The cycling performance, impedance variation, and cathode surface evolution of the Li/LiCoO2 cell using Li FSI–KFSI molten salt electrolyte are reported. It is found that this battery shows poor cycling performance, ...The cycling performance, impedance variation, and cathode surface evolution of the Li/LiCoO2 cell using Li FSI–KFSI molten salt electrolyte are reported. It is found that this battery shows poor cycling performance, with capacity retention of only about 67% after 20 cycles. It is essential to understand the origin of the instability. It is noticed that the polarization voltage and the impedance of the cell both increase slowly upon cycling. The structure and the properties of the pristine and the cycled LiCoO2 cathodes are investigated by x-ray diffraction（XRD）, scanning electron microscopy（SEM）, Raman spectroscopy, x-ray photoelectron spectroscopy（XPS）, and transmission electron microscopy（TEM）. It is found that the LiCoO2 particles are corroded by this molten salt electrolyte, and the decomposition by-product covers the surface of the LiCoO2 cathode after 20 cycles. Therefore, the surface side reaction explains the instability of the molten salt electrolyte with LiCoO2.展开更多
We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide(Ch TFSI)electrolyte with a cosolvent enabling low-...We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide(Ch TFSI)electrolyte with a cosolvent enabling low-temperature operation down to-30℃.For this purpose,a Mg O-templated hierarchical carbon(MP98B)with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900℃.To reach lower temperatures,the melting point and viscosity of the aqueous electrolyte were reduced by mixing water(W)with an organic solvent(methanol,M,or isopropanol,I)of high dielectric constant and low viscosity.5 mol kg^(-1)(5 m)Ch TFSI in an optimized volume fraction of cosolvent,M_(0.75)W_(0.25),and I_(0.75)W_(0.25),showed the highest conductivity;the higher conductivity in M_(0.75)W_(0.25)(22.8 and 3.1 m S cm^(-1) at 20 and-30℃,respectively)than in I_(0.75)W_(0.25)(8.5 and0.5 m S cm^(-1)at 20 and-30℃,respectively)is attributed to the lower viscosity of the M_(0.75)W_(0.25)solution.The electrochemical stability window(ESW)of 5 m Ch TFSI in M_(0.75)W_(0.25)and I_(0.75)W_(0.25)(1.6 V)on an MP98B electrode was determined by applying the S-method.Meanwhile,by adjusting the mass ratio of the two electrodes,a MP98B/MP98B capacitor using the 5 m electrolyte in M_(0.75)W_(0.25)could operate with a good life span up to 1.6 V while exhibiting a better charge propagation,greater specific capacitance,and higher specific energy than in I_(0.75)W_(0.25).展开更多
Facile and rapid polycondensation reactions of N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h were developed by using a domestic microwave oven in...Facile and rapid polycondensation reactions of N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h were developed by using a domestic microwave oven in the presence of a small amount of polar organic medium such as o-cresol. The polycondensation reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7-10 min, producing a series of novel optically active poly(amide-imide)s 3a-h with high yield and inherent viscosity of 0.35-0.65 dL/g. All of the above polymers were fully characterized by FT-IR, elemental analyses, inherent viscosity (η inh ), solubility test and specific rotation. Some structural characterization and physical properties of these optically active poly(amide-imide)s are reported.展开更多
Effective passivation of aluminum(Al)current collector at high potentials(>4.0 V vs.Li/Li^(+))is of essence for the long-term operation of lithium-based batteries.Unfortunately,the non-aqueous liquid electrolytes c...Effective passivation of aluminum(Al)current collector at high potentials(>4.0 V vs.Li/Li^(+))is of essence for the long-term operation of lithium-based batteries.Unfortunately,the non-aqueous liquid electrolytes comprising lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)and organic carbonates are corrosive toward Al current collector at high potentials(>4.0 V vs.Li/Li^(+)),despite their intriguing features(e.g.,good chemical stability and high ionic conductivity).Herein,we propose the utilization of N,N-dimethyl fluorosulfonamide(DMFSA)as