Improved capacity and stability of integrated Li and Mn rich layered-spinel Li 1.17 Ni 0.25 Mn 1.08 O 3 cathodes for Li-ion batteries (original) (raw)
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Materials Science and Engineering: B, 2016
This work continues our research on integrated "layered-spinel" high-capacity cathode material Li[Ni 1/3 Mn 2/3 ]O 2 [30]. This material operated at potentials >4.6 V and demonstrated an advantageous cycling stability compared to high-voltage spinel LiNi 0.5 Mn 1.5 O 4. In the present study, the Li[Ni 1/3 Mn 2/3 ]O 2 material was synthesized by a hydrothermal precipitation. The Rietveld analysis of XRD patterns indicated the presence of two layered structure phases: a monoclinic Li 2 MnO 3 (about 58%) and a rhombohedral LiNiO 2 (24%), along with spinel LiNi 0.5 Mn 1.5 O 4 (17%) and rock salt Li 0.2 Mn 0.2 Ni 0.5 O (1%) phases. We demonstrate an interesting phenomenon of this electrode activation upon cycling from 100 to 220 mAh g −1 in the potential range of 2.3-4.9 V and stabilization followed by lowering the capacity to 89.5% of the maximal value after 100 cycles. It is suggested that the high capacity resulted from the activation of Li[Li 1/3 Mn 2/3 ]O 2 and participation of spinel component upon cycling to potential ≥4.5 V.
Journal of The Electrochemical Society
Layered Li and Mn rich cathode materials of the xLi[Li1/3Mn2/3]O-2 center dot(1-x)LiMn1/3Ni1/3Co1/3O2 (x = 0.2, 0.4, 0.6) were synthesized by a self-combustion method, characterized by XRD, SEM, HRTEM and Raman spectroscopy and studied as positive electrode materials for Li-ion batteries. The cathode material with x = 0.6 exhibits an initial high discharge specific capacity of 270 mAh g(-1) at C/10 rate in galvanostatic charge-discharge cycling, which decreases to 220 mAh g(-1) after 50 cycles. It also exhibits a high rate capability as compared to other composites. Structural studies using the electron diffraction technique with TEM and spectral studies by Raman spectroscopy indicate continuous structural changes upon cycling that include formation of a spinel phase. The electrochemical impedance spectra recorded at various potentials present evidence of a substantial increase in the charge-transfer resistance at potentials higher than 4.4 V during charge and also at potentials low...
High-Capacity Layered-Spinel Cathodes for Li-Ion Batteries
ChemSusChem, 2016
Li and Mn-rich layered oxides with the general structure x Li2 MnO3 ⋅(1-x) LiMO2 (M=Ni, Mn, Co) are promising cathode materials for Li-ion batteries because of their high specific capacity, which may be greater than 250 mA h g(-1) . However, these materials suffer from high first-cycle irreversible capacity, gradual capacity fading, limited rate capability and discharge voltage decay upon cycling, which prevent their commercialization. The decrease in average discharge voltage is a major issue, which is ascribed to a structural layered-to-spinel transformation upon cycling of these oxide cathodes in wide potential ranges with an upper limit higher than 4.5 V and a lower limit below 3 V versus Li. By using four elements systems (Li, Mn, Ni, O) with appropriate stoichiometry, it is possible to prepare high capacity composite cathode materials that contain LiMn1.5 Ni0.5 O4 and Lix Mny Niz O2 components. The Li and Mn-rich layered-spinel cathode materials studied herein exhibit a high s...
Layered cathode materials Rate capability and cycle life a b s t r a c t The structure of the layered Li(Ni x Mn y Co 1ÀxÀy)O 2 in different amounts of x and y ranging between 0.2 and 0.6, have been synthesized and investigated by powder X-ray diffraction and electron microscopy techniques. In the current work spray pyrolysis was used to obtain spherical fine-sized morphology followed by heat treatment to obtain better elec-trochemical activity. The precursor powders were prepared using aqueous solution via spray pyrolysis. Synthesized samples were then heat treated at 850 C. X-Ray Diffraction patterns of synthesized cathode materials showed well defined splitting of [006]/[102] and [108]/[110] diffraction peaks indicating layered structure and good hexagonal ordering. In this study, Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 (111), Li(Ni 0.2 Mn 0.2 Co 0.6)O 2 (226), Li(Ni 0.6 Mn 0.2 Co 0.2)O 2 (622) and Li(Ni 0.2 Mn 0.6 Co 0.2)O 2 (262) were synthesized. The morphology of cathode materials was investigated by scanning electron microscopy and average crystallite size was measured to be between 0.2 mm and 0.6 mm. Moreover, particle sizes were verified by particle size measurement and transmission electron microscopy techniques. The electrochemical cells were cycled at 0.1C and 0.3C rate (1C ¼ 170 mAhg À1) and it was found that fast charging and discharging behavior were not sufficient. However, capacity retention after 32 cycles were determined to be 85.3% and 90%, for (111) and (262) samples, respectively.
