The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is...The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is a promising candidate [1,2]. Some noblemetal-based (e.g., Pt, Pd and Rh) catalysts exhibit significant catalytic activity to the conversion reaction of these biomass.展开更多
The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electroch...Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.展开更多
Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition...Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is studied.Amorphous cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning process.Upon heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are formed.During the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the nanofiber.To unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were adopted.Based on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)Se.Furthermore,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in detail.The anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).展开更多
SnO2-based anode materials have attracted much attention due to high capacity and relatively mild voltage platforms.However,limited by low initial Coulombic efficiency(ICE)and poor stability,its practical application ...SnO2-based anode materials have attracted much attention due to high capacity and relatively mild voltage platforms.However,limited by low initial Coulombic efficiency(ICE)and poor stability,its practical application is still challenging.Recently,it has been found that compositing carbon or metal particles with SnO2 is an effective strategy to achieve high alkaline-ion storages.Although this strategy may improve the kinetics and ICE of the electrochemical reaction,the specific mechanism has not been clearly elucidated.In this work,we found that the invalidation SnO2 may go through two steps:1)the conversion process from SnO2 to Sn and Li2O;2)the collapse of the electrode material resulted from huge volume changes during the alloyed Sn with alkaline ions.To address these issues,a unique robust Co-NC shell derived from ZIF-67 is introduced,in which the transited metallic Co nanoparticles could accelerate the decomposition of Sn-O and Li-O bonds,thus expedite the kinetics of conversion reaction.As a result,the SnO2@Co-NC electrode achieves a more complete and efficient transfer between SnO2 and Sn phases,possessing a potential to achieve high alkaline-ion(Li+/Na+/K+)storages.展开更多
Due to the unique interface and electronic structure,metal/metal oxide composite electrocatalysts have been designed and exploited for electrocatalytic oxygen evolution reaction(OER)in alkaline solution.However,how to...Due to the unique interface and electronic structure,metal/metal oxide composite electrocatalysts have been designed and exploited for electrocatalytic oxygen evolution reaction(OER)in alkaline solution.However,how to fabricate metal/metal oxides with abundant interfaces and well-dispersed metal phases is a challenge,and the synergistic effect between metal and metal oxides on boosting the electrocatalytic activities is still ambiguous.Herein,by controlling the lithium-induced conversion reaction of metal oxides,metal/metal oxide composites with plentiful interfaces and excellent electrical interconnection are fabricated,which can enhance the active sites,and accelerate the mass transfer during the electrocatalytic reaction.As a result,the electrocatalytic oxygen evolution activities of the as-fabricated metal/metal oxide composite catalysts including NiCo/NiCo2O4,NiMn/NiMn2O4 and CoMn/CoMn2O4 are greatly improved.The catalytic mechanism is also explored using the in-situ X-ray and Raman spectroscopic tracking to uncover the real active centers and the synergistic effect between the metal and metal oxides during water oxidation.Density functional theory plus U(DFT+U)calculation confirms the metal in the composite can optimize the catalytic reaction path and reduce the reaction barrier,thus boosting the electrocatalytic kinetics.展开更多
Contemporary social problems,such as energy shortage and environmental pollution,require developing green energy storage technologies in the context of sustainable development.With the application of secondary battery...Contemporary social problems,such as energy shortage and environmental pollution,require developing green energy storage technologies in the context of sustainable development.With the application of secondary battery technology becoming widespread,the development of traditional lithium(Li)-ion batteries,which are based on insertion/deinsertion reactions,has hit a bottleneck;instead,conversion-type lithium metal batteries(LMBs)have attracted considerable attention owing to the high theoretical capacity of Li metal anodes.In this review,Li-S,Li-O_(2),and Li-SOCl_(2)batteries are used as examples to summarize LMBs based on their conversion reactions from the perspectives of cathode material,anode material,electrolyte,separator,and current collector.Key challenges exist regarding the conversion reactions of various batteries.To achieve the optimum performance and improve the application effect,several improvement strategies have been proposed in relation to reasonable designs of next-generation high-performance rechargeable batteries.展开更多
Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid p...Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid performance degradation over long-term cycling.Herein,we report a high-entropy single-atom(HE-SA)catalyst to regulate the multi-step conversion of LiPS to attain a high-performance Li-S battery.Both the density functional theory calculations and the experimental results prove that the Fe atomic site with high spin configurations strongly interacts with Li_(2)S_(4)through d-p and s-p synergistic orbital hybridization which facilitates the reduction of LiPS.Moreover,S-dominant p-d hybridization between Li_(2)S and a high-spin Mn site weakens the Li-S bond and facilitates the rapid sulfur evolution reaction.Consequently,the Li-S battery with a bifunctional HE-SA catalyst shows an ultralow capacity decay of 0.026% per cycle over 1900 cycles at 1 C.This work proposes a high-entropy strategy for sculpting electronic structures to enable spin and orbital hybridization modulation in advanced catalysts toward longcycling Li-S batteries.展开更多
Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and ...Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.展开更多
Given the abundance of potassium resources,potassium-ion batteries are considered a low-cost alternative to lithium-ion types.However,their electrochemical performance remains rather unsatisfactory because potassium i...Given the abundance of potassium resources,potassium-ion batteries are considered a low-cost alternative to lithium-ion types.However,their electrochemical performance remains rather unsatisfactory because potassium ions have sluggish kinetics and large ionic radius.In this study,NiCo_(2)Se_(4)nanotube spheres are synthesized as efficient potassium storage hosts via a facile two-step hydrothermal process.The rationally designed electrode has various ameliorating morphological and functional features,including the following:(i)A hollow structure allows for relief of the volume expansion while offering an excellent electrochemical reac-tivity to accelerate the conversion kinetics;(ii)a high electrical conductivity for enhanced electron transfer;and(iii)myriad vacancies to supply active sites for electrochemical reactions.As such,the electrode delivers an initial reversible capacity of 458.1 mAh g^(−1)and retains 346.6 mAh g^(−1)after 300 cycles at 0.03 A g^(−1).The electrode sustains a high capacity of 101.4 mAh g^(−1)even at a high current density of 5 A g^(−1)and outperforms the majority of state-of-the-art anodes in terms of both cyclic capacity and rate capability,especially at above 1.0 A g^(−1).This study not only proves bimetallic selenides are promising candidates for potassium storage devices but also offers new insight into the rational design of electrode materials for high-rate potassium-ion batteries.展开更多
Mg secondary batteries are promising scalable secondary batteries for next-generation energy storage.However,Mg-storage cathode materials are greatly demanded to construct high-performance Mg batteries.Electrochemical...Mg secondary batteries are promising scalable secondary batteries for next-generation energy storage.However,Mg-storage cathode materials are greatly demanded to construct high-performance Mg batteries.Electrochemical conversion reaction provides plenty of cathode options,and strategy for cathode selection and performance optimization is of special significance.In this work,Ni0.85Se with nanostructures of dispersive hexagonal nanosheets(D-Ni0.85Se)and flower-like assembled nanosheets(F-Ni0.85Se)is synthesized and investigated as Mg-storage cathodes.Compared with F-Ni0.85Se,D-Ni0.85Se delivers a higher specific capacity of 168 mAh g^-1 at 50 mA g^-1 as well as better rate performance,owing to its faster Mg^2+-diffusion and lower resistance.D-Ni0.85Se also exhibits a superior cycling stability over 500cycles.An investigation on mechanism indicates an evolution of Ni0.85Se towards NiSe with cycling,and the Mg-storage reaction occurs between NiSe and metallic Ni^0.The present work demonstrates that advanced conversion-type Mg battery cathode materials could be constructed by soft selenide anions,and the electrochemical properties could be manipulated by rational material morphology optimization.展开更多
Low-cost and high-safety aqueous Zn-I_(2) batteries attract extensive attention for large-scale energy storage systems.However,polyiodide shuttling and sluggish iodine conversion reactions lead to inferior rate capabi...Low-cost and high-safety aqueous Zn-I_(2) batteries attract extensive attention for large-scale energy storage systems.However,polyiodide shuttling and sluggish iodine conversion reactions lead to inferior rate capability and severe capacity decay.Herein,a three-dimensional polyaniline is wrapped by carboxylcarbon nanotubes(denoted as C-PANI)which is designed as a catalytic cathode to effectively boost iodine conversion with suppressed polyiodide shuttling,thereby improving Zn-I_(2) batteries.Specifically,carboxyl-carbon nanotubes serve as a proton reservoir for more protonated-NH+=sites in PANI chains,achieving a direct I0/I−reaction for suppressed polyiodide generation and Zn corrosion.Attributing to this“proton-iodine”regulation,catalytic protonated C-PANI strongly fixes electrolytic iodine species and stores proton ions simultaneously through reversible-N=/-NH^(+)-reaction.Therefore,the electrolytic Zn-I_(2) battery with C-PANI cathode exhibits an impressive capacity of 420 mAh g^(−1) and ultra-long lifespan over 40,000 cycles.Additionally,a 60 mAh pouch cell was assembled with excellent cycling stability after 100 cycles,providing new insights into exploring effective organocatalysts for superb Zn-halogen batteries.展开更多
The photochromic ring-opening reaction of spiropyran（SP） has been investigated by a realistic semiclassical dynamics simulation,accompanied by SA3-CASSCF（12 10）/MS-CASPT2 potential energy curves（PECs） of S0–S2....The photochromic ring-opening reaction of spiropyran（SP） has been investigated by a realistic semiclassical dynamics simulation,accompanied by SA3-CASSCF（12 10）/MS-CASPT2 potential energy curves（PECs） of S0–S2.The main simulation results show the dominate pathway corresponds to the ringopening process of trans-SP to form the most stable merocyanine（MC） product.These findings provide more important complementarity for interpreting experimental observations.展开更多
