. The destruction of unstable 3b sites and phase transitions were discussed from the first and second charge–discharge curves of voltage vs. x in LixNi0.9Co0.1O2. The LiNi0.9Co0.1O2 sample synthesized from Li2CO3, NiO, and Co3O4 had the largest first discharge capacity (151 mA h/g), with a discharge capacity deterioration rate of −0.8 mA h/g/cycle (that is, a discharge capacity increasing 0.8 mA h/g per cycle). 相似文献
9.
A carbonate co-precipitation method was employed to prepare spherical Li[Ni1/3Co1/3Mn1/3]O2 cathode material. The precursor, [Ni1/3Co1/3Mn1/3]CO3, was prepared using ammonia as chelating agent under CO2 atmosphere. The spherical Li[Ni1/3Co1/3Mn1/3]O2 was prepared by mixing the precalcined [Ni1/3Co1/3Mn1/3]CO3 with LiOH followed by high temperature calcination. The preparation conditions such as ammonia concentration, co-precipitation temperature, calcination temperature and Li/[Ni1/3Co1/3Mn1/3] ratio were varied to optimize the physical and electrochemical properties of the prepared Li[Ni1/3Co1/3Mn1/3]O2. The structural, morphological, and electrochemical properties of the prepared LiNi1/3Co1/3Mn1/3O2 were characterized by XRD, SEM, and galvanostatic charge-discharge cycling. The optimized material has a spherical particle shape and a well ordered layered structure, and it also has an initial discharge capacity of 162.7 mAh g− 1 in a voltage range of 2.8-4.3 V and a capacity retention of 94.8% after a hundred cycles. The optimized ammonia concentration, co-precipitation temperature, calcination temperature, and Li/[Ni1/3Co1/3Mn1/3] ratio are 0.3 mol L− 1, 60 °C, 850 °C, and 1.10, respectively. 相似文献
10.
Abdelfattah Mahmoud Ismael Saadoune José Manuel Amarilla Rachid Hakkou 《Electrochimica acta》2011,(11):4081
LiCo2/3Ni1/6Mn1/6O2 layered oxide was synthesized by the combustion method that led to a crystalline phase with good homogeneity and low particles size. The structural properties of the prepared positive electrode material were investigated by performing XRD Rietveld refinement. Practically no Li/Ni mixing was detected evidencing that the studied compound adopts almost an ideal α-NaFeO2 type structure. The Li||LiCo2/3Ni1/6Mn1/6O2 cell showed a discharge capacity of 199 mAh g−1 when cycled in the 2.7–4.6 V potential range while the best cycling performances were recorded when the upper cut off is fixed at 4.5 V. Structural changes in LixCo2/3Ni1/6Mn1/6O2 with lithium electrochemical de-intercalation were studied using X-ray diffraction. This study clearly shows the existence of a solid solution domain in the 0.1 < x < 1.0 composition range while for x = 0.1, a new phase appears explaining the decrease of the electrochemical performance when the cell is cycled at high upper cut off voltage. 相似文献
11.
In order to get homogeneous layered oxide Li[Ni1/3Mn1/3Co1/3]O2 as a lithium insertion positive electrode material, we applied the metal acetates decomposition method. The oxide compounds were calcined at various temperatures, which results in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni1/3Mn1/3Co1/3]O2 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry and SEM. XRD experiment revealed that the layered Li[Ni1/3Mn1/3Co1/3]O2 material can be best synthesized at temperature of 800 °C. In that synthesized temperature, the sample showed high discharge capacity of 190 mAh g−1 as well as stable cycling performance at a current density of 0.2 mA cm−2 in the voltage range 2.3-4.6 V. The reversible capacity after 100 cycles is more than 190 mAh g−1 at room temperature. 相似文献
12.
Layered Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) have been prepared by the mixed hydroxide and molten-salt synthesis method. The individual particles of synthesized materials have a sub-microsize range of 200-500 nm, and LiNi0.475Mn0.475Zr0.05O2 has a rougher surface than that of LiNi0.5Mn0.5O2. The Li/Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) electrodes were cycled between 4.5 and 2.0 V at a current density of 15 mA/g, the discharge capacity of both cells increased during the first ten cycles. The discharge capacity of the Li/LiNi0.475Mn0.475Zr0.05O2 cell increased from 150 to 220 mAh/g, which is 50 mAh/g larger than that of the Li/LiNi0.5Mn0.5O2 cell. We found that the oxidation of oxygen and the Mn3+ ion concerned this phenomenon from the cyclic voltammetry (CV). Thermal stability of the charged Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) cathode was improved by Zr doping. 相似文献
13.
