ZnO-coated LiNi0.5Mn1.5O4 powders with excellent electrochemical cyclability and structural stability have been synthesized. The electrochemical performance and structural stability of ZnO-coated LiNi0.5Mn1.5O4 electrodes in the 5 V region at elevated temperature has been studied as function of the level of ZnO coating. The 1.5 wt% ZnO-coated LiNi0.5Mn1.5O4 electrode delivers an initial discharge capacity of 137 mAh g−1 with excellent cyclability at elevated temperature even at 55 °C. The reason for the excellent cycling performance of ZnO-coated LiNi0.5Mn1.5O4 electrode is largely attributed to ZnO playing an important role of HF getting in the electrolyte. 相似文献
Layered LiNi0.5Mn0.5O2 nanoparticles have been successfully prepared by the glycine-assisted combustion method under microwave irradiation. The
exothermic reaction can generate a large quantity of heat rapidly leading to the formation and crystallization of LiNi0.5Mn0.5O2. From the X-ray diffraction and scanning electronic microscopy results, the resulting powders have a well-developed layered
structure and average particle-size is about 80 nm. The chemical composition analysis and electrochemical characteristics
of the obtained LiNi0.5Mn0.5O2 nanoparticles as cathode material for rechargeable lithium-ion battery were also investigated. The improved electrochemical
performances of the layered LiNi0.5Mn0.5O2 nanoparticles might be ascribed to the nanostructure of the powders and the unique combustion synthesis under microwave irradiation. 相似文献
LiNi0.5Mn1.5O4 is regarded as a promising cathode material to increase the energy density of lithium‐ion batteries due to the high discharge voltage (ca. 4.7 V). However, the interface between the LiNi0.5Mn1.5O4 cathode and the electrolyte is a great concern because of the decomposition of the electrolyte on the cathode surface at high operational potentials. To build a stable and functional protecting layer of Li3PO4 on LiNi0.5Mn1.5O4 to avoid direct contact between the active materials and the electrolyte is the emphasis of this study. Li3PO4‐coated LiNi0.5Mn1.5O4 is prepared by a solid‐state reaction and noncoated LiNi0.5Mn1.5O4 is prepared by the same method as a control. The materials are fully characterized by XRD, FT‐IR, and high‐resolution TEM. TEM shows that the Li3PO4 layer (<6 nm) is successfully coated on the LiNi0.5Mn1.5O4 primary particles. XRD and FT‐IR reveal that the synthesized Li3PO4‐coated LiNi0.5Mn1.5O4 has a cubic spinel structure with a space group of Fd$\bar 3$ m, whereas noncoated LiNi0.5Mn1.5O4 shows a cubic spinel structure with a space group of P4332. The electrochemical performance of the prepared materials is characterized in half and full cells. Li3PO4‐coated LiNi0.5Mn1.5O4 shows dramatically enhanced cycling performance compared with noncoated LiNi0.5Mn1.5O4. 相似文献
Spinel LiNi0.5Mn1.5O4 cathode material is a promising candidate for next-generation rechargeable lithium-ion batteries. In this work, BiFeO3-coated LiNi0.5Mn1.5O4 materials were prepared via a wet chemical method and the structure, morphology, and electrochemical performance of the materials were studied. The coating of BiFeO3 has no significant impact on the crystal structure of LiNi0.5Mn1.5O4. All BiFeO3-coated LiNi0.5Mn1.5O4 materials exhibit cubic spinel structure with space group of Fd3m. Thin BiFeO3 layers were successfully coated on the surface of LiNi0.5Mn1.5O4 particles. The coating of 1.0 wt% BiFeO3 on the surface of LiNi0.5Mn1.5O4 exhibits a considerable enhancement in specific capacity, cyclic stability, and rate performance. The initial discharge capacity of 118.5 mAh g?1 is obtained for 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 with very high capacity retention of 89.11% at 0.1 C after 100 cycles. Meanwhile, 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 electrode shows excellent rate performance with discharge capacities of 117.5, 110.2, 85.8, and 74.8 mAh g?1 at 1, 2, 5, and 10 C, respectively, which is higher than that of LiNi0.5Mn1.5O4 (97.3, 90, 77.5, and 60.9 mAh g?1, respectively). The surface coating of BiFeO3 effectively decreases charge transfer resistance and inhibits side reactions between active materials and electrolyte and thus induces the improved electrochemical performance of LiNi0.5Mn1.5O4 materials. 相似文献