Lithium-sulfur battery(LSB)has attracted worldwide attention owing to its overwhelmingly high theoretical energy density of 2600Wh/kg due to the unique 16-electron electrochemical conversion reaction of elemental sulf...Lithium-sulfur battery(LSB)has attracted worldwide attention owing to its overwhelmingly high theoretical energy density of 2600Wh/kg due to the unique 16-electron electrochemical conversion reaction of elemental sulfur(S_(8))[1].However,the electrochemical conversion reaction of S_(8) is an exceedingly complex process that involves the generation of multiple intermediates(e.g.,lithium polysulfides(LiPSs))and multiphase transitions[1,2].Currently,the mechanistic investigations of the electrochemical conversion reaction of S_(8) upon discharging a LSB cell heavily rely on electrochemical titration and spectroscopic techniques[3].Nevertheless,the considerable complexity and intrinsic instability of the LSB system present substantial obstacles to obtaining accurate information for all sulfur-containing species,which significantly obstructs in-depth elucidation of the fundamental discharge mechanism of LSB[3,4].展开更多
Nowadays,lithium-ion batteries (LIBs) have held the dominant role in various electric energy storage devices.With the rapid development of new energy vehicles and large-scale energy storage fields,there is an urgent d...Nowadays,lithium-ion batteries (LIBs) have held the dominant role in various electric energy storage devices.With the rapid development of new energy vehicles and large-scale energy storage fields,there is an urgent demand for high-energy LIBs.While anode materials are important for determining energy density,commercialized graphite cannot meet the requirement for high specific capacity,and silicon-based materials always suffer from poor cycle stability.High-entropy oxides (HEOs) are emerging as a new category of single-phase material consisting of multiple principal elements with equimolar or quasi-equimolar ratios.Due to the design flexibility and interaction between multiple functional elements,HEOs can display improved comprehensive properties as LIBs anodes,which is expected to be a potential solution for high-energy LIBs.Herein,this review provides an extensive overview of the recent progress of HEOs anode materials in LIBs.The electrochemical properties of three typical HEOs are summarized,the synthesis methods for HEOs are subsequently elaborated,and current lithium storage mechanisms are analyzed in detail.Finally,the modification strategies are offered for further research to promote the development of HEO anodes in LIBs,including composition manipulations and the enhancement of conversion kinetic.It is aimed to propose practical guidance for exploration of HEO anode materials in next-generation high-energy batteries.展开更多
All-solid-state Li-S batteries(ASSLSBs)are more attractive owing to their achievable superior energy density at a reasonable cost and the solid electrolyte(SE)utilization mitigating the widely recognized polysulfide s...All-solid-state Li-S batteries(ASSLSBs)are more attractive owing to their achievable superior energy density at a reasonable cost and the solid electrolyte(SE)utilization mitigating the widely recognized polysulfide shuttle problem.While the volume expansion(~80%)that occurs during the initial transformation of sulfur to lithium sulfide induces mechanical stress,this can be avoided by using Li_(2)S as a cathode,which also permits the anode-free cell design.However,the high oxidation energy barrier of Li_(2)S cathode during the charging step limits its application in commercial devices.Redox mediators have been extensively used to reduce the oxidation energy barrier of Li_(2)S to the sulfur conversation and boost the reversible kinetics of the conversion reaction.In this review,we have summarized the available redox mediators for Li_(2)S cathode in ASSLSBs and its working mechanism.Moreover,we have proposed novel strategies and guidelines for designing effective redox mediators to boost the reversible conversion reaction.展开更多
Increasing battery voltage and electrode utilization is of great significance for improving the energy density of aqueous battery.Herein,for the first time,this work introduces an integrated design strategy to regulat...Increasing battery voltage and electrode utilization is of great significance for improving the energy density of aqueous battery.Herein,for the first time,this work introduces an integrated design strategy to regulate electrode potential and improve electrode utilization based on the concept of electrochemical precipitation energy.By coupling precipitation reaction with original electrode reaction,the Gibbs free energy change(ΔrG^(θ))of the precipitation reaction is coupled to battery reaction’sΔrG^(θ),thereby altering battery’s voltage.Besides,the electrode reaction changes to solid-to-solid reaction after coupling with precipitation reaction,which can improve electrode utilization.The potential of Cu is reduced from 0.34 to-0.96 V(the lowest value among all the reported Cu anode)with a Cu utilization of 87.93%(without additional copper in electrolyte)by coupling Cu_(2)S’s precipitation reaction.Furthermore,the potential of I_(2) is increased from 0.54 to 0.65 V(I_(2)/CuI)and 0.73 V(I_(2)/PbI_(2))by coupling precipitation reaction of CuI and PbI_(2) and the shutting effect of I_(3)^(-)is also limited.As proof of concept,a full Cu_(2)S battery(cathode:S/Cu_(2)S,anode:Cu/Cu_(2)S)is designed with average discharge voltage of 1.12 V,which is the highest value among all the Cu-based aqueous batteries.Due to the certain universality of this strategy,this work provides a new path to regulate the electrode reaction potential and improve electrode utilization.展开更多