Composite 'Layered-Layered-Spinel' Cathode Structures for Lithium-Ion Batteries
Journal of the Electrochemical Society, 2012
The concept of embedding a spinel component in high capacity, composite xLi 2 MnO 3 •(1−x)LiMO 2 (M = Mn, Ni) 'layeredlayered' structures to improve their electrochemical properties and cycling stability has been exploited. In this paper, we report the preparation and electrochemical characterization of three-component 'layered-layered-spinel' electrodes, synthesized by lowering the lithium content of a parent 'layered-layered' 0.3Li 2 MnO 3 •0.7LiMn 0.5 Ni 0.5 O 2 material while maintaining a Mn:Ni ratio of 0.65:0.35; such compounds can be designated generically by the system, Li x Mn 0.65 Ni 0.35 O y , for which the end members are 0.3Li 2 MnO 3 •0.7LiMn 0.5 Ni 0.5 O 2 (x = 1.3; y = 2.3), in which the average manganese and nickel oxidation states are 4+ and 2+, respectively, and LiMn 1.3 Ni 0.7 O 4 (x = 0.5; y = 2) in which the corresponding average oxidation states are expected to lie between 4+ and 3.77+ for Mn, and 2.57+ and 3+ for Ni, respectively. For this study, compounds with a lithium content of x = 1.3, i.e., the parent 'layered-layered' composition, and 1.25 were selected for detailed and comparative investigation, the latter value corresponding to a targeted spinel content of 6%. The beneficial effects of 1) using Mg 2+ as a dopant ion and 2) treating the electrode particle surface with an acidic solution of AlF 3 to enhance cycling stability, reduce first-cycle capacity loss, and to slow voltage decay on cycling are discussed.
ChemElectroChem, 2015
An integrated layered-spinel LiNi 0.33 Mn 0.54 Co 0.13 O 2 was synthesized by self-combustion reaction (SCR), characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. It was studied as a cathode material for Li-ion batteries and its electrochemical performance was compared with that of the layered cathode materialLiNi 0.33 Mn 0.33 Co 0.33 O 2 being operated at a wide potential window. The Rietveld analysis of LiNi 0.33 Mn 0.54 Co 0.13 O 2 indicated the presence of monoclinic Li[Li 1/3 Mn 2/3 ]O 2 (31%) and rhombohedral (LiNi x Mn y Co z O 2 ) (62 %) phases as the major components, and spinel (LiNi 0.5 Mn 1.5 O 4 ) (7 %) as a minor component, which is well supported by TEM and electron diffraction. A discharge specific capacity of about 170 mAh g -1 is obtained in the potential range of 2.3-4.9 V vs. Li at low rate (C/10) with excellent capacity retention upon cycling. On the other hand, LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC111) synthesized by SCR exhibits an initial discharge capacity of about 208 mAh g -1 in the potential range of 2.3-4.9 V, which decreases to a value of 130 mAh g -1 after only 50 cycles. In turn, the multiphase structure of LiNi 0.33 Mn 0.54 Co 0.13 O 2 seems to stabilize the behavior of this cathode material even when polarized to high potentials. LiNi 0.33 Mn 0.54 Co 0.13 O 2 shows superior retention of average discharge voltage upon cycling as compared to that of LiNi 0.33 Mn 0.33 Co 0.33 O 2 when cycled in a wide potential range. Overall, ChemElectroChem 10.1002/celc.201500339 2 LiNi 0.33 Mn 0.54 Co 0.13 O 2 can be considered as a promising low cobalt content cathode material for Li ion batteries.
A new lithium rich composite positive electrode material of the composition 0.3Li 2 MnO 3 .0.7LiNi 0.5 Co 0.5 O 2 (LLNC) was synthesized using the conventional co-precipitation method. Its crystal structure and electrochemistry in Li cells have been compared to that of the previously known material, 0.3Li 2 MnO 3 .0.7LiMn 0.33 Ni 0.33 Co 0.33 O 2 (LLNMC). The removal of Mn from the LiMO 2 (M = transition metal) segment of the composite cathode material allowed us to determine the location of the manganese oxide moiety in its structure that triggers the layered to spinel conversion during cycling. The new material resists the layered to spinel structural transformation under conditions in which LLNMC does. X-ray diffraction patterns revealed that both compounds, synthesized as approximately 300 nm crystals, have identical super lattice ordering attributed to Li 2 MnO 3 existence. Using X-ray absorption spectroscopy we elucidated the oxidation states of the K edges of Ni and Mn in the two materials with respect to different charge and discharge states. The XAS data along with electrochemical results revealed that Mn atoms are not present in the LiMO 2 structural segment of LLNC. Electrochemical cycling data from Li cells further revealed that the absence of Mn in the LiMO 2 segment significantly improves the rate capabilities of LLNC with good capacity maintenance during long term cycling. Removing the Mn from the LiMO 2 segment of lithium rich layered metal oxides appears to be a good strategy for improving the structural robustness and rate capabilities of these high capacity cathode materials for Li-ion batteries.
