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1.
LiNi1/3Co1/3Mn1/3O2 nanocrystallites were synthesized by a one-step hydrothermal method, and uniform second particles were formed by a subsequent calcination process. X-ray diffraction results indicate that the as-synthesized material can be indexed by α-NaFeO2 layered structure with R-3 m space group. The results of Rietveld refinements show the I 003/I 104 value of the material is 2.032, and the nanostructured material presents low cation mixing, small cell volume, and a consequent suppression of lattice strain. The rate performances of the as-synthesized material can be further improved by coating Al2O3. The discharging capacity of Al2O3-coated material reaches 154.4 mAh g?1, and the capacity retention maintains 80.3 % after 50 cycles at 5 C in the voltage range of 2.5 to 4.5 V, while those of the bare one is only 139.0 mAh g?1 and 71.6 %, respectively. The transmission electron microcopy observation shows no zigzag layer exists on the surface of particle after cycles for Al2O3-coated LiNi1/3Co1/3Mn1/3O2. Compared to bare LiNi1/3Co1/3Mn1/3O2, the de-intercalation potential difference before and after cycles of Al2O3-coated one is smaller. This indicates that Al2O3 coating can reduce the electrochemistry polarization in the electrode bulk.  相似文献   

2.
The high-voltage spinel is a promising cathode material in next generation of lithium-ion batteries. Samples LiNi0.5???xMn1.5?+?xO4 (x?=?0, 0.05, 0.1) are synthesized by a simple co-precipitation method, in which pH value and temperature conditions do not need control. In the simple co-precipitation method, NaHCO3 solution is poured into transition metal solution to produce precursor. Ni and Mn are distributed uniformly in the products. The as-prepared samples are composed of ~?200 nm primary particles. Samples LiNi0.5???xMn1.5?+?xO4 (x?=?0, 0.05, 0.1) are also tested to study the effects of different Ni/Mn ratios. Sample LiNi0.5Mn1.5O4 delivers discharge capacities of 130 mAh g?1 at 0.2 C. The decreasing of Ni/Mn ratio in samples reduces specific capacity. With the decreasing of Ni/Mn ratios in spinel, amount of Mn3+ are increased. Attributed to its high Mn3+ contents, sample LiNi0.4Mn1.6O4 delivers the highest discharge capacity of 106 mAh g?1 at a large current density of 15 C, keeping 84.5% of that at 0.2 C rate. With the increasing of Ni/Mn ratios in spinel, cycling performance is improved. Sample LiNi0.5Mn1.5O4 shows the best cycling stability, keeping 94.4% and 90.4% of the highest discharge capacities after 500 cycles at 1 C and 1000 cycles at 5 C.  相似文献   

3.
Fluoroethylene carbonate (FEC) is investigated as the electrolyte additive to improve the electrochemical performance of high voltage LiNi0.6Co0.2Mn0.2O2 cathode material. Compared to LiNi0.6Co0.2Mn0.2O2/Li cells in blank electrolyte, the capacity retention of the cells with 5 wt% FEC in electrolytes after 80 times charge-discharge cycle between 3.0 and 4.5 V significantly improve from 82.0 to 89.7%. Besides, the capacity of LiNi0.6Co0.2Mn0.2O2/Li only obtains 12.6 mAh g?1 at 5 C in base electrolyte, while the 5 wt% FEC in electrolyte can reach a high capacity of 71.3 mAh g?1 at the same rate. The oxidative stability of the electrolyte with 5 wt% FEC is evaluated by linear sweep voltammetry and potentiostatic data. The LSV results show that the oxidation potential of the electrolytes with FEC is higher than 4.5 V vs. Li/Li+, while the oxidation peaks begin to appear near 4.3 V in the electrolyte without FEC. In addition, the effect of FEC on surface of LiNi0.6Co0.2Mn0.2O2 is elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The analysis result indicates that FEC facilitates the formation of a more stable surface film on the LiNi0.6Co0.2Mn0.2O2 cathode. The electrochemical impedance spectroscopy (EIS) result evidences that the stable surface film could improve cathode electrolyte interfacial resistance. These results demonstrate that the FEC can apply as an additive for 4.5 V high voltage electrolyte system in LiNi0.6Co0.2Mn0.2O2/Li cells.  相似文献   

