Spinel phase LiMn2O4 was successfully embedded into monoclinic phase layered- structured Li2MnO3 nanorods, and these spineMayered integrate structured nanorods showed both high capacities and superior high-rate capabi...Spinel phase LiMn2O4 was successfully embedded into monoclinic phase layered- structured Li2MnO3 nanorods, and these spineMayered integrate structured nanorods showed both high capacities and superior high-rate capabilities as cathode material for lithium-ion batteries （LIBs）. Pristine Li2MnO3 nanorods were synthesized by a simple rheological phase method using α-MnO2 nanowires as precursors. The spinel-layered integrate structured nanorods were fabricated by a facile partial reduction reaction using stearic acid as the reductant. Both structural characterizations and electrochemical properties of the integrate structured nanorods verified that LiMn2O4 nanodomains were embedded inside the pristine Li2MnO3 nanorods. When used as cathode materials for LIBs, the spineMayered integrate structured Li2MnO3 nanorods （SL-Li2MnO3） showed much better performances than the pristine layered-structured Li2MnO3 nanorods （L-Li2MnO3）. When charge-discharged at 20 mA.g-1 in a voltage window of 2.0-4.8 V, the SL-Li2MnO3 showed discharge capacities of 272.3 and 228.4 mAh.g-1 in the first and the 60th cycles, respectively, with capacity retention of 83.8%. The SL-Li2MnO3 also showed superior high-rate performances. When cycled at rates of 1 C, 2 C, 5 C, and 10 C （1 C = 200 mA-g-1） for hundreds of cycles, the discharge capacities of the SL-Li2MnO3 reached 218.9, 200.5, 147.1, and 123.9 mAh-g-1, respectively. The superior performances of the SL-Li2MnO3 are ascribed to the spineMayered integrated structures. With large capacities and superior high-rate performances, these spinel-layered integrate structured materials are good candidates for cathodes of next-generation high-power LIBs.展开更多
Li1+xMn2?yO4 spinels with various Li/Mn ratios were synthesized by a solid-state reaction. By X-ray diffraction analysis, Li2MnO3 was detected as a second phase with increasing the Li/Mn ratio; and the role of Li2MnO3...Li1+xMn2?yO4 spinels with various Li/Mn ratios were synthesized by a solid-state reaction. By X-ray diffraction analysis, Li2MnO3 was detected as a second phase with increasing the Li/Mn ratio; and the role of Li2MnO3 in Li1+xMn2-yO4 spinel was discussed. A slow scanning cyclic voltammetry(CV) at the rate of 0.1 mV/s was adopted to characterize the evolutions of 4 V and 5 V plateaus of Li1+xMn2-yO4 spinels. An additional Li+ insertion in 4 V region was observed in both Li-lack and Li-rich spinels at 3.95 V, which is different from the general Li+ insertion with weak Li-Li interaction and strong Li-Li interaction; and this plateau disappeared in the subsequent cycles. The 4.4 V/3.8 V plateaus correspondent to Li+ insertion and extraction of Li2MnO3 were discussed, and these plateaus have a high reversibility with cycling. The 5 V plateau was found only in the Li-rich samples, and this plateau has a tendency to emerge at higher voltage region with increasing Li/Mn ratio.展开更多
The layered Li2MnO3 is investigated by using the first-principles calculations within the GGA and GGA-t-U scheme, respectively. Within the GGA4-U approach, the calculated intercalation voltage （ranges from 4,5 V to 4...The layered Li2MnO3 is investigated by using the first-principles calculations within the GGA and GGA-t-U scheme, respectively. Within the GGA4-U approach, the calculated intercalation voltage （ranges from 4,5 V to 4.9 V） is found to be in good agreement with experiments. From the analysis of electronic structure, the pure phase Li2MnO3 is insulating, which is indicative of poor electronic-conduction properties. However, further studies of lithium ion diffusion in bulk Li2MnO3 show that unlike the two-dimensional diffusion pathways in rock salt structure layered cathode materials, lithium can diffuse in a three-dimensional pathway in Li2MnO3, with moderate lithium migration energy barrier ranges from 0.57 to 0.63 e V.展开更多
