The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ...We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ions is 3.55, probably due to the small amount of lithium oxides on the surface. UPS and RPES data imply that Mn ions are in a high spin state, and RPES results show strong Mn3d-O2p hybridization in the LiMn2O4 valence band.展开更多
The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands ar...The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands are observed at 638 nm(1.94 eV),512 nm(2.42 eV),377 nm(3.29 eV)and 248 nm(5.00 eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7(AO7)under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9%under the irradiation of visible light for two hours.展开更多
采用溶胶-凝胶的方法低温制备石榴石结构的固体电解质Li5La3Ta2O12,并用其包覆Li Mn2O4来改善材料的电化学性能。通过XRD,SEM和TEM等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安、交流阻抗等测试分析材料的电化...采用溶胶-凝胶的方法低温制备石榴石结构的固体电解质Li5La3Ta2O12,并用其包覆Li Mn2O4来改善材料的电化学性能。通过XRD,SEM和TEM等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安、交流阻抗等测试分析材料的电化学性能。研究结果表明:Li5La3Ta2O12包覆的Li Mn2O4材料与未包覆的材料相比,其电化学性能得到明显改善,经过150次循环后包覆材料的放电比容量保持率为92%,在高倍率10C(C为倍率)下包覆材料放电比容量为61.2 m A·h/g,而未包覆材料放电比容量仅为40.7 m A·h/g;包覆Li5La3Ta2O12后,Li Mn2O4的阻抗明显减小,大幅度提高了其循环性能和倍率性能。展开更多
Improvement of elevated-temperature performance of Li1.02Cr0.1Mn1.9O4 cathode material by silicious surface modification was studied. The Li1.02Cr0.1Mn1.9O4 cathode material was treated by silanes coupling agent and t...Improvement of elevated-temperature performance of Li1.02Cr0.1Mn1.9O4 cathode material by silicious surface modification was studied. The Li1.02Cr0.1Mn1.9O4 cathode material was treated by silanes coupling agent and then heated at 580 ℃ to remove organic material. The structures of the modified and unmodified Li1.02Cr0.1Mn1.9O4 were characterized by SpectraPlus, SEM and XRD. The results show that the surface layer of Li1.02Cr0.1Mn1.9O4 material is found to be rich in silicious compound. X-ray diffraction show that all the samples have perfect spinel structure. The electrochemical characterization of modified Li1.02Cr0.1Mn1.9O4 cathode material was tested. The cycle stability of charge/discharge at 55℃ is improved. The results of the charge/discharge curves show that the modified Li1.02Cr0.1Mn1.9O4 has better performance than those unmodified according to the inhibition of decline of reversible capacity of spinel Li1.02Cr0.1Mn1.9O4. Therefore, cycle performance is improved so obviously that 86.03% of the initial capacity is preserved after 100 cycles.展开更多
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
文摘We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ions is 3.55, probably due to the small amount of lithium oxides on the surface. UPS and RPES data imply that Mn ions are in a high spin state, and RPES results show strong Mn3d-O2p hybridization in the LiMn2O4 valence band.
基金Supported by the National Natural Science Foundation of China under Grant Nos,10874087,11074124 and 11174113Jiangsu Provincial Natural Science Foundation under Grant No.200921555.
文摘The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands are observed at 638 nm(1.94 eV),512 nm(2.42 eV),377 nm(3.29 eV)and 248 nm(5.00 eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7(AO7)under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9%under the irradiation of visible light for two hours.
文摘采用溶胶-凝胶的方法低温制备石榴石结构的固体电解质Li5La3Ta2O12,并用其包覆Li Mn2O4来改善材料的电化学性能。通过XRD,SEM和TEM等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安、交流阻抗等测试分析材料的电化学性能。研究结果表明:Li5La3Ta2O12包覆的Li Mn2O4材料与未包覆的材料相比,其电化学性能得到明显改善,经过150次循环后包覆材料的放电比容量保持率为92%,在高倍率10C(C为倍率)下包覆材料放电比容量为61.2 m A·h/g,而未包覆材料放电比容量仅为40.7 m A·h/g;包覆Li5La3Ta2O12后,Li Mn2O4的阻抗明显减小,大幅度提高了其循环性能和倍率性能。
文摘Improvement of elevated-temperature performance of Li1.02Cr0.1Mn1.9O4 cathode material by silicious surface modification was studied. The Li1.02Cr0.1Mn1.9O4 cathode material was treated by silanes coupling agent and then heated at 580 ℃ to remove organic material. The structures of the modified and unmodified Li1.02Cr0.1Mn1.9O4 were characterized by SpectraPlus, SEM and XRD. The results show that the surface layer of Li1.02Cr0.1Mn1.9O4 material is found to be rich in silicious compound. X-ray diffraction show that all the samples have perfect spinel structure. The electrochemical characterization of modified Li1.02Cr0.1Mn1.9O4 cathode material was tested. The cycle stability of charge/discharge at 55℃ is improved. The results of the charge/discharge curves show that the modified Li1.02Cr0.1Mn1.9O4 has better performance than those unmodified according to the inhibition of decline of reversible capacity of spinel Li1.02Cr0.1Mn1.9O4. Therefore, cycle performance is improved so obviously that 86.03% of the initial capacity is preserved after 100 cycles.