4.
Layered lithium ion battery cathode material LiNi1/3Co1/3Mn1/3O2 with a uniform particle size of about 6 μm was synthesized by a spray pyrolysis method. The lithium ion diffusion kinetics in LiNi1/3Co1/3Mn1/3O2 composite cathode were systematically studied by the ratio of potentio-charge capacity to galvano-charge capacity method, galvanostatic intermittent titration technique, electrochemical impedance spectroscopy, and potential step chronoamperometry methods. The variations of lithium ion diffusion coefficients obtained by the four methods show a close similarity. They vary in the range of 10?8 to 10?10 cm2 s?1, with a maximum at 4.1- to 4.2-V voltage level.  相似文献   

5.
Spherical LiNi1/3Co1/3Mn1/3O2 particles were successfully synthesized using Na2CO3 as a precipitant. Electrochemical measurements indicate that the as-synthesized spherical particles deliver a high reversible capacity of above 180 mAh g?1 at 0.1 C in the voltage range of 2.8–4.4 V and display an excellent cyclic performance at 0.5 C. However, unsatisfactory rate capability was detected for the as-prepared spherical particles. The reason for the unsatisfactory rate capability was investigated through a comparison of the properties of the as-synthesized spherical particles versus the ball-milled samples via a combination of specific surface areas test, electronic conductivity measurement, and electrochemical impedance spectroscopy. The results show that both the rate capabilities of cathode materials and the electronic conductivities of the mixtures of active material, conductive additive, and binder are highly improved when the secondary spherical particles were broken, indicating that the poor electronic conductivity of electrode caused by the large secondary spherical particles with a great amount of nano-pores is a significant factor for the unsatisfactory rate capability.  相似文献   

6.
(Ni0.8Mn0.1Co0.1)(OH)2 and Co(OH)2 secondly treated by LiNi0.8Mn0.1Co0.1O2 have been prepared via co-precipitation and high-temperature solid-state reaction. The residual lithium contents, XRD Rietveld refinement, XPS, TG-DSC, and electrochemical measurements are carried out. After secondly treating process, residual lithium contents decrease drastically, and occupancy of Ni in 3a site is much lower and Li/Ni disorder decreases. The discharge capacity is 193.1, 189.7, and 182 mAh g?1 at 0.1 C rate, respectively, for LiNi0.8Mn0.1Co0.1O2-AP, -NT, and -CT electrodes between 3.0 and 4.2 V in pouch cell. The capacity retention has been greatly improved during gradual capacity fading of cycling at 1 C rate. The noticeably improved thermal stability of the samples after being treated can also be observed.  相似文献   

7.
A series of LiNi1/3Co1/3Mn1/3O2/LiFePO4 composite cathodes with the LiFePO4 mass content ranging from 10 to 30 wt% were prepared by ball milling in order to combine the merits of layered LiNi1/3Co1/3Mn1/3O2 and olivine LiFePO4. The structure and morphology of the samples were characterized by X-ray diffraction and scanning electron microscope. The composite cathodes exhibited improved electrochemical performance compared with pristine LiNi1/3Co1/3Mn1/3O2. Among all the composite cathodes, the one with 20 wt% of LiFePO4 showed the best electrochemical performance in terms of discharge capacity, cycle stability, and rate capability. Electrochemical impedance spectroscopy showed that mixing of LiFePO4 in LiNi1/3Co1/3Mn1/3O2 decreased the internal resistance of the electrode, retarded the formation of SEI film, and facilitated the charge transfer reaction. Differential scanning calorimetry showed that the composite cathode had better thermal stability than pristine LiNi1/3Co1/3Mn1/3O2.  相似文献   

