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Atomic pair distribution function research on Li_2MnO_3 electrode structure evolution

Science Bulletin 2019年第8期64卷 553-561页

作者： Yubo yang Heng Su Tianhao Wu Yuyuan Jiang Danmin Liu pengfei yan Haolai Tian Haijun Yu College of Materials Science and Engineering Key Laboratory of Advanced Functional Materials Ministry of Education Beijing University of Technology Institute of Solid State Microstructure and Properties Beijing Key Laboratory of Microstructure and Property of Advanced Materials Beijing University of Technology China Spallation Neutron Source Dongguan Institute of Neutron Science Institute of High Energy of Physics Chinese Academy of Sciences

The mechanism research of structure-related reactions on Li_2MnO_3 is important to enhance the electrochemical performance of lithium-manganese-rich layered *** there are some reports on the structure evolution of Li_2MnO_3 during cycling process,the employed research techniques are very limited,mainly in/ex-situ X-ray diffraction,X-ray absorption and transmission electron ***,atomic pair distribution function,a method to study the local atomic arrangement on the basis of average spectroscopic information,is used for the first time to study the local structure evolution of Li_2MnO_3 during electrochemical charge/discharge *** results clearly demonstrate that Mn^(3+)/Mn^(4+) redox couple is activated and Mn ions are reduced during discharging *** Mn ions in Mn layers can significantly migrate to Li layers and occupy the octahedral *** a result,a portion of inserted Li ions can occupy the face-shared tetrahedron sites,accompanied by the formation of local spinel-like *** work provides an important and suitable method based on the average spectroscopic information to investigate the local structure of electrode materials of lithium-ion batteries as well as other advanced battery systems.

关键词： Li-ion battery Lithium-manganese-rich layered oxides Local structure Pair distribution function Structure evolution

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Conductive metal-organic frameworks promoting polysulfides transformation in lithium-sulfur batteries

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Journal of Energy Chemistry 2021年第12期30卷 336-343,I0008页

作者： Shuai Wang Fanyang Huang Zhengfeng Zhang Wenbin Cai Yulin Jie Shiyang Wang pengfei yan Shuhong Jiao Ruiguo Cao Hefei National Laboratory for Physical Science at the Microscale Department of Material Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026AnhuiChina Beijing Key Laboratory of Microstructure and Properties of Solids Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing 100124China

Metal organic frameworks(MOFs) have been extensively investigated in Li-S batteries owing to high surface area, adjustable structures and abundant catalytic sites. Nevertheless, the insulating nature of traditional MOFs render retarded kinetics of polysulfides conversion, leading to insufficient utilization of sulfur. In comparison, conductive MOFs(c-MOFs) show great potential for promoting polysulfides transformation due to superb electronic conductivity. In this work, a nickel-catecholates based c-MOF, NiHHTP(HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), is designed to regulate surface chemistry of self-supported carbon paper for advanced Li-S batteries. Taking advantage of the porous structure and high conductivity, the as-prepared Ni-HHTP is conducive to synergising strengthening the chemisorption of polysulfides and accelerating the reaction kinetics in Li-S batteries, significantly mitigating the polysulfides diffusion from the non-encapsulated sulfur cathode, therefore promoting polysulfides transformation in Li-S batteries. This work points out a promising modification strategy for developing advanced sulfur cathode in Li-S batteries.

关键词： Li-S batteries Conductive metal-organic framework Surface modification Ni-HHTP

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The ring-shaped shadow of a rotating naked singularity with a complete photon sphere

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Chinese Physics C 2024年第10期48卷 284-294页

