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1.
SrF2-coated LiNi1/3Co1/3Mn1/3O2 cathode materials with improved cycling performance over 2.5–4.6 V were investigated. The structural and electrochemical properties of the materials were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), charge–discharge tests and electrochemical impedance spectra (EIS). The results showed that the crystalline SrF2 with about 10–50 nm particle size is uniformly coated on the surface of LiNi1/3Co1/3Mn1/3O2 particles. As the coating amount increased from 0.0 to 2.0 mol%, the initial capacity and rate capability of the coated LiNi1/3Co1/3Mn1/3O2 decreased slightly owing to the increase of the charge-transfer resistance; however, the cycling stability was improved by suppressing the increase of the resistance during cycling. 4.0 mol% SrF2-coated LiNi1/3Co1/3Mn1/3O2 showed remarkable decrease of the initial capacity. 2.0 mol% coated sample exhibited the best electrochemical performance. It presented an initial discharge capacity of 165.7 mAh g−1, and a capacity retention of 86.9% after 50 cycles at 4.6 V cut-off cycling.  相似文献   

2.
LiNi1/3Co1/3Mn1/3O2 is prepared by a rheological phase method. Homogeneous precursor derived from this method is calcined at 800 °C for 20 h in air, which results in the impressive differences in the morphology properties and electrochemical behaviors of LiNi1/3Co1/3Mn1/3O2 in contrast to that obtained by a solid-state method. The microscopic structural features of LiNi1/3Co1/3Mn1/3O2 are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD). The electrochemical properties of LiNi1/3Co1/3Mn1/3O2 are carried out by charge–discharge cycling test. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performances. The obtained results suggest that the rheological phase method may become an effective route to prepare LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium battery.  相似文献   

3.
A modified synthesis process was developed based on co-precipitation method followed by spray drying process. In this process, a spherical shaped (Co1/3Ni1/3Mn1/3)(OH)2 precursor was synthesized by co-precipitation and pre-heated at 500 °C to form a high structural stability spinel (CoNiMn)O4 to maintain its shape for further processing. The spherical LiNi1/3Co1/3Mn1/3O2 was then prepared by spray drying process using spherical spinel (CoNiMn)O4. LiNi1/3Co1/3Mn1/3O2 powders were then modified by coating their surface with a uniform and nano-sized layer of ZrO2. The ZrO2-coated LiNi1/3Co1/3Mn1/3O2 material exhibited an improved rate capability and cycling stability under a high cut-off voltage of 4.5 V. X-ray diffraction (XRD) measurements revealed that the material had a well-ordered layered structure and Zr was not doped into the LiNi1/3Co1/3Mn1/3O2. Electrochemical impedance spectroscopy measurements showed that the coated material has stable cell resistance regardless of cycle number. The interrupt charging/discharging test indicated that the ZrO2 coating can suppress the polarization effects during the charging and discharging process. From these results, it is believed that the improved cycling performance of ZrO2-coated LiNi1/3Co1/3Mn1/3O2 is attributed to the ability of ZrO2 layer in preventing direct contact of the active material with the electrolyte resulting in a decrease of electrolyte decomposition reactions.  相似文献   

4.
The surface of LiNi1/3Co1/3Mn1/3O2 (LNMCO) particles has been studied for material synthesized at 900 °C by a two-step process from a mixture of LiOH·H2O and metal oxalate [(Ni1/3Co1/3Mn1/3)C2O4] obtained by co-precipitation. Samples have been characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), Raman scattering (RS) spectroscopy, and magnetic measurements. We have investigated the effect of the heat treatment of particles at 600 °C with organic substances such as sucrose and starch. HRTEM images and RS spectra indicate that the surface of particles has been modified. The annealing does not lead to any carbon coating but it leads to the crystallization of the thin disordered layer on the surface of LiNi1/3Co1/3Mn1/3O2. The beneficial effect has been tested on the electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 cathode materials. The capacity at 10C-rate is enhanced by 20% for post-treated LNMCO particles at 600 °C for half-an-hour.  相似文献   

5.
Submicron-sized LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized using a simple self-propagating solid-state metathesis method with the help of ball milling and the following calcination. A mixture of Li(ac)·2H2O, Ni(ac)2·4H2O, Co(ac)2·4H2O, Mn(ac)2·4H2O (ac = acetate) and excess H2C2O4·2H2O was used as starting material without any solvent. XRD analyses indicate that the LiNi1/3Co1/3Mn1/3O2 materials were formed with typical hexagonal structure. The FESEM images show that the primary particle size of the LiNi1/3Co1/3Mn1/3O2 materials gradually increases from about 100 nm at 700 °C to 200–500 nm at 950 °C with increasing calcination temperature. Among the synthesized materials, the LiNi1/3Co1/3Mn1/3O2 material calcined at 900 °C exhibits excellent electrochemical performance. The steady discharge capacities of the material cycled at 1 C (160 mA g−1) rate are at about 140 mAh g−1 after 100 cycles in the voltage range 3–4.5 V (versus Li+/Li) and the capacity retention is about 87% at the 350th cycle.  相似文献   