Sen Zhang 《Electrochimica acta》2007,52(25):7337-7342
Li[Ni1/3Co1/3Mn1/3]O2 cathode material for lithium ion batteries was prepared by mixing metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2, with 6% excess LiOH followed by calcinations. The (Ni1/3Co1/3Mn1/3)(OH)2 with secondary particle of about 12 μm was prepared by hydroxide co-precipitation. The tap density of the obtained Li[Ni1/3Co1/3Mn1/3]O2 powder was 2.56 ± 0.21 g cm−3. The powder was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size distribution (PSD) and galvanostatic charge-discharge cycling. The XRD pattern of Li[Ni1/3Co1/3Mn1/3]O2 revealed a well ordered hexagonal layered structure with low cation mixing. Secondary particles with size of 13-14 μm and primary particles with size of about 1 μm can be identified from the SEM observations. In the voltage range of 2.8-4.3 V, the initial discharge capacity of the Li[Ni1/3Co1/3Mn1/3]O2 electrode was 166.6 mAh g−1, and 96.5% of the initial capacity was retained after 50 charge-discharge cycling. 相似文献
14.
Layered Li1+x(Ni0.3Co0.4Mn0.3)O2−δ (x = 0, 0.03 and 0.06) materials were synthesized through the different calcination times using the spray-dried precursor with the molar ratio of Li/Me = 1.25 (Me = transition metals). The physical and electrochemical properties of the lithium excess and the stoichiometric materials were examined using XRD, AAS, BET and galvanostatic electrochemical method. As results, the lithium excess Li1.06(Ni0.3Co0.4Mn0.3)O2−δ could show better electrochemical properties, such as discharge capacity, capacity retention and C rate ability, than those of the stoichiometric Li1.00(Ni0.3Co0.4Mn0.3)O2−δ. In this paper, the effect of excess lithium on the electrochemical properties of Li1+x(Ni0.3Co0.4Mn0.3)O2−δ materials will be discussed based on the experimental results of ex situ X-ray diffraction, transmission electron microscopy (TEM) and galvanostatic intermittent titration technique (GITT) 相似文献
15.
Spherical Li[Ni1/3Co1/3Mn1/3]O2 powders were synthesized from LiOH·H2O and coprecipitated spherical metal hydroxide, (Ni1/3Mn1/3Co1/3)(OH)2 and coated with Al(OH)3. The Al(OH)3-coated Li[Ni1/3Co1/3Mn1/3]O2 showed a capacity retention of 80% at 320 mA g−1 (2 C-rate) based on 20 mA g−1 (0.1 C-rate), while the pristine Li[Ni1/3Co1/3Mn1/3]O2 delivered only 45% at the same current density. Also, unlike pristine Li[Ni1/3Co1/3Mn1/3]O2, the Al(OH)3-coated Li[Ni1/3Co1/3Mn1/3]O2 cathode exhibits excellent rate capability and good thermal stability. 相似文献
16.
Uniform and spherical Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ powders were synthesized via NH3 and F− coordination hydroxide co-precipitation. The effect of F− coordination agent on the morphology, structure and electrochemical properties of the Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ were studied. The morphology, size, and distribution of (Ni1/3Co1/3Mn1/3)(OH)(2−δ)Fδ particle diameter were improved in a shorter reaction time through the addition of F−. The study suggested that the added F improves the layered characteristics of the lattice and the cyclic performance of Li(Ni1/3Co1/3Mn1/3)O2 in the voltage range of 2.8-4.6 V. The initial capacity of the Li(Ni1/3Co1/3Mn1/3)O1.96F0.04 was 178 mAh g−1, the maximum capacity was 186 mAh g−1 and the capacity after 50 cycles was 179 mAh g−1 in the voltage range of 2.8-4.6 V. 相似文献
17.
