Synthesis and Electrochemical Performance of Nickel-Rich Layered-Structure LiNi0.65Co0.08Mn0.27O2Cathode Materials Comprising Particles with Ni and Mn Full Concentration Gradients (original) (raw)
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Journal of The Electrochemical Society, 2016
Carbon-coated LiMnBO 3 /C is synthesized by a solgel method using polyethylene glycol 6000 (PEG-6000) as carbon source. The influences of different sintering temperatures on the crystal structure, morphology, and electrochemical performance of LiMnBO 3 /C composites are investigated. XRD results indicate that the samples consist of the monoclinic phase LiMnBO 3 (m-LiMnBO 3) and the hexagonal phase LiMnBO 3 (h-LiMnBO 3), and the amount of m-LiMnBO 3 is reduced and the h-LiMnBO 3 is increased with the increasing sintering temperature. The particle size of the samples is about 500 nm, and the surface of the particles is coated with a thick amorphous carbon layer. The LiMnBO 3 /C synthesized at 750°C exhibits the initial discharge capacities of 213.4, 170.8, and 109.7 mAh g −1 at 0.025, 0.05, and 0.5 C rates, respectively, and shows better cycling performance than that of bare LiMnBO 3. The enhanced electrochemical performance might be largely attributed to the uniformly coated carbon layers from decomposition of the PEG-6000.
Fabrication of high power LiNi0.5Mn1.5O4 battery cathodes by nanostructuring of electrode materials
Using nanoparticles, instead of microparticles, as active electrode materials in lithium ion batteries could provide a solution to slow charging rates due to long ion diffusion pathways in conventional bulk materials. In this work, we present a new strategy for the synthesis of high purity lithium nickel manganese oxide (LiNi0.5Mn1.5O4) nanoparticles as a high-voltage cathode. A sonochemical reaction is used to synthesize nickel hydroxide and manganese dioxide nanoparticles followed by a solid-state reaction with lithium hydroxide. The product shows a single spinel phase and uniform spherical nano-particles under the appropriate calcination conditions. The LiNi0.5Mn1.5O4 exhibits a high voltage plateau at about 4.7–4.9 V in the charge/discharge process and delivers a discharge capacity of more than 140 mA h g−1 and excellent cycling performance with 99% capacity retention after 70 cycles. The synthesized nano-particles show improved electrochemical performance at high rates. This electrode delivers a power density as high as 26.1 kW kg−1 at a discharge rate of 40 C. This power performance is about one order of magnitude higher than traditional lithium ion batteries. These findings may lead to a new generation of high power lithium ion batteries that can be recharged in minutes instead of hours.
LiFe0.5Mn0.5PO4/C prepared using a novel colloidal route as a cathode material for lithium batteries
Journal of Alloys and Compounds, 2018
A new colloidal route for the preparation of LiFe 0.5 Mn 0.5 PO 4 /C nanocomposite cathode material for lithium batteries is revealed. The method uses lithium dihydrogen phosphate (LiH 2 PO 4), ferrous chloride (FeCl 2) and manganese chloride(MnCl 2) in stoichiometric amounts with Nmethylimidazole (NMI) as the solvent and carbon source.The coating process is performed at 650 o C for 3 h under vacuum. Elemental analysis shows a carbon content of 3.71 wt.%, rendering the material to exhibit excellent electronic conductivity (9.29 x 10-2 S cm-1 at room temperature) and a significant increase in rate capability. Scanning electron and high-resolution transmission electron microscopy (SEM/HRTEM) images exhibited particles of uniform size (around 40-60 nm) that are covered by a 3-6 nm thick carbon layer. At a C/20 discharge rate and between 2.2 and 4.2 V vs. Li + /Li, the cell delivers a high capacity (140 mAh g −1) at the first cycle. The electrode stability was studied at C/10 rate, with only a small decrease (3.9 %) of discharge capacity over 100 cycles, which suggests that the new synthesis method for carbon-coated LiFe 0.5 Mn 0.5 PO 4 /C material is very promising.
Journal of Power Sources, 2019
The targeted optimization of Li-ion batteries (LIBs) requires a fundamental understanding of the wide variety of interdependencies between electrode design and electrochemical performance. In the present study, the effects of thickness and porosity on the electrochemical performance and Li-ion insertion kinetics of LiNi 0.6 Co 0.2 Mn 0.2 O 2-based (NCM-622) cathodes are investigated. Cathodes of different thickness and porosity are prepared and analyzed regarding their rate capability. The polarization behavior is investigated using electrochemical impedance spectroscopy. A simple mathematical model is employed to estimate the impact of Li-ion diffusion limitations in the electrolyte. The results are considered at both, the materials and the full-cell level. The design parameters are found to have distinct impact on the electrolyte, contact and charge transfer resistance as well as the Li-ion diffusion limitations in the electrolyte, significantly influencing the rate capability. The results attest an inherent tradeoff between energy and power density. The insights of this study can be used straightforward for the optimization of gravimetric and volumetric energy density of LIBs depending on the desired application.
Electrochimica Acta, 2013
Li[Li 0.2 Mn 0.56 Ni 0.16 Co 0.08 ]O 2 cathode materials with well-formed layered structure are synthesized by sol-gel process with different metal sources. Two normal metal salts (acetate and nitrate) are performed as the metal sources, and the effect of particle morphology on the electrochemical performance of the Li-rich layered oxide is investigated to show the importance of the choice of metal sources. Porosity with high specific surface area of 10.09 m 2 g −1 is only observed for the oxide powder synthesized with nitrate. Simultaneously, high discharge capacity of 247.8 mAh g −1 and 135.5 mAh g −1 are obtained at current densities of 200 mA g −1 and 2000 mA g −1 , respectively. In addition, the results of electrochemical impedance spectroscopy (EIS) indicate that such porous morphology with good particle contact can efficiently reduce the impedance of the oxide electrode.