A submicron LiNi0.5Mn1.5O4 cathode was synthesized via the pyrolysis of polyacrylate salts as precursor polymerized by reaction of the metal salts with
acrylate acid. The structure and morphology of the resulting compound was characterized by powder X-ray diffraction (XRD)
and transmission electron microscopy (TEM). The results reveal that the prepared LiNi0.5Mn1.5O4 cathode material has a pure cubic spinel structure and submicron-sized morphology even if calcined at 900 °C and quenched to room temperature. The LiNi0.5Mn1.5O4 electrodes exhibited promising high-rate characteristics and delivered stable discharge capacity (90 mAh/g) with excellent
retention capacity at the current density of 50 mA/g between 3.5 and 4.9 V. The capacity of the LiNi0.5Mn1.5O4 electrodes remains stable even after 30 cycles at low or high current density. This polymer-pyrolysis method is simple and
particularly suitable for preparation of the spinel LiNi0.5Mn1.5O4 cathode material compared to the conventional synthesis techniques. 相似文献
LiNi0.5Mn1.5O4 cathode materials were successfully prepared by sol–gel method with two different Li sources. The effect of both lithium
acetate and lithium hydroxide on physical and electrochemical performances of LiNi0.5Mn1.5O4 was investigated by scanning electron microscopy, Fourier transform infrared, X-ray diffraction, and electrochemical method.
The structure of both samples is confirmed as typical cubic spinel with Fd3m space group, whichever lithium salt is adopted. The grain size of LiNi0.5Mn1.5O4 powder and its electrochemical behaviors are strongly affected by Li sources. For the samples prepared with lithium acetate,
more spinel nucleation should form during the precalcination process, which was stimulated by the heat released from the combustion
of extra organic acetate group. Therefore, the particle size of the obtained powder presents smaller average and wider distribution,
which facilitates the initial discharge capacity and deteriorates the cycling performance. More seriously, there exists cation
replacement of Li sites by transition metal elements, which causes channel block for Li ion transference and deteriorates
the rate capability. The compound obtained with lithium hydroxide exhibits better electrochemical responses in terms of both
cycling and rate properties due to higher crystallinity, moderate particle size, narrow size distribution and lower transition
cation substitute content. 相似文献
The effect of different membranes and aluminum current collectors on the initial coulombic efficiency of LiNi0.5Mn1.5O4/Li was investigated, and the cycling performance at different rates and temperatures and the storage performance at 60 °C for a week are discussed for LiNi0.5Mn1.5O4/Li. The results show that the lower initial coulombic efficiency is associated with the lower decomposition voltage of the commercial membrane and electrolyte, and the instability of aluminum current collector under the higher voltage. In addition, both versions of LiNi0.5Mn1.5O4 can deliver about 115 mA?h g?1 of initial discharge capacity at 1 C at 25 °C and 60 °C; however, it retains only 61.57 % of its initial capacity after the 130th cycles at 60 °C, which is much lower than the 94.46 % rate observed for LiNi0.5Mn1.5O4 at 25 °C, and the cycling performance of the material at 1 C is better than that at 0.5 C. Meanwhile, the initial discharge capacity at 0.1 C after storing at 60 °C is 119.3 mA?h g?1, which is only a little lower than 121.5 mA?h g?1 recorded before storing; moreover, the spinel structure and surface state of LiNi0.5Mn1.5O4 after storing at 60 °C has not been changed basically. These results indicate that the electrochemical stability of electrolyte is also related to the temperature. The