Fluorinated carbons(CFx)have been widely applied as lithium primary batteries due to their ultra-high energy density.It will be a great promise if CFx can be rechargeable.In this study,we rationally tune the C-F bond ...Fluorinated carbons(CFx)have been widely applied as lithium primary batteries due to their ultra-high energy density.It will be a great promise if CFx can be rechargeable.In this study,we rationally tune the C-F bond strength for the alkaline intercalated CFx via importing an electronegative weaker element K instead of Li.It forms a ternary phase K_(x)FC instead of two phases(LiF+C)in lithium-ion batteries.Meanwhile,we choose a large layer distance and more defects CFx,namely fluorinated soft carbon,to accommodate K.Thus,we enable CFx rechargeable as a potassium-ion battery cathode.In detail fluorinated soft carbon CF_(1.01) presents a reversible specific capacity of 339 mA h g^(-1)(797 Wh kg^(-1))in the 2nd cycle and maintains 330 mA h g^(-1)(726 Wh kg^(-1))in the 15th cycle.This study reveals the importance of tuning chemical bond stability using different alkaline ions to endow batteries with rechargeability.This work provides good references for focusing on developing reversible electrode materials from popular primary cell configurations.展开更多
The two major limitations in the application of SnO_2 for lithium?ion battery(LIB) anodes are the large volume variations of SnO_2 during repeated lithiation/delithiation processes and a large irreversible capacity lo...The two major limitations in the application of SnO_2 for lithium?ion battery(LIB) anodes are the large volume variations of SnO_2 during repeated lithiation/delithiation processes and a large irreversible capacity loss during the first cycle, which can lead to a rapid capacity fade and unsatisfactory initial Coulombic e ciency(ICE). To overcome these limitations, we developed composites of ultrafine SnO_2 nanoparticles and in situ formed Co(CoSn) nanocrystals embedded in an N?doped carbon matrix using a Co?based metal–organic framework(ZIF?67). The formed Co additives and structural advantages of the carbon?confined SnO_2/Co nanocomposite e ectively inhibited Sn coarsening in the lithiated SnO_2 and mitigated its structural degradation while facilitating fast electronic transport and facile ionic di usion. As a result, the electrodes demonstrated high ICE (82.2%), outstanding rate capability(～ 800 mAh g^(-1) at a high current density of 5 A g^(-1)), and long?term cycling stability(～ 760 mAh g^(-1) after 400 cycles at a current density of 0.5 A g^(-1)). This study will be helpful in developing high?performance Si(Sn)?based oxide, Sn/Sb?based sulfide, or selenide electrodes for LIBs. In addition, some metal organic frameworks similar to ZIF?67 can also be used as composite templates.展开更多
Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) for large-scale energy storage considering the abundance and low cost of Na-containing resources. However, the energy density of S...Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) for large-scale energy storage considering the abundance and low cost of Na-containing resources. However, the energy density of SIBs has been limited by the typically low specific capacities of traditional intercalation-based cathodes. Metal fluorides, in contrast, can deliver much higher capacities based on multi-electron conversion reactions. Among metal fluorides, CuF_(2) presents a theoretical specific capacity as high as 528 mAh/g while its Na-ion storage mechanism has been rarely reported. Here, we report CuF_(2) as a SIB cathode, which delivers a high capacity of 502 mAh/g but suffers from poor electrochemical reversibility. As a solution, we adjust the cell configuration by inserting a carbon-coated separator, which hinders the transportation of dissolved Cu ions and improves the reversibility of the CuF_(2) cathode. By using in-situ XRD measurements and theoretical calculation, we propose that a one-step conversion reaction occurs during the discharge process, and a reconversion reaction competes with the oxidization of Cu to dissolved Cu ion during the charge process.展开更多
文摘The quest for sustainable energy solutions has intensified the search for alternative feedstocks that can supplement or replace fossil fuels. Obtaining fuels or chemicals through the conversion of renewable biomass is a promising candidate [1,2]. Some noblemetal-based (e.g., Pt, Pd and Rh) catalysts exhibit significant catalytic activity to the conversion reaction of these biomass.
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
基金financially supported by NSFC (Grant Nos.21621091,21373008)the National Key Research and Development Program of China (2016YFB0100202)
文摘Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.
基金financially supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.NRF2019R1A2C2088047)。
文摘Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is studied.Amorphous cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning process.Upon heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are formed.During the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the nanofiber.To unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were adopted.Based on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)Se.Furthermore,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in detail.The anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).
基金This work is financially supported by the National Key R&D Program of China(No.2017YFE0198100)the National Natural Science Foundation of China(Nos.21975250 and 52072145)+2 种基金Science and Technology Development Program of Jilin Province(No.YDZJ202101ZYTS185)the Open Pogram of Key Laboratory of Preparation and Application of Environmental Friendly Materials(Jilin Normal University),Ministry of Education,China(Nos.2020005 and 2021007)the Open Pogram of State Key Laboratory of Metastable Materials Science and Technology(Yanshan University),China(No.202110).