Nanocrystalline LiNi0.4Mn0.4Co0.2O2 cathode for lithium-ion batteries
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
h i g h l i g h t s • Layered LiNi 0.4 Mn 0.4 Co 0.2 O 2 materials were synthesized with and without different chelating agents. • Oxalic acid-assisted LiNi 0.4 Mn 0.4 Co 0.2 O 2 powders exhibit better developed diffraction fringes. • The magnetic moments carried by Ni 2+ and Mn 4+ are 2.83 and 3.87 B , respectively. • Oxalic acid-assisted LiNi 0.4 Mn 0.4 Co 0.2 O 2 shows better electrochemical performance. g r a p h i c a l a b s t r a c t XRD patterns of LiNi 0.4 Mn 0.4 Co 0.2 O 2 nanoparticles.
Australian Journal of Chemistry, 2013
Nickel-doped lithium manganate spinels are a potential material for future energy storage owing to high cell potential and low price. Phase-pure spinels are difficult to prepare by conventional solid-state synthesis methods owing to loss of oxygen from the crystal lattice at high temperature (,8008C). Loss of oxygen causes Jahn-Teller distortion and Mn 4þ is converted into Mn 3þ , which results in undesired double-plateau discharge and reduction in capacity and stability of the material. In this study, nanocrystalline phase-pure LiNi 0.5 Mn 1.5 O 4 was prepared by co-precipitation with cyclohexylamine followed by calcination at a low temperature of 5008C. X-ray diffraction studies confirmed that a highly crystalline face-centred cubic product is formed with F-d3m space group. Scanning electron microscopy and transmission electron microscope studies confirmed that the particles are in the nano range with a porous structure. The as-prepared LiNi 0.5 Mn 1.5 O 4 showed a high initial specific capacity (up to 130 mA h g À1 ) and retained up to 120 mA h g À1 up to 50 cycles. The material has high conductivity and remains stable up to a 20-C discharge rate.
The layered lithium-metal oxides are promising cathode materials for Li-ion batteries. Nevertheless, their widespread applications have been limited by the high cost, complex process, and poor stability resulting from the Ni 2+ /Li + mixing. Hence, we have developed a facile one-spot method combining glucose and urea to form a deep eutectic solvent, which could lead to the homogeneous distribution and uniform mixing of transition-metal ions at the atomic level. LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) polyhedron with high homogeneity could be obtained through in situ chelating Ni 2+ , Co 3+ , and Mn 4+ by the amid groups. The prepared material exhibits a relatively high initial electrochemical property, which is due to the unique single-crystal hierarchical porous nano/microstructure, the polyhedron with exposed active surfaces, and the negligible Ni 2+ /Li + mixing level. This one-spot approach could be expanded to manufacture other hybrid transition-metal-based cathode materials for batteries.
ACS Applied Materials & Interfaces, 2016
A concentration-gradient Ni-rich LiNi0.76Co0.1Mn0.14O2 layered oxide cathode has been developed by firing a core/double-shell [Ni0.9Co0.1]0.4[Ni0.7Co0.1Mn0.2]0.5[Ni0.5Co0.1Mn0.4]0.1(OH)2 hydroxide precursor with LiOH•H2O, where the Ni-rich interior (core) delivers high capacity and the Mn-rich exterior (shells) provides a protection layer to improve the cyclability and thermal stability for the Ni-rich oxide cathodes. The content of nickel and manganese, respectively, decreases and increases gradually from the center to the surface of each gradient sample particle, offering a high capacity with enhanced surface/structural stability and cyclability. The obtained concentration-gradient oxide cathode exhibits high energy density with long cycle life in both half-and full-cells. With high-loading electrode half-cells, the CG sample delivers 3.3 mA h cm-2 with 99% retention after 100 cycles. The material morphology, phase, and gradient structure are also maintained after cycling. The pouch-type full cells fabricated with a graphite anode delivers high capacity with 89% capacity retention after 500 cycles at C/3 rate.
LiNi0.5Mn0.3Co0.2O2/Au nanocomposite thin film cathode with enhanced electrochemical properties
Nano Energy, 2018
Li(Ni x Mn y Co 1−x−y)O 2 (NMC) is considered as one of the most promising cathode materials for Li-ion batteries. Highly textured LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) thin films with well dispersed Au nanoparticles (~5 nm in average diameter) were deposited by pulsed laser deposition. Microstructure studies reveal the epitaxial nature of the Au nanoparticles and NMC matrix, and their lattice matching relationships. The Au nanoparticles are uniformly distributed and form faceted interfaces with NMC matrix. NMC with 2 at.% Au shows the highest volumetric capacity, best initial columbic efficiency, highest cycling performance, best rate capability and highest capacity retention among all the samples, due to alteration of chemical environment of transition metal while keeping high crystallinity. Moreover, the electrochemical impedance spectroscopy shows that the incorporation of the Au nanoparticles also reduces charge transfer resistance compared to the pure NMC. The results suggest that appropriate Au 2 nanoparticle incorporation enhances the volumetric capacity and promotes the charge transfer process, and thus could lead to enhanced battery performance.