Layered F-doped cathode materials 0.3 Li_2 MnO_3-0.7 LiMn_(1/3)Ni_(1/3)CO_(1/3))O_(2-x)F_x(x = 0, 0.01, 0.02, 0.03, 0.04,0.05) microspheres made up of nanosized primary grains were prepared through co-precipitation me...Layered F-doped cathode materials 0.3 Li_2 MnO_3-0.7 LiMn_(1/3)Ni_(1/3)CO_(1/3))O_(2-x)F_x(x = 0, 0.01, 0.02, 0.03, 0.04,0.05) microspheres made up of nanosized primary grains were prepared through co-precipitation method. The sample of x = 0.02 demonstrates a large discharge capacity of226 mAh g^(-1) over 100 cycles at 0.1 C and excellent rate performance with discharge capacity of 96 mAh g-1 at 5.0 C and room temperature. Particularly, this material shows much enhanced electrochemical performances even at high temperature of 55 ℃. It delivers a quite high discharge capacity of 233.7 mAh·g^(-1) at 1.0 C with capacity retention as high as 97.9% after 100 cycles. The results demonstrate that the fluorine incorporation stabilizes the cathode structure and maintains stable interfacial resistances.展开更多
分别采用氢氧化物共沉淀、碳酸盐共沉淀、喷雾干燥的方法合成了层状α-Na Fe O2结构的富锂正极材料0.5Li2Mn O3·0.5Li(Ni1/3Co1/3Mn1/3)O2,通过X射线衍射分析(XRD)、扫描电子显微镜(SEM)和电化学性能测试对不同合成方法所得的样品...分别采用氢氧化物共沉淀、碳酸盐共沉淀、喷雾干燥的方法合成了层状α-Na Fe O2结构的富锂正极材料0.5Li2Mn O3·0.5Li(Ni1/3Co1/3Mn1/3)O2,通过X射线衍射分析(XRD)、扫描电子显微镜(SEM)和电化学性能测试对不同合成方法所得的样品进行了表征。实验结果表明:氢氧化物共沉淀合成的前驱体所制备的正极材料0.5Li2Mn O3·0.5Li(Ni1/3Co1/3Mn1/3)O2具有良好的电化学性能,0.05C倍率下首次放电容量可达247.1 m A·h/g,0.2C倍率条件下经过50次循环,容量保持率为98.7%。展开更多
基金supported by the National Key Basic Research Program of China(973)(2015CB251100)National Natural Science Foundation of China(51472032,51202083)+2 种基金Program for New Century Excellent Talents in University,China(NCET-13-0044)Special Fund of Beijing CoConstruction Project,China(20150939013)BIT Scientific and Technological Innovation Project,China(2013CX01003)
文摘Spinel phase LiMn2O4 was successfully embedded into monoclinic phase layered- structured Li2MnO3 nanorods, and these spineMayered integrate structured nanorods showed both high capacities and superior high-rate capabilities as cathode material for lithium-ion batteries （LIBs）. Pristine Li2MnO3 nanorods were synthesized by a simple rheological phase method using α-MnO2 nanowires as precursors. The spinel-layered integrate structured nanorods were fabricated by a facile partial reduction reaction using stearic acid as the reductant. Both structural characterizations and electrochemical properties of the integrate structured nanorods verified that LiMn2O4 nanodomains were embedded inside the pristine Li2MnO3 nanorods. When used as cathode materials for LIBs, the spineMayered integrate structured Li2MnO3 nanorods （SL-Li2MnO3） showed much better performances than the pristine layered-structured Li2MnO3 nanorods （L-Li2MnO3）. When charge-discharged at 20 mA.g-1 in a voltage window of 2.0-4.8 V, the SL-Li2MnO3 showed discharge capacities of 272.3 and 228.4 mAh.g-1 in the first and the 60th cycles, respectively, with capacity retention of 83.8%. The SL-Li2MnO3 also showed superior high-rate performances. When cycled at rates of 1 C, 2 C, 5 C, and 10 C （1 C = 200 mA-g-1） for hundreds of cycles, the discharge capacities of the SL-Li2MnO3 reached 218.9, 200.5, 147.1, and 123.9 mAh-g-1, respectively. The superior performances of the SL-Li2MnO3 are ascribed to the spineMayered integrated structures. With large capacities and superior high-rate performances, these spinel-layered integrate structured materials are good candidates for cathodes of next-generation high-power LIBs.