8.
Spherical LiNi1/3Co1/3Mn1/3O2 was successfully prepared by controlled crystallization. The preparation started with the spherical coprecipitate of Ni1/3Co1/3Mn1/3CO3 from NiSO4, CoSO4, MnSO4, NH4HCO3, and NH3·H2O, followed by pyrolysis of Ni1/3Co1/3Mn1/3CO3 at 600°C for 3 h. The X-ray diffraction analysis showed that the homogeneous cubic (Ni1/3Co1/3Mn1/3)3O4 was obtained after the pyrolysis. Spherical LiNi1/3Co1/3Mn1/3O2 was obtained by sintering of the mixture of as-obtained (Ni1/3Co1/3Mn1/3)3O4 and LiOH·H2O at 900°C for 6 h in air. As-prepared spherical LiNi1/3Co1/3Mn1/3O2 presented initial discharge capacity of 162.9 mA h g−1 and capacity retention of 98% at 50th cycle.  相似文献   

9.
The layered Li1.2Mn0.54Ni0.13Co0.13O2 lithium-rich manganese-based solid solution cathode material has been synthesized by a simple solid-state method. The as-prepared material has a typical layered structure with R-3m and C2/m space group. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 has an irregular shape with the size range from 200 to 500 nm, and the primary particle of Li1.2Mn0.54Ni0.13Co0.13O2 has regular sphere morphology with a diameter of 320 nm. Electrochemical performances also have been investigated. The results show that the cathode material Li1.2Mn0.54Ni0.13Co0.13O2 prepared at 900 °C for 12 h has a good electrochemical performance, which can deliver a high initial discharge capacity of 233.5, 214.2, 199.3, and 168.1 mAh g?1 at 0.1, 0.2, 0.5, and 1 C, respectively. After 50 cycles, the capacity retains 178.0, 166.3, 162.1, and 155.9 mAh g?1 at 0.1, 0.2, 0.5, and 1 C, respectively. The results indicate that the simple method has a great potential in synthesizing manganese-based cathode materials for Li-ion batteries.  相似文献   

10.
Guoqiang Liu  Lei Wen  Yue Li  Yulong Kou 《Ionics》2015,21(4):1011-1016
The pure phase P2-Na2/3Ni1/3Mn2/3O2 was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na2/3Ni1/3Mn2/3O2 is a potential cathode material for sodium-ion batteries.  相似文献   

11.
A hierarchical porous nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode is successfully prepared for the first time using a facile ammonia-induced method, wherein ammonia molecules play a key role in fabricating the complex architecture, and neither templates nor precipitants are employed. Hierarchical flower-like precursor with ultra-thin nanosheets is formed during the ammonia-induced reaction, and then, the porous product is obtained during the sintering process. The X-ray diffraction pattern demonstrates that the sample has a well-defined α-NaFeO2 structure with very low-cation disorder. The peculiar hierarchical porous morphology and ideal structure endow this material-enhanced electrochemical performance. It delivers discharge capacities of 173, 138, 111, 97, and 82 mAh g?1 at 0.1 C, 1 C, 5 C, 10 C, and 20 C, respectively, and maintains 91 % of its initial discharge capacity after 100 cycles at 1 C. The results reveal that this method is facile and feasible to synthesize high-rate Nickel-rich material.  相似文献   

12.
To improve the electrochemical performance of Nickel-rich cathode material LiNi0.8Co0.1Mn0.1O2, an in situ coating technique with Li2ZrO3 is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li2ZrO3 coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li2ZrO3 coating plays an important role to enhance the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 and reveal that choosing suitable temperature and current is critical for solving battery safety problem.  相似文献   