serious capacity fading of LiNi0.5Mn1.5O4 at 60 °C is attributed to the severe oxidation decomposition and the thermal decomposition in the range of cut-off voltage of the materials, and then the decomposition products interact with active materials to form a solid interface phase, leading to the larger electrode polarization and irreversible capacity loss. Meanwhile, the worse cycling performance at 0.5 C than that at 1 C is attributed to the longer interaction time between the electrolyte and the active materials. However, the storage performance of LiNi0.5Mn1.5O4 corresponds to the thermal stability of electrolyte to a certain extent. 相似文献
High performance LiNi0.5Mn1.5O4 was prepared by a combinational annealing method. All samples were characterized by X-ray diffraction, infrared, and cell measurements. With increasing the annealing time at 600 °C, LiNi0.5Mn1.5O4 showed a decreased lattice parameter and an enhanced Ni-ordering. The electrochemical property of LiNi0.5Mn1.5O4 was optimized by controlling the annealing time. It was found that after annealing at 600 °C for 8 h, LiNi0.5Mn1.5O4 can discharge up to 138 mA h g−1 with a superior cycling performance at the rate of 5/7 C. High-rate test indicated that LiNi0.5Mn1.5O4 exhibited excellent electrochemical performance when charged and discharged at 1.2 C and 2.5 C, respectively. The findings reported in this work are expected to pave the way for the practical application of LiNi0.5Mn1.5O4. 相似文献
Three samples, LiNi0.5Mn1.5O4, LiNi0.4Mn1.4Co0.2O4, and LiNi0.4Mn1.4Cr0.15Co0.05O4, were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi0.4Mn1.4Cr0.15Co0.05O4 exhibits an improved performance compared with the Co-doped sample LiNi0.4Mn1.4Co0.2O4 and the undoped sample LiNi0.5Mn1.5O4, especially at elevated temperature. At 25 °C, the discharge capacity of LiNi0.4Mn1.4Cr0.15Co0.05O4 is 130 mAh g?1 at 0.1 C and 103 mAh g?1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g?1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi0.4Mn1.4Co0.2O4 and LiNi0.475Mn1.475Co0.05O4, the co-doped sample LiNi0.4Mn1.4Cr0.15Co0.05O4, with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi0.5Mn1.5O4 by the co-doping was discussed. 相似文献
The rate capability and cyclic performance of the LiNi0.5Mn1.5O4 under high current density have been significantly improved by doping a small amount of ruthenium (Ru). Specifically, Li1.1Ni0.35Ru0.05Mn1.5O4 and LiNi0.4Ru0.05Mn1.5O4 synthesized by solid state reaction can respectively deliver a discharge capacity of 108 and 117 mAh g?1 at 10 C rate between 3 and 5 V. At 10 C charge/discharge rate, Li1.1Ni0.35Ru0.05Mn1.5O4 and LiNi0.4Ru0.05Mn1.5O4 can respectively maintain 91% and 84% of their initial capacity after 500 cycles, demonstrating that Ru-doping could be a way to enhance the electrochemical performance of spinel LiNi0.5Mn1.5O4. 相似文献
In this paper, the LiNi0.5Mn1.5O4 cathode materials of lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining process. The use of a spray-drying process to form particles, followed by a calcination treatment at the optimized temperature of 750 °C to produce spherical LiNi0.5Mn1.5O4 particles with a cubic crystal structure, a specific surface area of 60.1 m2 g?1, a tap density of 1.15 g mL?1, and a specific capacity of 132.9 mAh g?1 at 0.1 C. The carbon nanofragment (CNF) additives, introduced into the spheres during the co-precipitation spray-drying period, greatly enhance the rate performance and cycling stability of LiNi0.5Mn1.5O4. The sample with 1.0 wt.% CNF calcined at 750 °C exhibits a maximum capacity of 131.7 mAh g?1 at 0.5 C and a capacity retention of 98.9% after 100 cycles. In addition, compared to the LiNi0.5Mn1.5O4 material without CNF, the LiNi0.5Mn1.5O4 with CNF demonstrates a high-rate capacity retention that increases from 69.1% to 95.2% after 100 cycles at 10 C, indicating an excellent rate capability. The usage of CNF and the synthetic method provide a promising choice for the synthesis of a stabilized LiNi0.5Mn1.5O4 cathode material.
