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1.
AlF3-coating is attempted to improve the performance of LiNi0.5Mn1.5O4 cathode materials for Li-ion batteries. The prepared powders are characterized by scanning electron microscope, powder X-ray diffraction, charge/discharge, and impedance. The coated LiNi0.5Mn1.5O4 samples show higher discharge capacity, better rate capability, and higher capacity retention than the uncoated samples. Among the coated samples, 1.0 mol% AlF3-coated sample shows highest capacity after charge–discharged at 30 mA/g for 3 cycles, but 4.0 mol% coated sample exhibits the highest capacity and cycling stability when cycled at high rate of 150 and 300 mA/g. The 40th cycle discharge capacity at 300 mA/g current still remains 114.8 mAh/g for 4.0 mol% AlF3-coated LiNi0.5Mn1.5O4, while only 84.3 mAh/g for the uncoated sample.  相似文献   

2.
Spinel LiNi0.5Mn1.5O4 cathode materials with different lithium excess amount (0, 2%, 6%, 10%) were synthesized by a facile solid-state method. The effect of lithium excess amount on the microstructure, morphology, and electrochemical properties of LiNi0.5Mn1.5O4 materials was systematically investigated. The results show that the lithium excess amount does not change the particle morphology and size obviously; thus, the electrochemical properties of LiNi0.5Mn1.5O4 are mainly determined by structural characteristics. With the increase of lithium excess amount, the cation disordering degree (Mn3+ content) and phase purity first increase and then decrease, while the cation mixing extent has the opposite trend. Among them, the LiNi0.5Mn1.5O4 material with 6% lithium excess amount exhibits higher disordering degree and lower impurity content and cation mixing extent, thus leading to the optimum electrochemical properties, with discharge capacities of 125.0, 126.1, 124.2, and 118.9 mAh/g at 0.2-, 1-, 5-, and 10-C rates and capacity retention rate of 96.49% after 100 cycles at 1-C rate.  相似文献   

3.
The application of LiNi0.5Mn0.5O2 as a high-voltage cathode material for lithium-ion batteries is limited by its poor cycle performance. Therefore, we attempt to improve the cyclability of this material at high voltage by using a doping method and propose a detailed mechanism for the effect of the doping amount on the structure and electrochemical performance. In this work, LiNi0.5-zAlzMn0.5O2 (z?=?0.00, 0.03, 0.05, 0.08) electrodes were prepared via a simple co-precipitation followed by a solid-state method. X-ray diffraction and Rietveld refinement revealed that a suitable amount of Al doping into LiNi0.5Mn0.5O2 can stabilize the structure and lower the Li/Ni cation mixing, but an excessive doping would lead to Al-ion doping in the lithium layer, which can block lithium diffusion and affect the rate property. Specifically, LiNi0.47Al0.03Mn0.5O2 shows a much higher capacity retention compared to LiNi0.5Mn0.5O2 both at 25 °C (78.5 vs. 68.8% at 0.2 C) and 60 °C (70.8 vs. 69.0% at 0.2 C). Moreover, Al-doping can retard the voltage drop during the discharge-charge state, with the discharge voltage for LiNi0.5-zAlzMn0.5O2 (z?=?0.00, 0.03, 0.05, 0.08) decreasing slowly with increasing Al content.  相似文献   

4.
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   

5.
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   

6.
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   

7.
In this work, Li2ZrF6, a lithium salt additive, is reported to improve the interface stability of LiNi0.5Mn1.5O4 (LNMO)/electrolyte interface under high voltage (4.9 V vs Li/Li+). Li2ZrF6 is an effective additive to serve as an in situ surface coating material for high-voltage LNMO half cells. A protective SEI layer is formed on the electrode surface due to the involvement of Li2ZrF6 during the formation of SEI layer. Charge/discharge tests show that 0.15 mol L?1 Li2ZrF6 is the optimal concentration for the LiNi0.5Mn1.5O4 electrode and it can improve the cycling performance and rate property of LNMO/Li half cells. The results obtained by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) demonstrate that Li2ZrF6 can facilitate the formation of a thin, uniform, and stable solid electrolyte interface (SEI) layer. This layer inhibits the oxidation decomposition of the electrolyte and suppresses the dissolution of the cathode materials, resulting in improved electrochemical performances.  相似文献   