electrolyte solvent for suppressing Al corrosion in the LiTFSI-based electrolytes.It has been demonstrated that the electrolyte of 1.0 M LiTFSI-DMFSA shows decent ionic conductivities(1.76 mS·cm^(−1)at 25℃)with good fluidities(2.44 cP at 25℃).In particular,the replacement of organic carbonates(e.g.,ethylene carbonate and ethyl methyl carbonate)with DMFSA leads to significant suppressed Al corrosion.Morphological and compositional characterizations utilizing scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS)reveal that DMFSA favors the formation of insoluble species(i.e.,aluminum fluoride(AlF_(3)))on the surface of Al electrode,which effectively inhibits continuous exposure of fresh Al surface to electrolyte during cycling.This work provides not only a deeper understanding on the Al corrosion in LiTFSI-based electrolyte but also an elegant path to stabilize the Al current collector at high potentials(>4.0 V vs.Li/Li^(+)),which may give an impetus into the development of lithium-based batteries.展开更多
凝胶聚合物电解质(GPE)是当前最具商业化应用前景之一的准固态电解质,可以缓解甚至解决锂离子电池存在的漏液、挥发、燃烧等潜在安全问题。本文通过高温原位固化技术制备了一种以甲基丙烯酸甲酯为单体、聚乙二醇二甲基丙烯酸酯为交联剂...凝胶聚合物电解质(GPE)是当前最具商业化应用前景之一的准固态电解质,可以缓解甚至解决锂离子电池存在的漏液、挥发、燃烧等潜在安全问题。本文通过高温原位固化技术制备了一种以甲基丙烯酸甲酯为单体、聚乙二醇二甲基丙烯酸酯为交联剂、双(氟磺酰)亚胺锂为导电盐、碳酸乙烯酯/碳酸甲乙酯混合溶剂为增塑剂的GPE。通过热重分析对聚甲基丙烯酸甲酯(PMMA)基GPE的热力学性质进行了表征,采用计时安培法和电子扫描显微镜研究了PMMA基GPE对Al集流体的稳定性。研究结果表明,PMMA基GPE在室温拥有较高的电导率,达到6.61 mS/cm,同时可以将碳酸酯电解液的挥发温度由100.3℃提高至138.1℃。PMMA基GPE在高电位下对Al箔显示出良好的稳定性,4.3 V vs.Li/Li+以下不会发生铝箔腐蚀,而且在商用石墨/LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)软包电池中展现出良好的循环稳定性和容量保持能力,循环1000次后容量保持率为93.4%。展开更多
Bis[（perfluoroalkyl）sulfonyl]imides [HN（SO2Rf）2, and Rf represents the perfluorinated alkyl group] supported on MCM-41 were synthesized and characterized by XRD, FTIR, SEM, TGA and N2-adsorption techniques. The su...Bis[（perfluoroalkyl）sulfonyl]imides [HN（SO2Rf）2, and Rf represents the perfluorinated alkyl group] supported on MCM-41 were synthesized and characterized by XRD, FTIR, SEM, TGA and N2-adsorption techniques. The supported catalysts, HN（SO2Rf）2/MCM-41, were used as the catalysts for the tert-butylafion of hydroquinone （HQ） with tert-butyl alcohol （TBA） in the liquid phase. A high yield （52.0%） of 2-tert-butyl hydroquinone （TBHQ） could be obtained in the presence of 5 tool% HN（SO2C4F9）2/MCM-41 under the optimized reaction conditions and the heterogeneous catalyst could be recycled at least 6 times without substantial loss of activity.展开更多
Hafnium（Ⅳ） bis（perfluorooctanesulfonyl）imide complex is found to be an efficient catalyst for the multicomponent condensation ofβ-naphthol,aromatic aldehydes and urea or amides in perfluorodecalin to afford the ...Hafnium（Ⅳ） bis（perfluorooctanesulfonyl）imide complex is found to be an efficient catalyst for the multicomponent condensation ofβ-naphthol,aromatic aldehydes and urea or amides in perfluorodecalin to afford the corresponding substituted amidomethyl naphthols in good yields.The remarkable features of this new procedure are high yields,shorter reaction times, reusability of catalyst and simple work-up procedures.展开更多
基金Project supported by the Beijing S&T Project,China(Grant No.Z13111000340000)the National Basic Research Program of China(Grant No.2012CB932900)the National Natural Science Foundation of China(Grants Nos.51325206 and 51421002)
文摘The cycling performance, impedance variation, and cathode surface evolution of the Li/LiCoO2 cell using Li FSI–KFSI molten salt electrolyte are reported. It is found that this battery shows poor cycling performance, with capacity retention of only about 67% after 20 cycles. It is essential to understand the origin of the instability. It is noticed that the polarization voltage and the impedance of the cell both increase slowly upon cycling. The structure and the properties of the pristine and the cycled LiCoO2 cathodes are investigated by x-ray diffraction（XRD）, scanning electron microscopy（SEM）, Raman spectroscopy, x-ray photoelectron spectroscopy（XPS）, and transmission electron microscopy（TEM）. It is found that the LiCoO2 particles are corroded by this molten salt electrolyte, and the decomposition by-product covers the surface of the LiCoO2 cathode after 20 cycles. Therefore, the surface side reaction explains the instability of the molten salt electrolyte with LiCoO2.
