查看更多>>摘要：In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxy-gen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectan-gular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relation-ships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concen-tration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structure-performance relationships.
查看更多>>摘要：Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(LiPSs)undergo notorious shuttle effect,which seriously hinders the commercialization of Li-S batteries.Herein,a unique VSe2/V2C heterostructure with local built-in electric field was rationally engineered from V2C parent via a facile thermal selenization process.It exquisitely synergizes the strong affinity of V2C with the effective elec-trocatalytic activity of VSe2.More importantly,the local built-in electric field at the heterointerface can sufficiently promote the electron/ion transport ability and eventually boost the conversion kinetics of sulfur species.The Li-S battery equipped with VSe2/V2C-CNTs-PP separator achieved an outstanding initial specific capacity of 1439.1 mA h g-1 with a high capacity retention of 73％after 100 cycles at 0.1 C.More impressively,a wonderful capacity of 571.6 mA h g-1 was effectively maintained after 600 cycles at 2 C with a capacity decay rate of 0.07％.Even under a sulfur loading of 4.8 mg cm-2,areal capac-ity still can be up to 5.6 mA h cm-2.In-situ Raman tests explicitly illustrate the effectiveness of VSe2/V2C-CNTs modifier in restricting LiPSs shuttle.Combined with density functional theory calculations,the underlying mechanism of VSe2/V2C heterostructure for remedying LiPSs shuttling and conversion kinet-ics was deciphered.The strategy of constructing VSe2/V2C heterocatalyst in this work proposes a univer-sal protocol to design metal selenide-based separator modifier for Li-S battery.Besides,it opens an efficient avenue for the separator engineering of Li-S batteries.
查看更多>>摘要：LiMn2O4(LMO)electrochemical lithium-ion pump has gained widespread attention due to its green,high efficiency,and low energy consumption in selectively extracting lithium from brine.However,collapse of crystal structure and loss of lithium extraction capacity caused by Mn dissolution loss limits its industri-alized application.Hence,a multifunctional coating was developed by depositing amorphous AlPO4 on the surface of LMO using sol-gel method.The characterization and electrochemical performance test pro-vided insights into the mechanism of Li+embedment and de-embedment and revealed that multifunc-tional AlPO4 can reconstruct the physical and chemical state of LMO surface to improve the interface hydrophilicity,promote the transport of Li+,strengthen cycle stability.Remarkably,after 20 cycles,the capacity retention rate of 0.5AP-LMO reached 93.6％with only 0.147％Mn dissolution loss.The average Li+release capacity of 0.5AP-LMO//Ag system in simulated brine is 28.77 mg/(g h),which is 90.4％higher than LMO.Encouragingly,even in the more complex Zabuye real brine,0.5AP-LMO//Ag can still maintain excellent lithium extraction performance.These results indicate that the 0.5AP-LMO//Ag lithium-ion pump shows promising potential as a Li+selective extraction system.
查看更多>>摘要：Transition metal-nitrogen-carbon(M-N-C)as a promising substitute for the conventional noble metal-based catalyst still suffers from low activity and durability for oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).To tackle the issue,herein,a new type of sulfur-doped iron-nitrogen-hard carbon(S-Fe-N-HC)nanosheets with high activity and durability in acid media were devel-oped by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymer-izing two monomers of 2,5-thiophene dicarboxylic acid(TDA)as S source and 1,8-diaminonaphthalene(DAN)as N source via an amination reaction.The as-synthesized S-Fe-N-HC features highly dispersed atomic FeNx moieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals,which is distinguished from the majority of M-N-C with soft or gra-phitic carbon structures.These unique characteristics endow S-Fe-N-HC with high ORR activity and out-standing durability in 0.5 M H2S04.Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 mV after 30,000 cycles.Meanwhile,its practical PEMFC performance is a maximum power output of 628.0 mW cm-2 and a slight power density loss is 83.0 mW cm-2 after 200-cycle practical operation.Additionally,theoretical calculation shows that the activity of FeNx moieties on ORR can be further enhanced by sulfur doping at meta-site near FeN4C.These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts,providing a new guidance for developing advanced M-N-C catalysts for ORR.
查看更多>>摘要：Exploration of advanced gel polymer electrolytes(GPEs)represents a viable strategy for mitigating den-dritic lithium(Li)growth,which is crucial in ensuring the safe operation of high energy density Li metal batteries(LMBs).Despite this,the application of GPEs is still hindered by inadequate ionic conductivity,low Li+transference number,and subpar physicochemical properties.Herein,TiO2-x nanofibers(NF)with oxygen vacancy defects were synthesized by a one-step process as inorganic fillers to enhance the thermal/mechanical/ionic-transportation performances of composite GPEs.Various characterizations and theoretical calculations reveal that the oxygen vacancies on the surface of TiO2-x NF accelerate the dis-sociation of LiPF6,promote the rapid transfer of free Li+,and influence the formation of LiF-enriched solid electrolyte interphase.Consequently,the composite GPEs demonstrate enhanced ionic conductivity(1.90 mS cm-1 at room temperature),higher lithium-ion transference number(0.70),wider electrochemical sta-bility window(5.50 V),superior mechanical strength,excellent thermal stability(210 ℃),and improved compatibility with lithium,resulting in superior cycling stability and rate performance in both Li‖Li,Li‖LiFePO4,and Li[[LiNi0.8Co0.1Mn0.1O2 cells.Overall,the synergistic influence of nanofiber morphology and enriched oxygen vacancy structure of fillers on electrochemical properties of composite GPEs is compre-hensively investigated,thus,it is anticipated to shed new light on designing high-performance GPEs LMBs.
