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Understanding the sluggish and highly variable transport kinetics of lithium ions in LiFePO_4

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Science China Chemistry 2023年第11期66卷 3297-3306页

作者： Youcheng Hu Xiaoxiao Wang Peng Li junxiang chen Shengli chen Hubei Electrochemical Power Sources Key Laboratory Department of ChemistryWuhan UniversityWuhan 430072China CAS Key Laboratory of Design and Assembly of Functional Nanostructures Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China

LiFePO_(4),one of the mainstream cathode materials of current EV batteries,exhibits experimental diffusion coefficients(D_(c))of Li^(+)which are not only several orders of magnitude lower than those predicted by the ionic hopping barriers obtained from theoretical calculations and spectroscopic measurements,but also span several orders from 10^(-14)to 10^(-18)cm^(2)s^(-1)under different states of charge(SOC)and the charging rates(C-rates).Atomic level understanding of such sluggishness and diversity of Li^(+)transport kinetics would be of significance in improving the rate performance of LiFePO_(4)through material and operation optimization but remain ***,we show that the high sensitivity of Li^(+)hopping barriers on the local Li–Li coordination environments(numbers and configurations)plays a key role in the ion transport *** is due a neural network-based deep potential(DP)which allows accurate and efficient calculation of hopping barriers of Li^(+)in LiFePO_(4)with various Li–Li coordination environments,with which the kinetic Monte-Carlo(KMC)method was employed to determine the D_(c)values at various C-rates and SOC across a broad ***,an accelerated KMC simulation strategy is proposed to obtain the D_(c)values under a wide range of SOC at low C-rates,which agree well with that obtained from the galvanostatic intermittent titration technique(GITT).The present study provides accurate descriptions of Li^(+)transport kinetics at both very high and low C-rates,which remains challenging to experiments and first-principles calculations,***,it is revealed that the gradient distributions of Li^(+)density along the diffusion path result in great asymmetry in the barriers of the forward and backward hopping,causing very slow diffusion of Li^(+)and the diverse variation of D_(c).

关键词： lithium iron phosphate diffusion coefficient machine-learning potential kinetic Monte Carlo simulations

Light emission properties of sapphire under shock loading in the stress range of 40-120 GPa

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Science China(Physics,Mechanics & Astronomy) 2013年第3期56卷 562-567页

作者： ZHANG NingChao LIU FuSheng PENG XiaoJuan ZHANG MingJian chen junxiang Laboratory of High Temperature and High Pressure Physics Southwest Jiaotong University National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChinese Academy of Engineering Physics

The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40-120 *** results showed that the spectral distribution with wavelength clearly fit well with the grey-body *** have analyzed the emissions and discovered they mostly came from the shear banding,which is a typical thermal *** radiance intensity changing linearly with time revealed it was a volume *** of the data from pyrometer can be explained by the model of Boslough’s study,especially for pressures over *** color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the different phase structures of sapphire.

关键词： sapphire shock-induced light emission temperature

A General Self-Sacrifice Template Strategy to 3D Heteroatom-Doped Macroporous Carbon for High-Performance Potassium-Ion Hybrid Capacitors

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Nano-Micro Letters 2021年第9期13卷 1-15页

作者： Junwei Li Xiang Hu Guobao Zhong Yangjie Liu Yaxin Ji junxiang chen Zhenhai Wen CAS Key Laboratory of Design and Assembly of Functional Nanostructures and Fujian Provincial Key Laboratory of NanomaterialsFujian Institute of Research On the Structure of MatterChinese Academy of SciencesFuzhouFujian 350002People’s Republic of China

Potassium-ion hybrid capacitors(PIHCs)tactfully combining capacitor-type cathode with battery-type anode have recently attracted increasing attentions due to their advantages of decent energy density,high power density,and low cost;the mismatches of capacity and kinetics between capacitor-type cathode and battery-type anode in PIHCs yet hinder their overall performance ***,based on prediction of density functional theory calculations,we find Se/N co-doped porous carbon is a promising candidate for K+storage and thus develop a simple and universal self-sacrifice template method to fabricate Se and N co-doped three-dimensional(3D)macroporous carbon(Se/N-3DMpC),which features favorable properties of connective hier-archical pores,expanded interlayer structure,and rich activity site for boosting pseudocapacitive activity and kinetics toward K^(+)storage anode and enhancing capacitance performance for the reversible anion adsorption/desorption *** expected,the as-assembled PIHCs full cell with a working voltage as high as 4.0 V delivers a high energy density of 186 Wh kg^(−1) and a power output of 8100 W kg^(−1) as well as excellent long service *** proof-of-concept PIHCs with excellent performance open a new avenue for the development and application of high-performance hybrid capacitors.