基金financially supported by the National Science Centre(MAESTRO project UMO-2016/22/A/ST4/00092)。
文摘We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide(Ch TFSI)electrolyte with a cosolvent enabling low-temperature operation down to-30℃.For this purpose,a Mg O-templated hierarchical carbon(MP98B)with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900℃.To reach lower temperatures,the melting point and viscosity of the aqueous electrolyte were reduced by mixing water(W)with an organic solvent(methanol,M,or isopropanol,I)of high dielectric constant and low viscosity.5 mol kg^(-1)(5 m)Ch TFSI in an optimized volume fraction of cosolvent,M_(0.75)W_(0.25),and I_(0.75)W_(0.25),showed the highest conductivity;the higher conductivity in M_(0.75)W_(0.25)(22.8 and 3.1 m S cm^(-1) at 20 and-30℃,respectively)than in I_(0.75)W_(0.25)(8.5 and0.5 m S cm^(-1)at 20 and-30℃,respectively)is attributed to the lower viscosity of the M_(0.75)W_(0.25)solution.The electrochemical stability window(ESW)of 5 m Ch TFSI in M_(0.75)W_(0.25)and I_(0.75)W_(0.25)(1.6 V)on an MP98B electrode was determined by applying the S-method.Meanwhile,by adjusting the mass ratio of the two electrodes,a MP98B/MP98B capacitor using the 5 m electrolyte in M_(0.75)W_(0.25)could operate with a good life span up to 1.6 V while exhibiting a better charge propagation,greater specific capacitance,and higher specific energy than in I_(0.75)W_(0.25).
基金This project was supported by the Research Affairs Division of Arak University.
文摘Facile and rapid polycondensation reactions of N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h were developed by using a domestic microwave oven in the presence of a small amount of polar organic medium such as o-cresol. The polycondensation reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7-10 min, producing a series of novel optically active poly(amide-imide)s 3a-h with high yield and inherent viscosity of 0.35-0.65 dL/g. All of the above polymers were fully characterized by FT-IR, elemental analyses, inherent viscosity (η inh ), solubility test and specific rotation. Some structural characterization and physical properties of these optically active poly(amide-imide)s are reported.
基金supported by the Fundamental Research Funds for the Central Universities,HUST(No.52020kfyXJJS09)。
文摘Effective passivation of aluminum(Al)current collector at high potentials(>4.0 V vs.Li/Li^(+))is of essence for the long-term operation of lithium-based batteries.Unfortunately,the non-aqueous liquid electrolytes comprising lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)and organic carbonates are corrosive toward Al current collector at high potentials(>4.0 V vs.Li/Li^(+)),despite their intriguing features(e.g.,good chemical stability and high ionic conductivity).Herein,we propose the utilization of N,N-dimethyl fluorosulfonamide(DMFSA)as electrolyte solvent for suppressing Al corrosion in the LiTFSI-based electrolytes.It has been demonstrated that the electrolyte of 1.0 M LiTFSI-DMFSA shows decent ionic conductivities(1.76 mS·cm^(−1)at 25℃)with good fluidities(2.44 cP at 25℃).In particular,the replacement of organic carbonates(e.g.,ethylene carbonate and ethyl methyl carbonate)with DMFSA leads to significant suppressed Al corrosion.Morphological and compositional characterizations utilizing scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS)reveal that DMFSA favors the formation of insoluble species(i.e.,aluminum fluoride(AlF_(3)))on the surface of Al electrode,which effectively inhibits continuous exposure of fresh Al surface to electrolyte during cycling.This work provides not only a deeper understanding on the Al corrosion in LiTFSI-based electrolyte but also an elegant path to stabilize the Al current collector at high potentials(>4.0 V vs.Li/Li^(+)),which may give an impetus into the development of lithium-based batteries.