文摘SnO2-based anode materials have attracted much attention due to high capacity and relatively mild voltage platforms.However,limited by low initial Coulombic efficiency(ICE)and poor stability,its practical application is still challenging.Recently,it has been found that compositing carbon or metal particles with SnO2 is an effective strategy to achieve high alkaline-ion storages.Although this strategy may improve the kinetics and ICE of the electrochemical reaction,the specific mechanism has not been clearly elucidated.In this work,we found that the invalidation SnO2 may go through two steps:1)the conversion process from SnO2 to Sn and Li2O;2)the collapse of the electrode material resulted from huge volume changes during the alloyed Sn with alkaline ions.To address these issues,a unique robust Co-NC shell derived from ZIF-67 is introduced,in which the transited metallic Co nanoparticles could accelerate the decomposition of Sn-O and Li-O bonds,thus expedite the kinetics of conversion reaction.As a result,the SnO2@Co-NC electrode achieves a more complete and efficient transfer between SnO2 and Sn phases,possessing a potential to achieve high alkaline-ion(Li+/Na+/K+)storages.
基金the National Natural Science Foundation of China(21603157)Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)the support of Suzhou Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies and Soochow University Analysis and Testing Center。
文摘Due to the unique interface and electronic structure,metal/metal oxide composite electrocatalysts have been designed and exploited for electrocatalytic oxygen evolution reaction(OER)in alkaline solution.However,how to fabricate metal/metal oxides with abundant interfaces and well-dispersed metal phases is a challenge,and the synergistic effect between metal and metal oxides on boosting the electrocatalytic activities is still ambiguous.Herein,by controlling the lithium-induced conversion reaction of metal oxides,metal/metal oxide composites with plentiful interfaces and excellent electrical interconnection are fabricated,which can enhance the active sites,and accelerate the mass transfer during the electrocatalytic reaction.As a result,the electrocatalytic oxygen evolution activities of the as-fabricated metal/metal oxide composite catalysts including NiCo/NiCo2O4,NiMn/NiMn2O4 and CoMn/CoMn2O4 are greatly improved.The catalytic mechanism is also explored using the in-situ X-ray and Raman spectroscopic tracking to uncover the real active centers and the synergistic effect between the metal and metal oxides during water oxidation.Density functional theory plus U(DFT+U)calculation confirms the metal in the composite can optimize the catalytic reaction path and reduce the reaction barrier,thus boosting the electrocatalytic kinetics.
基金supported by the National Natural Science Foundation of China(Nos.52025013,52071184,52171228,21705103,and 52202266)the Natural Science Foundation of Tianjin(No.22JCZDJC00170)+1 种基金the 111 Project(No.B12015)the Fundamental Research Funds for the Central Universities,the Applied Basic Research Project of Shanxi Province(Nos.202103021224251 and 202103021223259).
文摘Contemporary social problems,such as energy shortage and environmental pollution,require developing green energy storage technologies in the context of sustainable development.With the application of secondary battery technology becoming widespread,the development of traditional lithium(Li)-ion batteries,which are based on insertion/deinsertion reactions,has hit a bottleneck;instead,conversion-type lithium metal batteries(LMBs)have attracted considerable attention owing to the high theoretical capacity of Li metal anodes.In this review,Li-S,Li-O_(2),and Li-SOCl_(2)batteries are used as examples to summarize LMBs based on their conversion reactions from the perspectives of cathode material,anode material,electrolyte,separator,and current collector.Key challenges exist regarding the conversion reactions of various batteries.To achieve the optimum performance and improve the application effect,several improvement strategies have been proposed in relation to reasonable designs of next-generation high-performance rechargeable batteries.
基金supported by the National Natural Science Foundation of China(52302240)the Macao Young Scholars Program(AM2023011)the Yuanguang Scholars Program,Hebei University of Technology(282022554)。
文摘Lithium-sulfur(Li-S)batteries are considered a potential candidate for next-generation energy-dense and sustainable energy storage.However,the slow conversion and severe shuttle of polysulfides(LiPSs)result in rapid performance degradation over long-term cycling.Herein,we report a high-entropy single-atom(HE-SA)catalyst to regulate the multi-step conversion of LiPS to attain a high-performance Li-S battery.Both the density functional theory calculations and the experimental results prove that the Fe atomic site with high spin configurations strongly interacts with Li_(2)S_(4)through d-p and s-p synergistic orbital hybridization which facilitates the reduction of LiPS.Moreover,S-dominant p-d hybridization between Li_(2)S and a high-spin Mn site weakens the Li-S bond and facilitates the rapid sulfur evolution reaction.Consequently,the Li-S battery with a bifunctional HE-SA catalyst shows an ultralow capacity decay of 0.026% per cycle over 1900 cycles at 1 C.This work proposes a high-entropy strategy for sculpting electronic structures to enable spin and orbital hybridization modulation in advanced catalysts toward longcycling Li-S batteries.