8.
High-voltage spinel LiNi0.5Mn1.5O4 nano/microspheres with adjustable hollow structures have been fabricated based on the Kirkendall effect. The main characteristic is that the wall thickness of the hollow structure as well as the cavity size of the hollow structure can be adjusted by the different ratio of mixed precipitation agents. Especially, the diagrammatic sketch for the formation process of various LiNi0.5Mn1.5O4 materials with adjustable hollow structures is discussed. Besides, the results of electrochemical performance test show that LiNi0.5Mn1.5O4 obtained from 10:1 Na2CO3/NaOH (in mole) ratio is worth looking forward to, owing to its special hierarchical nano/microsphere and moderate hollow structures.  相似文献   

9.
LiNi0.5Mn1.5O4 cathode material was prepared by electrospinning using lithium hydroxide, manganese acetate, nickel acetate, acetic acid, ethanol, and poly(vinyl pyrrolidone) as raw materials. The effect of calcination temperature on the structure, morphology, and electrochemical properties was investigated. XRD results indicate that the LiNi0.5Mn1.5O4 composite is well crystallized as a spinel structure at calcination temperature of 650 °C for 3 h. SEM results reveal that this composite has a nanofiber shape with average size of about 300–500 nm. Electrochemical performance tests reveal that this composite shows the initial discharge capacity of 127.8 and 105 mAhg?1 at 0.1 and 3 C rates, respectively, and exhibits good cycling performance.  相似文献   

10.
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   

11.
The LaF3-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 nanoparticles were synthesized via co-precipitation method followed by simple chemical deposition process. The crystal structure, particle morphology, and electrochemical properties of the bare and coated materials were studied by XRD, SEM, TEM, charge–discharge tests. The results showed that the surface coating on Li[Li0.2Mn0.54Ni0.13Co0.13]O2 nanoparticles were amorphous LaF3 layer with a thickness of about 10–30 nm. After the surface modification with LaF3 films, the coating layer served as a protective layer to suppress the side reaction between the positive electrode and electrolyte, and the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 oxide demonstrated the improved electrochemical properties. The LaF3-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrode delivered the capacities of 270.5, 247.9, 197.1, 170.0, 142.7, and 109.5 mAh g?1 at current rates of 0.1, 0.2, 0.5, 1, 2, and 5 C rate, respectively. Besides, the capacity retention was increased from 85.1 to 94.8 % after 100 cycles at 0.5 C rate. It implied surface modification with LaF3 played an important role to improve the cyclic stability and rate capacity of the Li-rich nickel manganese oxides.  相似文献   

12.
The thermodynamic stability is a very important quantity for the electrode materials, because it is not only related to the electrochemical performances of the materials but also the safety issue of the cells. To evaluate the thermodynamic stability of Li x Ni0.5Mn1.5O4 (x = 0, 1), the formation enthalpies from elemental phases and oxides were obtained. The values for LiNi0.5Mn1.5O4 were calculated to be ?1341.10 and ?141.84 kJ mol?1, while those for Ni0.5Mn1.5O4 were ?949.11 and ?49.21 kJ mol?1. These values are much more negative than those of LiCoO2 and LiNiO2 compounds, indicating that the thermodynamic stability of Li x Ni0.5Mn1.5O4 is better than the two classic compounds. To clarify the microscopic origin, the density of states, magnetic moments, and bond orders were systematically investigated. The results showed that the excellent thermodynamic stability of LiNi0.5Mn1.5O4 is attributed to the absence of Jahn-Teller distortions, strong electrostatic interactions of Li–O ionic bond, and strong Ni–O/Mn–O ionic-covalent mixing bonds. After lithium extraction, the disappearance of the pure Li–O bonds leads to an increase of formation enthalpy, indicating a decreasing thermodynamic stability for Ni0.5Mn1.5O4 with respect to LiNi0.5Mn1.5O4.  相似文献   