查看更多>>摘要：Metal-organic frameworks(MOFs)are among the most promising materials for lithium-ion batteries(LIBs)owing to their high surface area,periodic porosity,adjustable pore size,and controllable chemical composition.For instance,their unique porous structures promote electrolyte penetration,ions transport,and make them ideal for battery separators.Regulating the chemical composition of MOF can introduce more active sites for electrochemical reactions.Therefore,MOFs and their related composites have been extensively and thoroughly explored for LIBs.However,the reported reviews solely include the applica-tions of MOFs in the electrode materials of LIBs and rarely involve other aspects.A systematic review of the application of MOFs in LIBs is essential for understanding the mechanism of MOFs and better design-ing related MOFs battery materials.This review systematically evaluates the latest developments in pris-tine MOFs and MOF composites for LIB applications,including MOFs as the main materials(anode,cathode,separators,and electrolytes)to auxiliary materials(coating layers and additives for electrodes).Furthermore,the synthesis,modification methods,challenges,and prospects for the application of MOFs in LIBs are discussed.
查看更多>>摘要：The unparalleled energy density has granted lithium-sulfur batteries(LSBs)with attractive usages.Unfortunately,LSBs still face some unsurpassed challenges in industrialization,with polysulfides shut-tling,dendrite growth and thermal hazard as the major problems triggering the cycling instability and low safety.With the merit of convenience,the method of designing functional separator has been adapted.Concretely,the carbon aerogel confined with CoS2(CoS2-NCA)is constructed and coated on Celgard separator surface,acquiring CoS2-NCA modified separator(CoS2-NCA@C),which holds the pro-moted electrolyte affinity and flame retardance.As revealed,CoS2-NCA@C cell gives a high discharge capacity 1536.9 mAh/g at 1st cycle,much higher than that of Celgard cell(987.1 mAh/g).Moreover,the thermal runaway triggering time is dramatically prolonged by 777.4 min,corroborating the promoted thermal safety of cell.Noticeably,the higher coulombic efficiency stability and lower overpotential jointly confirm the efficacy of CoS2-NCA@C in suppressing the lithium dendrite growth.Overall,this work can provide useful inspirations for designing functional separator,coping with the vexing issues of LSBs.
查看更多>>摘要：With the rapid development of rechargeable metal-ion batteries(MIBs)with safety,stability and high energy density,significant efforts have been devoted to exploring high-performance electrode materials.In recent years,two-dimensional(2D)molybdenum-based(Mo-based)materials have drawn consider-able attention due to their exceptional characteristics,including low cost,unique crystal structure,high theoretical capacity and controllable chemical compositions.However,like other transition metal com-pounds,Mo-based materials are facing thorny challenges to overcome,such as slow electron/ion transfer kinetics and substantial volume changes during the charge and discharge processes.In this review,we summarize the recent progress in developing emerging 2D Mo-based electrode materials for MIBs,encompassing oxides,sulfides,selenides,carbides.After introducing the crystal structure and common synthesis methods,this review sheds light on the charge storage mechanism of several 2D Mo-based materials by various advanced characterization techniques.The latest achievements in utilizing 2D Mo-based materials as electrode materials for various MIBs(including lithium-ion batteries(LIBs),sodium-ion batteries(SIBs)and zinc-ion batteries(ZIBs))are discussed in detail.Afterwards,the modu-lation strategies for enhancing the electrochemical performance of 2D Mo-based materials are high-lighted,focusing on heteroatom doping,vacancies creation,composite coupling engineering and nanostructure design.Finally,we present the existing challenges and future research directions for 2D Mo-based materials to realize high-performance energy storage systems.
查看更多>>摘要：Safe batteries are the basis for next-generation application scenarios such as portable energy storage devices and electric vehicles,which are crucial to achieving carbon neutralization.Electrolytes,separa-tors,and electrodes as main components of lithium batteries strongly affect the occurrence of safety acci-dents.Responsive materials,which can respond to external stimuli or environmental change,have triggered extensive attentions recently,holding great promise in facilitating safe and smart batteries.This review thoroughly discusses recent advances regarding the construction of high-safety lithium bat-teries based on internal thermal-responsive strategies,together with the corresponding changes in elec-trochemical performance under external stimulus.Furthermore,the existing challenges and outlook for the design of safe batteries are presented,creating valuable insights and proposing directions for the practical implementation of safe lithium batteries.
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