Stabilized Layered-Layered-Spinel Cathode Materials for Lithium-Ion Batteries
The concept of embedding a spinel component in high capacity, composite xLi 2 MnO 3 •(1−x)LiMO 2 (M = Mn, Ni) 'layeredlayered' structures to improve their electrochemical properties and cycling stability has been exploited. In this paper, we report the preparation and electrochemical characterization of three-component 'layered-layered-spinel' electrodes, synthesized by lowering the lithium content of a parent 'layered-layered' 0.3Li 2 MnO 3 •0.7LiMn 0.5 Ni 0.5 O 2 material while maintaining a Mn:Ni ratio of 0.65:0.35; such compounds can be designated generically by the system, Li x Mn 0.65 Ni 0.35 O y , for which the end members are 0.3Li 2 MnO 3 •0.7LiMn 0.5 Ni 0.5 O 2 (x = 1.3; y = 2.3), in which the average manganese and nickel oxidation states are 4+ and 2+, respectively, and LiMn 1.3 Ni 0.7 O 4 (x = 0.5; y = 2) in which the corresponding average oxidation states are expected to lie between 4+ and 3.77+ for Mn, and 2.57+ and 3+ for Ni, respectively. For this study, compounds with a lithium content of x = 1.3, i.e., the parent 'layered-layered' composition, and 1.25 were selected for detailed and comparative investigation, the latter value corresponding to a targeted spinel content of 6%. The beneficial effects of 1) using Mg 2+ as a dopant ion and 2) treating the electrode particle surface with an acidic solution of AlF 3 to enhance cycling stability, reduce first-cycle capacity loss, and to slow voltage decay on cycling are discussed.
Ionics, 2017
The enriched lithium ion containing layered oxide cathode materials Li(Li 0.05 Ni 0.7 -x Mn 0.25 Co x )O 2 have been prepared by using facile sol-gel technique. The phase purity and crystalline nature of the layered oxide cathodes have determined by X-ray diffraction analysis. Surface morphology and elemental analysis have been carried out using scanning electron microscopy with energy dispersive analysis by X-rays and HR-TEM. Cyclic voltammetry analysis of the lithium-enriched cathode material shows a well redox performance at electrode-electrolytic interface. The Li(Li 0.05 Ni 0.7 -x Mn 0.25 Co x )O 2 cathode shows the most promising electrochemical properties under different conditions in which an appropriate rising of discharge capacity (i.e., 167 mAh g -1 at 0.5 C) and cycling stability (i.e., capacity retention: 83% at 1 C after 20 cycles, cutoff voltage 2.8-4.5 V) at ambient temperature. These unique properties allow the effective use of these cathode materials as positive electrodes for the development of rechargeable lithium ion batteries.
Journal of Alloys and Compounds, 2016
Mesoporous cathode active materials that included undoped and separated Cu 2+ and Co 3+ doped spinels were prepared. The "doped spinel-Layered-Li-rich spinel" composite nanoparticles within the three integrated phased (LiM 0,02 Mn 1,98 O 4-Li 2 MnO 3-Li 1,27 Mn 1,73 O 4 ; where M is Cu 2+ and Co 3+) were synthesized by a microwave assisted hydrothermal synthesis. These materials were investigated with X-Ray powder Diffraction spectroscopy (XRD), Scanning Electron Microscopy (SEM and FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM), galvanostatic cycling at 0.1 C and 0.5 C rates, Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The effects of the calcination temperature and the partial substitution of Mn 3+ in the spinel by Cu 2+ and Co 3+ , and onto the spinel structure were investigated with XRD. The lattice parameters of the spinel structured compounds were calculated from the XRD data using the Williamson-Hall equation. However, the morphological changes, which depended on the calcination temperature, were examined by SEM, FE-SEM and HRTEM. Furthermore, the two other phases which were different from LiM 0,02 Mn 1,98 O 4 had a great impact on the electrochemical performance over the potential range of the 3-5 V. At the 0.1 C rate, the first discharge capacities of undoped and Cu 2+ , Co 3+ doped materials were 577, 285, 560 mAh/g respectively. After 50 cycles at 0.5 C rate, we achieved 96.2%; 52.5%; 95.4% capacity retention for the undoped and Cu 2+ , Co 3+ doped materials respectively.