13.
Layered lithium-enriched nickel manganese oxides Li1.2Ni0.2Mn0.6O2 have been synthesized and coated by fast ionic conductor Li3VO4 with varying amounts (1, 3, and 5 wt%) in this paper. The effect of Li3VO4 on the physical and electrochemical properties of Li1.2Ni0.2Mn0.6O2 has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), discharge, cyclic performance, rate capability, and electrochemical impedance spectroscopy (EIS). The discharge capacity and coulomb efficiency of Li1.2Ni0.2Mn0.6O2 in the first cycle have been improved after Li3VO4 coating. And, the 3 wt% Li3VO4-coated Li1.2Ni0.2Mn0.6O2 shows the best discharge capacity (246.8 mAh g?1), capacity retention (97.3 % for 50 cycles), and rate capability (90.4 mAh g?1 at 10 C). Electrochemical impedance spectroscopy (EIS) results show that the R ct of Li1.2Ni0.2Mn0.6O2 electrode decreases after Li3VO4 coating, which is due to high lithium ion diffusion coefficient of Li3VO4, is responsible for superior rate capability.  相似文献   

14.
Yttrium fluoride YF3 layer with different coating contents is successfully covered on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 via a common wet chemical approach. The XRD, SEM, TEM, and charge-discharge tests are applied to investigate the influence of YF3 layer on the micro-structural, morphology, and electrochemical properties of Li1.2Mn0.54Ni0.13Co0.13O2. And the electrochemical test results demonstrate that the YF3-coated LMNCO samples exhibit the improved electrochemical properties. The 2wt.%YF3-coated LMNCO delivers a discharge capacity of 116.6 mAh g?1 at 5 C rate, much larger than that (95.6 mAh g?1) of the pristine one. Besides, the electrochemical impedance spectroscopy (EIS) and cyclic voltammetric results indicate that the YF3 coating layer can promote the optimization formation of SEI film and reversibility of the electrochemical redox.  相似文献   

15.
Layered LiNi0.5Mn0.5O2 has been successfully synthesized via urea hydrolysis coprecipitation method. Well-crystallized LiNi0.5Mn0.5O2 was obtained after calcinations of coprecipitation precursors and lithium salts at 450 °C for 3 h and following 900 °C for 10 h in air. Both the precursors and LiNi0.5Mn0.5O2 powders show an agglomerated secondary structure with crystalline particles inside. The quasi-spherical morphology of the precursors was maintained during the calcinations. The first charge and discharge capacities of as-prepared LiNi0.5Mn0.5O2 were 200 and 165mAh/g respectively. The discharge capacity of about 160mAh/g was retained after 10cycles for as-prepared samples.  相似文献   

16.
This paper addresses the synthesis structural and electrochemical properties of LiFe0.5Mn0.5PO4 electrode materials for Li-ion batteries. The charge–discharge reaction of Li/LiPF6-EC–DEC/LiFe0.5Mn0.5PO4 cell carried out at the 1-C rate shows a capacity retention of 128 mAh/g. The local structure of the delithiated Li x Fe0.5Mn0.5PO4 phases have been studied by Fourier transform infrared spectroscopy and magnetometry. Spectral features indicate that the structure of the delithiated phase remains in the orthorhombic system. The compositional dependence of the magnetic moment is found to be in quantitative agreement with the theoretical value predicted for oxidation of M 2+ ions in the high spin state. Paper presented at the 11th Euro-Conference on Science and Technology of Ionics, Batz-sur-Mer, France, 9–15 Sept. 2007  相似文献   