作者： Mingzhi Wang Guanghai Guo pengfei yan Songbai Chen Jiliang Jing School of Mathematics and Physics Qingdao University of Science and TechnologyQingdao 266061China Institute of Physics and Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We investigate the shadows of the Konoplya-Zhidenko naked *** the spacetime of the Konoplya-Zhidenko naked singularity,not only an unstable retrograde light ring(LR)but also an unstable prograde LR exists,leading to the formation of a complete photon sphere(PS).Due to the absence of an event horizon,a dark discshaped shadow does not appear;instead,a ring-shaped shadow is *** ring-shaped shadow appears as an infinite number of relativistic Einstein rings in the image of the naked *** some parameter values,only the unstable retrograde LR exists,resulting in an incomplete unstable PS and thus giving rise to an arc-shaped shadow for the Konoplya-Zhidenko naked *** shadow of the Konoplya-Zhidenko naked singularity gradually shifts to the right as the rotation parameter a increases and gradually becomes smaller as the deformation parameter |η| ***,stable LRs and stable photon spherical orbits can exist in the Konoplya-Zhidenko naked singularity spacetime,but they have no effect on the image of the naked *** study demonstrates that a rotating naked singularity can exhibit not only an arc-shaped shadow but also a ring-shaped shadow.

关键词： black hole shadow naked singularity photon sphere light ring

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Interfacial Chemistry Enables Highly Reversible Na Extraction/Intercalation in Layered-Oxide Cathode Materials

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Chinese Journal of Chemistry 2023年第15期41卷 1791-1796页

作者： Chenchen Wang Kuan Wang Meng Ren Yaohui Huang Kai Zhang Changzhong Liao Kaimin Shih pengfei yan Fujun Li Key Laboratoryof Advanced Energy Materials Chemistry(Ministry of Education) Renewable Energy Conversion and Storage Center(RECAST)College of ChemistryNankai UniversityTianjin 300071China Haihe Laboratory of Sustainable Chemical Transformations Tianjin.300192China Beijing Key Laboratory of Microstructure and Properties of Solids Institute of Microstructure and Properties of Advanced Materials BeijingUniversityofTechnology Beijing100124China School of Resources Environment and MaterialsGuangxi UniversityNanningGuangxi 530004China Department of Civil Engineering The University of Hong KongPokfulam RoadHong KongChina

Comprehensive Summary Layered transition-metal oxides are promising cathode candidates for sodium-ion ***,the inferior interphase formation and particulate fracture during sodiation/desodiation result in structure degradation and poor ***,the interface chemistry of P2-Na_(0.640)Ni_(0.343)Mn_(0.657)O_(2)in an electrolyte of 1.0 mol/L NaPF6 in diglyme is unveiled to enable highly reversible Na extraction and *** uniform and robust cathode-electrolyte interphase layer is in situ formed with decomposition of diglyme molecules and anions in initial *** NaF-and CO-rich CEI film exhibits high mechanical strength and ionic conductivity,which suppresses the reconstruction of its electrode interphase from P2 phase to spinel-like structure and reinforces its structure integrity without *** favours facile Na+transport and stable bulk redox *** is demonstrated to show long cycling stability with capacity retention of 94.4%for 180 cycles and superior rate *** investigation highlights the cathode interphase chemistry in sodium-ion batteries.

关键词： Sodium-ion batteries Cathodes Layered oxides Ether electrolyte Surface Chemistry Reversibility

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Circularly polarized luminescence switch based on a photochromic europium(Ⅲ) helicate derived coordination polymer

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Chinese Chemical Letters 2024年第2期35卷 272-277页

作者： Mei Li yanyan Zhou Jingya Li Wenru Huang Zhiwei Yao Yuying Li Ting Gao pengfei yan Hongfeng Li Key Laboratory of Functional Inorganic Material Chemistry Ministry of EducationSchool of Chemistry and Materials ScienceHeilongjiang UniversityHarbin 150080China State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization Institution Baotou 014030China