关键词： Potassium-ion hybrid capacitors Self-sacrifice template Se/N co-doped 3D macroporous Long service life

Locating the cocktail and scaling-relation breaking effects of high-entropy alloy catalysts on the electrocatalytic volcano plot

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Chinese Journal of Catalysis 2022年第11期43卷 2889-2897页

作者： junxiang chen Yaxin Ji State Key Laboratory of Structural Chemistry and CAS Key Laboratory of Design and Assembly of Functional NanostructuresFujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002FujianChina College of Chemistry and Materials Science Fujian Normal UniversityFuzhou 350007FujianChina

High entropy alloys(HEAs)have been the star materials in electrocatalysis research in recent *** of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic *** increased multiplicity stimulates a cocktail effect and a scaling-relation breaking effect,and results in improved ***,the multiplicity of active sites in HEAs also poses new problems for mechanistic *** apparent problem is the inapplicability to HEA catalysts of the currently most popular mechanistic study method,which uses the electrocatalytic theoretical framework(ETF)based on the computational hydrogen electrode(CHE).The ETF uses a single adsorption energy to represent the catalyst,i.e.,a catalyst is represented by a'point'in the volcanic *** naturally does not involve the multiplicity of active sites of a catalyst,and hence loses brevity in expressing the cocktail effect and scaling-relation breaking effect in HEA *** paper attempts to solve this *** on the fact that the adsorption energy distribution of HEAs is close to a normal distribution,the mean and variance of the adsorption energy distribution are introduced as descriptors of the ETF,replacing the original single adsorption energy.A quantitative relationship between the variance and the cocktail and scaling-relation braking effects is *** believe the method described in this work will make the ETF more effective in mechanistic studies of HEA electrocatalysis.

关键词： High-entropy alloy Electrocatalysis Volcano plot Cocktail effect Scaling-relation breaking effect Adsorption energy distribution

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Electrocatalytic volcano relations:surface occupation effects and rational kinetic models

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Chinese Journal of Catalysis 2022年第1期43卷 2-10页

作者： Yongting chen junxiang chen Shengli chen Hubei Key Laboratory of Electrochemical Power Sources College of Chemistry and Molecular SciencesWuhan UniversityWuhan 430072HubeiChina CAS Key Laboratory of Design and Assembly of Functional Nanostructures Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhouFujian 350002China

Electrocatalysis plays a vital role in technologies of energy and environment relevance,such as water electrolysis,fuel cells,synthesis of carbon and nitrogen-based fuels,*** volcano relations(VRs)are general and standard tools for predicting and understanding the activity trends of *** modern electrocatalytic VRs are generally based on the kinetic models with the maximum free energy(△G^(0)_(max))of reaction steps as the rate-determining term(RDT),in which some important factors that crucially impact the reaction kinetics are missed,for examples,the surface structures and coverages of reaction intermediates and spectators,other free energy demanding steps than that associated with the △G^(0)_(max),and so *** this perspective,we first give a brief introduction of the theoretical framework of current electrocatalytic VRs and the underlying problems in the oversimplifiedDG0max-based kinetic models,and then provide an account of our effort in constructing more rational VRs for electrocatalytic *** introduce a new theoretical framework of electrocatalytic VRs based on kinetic model with the so-called energetic span(δE)serving as *** the surface-coverage effects and multiple free energy-demanding steps are considered,the VRs thus obtained show several new features such as strong potential dependence,asymmetric ascending and descending branches,relatively flat tops,and so *** effectiveness of theδE-based VRs is verified for hydrogen and oxygen electrocatalytic ***,research directions to further rationalize the electrocatalytic VRs are discussed.

关键词： Electrocatalysis Volcano relations Energetic span Hydrogen electrocatalytic reaction Oxygen electrocatalytic reaction

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The Enhancement of Selectivity and Activity for Two-Electron Oxygen Reduction Reaction by Tuned Oxygen Defects on Amorphous Hydroxide Catalysts

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CCS Chemistry 2022年第2期4卷 566-583页

作者： Junheng Huang Changle Fu junxiang chen Nangan Senthilkumar Xinxin Peng Zhenhai Wen CAS Key Laboratory of Design and Assembly of Functional Nanostructures Fujian Provincial Key Laboratory of NanomaterialsFujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhouFujian 350002 University of the Chinese Academy of Science Beijing 100049

