Due to their extensive microporous structure,metal-organic frameworks(MOFs)find widespread application in constructing modification layers,functioning as ion sieves.However,the modification layers prepared by existing...Due to their extensive microporous structure,metal-organic frameworks(MOFs)find widespread application in constructing modification layers,functioning as ion sieves.However,the modification layers prepared by existing methods feature gaps between MOFs that are noticeably larger than the inherent MOF pore dimensions.Polysulfides and lithium ions unavoidably permeate through these gaps,hindering the full exploitation of the structural advantages.Herein,an ultrathin(20 nm)and crack-free MOF film is formed on the separator by atomic layer deposition for the first time.Based on the separator,the mechanism of different MOF layers has been verified by phase field simulation and in situ Raman spectroscopy.The results accurately prove that the MOF particle layer can relieve the shuttle of polysulfides,but it does not have the effect of homogenizing lithium ions.Only the ultrathin and crack-free MOF film with proper pore size can act as the ion sieve for both polysulfides and lithium ions.As a result,under the test condition of 2mA cm^(-2)-2 mAh cm^(-2),the overpotential of the Li/Li symmetric battery is only 18 mV after 2500 h.The capacity retention rate of the lithium-sulfur battery is 95.6% after 500 cycles and 80% after 1000 cycles at 2 C.展开更多
The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work...The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work,a dense metal-organic-framework(MOF)modification layer is in-situ prepared by the assistant of polydopamine on the polypropylene separators.Due to the unique structure and synergistic effect of polydopamine(PDA)and zeolitic imidazolate framework-8(ZIF-8),the functional separator can not only trap the polysulfides effectively but also promote the transport of lithium ions.As a result,the battery assembled with the functional separator exhibits excellent cycle stability.The capacity remains 711 mAh·g^(−1)after 500 cycles at 2 C,and the capacity decay rate is as low as 0.013%per cycle.The symmetrical battery is cycled for 1,000 h at 2 mA·cm^(−2)(2 mAh·cm^(−2))with the plating/stripping overpotential of 20 mV.At the same time,the modification separator shows a higher lithium ion transference number(0.88),better thermal stability and electrolyte wettability than the unmodified separator.展开更多
The authors introduce the Hausdorff convergence to discuss the differentiable sphere theorem with excess pinching. Finally, a type of rigidity phenomenon on Riemannian manifolds is derived.
引言中央对省及省对地方的财政转移支付,是中国各省及地方政府的一项主要收入来源。2003年,省级政府支出的67%,县政府支出的57%以及县以下政府支出的66%都是由转移支付资金承担的(Qiao and Shah,2006)。在中国,主要由地方政府承担公共...引言中央对省及省对地方的财政转移支付,是中国各省及地方政府的一项主要收入来源。2003年,省级政府支出的67%,县政府支出的57%以及县以下政府支出的66%都是由转移支付资金承担的(Qiao and Shah,2006)。在中国,主要由地方政府承担公共服务供给的职责。展开更多
基金Fundamental Research Funds for the Central Universities,Grant/Award Numbers:WUT:2020Ⅲ023,2020Ⅲ050,2021Ⅲ009,2021ⅣA123National Key Research and Development Program of China,Grant/Award Number:2022YFB3803502。
文摘Due to their extensive microporous structure,metal-organic frameworks(MOFs)find widespread application in constructing modification layers,functioning as ion sieves.However,the modification layers prepared by existing methods feature gaps between MOFs that are noticeably larger than the inherent MOF pore dimensions.Polysulfides and lithium ions unavoidably permeate through these gaps,hindering the full exploitation of the structural advantages.Herein,an ultrathin(20 nm)and crack-free MOF film is formed on the separator by atomic layer deposition for the first time.Based on the separator,the mechanism of different MOF layers has been verified by phase field simulation and in situ Raman spectroscopy.The results accurately prove that the MOF particle layer can relieve the shuttle of polysulfides,but it does not have the effect of homogenizing lithium ions.Only the ultrathin and crack-free MOF film with proper pore size can act as the ion sieve for both polysulfides and lithium ions.As a result,under the test condition of 2mA cm^(-2)-2 mAh cm^(-2),the overpotential of the Li/Li symmetric battery is only 18 mV after 2500 h.The capacity retention rate of the lithium-sulfur battery is 95.6% after 500 cycles and 80% after 1000 cycles at 2 C.
基金the Ministry of Science and Technology of the People’s Republic of China(No.2017YFE0127600)the National Natural Science Foundation of China(No.51702247)+3 种基金the Fundamental Research Funds for the Central Universities(No.WUT:2020III023,2020III050,2021IVA123,2021III009)Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(No.520LH056)Sanya Science and Education Innovation Park of Wuhan University of Technology(No.2020KF0021)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(WUT:2021-ZD-1).
文摘The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work,a dense metal-organic-framework(MOF)modification layer is in-situ prepared by the assistant of polydopamine on the polypropylene separators.Due to the unique structure and synergistic effect of polydopamine(PDA)and zeolitic imidazolate framework-8(ZIF-8),the functional separator can not only trap the polysulfides effectively but also promote the transport of lithium ions.As a result,the battery assembled with the functional separator exhibits excellent cycle stability.The capacity remains 711 mAh·g^(−1)after 500 cycles at 2 C,and the capacity decay rate is as low as 0.013%per cycle.The symmetrical battery is cycled for 1,000 h at 2 mA·cm^(−2)(2 mAh·cm^(−2))with the plating/stripping overpotential of 20 mV.At the same time,the modification separator shows a higher lithium ion transference number(0.88),better thermal stability and electrolyte wettability than the unmodified separator.
基金supported by the National Natural Science Foundation of China (No. 10671066)the Scientific Research Foundation of Qufu Normal University and the Shanghai and Shandong Priority Academic Discipline
文摘The authors introduce the Hausdorff convergence to discuss the differentiable sphere theorem with excess pinching. Finally, a type of rigidity phenomenon on Riemannian manifolds is derived.
基金supported by Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(520LH056)the National Key Research and Development Program of China(2022YFB3803502)。
文摘锂硫电池(LSBs)的实际应用受到硫利用率低、严重的穿梭效应和缓慢的氧化还原反应的限制.本工作通过使用新型莫特-肖特基异质结构对隔膜进行改性的策略有效地缓解上述问题.具体而言,这种特殊结构通过导电聚合物聚吡咯(PPy)在Bi_(2)MoO_(6)纳米片表面原位聚合形成Bi_(2)MoO_(6)-PPy纳米片来合成.基于Bi_(2)MoO_(6)-PPy纳米片的强吸附效应、高催化活性和内置电场,这种新型异质结构可以降低多硫化物上的氧化还原能垒.使用由Bi_(2)MoO_(6)-PPy纳米片改性的功能隔膜组装的电池显示出良好的循环稳定性,在2 C下500次循环中,每次循环的容量衰减低至0.045%.此外,即使在高硫负载(7.5 mg cm^(-2))下,电池在80次循环后仍显示出6.3mA h cm^(-2)的面积容量.因此,Bi_(2)MoO_(6)-PPy纳米片改性隔膜(Bi_(2)MoO_(6)-PPy@PP隔膜)有效地抑制了穿梭效应,为锂硫电池高效催化剂的应用提供了有效策略.
