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Design of Flexible Films Based on Kinked Carbon Nanofibers for High Rate and Stable Potassium-Ion Storage

Nano-Micro Letters 2022年第3期14卷 184-200页

作者： qiaotian xiong Hongcheng He Ming Zhang Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education&Hunan Provincial Key Laboratory of Low‑Dimensional Structural Physics&Devices School of Physics and ElectronicsCollege of Semiconductors(College of Integrated Circuits)Hunan UniversityChangsha 410082People’s Republic of China Semiconductor Technology and Application Innovation Institute of Changsha Changsha 410012People’s Republic of China

With the emergence of wearable electronics,flexible energy storage materials have been extensively studied in recent years.However,most studies focus on improving the electrochemical properties,ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability.In this study,porous,kinked,and entangled network structures are designed for highly flexible fiber films.Based on theoretical analysis and finite element simulation,the bending degree of the porous structure(30%porosity)increased by 192%at the micro-level.An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films.Therefore,a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers(S/N-KCNFs)is synthesized.The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous,kinked,and entangled network structure,and the stretching degree increased several times.The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3%after 2000 cycles.Moreover,the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88%capacity retention after 4000 cycles.This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials.

关键词： Flexible design Finite element simulation Sulfur-/nitrogen-Co-doped Anode Potassium-ion storage

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Enabling Multi-Chemisorption Sites on Carbon Nanofibers Cathodes by an In-situ Exfoliation Strategy for High-Performance Zn–Ion Hybrid Capacitors

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Nano-Micro Letters 2022年第7期14卷 1-15页

作者： Hongcheng He Jichun Lian Changmiao Chen qiaotian xiong Cheng Chao Li Ming Zhang Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and DevicesHunan Joint International Laboratory of Advanced Materials and Technology for Clean EnergySchool of Physics and ElectronicsCollege of Semiconductors(College of Integrated Circuits)Hunan UniversityChangsha 410082People’s Republic of China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055People’s Republic of China School of Chemical Engineering and Light Industry Guangdong University of TechnologyGuangzhou 510006People’s Republic of China

Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption sites.In this work,an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization.The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Z n2+by inducing charge delocalization of the carbonyl group,but also promote the adsorption of Zn2+by bonding with the carbonyl group to form N–Zn–O bond.Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms,the resulting carbon nanofibers film cathode displays a high energy density,an ultralong-term lifespan,and excellent capacity reservation under commercial mass loading(14.45 mg cm-2).Particularly,the cathodes can also operate stably in flexible or quasi-solid devices,indicating its application potential in flexible electronic products.This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.

关键词： Nitrogen doping Carbonyl functionalization Chemisorption sites Flexible Zn-ion hybrid capacitors

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不同参数对带粗糙冰翼型绕流流场结构影响的实验研究

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上海交通大学学报 2023年第9期57卷 1221-1230页

作者：郑诚毅杜旭之东乔天杨志刚熊兵徐毅吴凌昊金哲岩同济大学航空航天与力学学院上海200092 中国商用飞机上海飞机设计研究院上海201203 上海市地面交通工具空气动力与热环境模拟重点实验室上海201804 中国航发四川燃气涡轮研究院四川绵阳621000

粗糙冰会改变翼型前缘轮廓从而影响翼型整体的气动特性.研究过冷大水滴结冰条件下产生的粗糙冰对翼型绕流流场结构的影响可以为飞机的防/除冰设计提供参考.利用粒子图像测速技术在低速直流风洞内对表面覆盖粗糙冰的翼型模型的绕流流场... 详细信息

粗糙冰会改变翼型前缘轮廓从而影响翼型整体的气动特性.研究过冷大水滴结冰条件下产生的粗糙冰对翼型绕流流场结构的影响可以为飞机的防/除冰设计提供参考.利用粒子图像测速技术在低速直流风洞内对表面覆盖粗糙冰的翼型模型的绕流流场结构开展了详细的实验测量研究,主要探究了粗糙冰对涡量和标准化雷诺应力分布的影响.研究参数包括雷诺数、粗糙冰的粗糙度和翼型的攻角.结果表明:随着雷诺数增大,带冰翼型尾流处的涡量范围和数值增大,标准化雷诺应力值略微减小;粗糙冰的存在降低了翼型近壁面处气流速度,增加了尾流的涡量并严重影响切应力分布;与光滑翼型相比,粗糙冰会使气流提前分离,且分离泡内的气流速度波动更剧烈.

关键词：雷诺数过冷大水滴粗糙冰攻角绕流流场结构

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