| 1. |
- Fan, Jianming, et al.
(författare)
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Hydrothermal-assisted synthesis of Li-rich layered oxide microspheres with high capacity and superior rate-capability as a cathode for lithium-ion batteries
- 2015
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Ingår i: Electrochimica Acta. - 0013-4686. ; 173, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- Li-rich layered oxide materials possess high voltage and high specific capacity, which makes them attractive cathode candidates for lithium-ion batteries. However, they still suffer from a poor rate capability, which seriously blocks their widespread practical applications. In this work, Li(Li0.167Mn0.5Co0.167Ni0.167)O2 microspheres were synthesized by a hydrothermal-assisted method, in which Ni-Co-Mn-based microspherical precursors obtained by a hydrothermal process with polyethylene glycol-600 (PEG-600) as a surfactant were mixed with lithium sources and then sintered to yield the final products. It is found that the as-prepared Li-rich layered oxide microspheres exhibit high discharge capacity and superior rate performance: delivering an initial discharge capacity of 292 mAh g−1 at a current density of 20 mA g−1, 189 mAh g−1 at a current density of 600 mA g−1 and 142 mAh g−1 at a current density of 2000 mA g−1 (10C), which are better than that of the sample as-prepared by co-precipitation method. The high discharge capacity and improved rate-capability were beneficial from the microspheres assembled by uniform primary particles around 250 nm, more reversible redox and better electrode kinetics comparing to that of the co-precipitation sample. The preparation strategy reported here may offer hints for achieving various advanced Li-rich layered composite materials that would be used in high-performance energy storage.
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| 2. |
- Li, Qi, 1990, et al.
(författare)
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A Study on Storage Characteristics of Pristine Li-rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2: Effect of Storage Temperature and Duration
- 2015
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Ingår i: Electrochimica Acta. - 0013-4686. ; 154, s. 249-158
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion batteries always suffer from serious capability decay, especially when stored at high temperature and/or for prolonged duration. In this work, electrochemical performance for Li-rich layered oxides Li1.20Mn0.54Co0.13Ni0.13O2 was systematically investigated as a function of temperature and duration. Plenty of techniques like SEM, EDS, EIS, ARC, Raman, XRD, and XPS were utilized to characterize the structures, valence states, compositions, particle sizes, and morphologies of the layered oxides with varying temperature and duration. The results reveal that room temperature storage may alter surface kinetics, but hardly influence the electrochemical performance. While in the case of high temperature storage in pristine state, cycling stability is highly dependent on the storage duration. The degradation mechanism at high temperature storage with prolonged duration is demonstrated to be the accumulation of surface species like LiF/LixPFyOz initiated by the strong reactions between LiPF6 electrolyte and electrode. The results reported here may shed light on predicting electrochemical performance by surface analysis and also provide vital hints on enhancing the high-temperature storage stability of Li-rich layered oxides.
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| 3. |
- Li, Qi, 1990, et al.
(författare)
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Balancing stability and specific energy in Li-rich cathodes for lithium ion batteries: a case study of a novel Li–Mn–Ni–Co oxide
- 2015
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Ingår i: Journal of Materials Chemistry. - 1364-5501 .- 0959-9428. ; 3:19, s. 10592-10602
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Tidskriftsartikel (refereegranskat)abstract
- Lithium batteries for UPS, portable electronics and electrical vehicles rely on high-energy cathodes. Li-rich manganese-rich oxide (xLi2MnO3·(1 − x)LiMO2, M = transition metals) is one of the few materials that might meet such a requirement, but it suffers from poor energy retention due to serious voltage and/or capacity fade, which challenges its applications. Here we show that this challenge can be addressed by optimizing the interactions between the components Li2MnO3 and LiMO2 in the Li-rich oxide (i.e. stabilizing the layered structure through Li2MnO3 and controlling Li2MnO3 activation through LiMO2). To realize this synergistic effect, a novel Li2MnO3-stabilized Li1.080Mn0.503Ni0.387Co0.030O2 was designed and prepared using a hierarchical carbonate precursor obtained by a solvo/hydro-thermal method. This layered oxide is demonstrated to have a high working voltage of 3.9 V and large specific energy of 805 W h kg−1 at 29 °C as well as impressive energy retention of 92% over 100 cycles. Even when exposed to 55 °C, energy retention is still as high as 85% at 200 mA g−1. The attractive performance is most likely the consequence of the balanced stability and specific energy in the present material, which is promisingly applicable to other Li-rich oxide systems. This work sheds light on harnessing Li2MnO3 activation and furthermore efficient battery design simply through compositional tuning and temperature regulation.
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| 4. |
- Luo, Dong, et al.
(författare)
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LiMO2 (M = Mn, Co, Ni) hexagonal sheets with (101) facets for ultrafast charging–discharging lithium ion batteries
- 2015
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Ingår i: Journal of Power Sources. - 0378-7753. ; 276, s. 238-246
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Tidskriftsartikel (refereegranskat)abstract
- Developing energy storage equipments that can work at very high charge–discharge rate is crucial, but highly challenging for more efficient use of energy. From the perspective of chemistry, high-rate property of Li-ion batteries can only be achieved by significantly improving the kinetics of lithium ions and electrons in electrode. Here, we for the first time report on a simple method to resolve kinetics problems of ultrafast charging–discharging Li-ion batteries by fabrication of layered LiMO2 (M = Mn, Co, Ni) hexagonal sheet exposing with facets {101}. The synthetic procedure of hexagonal sheets is proceeded via a simple PVP-assisted co-precipitation, which is followed by a heat treatment. All hexagonal sheets LiMnxCoyNizO2 were demonstrated to deliver a superior excellent rate capability and outstanding cycle stability at high current density of 3000 mA g−1 and under a high cutoff voltage of 4.4 V. The discharge capacity for the composition LiMn0.075Co0.775Ni0.15O2 at an ultrahigh charge–discharge rate of 10,000 mA g−1 is almost as large as that for LiMn2O4 and commercial LiFePO4 at low rate of 1C. The methodology reported here to resolve the kinetic problems of lithium ions and electrons in electrodes may have many implications that would help scientists to find more high-rate lithium-ion batteries for powering electric vehicles and other applications.
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