6.
LiNi1/3Co1/3Mn1/3O2 has aroused much interest as a new generation of cathode material for Li-ion batteries, due to its great advantages in capacity, stability, low cost and low toxicity, etc. Here we report a novel single-crystalline spherical LiNi1/3Co1/3Mn1/3O2 material that is prepared by a convenient rheological phase reaction route. The X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy indicate that the particles are highly dispersed with spherical morphologies and diameters of about 1-4 μm, and more interestingly, they show a perfect single-crystalline nature, which is not usual according to the crystal growth theories and may bring extra benefits to applications. Electrochemical tests show good performance of the material in both the capacity and cycling stability as cathode material in a model cell.  相似文献   

7.
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   

8.
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   

9.
Using analytical transmission electron microscopy (TEM) techniques reveal a zigzag layer on surface of the cycled particles of LiNi1/3Co1/3Mn1/3O2 cathode after 300 discharge/charge cycles. The Ni, Mn content in the zigzag layer of the cycled particle has decreased rapidly from interior to edge of the zigzag layer of the cycled particles. The structure of LiNi1/3Co1/3Mn1/3O2 oxide was gradually destructed from hexagonal cell with P3112 at interior region to fcc lattice of α-NaFeO2 at edge of the zigzag layer of the cycled particles. These experimental data provide the compositional and structural origins of the capacity decrease in the Li-ion battery.  相似文献   

10.
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   

11.
The low-heating solid-state method has been adopted to synthesize LiNi1/3Co1/3Mn1/3O2 materials. The final product, with homogeneous phase and smooth crystals indicated by XRD and SEM results, can be synthesized at 700 °C, much lower than the synthesis temperatures of co-precipitation method. The reaction process and microstructure of precursor has been investigated by IR spectrum. By comparative studies with the mixture of CH3COOLi and (Ni, Co, Mn)(C2O4), it is testified that the precursor is homogeneous, rather than a mixture. The decomposition process and the reaction energy have been studied to investigate the reaction mechanism of the precursor when heated at high temperature. The as-synthesized LiNi1/3Co1/3Mn1/3O2 exhibits excellent electrochemical properties, exhibiting initial specific capacity of 167 mAh g−1 with stable cyclic performance.  相似文献   

12.
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   

13.
Polypyrrole is successfully introduced to enhance the reaction stability and ionic conductivity of LiNi1/3Co1/3Mn1/3O2 material through an ultrasound dispersion method and applied as cathode materials for lithium-ion batteries. This polymer can significantly advance the electrochemical properties. Expectedly, the 8 wt.% LiNi1/3Co1/3Mn1/3O2/polypyrrole composite has lower mixing degree of Li+/Ni2+, higher c/a value, which delivers the first discharge capacity of 199.2 mAh g−1, which abate to 121.3 mAh g−1 in the 300th cycle at 0.2 C between 2.5 and 4.5 V. Even at 3 C, it continues to reveal a reversible capacity of 86.4 mAh g−1 after 100 cycles. All the consequences implied that the 8 wt.% LiNi1/3Co1/3Mn1/3O2/polypyrrole verified a minor charge transfer resistance and better Li+ diffusion ability, hence establishing preferable rate and cycling performance compared with the primordial LiNi1/3Co1/3Mn1/3O2.  相似文献   

14.
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   

15.
The gas generation associated with the use of the lithium bis(oxalate)borate—(LiBoB) based electrolyte at the elevated temperature were detected in the pouch cell (MCMB/LiNi1/3Co1/3Mn1/3O2 with 10% excess Li), which might prevent the LiBoB usage as a salt. However, the cell capacity retention was improved significantly, from 87 to 96% at elevated temperature, when using LiBoB as an electrolyte additive. The capacity fade during cycling is discussed using dQ/dE, area specific impedance, and frequency response analysis results. Most of the capacity loss in the cell is associated with the rise in the cell impedance. Moreover, results from the differential scanning calorimetry indicate that the thermal stability of the negative electrode with the solid electrolyte interface (SEI) formed by the reduction of the LiBoB additive was greatly improved compared with that obtained from the reduction of LiPF6-based electrolyte without additive. In this case, the onset temperature of the breakdown of the LiBoB-based SEI is 150 °C which is higher than that of the conventional electrolyte without additive. Furthermore, the total heat generated between 60 and 170 °C is reduced from 213 to 70 J g−1 when using LiBoB as electrolyte additive compared to the one without additive. In addition, the thermal stability of the charged LiNi1/3Co1/3Mn1/3O2 with 10% excess Li was not affected when using LiBoB as an electrolyte additive.  相似文献   