13.
Layered LiNi1/3Co1/3Mn1/3O2 cathode material is synthesized via a sol-gel method and subsequently surface-modified with Eu2O3 layer by a wet chemical process. The effect of Eu2O3 coating on the electrochemical performances and thermal stability of LiNi1/3Co1/3Mn1/3O2@Eu2O3 cells is investigated systematically by the charge/discharge testing, cyclic voltammograms, AC impedance spectroscopy, and DSC measurements, respectively. In comparison, the Eu2O3-coated sample demonstrates better electrochemical performances and thermal stability than that of the pristine one. After 100 cycles at 1C, the Eu2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode demonstrates stable cyclability with capacity retention of 92.9 %, which is higher than that (75.5 %) of the pristine one in voltage range 3.0–4.6 V. Analysis from the electrochemical measurements reveals that the remarkably improved performances of the surface-modified composites are mainly ascribed to the presence of Eu2O3-coating layer, which could efficiently suppress the undesirable side reaction and increasing impedance, and enhance the structural stability of active material.  相似文献   

14.
The LiNi0.8Co0.1Mn0.1O2 with LiAlO2 coating was obtained by hydrolysis–hydrothermal method. The morphology of the composite was characterized by SEM, TEM, and EDS. The results showed that the LiAlO2 layer was almost completely covered on the surface of particle, and the thickness of coating was about 8–12 nm. The LiAlO2 coating suppressed side reaction between composite and electrolyte; thus, the electrochemical performance of the LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 was improved at 40 °C. The LiAlO2-coated sample delivered a high discharge capacity of 181.2 mAh g?1 (1 C) with 93.5% capacity retention after 100 cycles at room temperature and 87.4% capacity retention after 100 cycles at 40 °C. LiAlO2-coated material exhibited an excellent cycling stability and thermal stability compared with the pristine material. These works will contribute to the battery structure optimization and design.  相似文献   

15.
LiNi0.5Co0.2Mn0.3O2 particles of uniform size were prepared through carbonate co-precipitation method with acacia gum. The precursor of carbonate mixture was calcined at 800 °C, and a well-crystallized Ni-rich layered oxide was got. The phase structure and morphology were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micro-sized particles delivered high initial discharge capacity of 164.3 mA h g?1 at 0.5 C (1 C?=?200 mA g?1) between 2.5 and 4.3 V with capacity retention of 87.5 % after 100 cycles. High reversible discharge capacities of 172.4 and 131.4 mA h g?1 were obtained at current density of 0.1 and 5 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to further study the LiNi0.5Co0.2Mn0.3O2 particles. Anyway, the excellent electrochemical performances of LiNi0.5Co0.2Mn0.3O2 sample should be attributed to the use of acacia gum.  相似文献   

16.
LiNi1/3Co1/3Mn1/3O2 (LNMCO) powders were formed by a two-step synthesis including preparation of an oxalate precursor by ??chimie douce?? followed by a solid-state reaction with lithium hydroxide. The product was characterized by TG-DTA, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Raman spectroscopy, electron spin resonance (ESR), and SQUID magnetometry. XRD data revealed well-crystallized layered LNMCO with ??-NaFeO2-type structure (R-3?m space group). Morphology studied by SEM and TEM shows submicronic particles of 400?C800?nm with a tendency to agglomerate. The local structure investigated by vibrational spectroscopy (FTIR, Raman), ESR, and SQUID measurements confirms the well-crystallized lattice with a cation disorder of 2.6% Ni2+ ions in Li(3b) sites. Electrochemical tests were carried out in the potential range 2.5?C4.5?V vs. lithium metal on samples heated at 900?°C for 12?h. Initial discharge capacity is 154 mAh/g at C/5, while a capacity of 82 mAh/g is still delivered at 10 C by the two-step synthesized LiNi1/3Co1/3Mn1/3O2 as cathode material.  相似文献   