Graphical Abstract Micro/nanostructured LiNi0.5Mn0.5O4 cathode materials with enhanced electrochemical performances for high voltage lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining routine and using carbon nanofragments (CNFs) as additive.
The ternary-layered oxide (LiNixCoyMnzO2) has become the most promising cathode material for lithium-ion batteries due to the advantages of higher discharge platform, better conductivity, and higher theoretical capacity. The [NixCoyMnz](OH)2 with different ratios of nickel, cobalt, and manganese (NCM) was prepared by solvothermal method, and then ternary cathode material LiNixCoyMnzO2 was obtained by mixing lithium and calcining. In this paper, ternary cathode materials with different ratios of NCM were prepared by the solvothermal method. The structure and morphology of the materials were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The effects of the ratio on the electrochemical properties of the materials were investigated by constant current charge and discharge test and electrochemical impedance spectroscopy test. The synthesized lithium-nickel-cobalt-manganese oxide belongs to the hexagonal system and has an α-NaFeO2 layered structure, which is an R-3m space group. The NCM ternary cathode materials with different morphologies were obtained by changing the ratio of NCM. The sample with NCM ratio of 5:3:2 has a unique sheet-like spherical shape and has the best rate performance. 相似文献
Cathode materials LiNi0.5Mn1.5O4 and LiNi0.5 ? x/2LaxMn1.5 ? x/2O4 (x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNi0.5Mn1.5O4 material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L?1 lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L?1 LiPF6-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNi0.45La0.1Mn1.45O4/Li cell performed better than LiNi0.5Mn1.5O4/Li cell at cycle performance, median voltage, and efficiency. 相似文献
LiNi0.5Mn1.5O4 powders were prepared through polymer-pyrolysis method. XRD and TEM analysis indicated that the pure spinel structure was
formed at around 450 °C due to the very homogeneous intermixing of cations at the atomic scale in the starting precursor in
this method, while the well-defined octahedral crystals appeared at a relatively high calcination temperature of 900 °C with
a uniform particle size of about 100 nm. When cycled between 3.5 and 4.9 V at a current density of 50 mA/g, the as prepared
LiNi0.5Mn1.5O4 delivered an initial discharge capacity of 112.9 mAh/g and demonstrated an excellent cyclability with 97.3% capacity retentive
after 50 cycles. 相似文献
We report a method to eliminate the irreversible capacity of 0.4Li_2MnO_3·0.6LiNi_(0.5)Mn_(0.5)O_2(Li_(1.17)Ni_(0.25)Mn_(0.583)O_2) by decreasing lithium content to yield integrated layered-spinel structures.XRD patterns,High-resolution TEM image and electrochemical cycling of the materials in lithium cells revealed features consistent with the presence of spinel phase within the materials.When discharged to about 2.8 V,the spinel phase of LiM_2O_4(M=Ni,Mn) can transform to rock-salt phase of Li_2M_2O_4(M=Ni,Mn) during which the tetravalent manganese ions are reduced to an oxidation state of 3.0.So the spinel phase can act as a host to insert back the extracted lithium ions(from the layered matrix) that could not embed back into the layered lattice to eliminate the irreversible capacity loss and increase the discharge capacity.Their electrochemical properties at room temperature showed a high capacity(about 275 mAh g~(-1) at 0.1 C) and exhibited good cycling performance. 相似文献