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- Xie, Dongjiu, et al.
(författare)
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Improved Cycling Stability of Cobalt-free Li-rich Oxides with a Stable Interface by Dual Doping
- 2016
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Ingår i: Electrochimica Acta. - 0013-4686. ; 196, s. 505-516
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Tidskriftsartikel (refereegranskat)abstract
- Li-rich cobalt-free oxides, popularly used as a cathode with high capacity in lithium ion battery, always suffer from poor cycling stability between 2.0 and 4.8 V vs Li+/Li, especially when cycled at high temperatures (>50 °C). To overcome this issue, Na+ and Al3+ dual-doped NaxLi1.2-xMn0.6-xAlxNi0.2O2 Li-rich cathode is prepared in this study. It is shown that the side reactions between cathode and electrolyte during cycling are suppressed. The improved cycling performance is observed for all of the doped samples, among which the sample with x = 0.03 exhibits the highest capacity retention of 86.1% after 200 cycles between 2.0 and 4.8 V at 2C (1C = 200 mA g−1) and shows a remarkable cycling stability, even at a high temperature of 55 °C (a capacity retention of 92.2% after 100 cycles). Moreover, the average voltage of the sample with x = 0.03 after 100 cycles at 0.5C remains at 3.11 V with a retention ratio of 86.6%. This work provides a new strategy to develop Li-rich cobalt-free cathodes with excellent cycling stability for lithium ion batteries at high temperatures.
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| 2. |
- Zhang, Yuelan, et al.
(författare)
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Smart Solution Chemistry to Sn-Containing Intermetallic Compounds through a Self-Disproportionation Process
- 2016
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Ingår i: Chemistry - A European Journal. - 1521-3765 .- 0947-6539. ; 22:40, s. 14196-14204
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Tidskriftsartikel (refereegranskat)abstract
- Developing new methods to synthesize intermetallics is one of the most critical issues for the discovery and application of multifunctional metal materials; however, the synthesis of Sn-containing intermetallics is challenging. In this work, we demonstrated for the first time that a self-disproportionation-induced in situ process produces cavernous Sn−Cu intermetallics (Cu3Sn and Cu6Sn5). The successful synthesis is realized by introducing inorganic metal salts (SnCl2⋅2 H2O) to NaOH aqueous solution to form an intermediate product of reductant (Na2SnO2) and by employing steam pressures that enhance the reduction ability. Distinct from the traditional in situ reduction, the current reduction process avoided the uncontrolled phase composition and excessive use of organic regents. An insight into the mechanism was revealed for the Sn−Cu case. Moreover, this method could be extended to other Sn-containing materials (Sn−Co, Sn−Ni). All these intermetallics were attempted in the catalytic effect on thermal decompositions of ammonium perchlorate. It is demonstrated that Cu3Sn showed an outstanding catalytic performance. The superior property might be primarily originated from the intrinsic chemical compositions and cavernous morphology as well. We supposed that this smart solution reduction methodology reported here would provide a new recognition for the reduction reaction, and its modified strategy may be applied to the synthesis of other metals, intermetallics as well as some unknown materials.
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