17.
Lithium-rich cathode materials Li1.2Ni0.13Co0.13Mn0.54O2 with (sample SF) and without (sample SP) formamide was synthesized by a spray-dry method. The crystalline structure and particle morphology of as-prepared materials were characterized by X-ray diffraction and scanning electron microscope. The specific surface area (SSA) of the Li1.2Ni0.13Co0.13Mn0.54O2 prepared from different routes was determined by a five-point Brunauer–Emmett–Teller (BET) method using N2 as absorbate gas. Being compared with the material synthesized without spray-drying process (sample CP), sample SP has much higher SSA. The additive formamide is helpful to form regular and solid precursor particles in spray-drying process, which results in a slightly aggregation of grains and reduction of SSA for sample SF. The electrochemical activities of the materials are closely related to their morphology and SSA. In the voltage range of 2–4.8 V at 25 °C, sample SP present a discharge capacity of 257 mAh g?1 at 0.1 C rate and 170 mAh g?1 at 1 C rate. The sample CP delivered only 136 mAh g?1 when discharged at 1 C rate. The elevated specific capacity and rate capability are attributed to smaller primary particle and higher SSA. Both cycle performance and rate capability of Li1.2Ni0.13Co0.13Mn0.54O2 were improved when formamide was used in spray-dry process. Discharge capacity of SF is 140.5 mAh g?1 at 2 C rate, and that of SP is 132.3 mAh g?1. Overlarge SSA of SP may provoke serious side reaction, so that its electrochemical performance was deteriorated.  相似文献   

18.
A series of spherical LiNi0.8Co0.15Ti0.05O2 cathode materials were synthesized through co-oxidation-controlled crystallization method followed by solid-state reaction at different calcination temperatures under oxygen flowing. The crystal structure and particles morphology of the as-prepared powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. All samples correspond to the layered α-NaFeO2 structure with R-3m space group. The LiNi0.8Co0.15Ti0.05O2 prepared at 800 °C presents a better hexagonal ordering structure and better spherical particles and possesses a high tap density of 3.22 g cm?3. Meanwhile, the NCT-2 sample exhibits an advanced electrochemical performance with an initial discharge capacity of 174.2 mAh g?1 and capacity retention of 86.7 % after 30 cycles at 0.2 C.  相似文献   

19.
Li[Ni1/3Co(1-x)/3Mn1/3Fe x/3] O2(x?=?0.0, 0.1, 0.3, 0.5, 0.7, and 0.9) cathode materials have been synthesized via hydroxide co-precipitation method followed by a solid state reaction. Thermogravimetry (TG) and differential thermal analysis (DTA) measurements were utilized to determine the calcination temperature of precursor sample. The crystal structure features were characterized by X-ray diffraction (XRD). The electrochemical properties of Li[Ni1/3Co(1-x)/3Mn1/3Fe x/3]O2 were compared by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy(EIS), and galvanostatic charge/discharge test. Electrochemical test results indicate that Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3] O2 decrease charge transfer resistance and enhance Li+ ion diffusion velocity and thus improve cycling and high-rate capability compared with Li[Ni1/3Co1/3Mn1/3]O2. The initial discharge specific capacity of Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3] O2 was 178.5 mAh/g and capacity retention was 87.11 % after 30 cycles at 0.1C, with the battery showing good cycle performance.  相似文献   

20.
LiNi1 - y − zCoyMnzO2 (y = 0.25, 0.35, 0.5, 0.6; z = 0.1, 0.2), LiNi0.63Cu0.02Co0.25Mn0.1O2, LiNi0.65Co0.25Mn0.08Al0.02O2, LiNi0.65Co0.25Mn0.08Mg0.02O2 and LiNi0.65Co0.25Mn0.08Al0.01Mg0.01O2 cathode materials were synthesized by a soft chemistry EDTA-based method. Structural and transport properties of pristine and delithiated materials (LixNi0.65Co0.25Mn0.1O2, LixNi0.55Co0.35Mn0.1O2 and LiNi0.63Cu0.02Co0.25Mn0.1O2 oxides) are presented. In the considered group of oxides there is no correlation between electrical conductivity and the a parameter (M-M distance in the octahedra layers). The results of electrochemical performance of cathode materials are presented. The best stability during first 10 cycles was obtained for Li/LixNi0.63Cu0.02Co0.25Mn0.1O2 cell due to enhanced kinetics of intercalation process.  相似文献   

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