Chiroptical switches based on circularly polarized luminescence(CPL)have shown the promising applications in advanced information ***,a pair of lanthanide coordination polymer enantiomers[Eu_(2)(L^(R))_(3)(BTFPO)_(2)]_(n) and[Eu_(2)(L^(S))_(3)(BTFPO)_(2)]_(n) with light-regulated CPL property are designed,which are assembled by a chiral binuclear triple-stranded Eu^(3+) helicates[Eu_(2)(L^(R/S))_(3)]coordinated with two photochromic triphenylphosphine oxides(BTFPO).Upon the alternative UV and 526 nm light irradiation,the complexes show the reversible photochromism,PL and CPL ***,the luminescence dissymmetry factor,g lum of ^(5)D_(0)→^(7)F_(1)(591 nm)transition shows an obvious increase from 0.19 to 0.29 before and after 275 nm light ***,the emission from Eu^(3+) center is not completely quenched in closed-ring state due to the low photocyclization(Ф_(o-c))quantum yield of the *** partial maintenance of emissive intensity is of essential importance for the monitor of CPL *** importantly,the CPL photo-switching property of the complexes in solid hybrid film is maintained,and still displays the enhanced CPL emission in photostationary ***,the potential applications of the doping film in logic gate and anti-counterfeiting were investigated.

关键词： Chiroptical switches Coordination polymer CPL Anti-counterfeiting Logic gate

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Precipitate-stabilized surface enabling high-performance Na_(0.67)Ni_(0.33-x)Mn_(0.67)Zn_(x)O_(2) for sodium-ion battery

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eScience 2022年第5期2卷 529-536页

作者： Kuan Wang Zhengfeng Zhang Sulan Cheng Xiao Han Junjie Fu Manling Sui pengfei yan Beijing Key Laboratory of Microstructure and Properties of Solids Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China

Electrode interfacial degradations are the key challenges for high-performance rechargeable batteries,usually mitigated through surface modification/coating ***,we report a novel mechanism to enhance the surface stability of P2 layered cathodes by introducing a high density of dopant-enriched *** on microscopic analysis,we show that forming a high density of precipitates at the grain surface can effectively suppress surface cracking and corrosion,which not only improves the surface/interface stability but also effectively suppresses the intergranular cracking *** the doping level can lead to a greater density of precipitates at the surface region,which results in higher surface stability and increased cycling stability of the P2 layered cathode for a sodium-ion *** further reveal that prolonged cycling can induce the formation of a precipitate-free surface region due to the loss of Zn dopant and *** in-depth microanalysis reveals cycling-induced dynamic structural evolution of the P2 layered cathodes,highlighting that dopant segregation-induced precipitation is a new approach to achieving high interfacial stability.

关键词： Layered cathode TEM Precipitate Sodium-ion battery Surface stability

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Suppressed oxygen extraction and degradation of LiNixMnyCo2O2 cathodes at high charge cut-off voltages

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Nano Research 2017年第12期10卷 4221-4231页

作者： Jianming Zheng pengfei yan Jiandong Zhang Mark H. Engelhard Zihua Zhu Bryant J. Polzin Steve Trask Jie Xiao Chongmin Wang Jiguang Zhang Energy and Environment Directorate Pacific Northwest National Laboratory 902 Battelle Boulevard Richland WA 99354 USA Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory 3335 Innovation Boulevard Richland WA 99354 USA Chemical Sciences and Engineering Division Argonne National Laboratory 9700 South Cass Avenue Argonne IL 60439 USA

The capacity degradation mechanism in lithium nickel-manganese-cobalt oxide （NMC） cathodes （LiNi1/3Mn1/3Co1/3O2 （NMC333） and LiNi0.4Mn0.4Co0.2O2 （NMC442）） during high-voltage （cut-off of 4.8 V） operation has been investigated. In contrast to NMC442, NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interracial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3＋/4＋ t2g and O2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems.