基金the financial support of the Scientific Research Projects Coordination Unit of Istanbul University (Project number: 17344 and 31088)
文摘Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.
基金supported by the Research Grants Council(GRF project 16208718)the Innovation and Technology Commission(ITF project ITS/001/17)of Hong Kong SARthe National Natural Science Foundation of China(No.52202297).
文摘Given the abundance of potassium resources,potassium-ion batteries are considered a low-cost alternative to lithium-ion types.However,their electrochemical performance remains rather unsatisfactory because potassium ions have sluggish kinetics and large ionic radius.In this study,NiCo_(2)Se_(4)nanotube spheres are synthesized as efficient potassium storage hosts via a facile two-step hydrothermal process.The rationally designed electrode has various ameliorating morphological and functional features,including the following:(i)A hollow structure allows for relief of the volume expansion while offering an excellent electrochemical reac-tivity to accelerate the conversion kinetics;(ii)a high electrical conductivity for enhanced electron transfer;and(iii)myriad vacancies to supply active sites for electrochemical reactions.As such,the electrode delivers an initial reversible capacity of 458.1 mAh g^(−1)and retains 346.6 mAh g^(−1)after 300 cycles at 0.03 A g^(−1).The electrode sustains a high capacity of 101.4 mAh g^(−1)even at a high current density of 5 A g^(−1)and outperforms the majority of state-of-the-art anodes in terms of both cyclic capacity and rate capability,especially at above 1.0 A g^(−1).This study not only proves bimetallic selenides are promising candidates for potassium storage devices but also offers new insight into the rational design of electrode materials for high-rate potassium-ion batteries.
基金financially supported by Intergovernmental International Science and Technology Innovation Cooperation Project(2019YFE010186)the Hubei Provincial Natural Science Foundation(2019CFB452 and 2019CFB620)the Fundamental Research Funds for the Central Universities。
文摘Mg secondary batteries are promising scalable secondary batteries for next-generation energy storage.However,Mg-storage cathode materials are greatly demanded to construct high-performance Mg batteries.Electrochemical conversion reaction provides plenty of cathode options,and strategy for cathode selection and performance optimization is of special significance.In this work,Ni0.85Se with nanostructures of dispersive hexagonal nanosheets(D-Ni0.85Se)and flower-like assembled nanosheets(F-Ni0.85Se)is synthesized and investigated as Mg-storage cathodes.Compared with F-Ni0.85Se,D-Ni0.85Se delivers a higher specific capacity of 168 mAh g^-1 at 50 mA g^-1 as well as better rate performance,owing to its faster Mg^2+-diffusion and lower resistance.D-Ni0.85Se also exhibits a superior cycling stability over 500cycles.An investigation on mechanism indicates an evolution of Ni0.85Se towards NiSe with cycling,and the Mg-storage reaction occurs between NiSe and metallic Ni^0.The present work demonstrates that advanced conversion-type Mg battery cathode materials could be constructed by soft selenide anions,and the electrochemical properties could be manipulated by rational material morphology optimization.
基金supported by the National Natural Science Foundation of China(22209006,21935001)the Natural Science Foundation of Shandong Province(ZR2022QE009)+1 种基金Fundamental Research Funds for the Central Universities(buctrc202307)the Beijing Natural Science Foundation(Z210016).
文摘Low-cost and high-safety aqueous Zn-I_(2) batteries attract extensive attention for large-scale energy storage systems.However,polyiodide shuttling and sluggish iodine conversion reactions lead to inferior rate capability and severe capacity decay.Herein,a three-dimensional polyaniline is wrapped by carboxylcarbon nanotubes(denoted as C-PANI)which is designed as a catalytic cathode to effectively boost iodine conversion with suppressed polyiodide shuttling,thereby improving Zn-I_(2) batteries.Specifically,carboxyl-carbon nanotubes serve as a proton reservoir for more protonated-NH+=sites in PANI chains,achieving a direct I0/I−reaction for suppressed polyiodide generation and Zn corrosion.Attributing to this“proton-iodine”regulation,catalytic protonated C-PANI strongly fixes electrolytic iodine species and stores proton ions simultaneously through reversible-N=/-NH^(+)-reaction.Therefore,the electrolytic Zn-I_(2) battery with C-PANI cathode exhibits an impressive capacity of 420 mAh g^(−1) and ultra-long lifespan over 40,000 cycles.Additionally,a 60 mAh pouch cell was assembled with excellent cycling stability after 100 cycles,providing new insights into exploring effective organocatalysts for superb Zn-halogen batteries.