Amorphous catalysts,thanks to their uniquely coordinated unsaturated properties and abundance of defect sites,tend to possess higher activity and selectivity than their crystalline *** this work,we report a facile and general solventcontrolled precipitation method to prepare hybrids of graphene oxide(GO)supporting amorphous metal hydroxide[A-M(OH)_(x)/GO,M=Cu,Co,and Mn],which provides us with tangible materials to study the structure–performance relationship of various amorphous *** systematic investigation of A-Cu(OH)_(2)/GO by coupling ex situ/in situ characteristic techniques with electrochemical studies reveals that electrocatalytic activity and selectivity toward a two-electron oxygen reduction reaction(ORR)is highly dependent on the coordinated Cu catalytic sites and the disordered structure of A-Cu(OH)_(2).In situ X-ray absorption near-edge structure(XANES)and density functional theory(DFT)calculation verify that the degree of OH*poisoning(ΔG0 OH*)tuned by three-OH-coordinated Cu sites in amorphous structures plays a crucial role in selective catalysis of ORR for H_(2)O_(2) *** optimized A-Cu(OH)_(2)/GO shows superior activity and high selectivity(~95%)toward H_(2)O_(2),as demonstrated by a zinc–air battery capable of on-site H_(2)O_(2) production with a rate as high as 3401.5 mmol h^(−1) g^(−1).

关键词： amorphous hydroxide general preparation two-electron ORR on-site H_(2)O_(2)production three-OH-coordinated Cu sites

CeO_(2)quantum-dots engineering 3D carbon architectures toward dendrite-free Na anode and reversible Te cathode for high-performance Na-Te batteries

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InfoMat 2022年第10期4卷 90-101页

作者： Yangjie Liu Junwei Li Xiang Hu Jun Yuan Guobao Zhong Lu Zhang junxiang chen Hongbing Zhan Zhenhai Wen CAS Key Laboratory of Design and Assembly of Functional Nanostructures and Fujian Provincial Key Laboratory of NanomaterialsFujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhouFujianChina College of Materials Science and Engineering Fuzhou UniversityFuzhouChina Department of Chemical Engineering KU LeuvenHeverleeBelgium

Sodium-tellurium(Na-Te)battery,thanks to high theoretical capacity and abundant sodium source,has been envisaged as one promising battery technology,its practical application yet faces daunting challenges regarding how to mitigate the critical issues of uncontrollable dendrites growth at Na anode and polytellurides shuttling effect at Te *** here report an elaborative design for fabrication of microsphere skeleton nanohybrids with three-dimensional(3D)hierarchical porous carbon loading CeO_(2)quantum dots(CeO_(2)-QDs/HPC),which feature highly favorable properties of sodiophilic and catalysis for hosting sodium and tellurium,*** systematic investigations coupling with first-principle calculations demonstrate the CeO_(2)-QDs/HPC not only offers favorable structure and abundant electrocatalytic sites for facilitating interconversion between Te and NaxTe as a cathode host,but also can function as dendrite inhibitor anode host for reversible sodium electro-plating/*** Na-Te battery exhibits admiring electrochemical performance with an impressive specific capacity of 392 mAh g1,a long cycling stability over 1000 cycles,as well as remarkably high energy density of 192 Wh kg1 based on the total mass of anode and *** proof-of-concept bifunctional host design for active electrode materials can render a new insight and direction to the development of high-performance Na-Te batteries.

关键词： CeO_(2)quantum dots dual-functional hosts hierarchical porous carbon microsphere skeleton nanohybrids Na-Te batteries

Light emission properties of sapphire under shock loading in the stress range of 40-120 GPa

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Science China Chemistry 2013年第3期56卷 562-567页

The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40 -120 GPa. The results showed that the spectral distribution with wavelength clearly fit well with the grey-body spectrum. We have analyzed the emissions and discovered they mostly came from the shear banding, which is a typical thermal radiation. The radiance intensity changing linearly with time revealed it was a volume effect. All of the data from pyrometer can be explained by the model of Boslough＇s study, especially for pres- sures over megabar. The color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the differcnt phase structures of sapphire.

关键词： sapphire shock-induced light emission temperature

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原料选择处理与原料利用率的关系

中国调味品 2000年第6期25卷 21-23页

作者：陈俊香福建莆糖核苷酸酱油有限公司 351100

提高原料利用率是酱油生产技术与管理的重要内容之一。原料利用率的高低标志着一个生产企业的管理水平 ,而要进一步提高原料利用率就必须在原料选择处理上下功夫。要选择优质高蛋白质的豆粕原料 ;要讲求原料的处理。

关键词：原料选择原料处理原料利用率酱油