17.
In this wok, a uniform layer of La2O3 is coated on the surface of LiNi0.91Co0.06Mn0.03O2 Ni-rich cathode material by using a wet coating process. The XPS and EDX analysis confirms the presence of La2O3 coating on the surface of NCM. The coated samples deliver the superior electrochemical performance, 0.2 wt % La2O3 (LaO-0.2) NCM exhibits discharge capacity of 202.7 mAh g−1 in 1st cycle and delivered the cycle stability of 87.2% after 100 cycles. Besides, the enhanced capacity retention, LaO-0.2 has delivered very high discharge capacity of 80.3 mAh g−1 at very high C-rate of 5C while the pristine sample shows very low discharge capacity (33.4 mAh g−1). CV results shows the significant suppression in the intensity of H2–H3 which indicates the superior electrochemical stability of LaO-0.2 NCM. Thus, we can confirm that La2O3 coating is promising technique to achieve superior electrochemical performance in the long term cycling process.  相似文献   

18.
A precursor of TiO2–LiCo1/3Ni1/3Mn1/3O2 was prepared by electrostatic self-assembly method. The final product was obtained by heating the precursor at 400–450 °C for 4–6 h in air. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical tests were used to examine the structural, morphology, elementary valence, and electrochemical characteristics. XRD indicated that the TiO2-coated material can be indexed by α-NaFeO2 layered structure, which belongs to hexagonal-type space group R3m. XPS results confirmed the existence of TiO2 compound on the surface of the coated sample. The SEM image showed that the material had spherically porous morphology with the uniform size about 6 μm. The initial charge–discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 material was 168.8/160.0 mAh/g. After 60 cycles, the discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 sample was 147.0 mAh/g, and the coulombic efficiency was 94.0%. Compared with the uncoated sample, the electrochemical performance of TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was improved.  相似文献   

19.
Zhenye Zhu  Fangyuan Cai  Jie Yu 《Ionics》2016,22(8):1353-1359
Li-rich layered-layered-Spinel structure spherical Li1.3Mn4/6Ni1/6Co1/6O2.40 particles was successfully prepared and coated with a uniform layer by a two-step co-precipitation method and evaluated in lithium cells. The structures and electrochemical properties of pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 and AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 were characterized. When the coating amount was 2 wt%, the cathode showed the best cycling performance and rate capability compared to others. The AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 Li-ion cell cathode had a capacity retention of 90.07 % after 50 cycles at 0.5 C over 2.0–4.8 V, while the pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 exhibited capacity retention of only 80.73 %. Moreover, the rate capability and cyclic performance also improved. Electrochemical impedance spectroscopy testing revealed that the improved electrochemical performance might attribute to the AlF3 coating layer which can suppress the increase of impedance during the charging and discharging process by preventing direct contact between the highly delithiated active material and electrolyte.  相似文献   

20.
Yan-Rong Zhu  Ting-Feng Yi 《Ionics》2016,22(10):1759-1774
High-voltage spinel LiNi0.5Mn1.5O4 has been considered one of the most promising cathode materials for lithium-ion power batteries used in electrical vehicles (EVs) or hybrid electrical vehicles (HEVs) because the high voltage plateau at around 4.7 V makes its energy density (658 Wh kg?1) 30 and 25 % higher than that of conventional pristine spinel LiMn2O4 (440 Wh kg?1) or olivine LiFePO4 (500 Wh kg?1) materials, respectively. Unfortunately, LiNi0.5Mn1.5O4-based batteries with LiPF6-based carbonate electrolytes always suffer from severe capacity deterioration and poor thermostability because of the oxidization of organic carbonate solvents and decomposition of LiPF6, especially at elevated temperatures and water-containing environment. The major goal of this review is to highlight the recent advancements in the development of advanced electrolytes for improving the cycling stability and rate capacity of LiNi0.5Mn1.5O4-based batteries. Finally, an insight into the future research and further development of advanced electrolytes for LiNi0.5Mn1.5O4-based batteries is discussed.  相似文献   

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