16.
Three kinds of surface modifications were carried out on LiNi1/2Mn3/2O4 thin-films to improve the charge and discharge characteristics of LiNi1/2Mn3/2O4 positive electrodes. Among them, Zr(OBu)4/poly(methyl methacrylate) (PMMA)-treated LiNi1/2Mn3/2O4 thin-film electrodes showed charge and discharge efficiency of 80–84% in the first cycle, which was much higher than that for an untreated LiNi1/2Mn3/2O4 thin-film electrode (73%). The values of the charge and discharge efficiency were still higher than that for an untreated electrode after the 30th cycle. The charge and discharge curves gave two plateaus at around 4.72 and 4.76 V, which were very similar to those for the untreated electrode. Ac impedance spectroscopy revealed that the surface film resistance should not increase by Zr(OBu)4/PMMA treatment. XPS measurements suggest that a composite layer should be formed on a LiNi1/2Mn3/2O4 thin-film electrode from PMMA and Zr(OBu)4-derived compounds introducing an electrolyte. This composite layer was lithium-ion conductive, and was sustainable enough to suppress subsequent decomposition of an electrolyte at potentials as high as 4.7 V.  相似文献   

17.
The particle surface of Li[Ni1/3Co1/3Mn1/3]O2 was modified by AlF3 as a new coating material to improve the electrochemical properties in the high cutoff voltage of 4.5 V. The AlF3-coated Li[Ni1/3Co1/3Mn1/3]O2 showed no difference in the bulk structure compared with the pristine one and the uniform AlF3 coating layers whose thickness is of about 10 nm covered Li[Ni1/3Co1/3Mn1/3]O2 particles, as confirmed by a transmission electron microscopy. The AlF3 coating on Li[Ni1/3Co1/3Mn1/3]O2 particles improved the overall electrochemical properties such as the cyclability, rate capability and thermal stability compared with those of the pristine Li[Ni1/3Co1/3Mn1/3]O2. Such enhancements were attributed to the presence of the stable AlF3 layer which acts as the interfacial stabilizer on the surface of Li[Ni1/3Co1/3Mn1/3]O2.  相似文献   

18.
A novel method to improve the cycling performance of LiCo1/3Ni1/3Mn1/3O2 in lithium-ion batteries by TiO2-coating with an in situ dipping and hydrolyzing method was presented in this work. The microstructure of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was characterized by XRD, SEM and TEM, and their electrochemical performances were evaluated by EIS and galvonostatic charge-discharge test. SEM and TEM images show that the TiO2 are pasted on the surface of the LiCo1/3Ni1/3Mn1/3O2 with nano-size. The XRD patterns indicate that the crystal structure of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 shows no obvious change compares with the bare material. The TiO2-coated LiCo1/3Ni1/3Mn1/3O2 possesses improved cycle performance and rate capability. The capacity retention of 1.0 wt.% TiO2-coated material is more than 99.0% after 12 cycles at 3.0 C while that of the bare sample is only 86.6%. The capacity of coated material at 5.0 C remains 66.0% of the capacity at 0.2 C, while that of the bare LiCo1/3Ni1/3Mn1/3O2 is only 31.5%.  相似文献   

19.
Surface modifications of electrode materials can improve the electrochemical and thermal properties of cathodes for use in lithium batteries. In this study, AlF3-coated LiCoO2 and AlF3-coated Li[Ni1/3Co1/3Mn1/3]O2 cathode materials are blended, as both have the same crystal structure and exhibit similar electrochemical properties. The composite electrodes exhibit high discharge capacities of 180-188 mAh g−1 in a voltage range of 3.0-4.5 V at room temperature. The capacity retention of the composite electrode is greater than 95% of the initial capacity after 50 cycles. The thermal stability of these composite electrodes is greatly improved because of the superior thermal stability of AlF3-coated Li[Ni1/3Co1/3Mn1/3]O2. The blended AlF3-coated LiCoO2 and AlF3-coated Li[Ni1/3Co1/3Mn1/3]O2 electrode shows two exothermic peaks, one at 227 °C from AlF3-coated LiCoO2 and another at 277 °C from AlF3-coated Li[Ni1/3Co1/3Mn1/3]O2, accompanied by significantly reduced exothermic heat generation.  相似文献   

20.
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   

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