基金Project(2002CB211800) supported by the National Basic Research Program of China
文摘Li1+xMn2?yO4 spinels with various Li/Mn ratios were synthesized by a solid-state reaction. By X-ray diffraction analysis, Li2MnO3 was detected as a second phase with increasing the Li/Mn ratio; and the role of Li2MnO3 in Li1+xMn2-yO4 spinel was discussed. A slow scanning cyclic voltammetry(CV) at the rate of 0.1 mV/s was adopted to characterize the evolutions of 4 V and 5 V plateaus of Li1+xMn2-yO4 spinels. An additional Li+ insertion in 4 V region was observed in both Li-lack and Li-rich spinels at 3.95 V, which is different from the general Li+ insertion with weak Li-Li interaction and strong Li-Li interaction; and this plateau disappeared in the subsequent cycles. The 4.4 V/3.8 V plateaus correspondent to Li+ insertion and extraction of Li2MnO3 were discussed, and these plateaus have a high reversibility with cycling. The 5 V plateau was found only in the Li-rich samples, and this plateau has a tendency to emerge at higher voltage region with increasing Li/Mn ratio.
基金Supported by the National Natural Science Foundation of China under Grant No 21363016the Natural Science Foundation of Jiangxi Province under Grant No 20142BAB216030the PhD Early Development Program of Nanchang Hangkong University under Grant No EA201502007
文摘The layered Li2MnO3 is investigated by using the first-principles calculations within the GGA and GGA-t-U scheme, respectively. Within the GGA4-U approach, the calculated intercalation voltage （ranges from 4,5 V to 4.9 V） is found to be in good agreement with experiments. From the analysis of electronic structure, the pure phase Li2MnO3 is insulating, which is indicative of poor electronic-conduction properties. However, further studies of lithium ion diffusion in bulk Li2MnO3 show that unlike the two-dimensional diffusion pathways in rock salt structure layered cathode materials, lithium can diffuse in a three-dimensional pathway in Li2MnO3, with moderate lithium migration energy barrier ranges from 0.57 to 0.63 e V.
基金financially supported by the National Natural Science Foundation of China (No. 51372136)the NSFC-Guangdong United Fund (No. U1401246)
文摘Layered F-doped cathode materials 0.3 Li_2 MnO_3-0.7 LiMn_(1/3)Ni_(1/3)CO_(1/3))O_(2-x)F_x(x = 0, 0.01, 0.02, 0.03, 0.04,0.05) microspheres made up of nanosized primary grains were prepared through co-precipitation method. The sample of x = 0.02 demonstrates a large discharge capacity of226 mAh g^(-1) over 100 cycles at 0.1 C and excellent rate performance with discharge capacity of 96 mAh g-1 at 5.0 C and room temperature. Particularly, this material shows much enhanced electrochemical performances even at high temperature of 55 ℃. It delivers a quite high discharge capacity of 233.7 mAh·g^(-1) at 1.0 C with capacity retention as high as 97.9% after 100 cycles. The results demonstrate that the fluorine incorporation stabilizes the cathode structure and maintains stable interfacial resistances.
文摘分别采用氢氧化物共沉淀、碳酸盐共沉淀、喷雾干燥的方法合成了层状α-Na Fe O2结构的富锂正极材料0.5Li2Mn O3·0.5Li(Ni1/3Co1/3Mn1/3)O2,通过X射线衍射分析(XRD)、扫描电子显微镜(SEM)和电化学性能测试对不同合成方法所得的样品进行了表征。实验结果表明:氢氧化物共沉淀合成的前驱体所制备的正极材料0.5Li2Mn O3·0.5Li(Ni1/3Co1/3Mn1/3)O2具有良好的电化学性能,0.05C倍率下首次放电容量可达247.1 m A·h/g,0.2C倍率条件下经过50次循环,容量保持率为98.7%。