Ling-jun Li Zhi-xing Wang Hua-jun Guo Peng Yue Wei Chen Ling Wu 《Powder Technology》2011,206(3):353-357
Nanocrystalline materials of Ni0.8Co0.1Mn0.1(OH)2 are successfully synthesized by fast co-precipitation method. The crystalline structure and morphology of the precursors and LiNi0.8Co0.1Mn0.1O2 materials are characterized by XRD, SEM and Rietveld refinement analyses. It is found that the nanocrystalline phase and low crystallinity of Ni0.8Co0.1Mn0.1(OH)2 could help achieve its uniform mixing with lithium source, and further attribute to highly ordered layered LiNi0.8Co0.1Mn0.1O2 with low cation mixing degree. Electrochemical studies confirm that the LiNi0.8Co0.1Mn0.1O2 exhibits a good electrochemical property with initial discharge specific capacity of 192.4 mAh g− 1 at a current density of 18 mA g− 1, and the capacity retention after 40 cycles is 91.56%. This method is a simple and effective method to synthesize cathode material. 相似文献
18.
A positive electrode material for lithium ion battery applications was successfully synthesized using microwave irradiation. This microwave synthesis has several merits such as homogeneity of final product and much shorter reaction time compared to conventional synthetic methods. We synthesized spherical [Ni0.4Co0.2Mn0.4](OH)2 as a precursor by a co-precipitation method. The pelletized mixture of the precursor and lithium hydroxide was calcined under different reaction times and temperatures by applying 1200 W of microwave irradiation at 2.45 GHz. We determined the optimum conditions of microwave synthesis for positive electrode materials. The powders were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. The capacity, its retention, and thermal stability of Li[Ni0.4Co0.2Mn0.4]O2 synthesized by the microwave synthesis were comparable to the Li[Ni0.4Co0.2Mn0.4]O2 prepared by the high temperature calcination method. 相似文献
19.
The layered Li[Ni1/3Co1/3Mn1/3]O2 powder with good crystalline and spherical shape was prepared by hydroxide co-precipitation method. The effects of pH value, NH4OH amount, calcination temperature and extra Li amount on the morphology, structure and electrochemical properties of the cathode material were investigated in detail. SEM results indicate that pH value affected both the morphology and the property of the cathode material, and the highest discharge capacity in the first cycle of 163 mAh g−1 (2.8-4.3 V) was obtained at pH value was 12. On the contrary, the NH4OH amount, which was used as a chelating agent, only affected the particle size distribution of the material. The calcination temperatures caused great difference in the structure and property of layered Li[Ni1/3Co1/3Mn1/3]O2, and the best electrochemical properties were obtained at the calcination temperature of 800 °C. Extra Li amount not only caused difference in the material structure, but also affected their electrochemical properties. With increasing Li amount, the lattice parameters (a and c) increased monotonously, and the highest first cycle coulombic efficiency (the ratio of discharge capacity to charge capacity in the first cycle) was obtained with the Li/M of 1.10. Therefore, the optimum synthetic conditions for the hydroxide co-precipitation reaction were: pH value was 12, NH4OH amount was 0.36 mol L−1, calcination temperature was 800 °C and the Li/M molar ratio was 1.10. 相似文献
20.
Hansan Liu 《Electrochimica acta》2004,49(7):1151-1159
Multiple substitution compounds with the formula LiNi0.8−yTiyCo0.2O2 (0≤y≤0.1) were synthesized by sol-gel method using citric acid as a chelating agent. The effects of titanium substitution on the structural, electrochemical and thermal properties of the cathode materials are investigated. A solid solution phase (R-3m) is observed in the range of 0≤y≤0.1 for the titanium-doped materials. X-ray photoelectron spectroscopy (XPS) shows that there are Ni3+, Ni2+, Co3+, Co2+ and Ti4+ five transition metal ions in titanium-doped materials. Rietveld refinement of X-ray diffraction (XRD) patterns indicates that titanium substitution changes the materials’ structure with different cationic distribution. An increase of the Ni/Co amount in the 3a Li site is found with the addition of titanium amount. An improved cycling performance is observed for titanium-doped cathode materials, which is interpreted to a significant suppression of phase transitions and lattice changes during cycling. The thermal stability of titanium-doped materials is also improved, which can be attributed to its lower oxidation ability and enhanced structural stability at delithiated state. 相似文献