基金supported by the National Natural Science Foundation of China (Nos. 21003100 and 21073242)Natural Science Basic Research Plan in Shaanxi Province of China (No. 2011JQ2013)Special Fund of Education Department of Shaanxi Province (No. 12JK0619)
文摘The photochromic ring-opening reaction of spiropyran（SP） has been investigated by a realistic semiclassical dynamics simulation,accompanied by SA3-CASSCF（12 10）/MS-CASPT2 potential energy curves（PECs） of S0–S2.The main simulation results show the dominate pathway corresponds to the ringopening process of trans-SP to form the most stable merocyanine（MC） product.These findings provide more important complementarity for interpreting experimental observations.
文摘Lithium-sulfur battery(LSB)has attracted worldwide attention owing to its overwhelmingly high theoretical energy density of 2600Wh/kg due to the unique 16-electron electrochemical conversion reaction of elemental sulfur(S_(8))[1].However,the electrochemical conversion reaction of S_(8) is an exceedingly complex process that involves the generation of multiple intermediates(e.g.,lithium polysulfides(LiPSs))and multiphase transitions[1,2].Currently,the mechanistic investigations of the electrochemical conversion reaction of S_(8) upon discharging a LSB cell heavily rely on electrochemical titration and spectroscopic techniques[3].Nevertheless,the considerable complexity and intrinsic instability of the LSB system present substantial obstacles to obtaining accurate information for all sulfur-containing species,which significantly obstructs in-depth elucidation of the fundamental discharge mechanism of LSB[3,4].
基金financially supported by the National Natural Science Foundation of China(No.22109176)
文摘Nowadays,lithium-ion batteries (LIBs) have held the dominant role in various electric energy storage devices.With the rapid development of new energy vehicles and large-scale energy storage fields,there is an urgent demand for high-energy LIBs.While anode materials are important for determining energy density,commercialized graphite cannot meet the requirement for high specific capacity,and silicon-based materials always suffer from poor cycle stability.High-entropy oxides (HEOs) are emerging as a new category of single-phase material consisting of multiple principal elements with equimolar or quasi-equimolar ratios.Due to the design flexibility and interaction between multiple functional elements,HEOs can display improved comprehensive properties as LIBs anodes,which is expected to be a potential solution for high-energy LIBs.Herein,this review provides an extensive overview of the recent progress of HEOs anode materials in LIBs.The electrochemical properties of three typical HEOs are summarized,the synthesis methods for HEOs are subsequently elaborated,and current lithium storage mechanisms are analyzed in detail.Finally,the modification strategies are offered for further research to promote the development of HEO anodes in LIBs,including composition manipulations and the enhancement of conversion kinetic.It is aimed to propose practical guidance for exploration of HEO anode materials in next-generation high-energy batteries.
基金supported by the“Regional Innovation Strategy(RIS)”through the National Research Foundation of Korea(NRF),funded by the Ministry of Education(MOE)(2021RIS-003),South Koreasupported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2023-00241916),South Korea+4 种基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(IRIS RS-2024-00352303),South Koreathe results of a study on the“Leaders in Industry-university Cooperation 3.0”project,supported by the Ministry of Education and National Research Foundation of Korea,South Koreasupported by the Basic Science Research Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Education(2020R1A6A03038697),South Koreasupported by Learning&Academic research institution for Master’s PhD students,and Postdocs(LAMP)Program of the National Research Foundation of Korea(NRF)grant funded by the Ministry of Education(No.RS-2023-00301974),South Koreasupported by the Technology Innovation Program(RS-2024-00432013)funded By the Ministry of Trade,Industry&Energy(MOTIE,South Korea)。
文摘All-solid-state Li-S batteries(ASSLSBs)are more attractive owing to their achievable superior energy density at a reasonable cost and the solid electrolyte(SE)utilization mitigating the widely recognized polysulfide shuttle problem.While the volume expansion(~80%)that occurs during the initial transformation of sulfur to lithium sulfide induces mechanical stress,this can be avoided by using Li_(2)S as a cathode,which also permits the anode-free cell design.However,the high oxidation energy barrier of Li_(2)S cathode during the charging step limits its application in commercial devices.Redox mediators have been extensively used to reduce the oxidation energy barrier of Li_(2)S to the sulfur conversation and boost the reversible kinetics of the conversion reaction.In this review,we have summarized the available redox mediators for Li_(2)S cathode in ASSLSBs and its working mechanism.Moreover,we have proposed novel strategies and guidelines for designing effective redox mediators to boost the reversible conversion reaction.
基金financially supported by Ten-thousand Talents Program,K.C.Wong Pioneer Talent Program,China Three Gorges Corporation(No.WWKY-2021-0027)Inner Mongolia Science and Technology Plan(No.2021ZD0033)Shanghai Post-doctoral Excellence Program,Special Research Assistant Project and the National Natural Science Foundation of China(Grant No.52202121).