关键词： layered structure high-voltage cycling structural stability interfacial stability material composition Li-ion battery

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One-dimensional metal phosphonates based on 6-phosphononicotinic acid:A structural and magnetic study

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Science China Chemistry 2010年第10期53卷 2112-2117页

作者： WANG pengfei, DUAN yan & ZHENG LiMin State Key Laboratory of Coordination Chemistry Coordination Chemistry Institute, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China 1. State Key Laboratory of Coordination Chemistry Coordination Chemistry Institute School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China

The reactions of 6-phosphononicotinic acid (pnaH3) and metal salts result in three new compounds, namely, M(pnaH)-(H2O)3·H2O [M = Co(Ⅱ) (1), Ni(Ⅱ) (2), Zn(Ⅱ) (3)]. These compounds are isostructural and contain 21 helical chains made up of corner-sharing {MO5N} octahedra and {PO3C} tetrahedra. The chains are further connected by extensive hydrogen bonds to form a three-dimensional supramolecular structure. Magnetic studies reveal that dominant antiferromagnetic interactions are mediated in both 1 and 2. Interestingly the dehydrated compound 1 shows metamagnetic behavior at low temperature.

关键词： carboxylate-phosphonate coordination polymer magnetic property metamagnetism

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Current-perpendicular-to-plane transport properties of 2D ferromagnetic material CrTe_(2)

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Chinese Physics B 2024年第9期33卷 535-539页

作者： Jin Wang Yu Liu Taikun Wang Yongkang Xu ShuanghaiWang Kun He Yafeng Deng pengfei yan Liang He School of Electronic Science and Engineering Nanjing UniversityNanjing 210023China State Key Laboratory of Spintronics Nanjing UniversitySuzhou 215163China

Heterostructures of van der Waals(vdW)ferromagnetic materials have become a focal point in research of lowdimensional spintronic *** current direction in spin valves is commonly perpendicular to the plane(CPP).However,the transport properties of the CPP mode remain largely *** this work,current-in-plane(CIP)mode and CPP mode for CrTe_(2) thin films are carefully *** temperature-dependent longitudinal resistance transitions from metallic(CIP)to semiconductor behavior(CPP),with the electrical resistivity of CPP increased by five orders of *** importantly,the transport properties of the CPP can be categorized into a single-gap tunneling-through model with the activation energy(Ea)of1.34 meV/gap at 300–150 K,the variable range hopping model with a linear negative magnetoresistance at 150–20 K,and weak localization region with a nonlinear magnetic resistance below 20 *** study explores the vertical transport in CrTe_(2) materials for the first time,contributing to understand its unique properties and to pave the way for its potential in spin valve devices.

关键词： 2D vdW CrTe_(2) current-perpendicular-to-plane negative magnetic resistance

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CO_(2) coordination-driven top-down synthesis of a 2D non-layered metal-organic framework

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Fundamental Research 2022年第5期2卷 674-681页

作者： yannan Zhou pengfei yan Suoying Zhang Yunxiao Zhang Hongwei Chang Xiaoli Zheng Jingyun Jiang Qun Xu College of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450052China Henan Institute of advanced technology Zhengzhou UniversityZhengzhou 450052China Key Laboratory of Flexible Electronics&Institute of Advanced Materials Nanjing Tech University30 South Puzhu RoadNanjing 211816China

Combining the physical advantages of two-dimensional(2D)inorganic nanosheets and the modular design and programmed structure of metal-organic frameworks(MOFs),2D MOFs remain at the forefront of functional material *** tremendous efforts,precise control in the synthesis of 2D nonlayered MOFs with predesigned topology for desired applications remains *** in the bottom-up synthesis of 2D nonlayered MOFs via ligand exchange motivated us to incorporate partial BTC(BTC=1,3,5-benzenetricarboxylate)ligand dissociation and CO_(2) capped coordination into the top-down treatment of bulk Cu-BTC MOF,leading to successful conversion of a 3D nonlayered network to a 2D Cu-based topological ***,a supercritical CO_(2)-containing solvent mixture is employed to provide the desired defect and coordination ***,our work introduces a new top-down concept based on modulated synthesis to fabricate high-quality 2D nonlayered MOFs for the first time.

关键词： Top-down Metal-organic frameworks 2D nonlayered Cu-BTC CO_(2)coordination Defect engineering

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