文摘凝胶聚合物电解质(GPE)是当前最具商业化应用前景之一的准固态电解质,可以缓解甚至解决锂离子电池存在的漏液、挥发、燃烧等潜在安全问题。本文通过高温原位固化技术制备了一种以甲基丙烯酸甲酯为单体、聚乙二醇二甲基丙烯酸酯为交联剂、双(氟磺酰)亚胺锂为导电盐、碳酸乙烯酯/碳酸甲乙酯混合溶剂为增塑剂的GPE。通过热重分析对聚甲基丙烯酸甲酯(PMMA)基GPE的热力学性质进行了表征,采用计时安培法和电子扫描显微镜研究了PMMA基GPE对Al集流体的稳定性。研究结果表明,PMMA基GPE在室温拥有较高的电导率,达到6.61 mS/cm,同时可以将碳酸酯电解液的挥发温度由100.3℃提高至138.1℃。PMMA基GPE在高电位下对Al箔显示出良好的稳定性,4.3 V vs.Li/Li+以下不会发生铝箔腐蚀,而且在商用石墨/LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)软包电池中展现出良好的循环稳定性和容量保持能力,循环1000次后容量保持率为93.4%。
文摘Bis[（perfluoroalkyl）sulfonyl]imides [HN（SO2Rf）2, and Rf represents the perfluorinated alkyl group] supported on MCM-41 were synthesized and characterized by XRD, FTIR, SEM, TGA and N2-adsorption techniques. The supported catalysts, HN（SO2Rf）2/MCM-41, were used as the catalysts for the tert-butylafion of hydroquinone （HQ） with tert-butyl alcohol （TBA） in the liquid phase. A high yield （52.0%） of 2-tert-butyl hydroquinone （TBHQ） could be obtained in the presence of 5 tool% HN（SO2C4F9）2/MCM-41 under the optimized reaction conditions and the heterogeneous catalyst could be recycled at least 6 times without substantial loss of activity.
基金the project of"Excellence Initiative"and"Zijin Star"in NJUST for financial support
文摘Hafnium（Ⅳ） bis（perfluorooctanesulfonyl）imide complex is found to be an efficient catalyst for the multicomponent condensation ofβ-naphthol,aromatic aldehydes and urea or amides in perfluorodecalin to afford the corresponding substituted amidomethyl naphthols in good yields.The remarkable features of this new procedure are high yields,shorter reaction times, reusability of catalyst and simple work-up procedures.
文摘采用简单的溶液浇铸法制备出由双(三氟甲基磺酰)亚胺钠(Na TFSI)/聚氧乙烯(PEO)构筑的固态聚合物电解质(SPE),并针对其相转变、结晶性、热稳定性、电导率以及电化学稳定性等基础理化及电化学性质进行了系统表征。结果表明,Na TFSI/PEO([EO]/[Na+]=15)SPE具有相对高的电导率(σ≈10^(-3)S·cm^(-1),80°C)、高的耐氧化能力(4.86 V vs Na+/Na)和热稳定性高达350°C。电池测试结果表明,该Na TFSI基SPE不仅对金属钠电极能够呈现出优异的界面稳定性,而且在Na|SPE|NaCu_(1/9)Ni_(2/9) Fe_(1/3) Mn_(1/3)O_2电池中展现出良好的循环和倍率性能。