文摘Increasing battery voltage and electrode utilization is of great significance for improving the energy density of aqueous battery.Herein,for the first time,this work introduces an integrated design strategy to regulate electrode potential and improve electrode utilization based on the concept of electrochemical precipitation energy.By coupling precipitation reaction with original electrode reaction,the Gibbs free energy change(ΔrG^(θ))of the precipitation reaction is coupled to battery reaction’sΔrG^(θ),thereby altering battery’s voltage.Besides,the electrode reaction changes to solid-to-solid reaction after coupling with precipitation reaction,which can improve electrode utilization.The potential of Cu is reduced from 0.34 to-0.96 V(the lowest value among all the reported Cu anode)with a Cu utilization of 87.93%(without additional copper in electrolyte)by coupling Cu_(2)S’s precipitation reaction.Furthermore,the potential of I_(2) is increased from 0.54 to 0.65 V(I_(2)/CuI)and 0.73 V(I_(2)/PbI_(2))by coupling precipitation reaction of CuI and PbI_(2) and the shutting effect of I_(3)^(-)is also limited.As proof of concept,a full Cu_(2)S battery(cathode:S/Cu_(2)S,anode:Cu/Cu_(2)S)is designed with average discharge voltage of 1.12 V,which is the highest value among all the Cu-based aqueous batteries.Due to the certain universality of this strategy,this work provides a new path to regulate the electrode reaction potential and improve electrode utilization.
基金supported by the National Natural Science Foundation of China(52072061)21C Innovation Laboratory,Contemporary Amperex Technology Ltd.by project No.21C–OP–202103。
文摘Fluorinated carbons(CFx)have been widely applied as lithium primary batteries due to their ultra-high energy density.It will be a great promise if CFx can be rechargeable.In this study,we rationally tune the C-F bond strength for the alkaline intercalated CFx via importing an electronegative weaker element K instead of Li.It forms a ternary phase K_(x)FC instead of two phases(LiF+C)in lithium-ion batteries.Meanwhile,we choose a large layer distance and more defects CFx,namely fluorinated soft carbon,to accommodate K.Thus,we enable CFx rechargeable as a potassium-ion battery cathode.In detail fluorinated soft carbon CF_(1.01) presents a reversible specific capacity of 339 mA h g^(-1)(797 Wh kg^(-1))in the 2nd cycle and maintains 330 mA h g^(-1)(726 Wh kg^(-1))in the 15th cycle.This study reveals the importance of tuning chemical bond stability using different alkaline ions to endow batteries with rechargeability.This work provides good references for focusing on developing reversible electrode materials from popular primary cell configurations.
基金supported by the National Key R&D Program of China (No. 2016YFA0202602)the National Natural Science Foundation of China (Grant Nos. 21503178 and 21703185)supported by XMU Undergraduate Innovation and Entrepreneurship Training Programs (Grants No. 2017X0695 for Huijiao Yang and Xiaocong Tang)
文摘The two major limitations in the application of SnO_2 for lithium?ion battery(LIB) anodes are the large volume variations of SnO_2 during repeated lithiation/delithiation processes and a large irreversible capacity loss during the first cycle, which can lead to a rapid capacity fade and unsatisfactory initial Coulombic e ciency(ICE). To overcome these limitations, we developed composites of ultrafine SnO_2 nanoparticles and in situ formed Co(CoSn) nanocrystals embedded in an N?doped carbon matrix using a Co?based metal–organic framework(ZIF?67). The formed Co additives and structural advantages of the carbon?confined SnO_2/Co nanocomposite e ectively inhibited Sn coarsening in the lithiated SnO_2 and mitigated its structural degradation while facilitating fast electronic transport and facile ionic di usion. As a result, the electrodes demonstrated high ICE (82.2%), outstanding rate capability(～ 800 mAh g^(-1) at a high current density of 5 A g^(-1)), and long?term cycling stability(～ 760 mAh g^(-1) after 400 cycles at a current density of 0.5 A g^(-1)). This study will be helpful in developing high?performance Si(Sn)?based oxide, Sn/Sb?based sulfide, or selenide electrodes for LIBs. In addition, some metal organic frameworks similar to ZIF?67 can also be used as composite templates.
基金financial support by the National Natural Science Foundation of China (No. 21975186)“Shanghai Rising-Star Program”(No. 19QA1409300)。
文摘Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) for large-scale energy storage considering the abundance and low cost of Na-containing resources. However, the energy density of SIBs has been limited by the typically low specific capacities of traditional intercalation-based cathodes. Metal fluorides, in contrast, can deliver much higher capacities based on multi-electron conversion reactions. Among metal fluorides, CuF_(2) presents a theoretical specific capacity as high as 528 mAh/g while its Na-ion storage mechanism has been rarely reported. Here, we report CuF_(2) as a SIB cathode, which delivers a high capacity of 502 mAh/g but suffers from poor electrochemical reversibility. As a solution, we adjust the cell configuration by inserting a carbon-coated separator, which hinders the transportation of dissolved Cu ions and improves the reversibility of the CuF_(2) cathode. By using in-situ XRD measurements and theoretical calculation, we propose that a one-step conversion reaction occurs during the discharge process, and a reconversion reaction competes with the oxidization of Cu to dissolved Cu ion during the charge process.
