Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(Li PSs)undergo notorious shuttle effect,which seriou...Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(Li PSs)undergo notorious shuttle effect,which seriously hinders the commercialization of Li-S batteries.Herein,a unique VSe_(2)/V_(2)C heterostructure with local built-in electric field was rationally engineered from V_(2)C parent via a facile thermal selenization process.It exquisitely synergizes the strong affinity of V_(2)C with the effective electrocatalytic activity of VSe_(2).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 VSe_(2)/V_(2)C-CNTs-PP separator achieved an outstanding initial specific capacity of 1439.1 m A h g^(-1)with a high capacity retention of 73%after 100 cycles at0.1 C.More impressively,a wonderful capacity of 571.6 mA h g^(-1)was effectively maintained after 600cycles at 2 C with a capacity decay rate of 0.07%.Even under a sulfur loading of 4.8 mg cm^(-2),areal capacity still can be up to 5.6 m A h cm^(-2).In-situ Raman tests explicitly illustrate the effectiveness of VSe_(2)/V_(2)C-CNTs modifier in restricting Li PSs shuttle.Combined with density functional theory calculations,the underlying mechanism of VSe_(2)/V_(2)C heterostructure for remedying Li PSs shuttling and conversion kinetics was deciphered.The strategy of constructing VSe_(2)/V_(2)C heterocatalyst in this work proposes a universal 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.展开更多
NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is...NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is significant for industrial applications.In this work,a porous Na_(3)V_(2)(PO_(4))_(3)/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method.The Na_(3)V_(2)(PO_(4))_(3)/C cathode displayed specific capacities of 113.4 mAh·g^(-1),107.0 mAh·g^(-1) and 87.1 mAh·g^(-1) at 0.1 C,1 C and 10 C,respectively.For the first time,the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C electrodes are successfully fabricated.The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83%at 0℃ owing to the rapid sodium ion migration ability and structural stability of Na_(3)V_(2)(PO_(4))_(3)/C.Moreover,the thermal runaway features are revealed by accelerating rate calorimetry(ARC)test for the first time.Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries.Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C have a prospect of practical application in high safety requirement fields.展开更多
MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years...MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.展开更多
Magnesium hydride(MgH_(2))is a potential material for solid-state hydrogen storage.However,the thermodynamic and kinetic properties are far from practical application in the current stage.In this work,two-dimensional ...Magnesium hydride(MgH_(2))is a potential material for solid-state hydrogen storage.However,the thermodynamic and kinetic properties are far from practical application in the current stage.In this work,two-dimensional vanadium carbide(V_(2)C)MXene with layer thickness of 50−100 nm was fist synthesized by selectively HF-etching the Al layers from V_(2)AlC MAX phase and then introduced into MgH_(2) to improve the hydrogen sorption performances of MgH_(2).The onset hydrogen desorption temperature of MgH_(2) with V_(2)C addition is significantly reduced from 318℃ for pure MgH_(2) to 190℃,with a 128℃ reduction of the onset temperature.The MgH_(2)+10 wt%V_(2)C composite can release 6.4 wt%of H_(2) within 10 min at 300℃ and does not loss any capacity for up to 10 cycles.The activation energy for the hydrogen desorption reaction of MgH_(2) with V_(2)C addition was calculated to be 112 kJ mol^(−1) H_(2) by Arrhenius’s equation and 87.6 kJ mol^(−1) H_(2) by Kissinger’s equation.The hydrogen desorption reaction enthalpy of MgH_(2)+10 wt%V_(2)C was estimated by van’t Hoff equation to be 73.6 kJ mol^(−1) H_(2),which is slightly lower than that of the pure MgH_(2)(77.9 kJ mol^(−1) H_(2)).Microstructure studies by XPS,TEM,and SEM showed that V_(2)C acts as an efficient catalyst for the hydrogen desorption reaction of MgH_(2).The first-principles density functional theory(DFT)calculations demonstrated that the bond length of Mg−H can be reduced from 1.71A for pure MgH_(2) to 2.14A for MgH_(2) with V_(2)C addition,which contributes to the destabilization of MgH_(2).This work provides a method to significantly and simultaneously tailor the hydrogen sorption thermodynamics and kinetics of MgH_(2) by two-dimensional MXene materials.展开更多
The effect of etching environment(opened or closed)on the synthesis and electrochemical properties of V_(2)C MXene was studied.V_(2)C MXene samples were synthesized by selectively etching of V2AlC at 90℃in two differ...The effect of etching environment(opened or closed)on the synthesis and electrochemical properties of V_(2)C MXene was studied.V_(2)C MXene samples were synthesized by selectively etching of V2AlC at 90℃in two different environments:opened environment(OE)in oil bath pans under atmosphere pressure and closed environment(CE)in hydrothermal reaction kettles under higher pressures.In OE,only NaF(sodium fluoride)+HCl(hydrochloric acid)etching solution can be used to synthesize highly pure V_(2)C MXene.However,in CE,both LiF(lithium fluoride)+HCl and NaF+HCl etchant can be used to prepare V_(2)C MXene.Moreover,the V_(2)C MXene samples made in CE had higher purity and better-layered structure than those made in OE.Although the purity of V_(2)C obtained by LiF+HCl is lower than that of V_(2)C obtained using NaF+HCl,it shows better electrochemical performance as anodes of lithium-ion batteries(LIBs).Therefore,etching in CE is a better method for preparing highly pure V_(2)C MXene,which provides a reference for expanding the synthesis methods of V_(2)C with better electrochemical properties.展开更多
The structural and electrophysical characteristics of a number of solid solutions of layered oxides of the perovskite-type Bi_(7)Ti_(4+x)WxNb_(1-2x-0.1)V_(0.1)O_(21)(x=0.1-0.4)are studied.According to X-ray powder dif...The structural and electrophysical characteristics of a number of solid solutions of layered oxides of the perovskite-type Bi_(7)Ti_(4+x)WxNb_(1-2x-0.1)V_(0.1)O_(21)(x=0.1-0.4)are studied.According to X-ray powder diffraction data,all the compounds studied are single-phase and have the structure of Aurivillius phases(m=2.5)with a rhombic crystal lattice(space group I2 cm,Z=2).Changes in tetragonal and rhombic distortions of perovskite-like layers in compounds were considered depending on their chemical composition.The temperature dependences of the relative permittivityε(T)were measured.It was shown that the Curie temperature T_(C) of the perovskite-type oxides Bi_(7)Ti_(4+x)WxNb_(1-2x-0.1)V_(0.1)O_(21)(x=0.1-0.4)linearly decreases with increasing parameter x.The activation energies of charge carriers were obtained in different temperature ranges.It was found that there are three temperature regions with very different activation energies due to the different nature of the charge carriers in the studied compounds.The effect of substitution of Nb^(5+) ions by V^(5+) ions is investigated.It was found that for a number of compounds,the substitution of niobium ions by vanadium ions led to an increase in the dielectric constant and a decrease in the dielectric loss tangent.展开更多
基金supported by the National Natural Science Foundation of China(No.52072099)the Joint Guidance Project of the Natural Science Foundation of Heilongjiang Province,China(No.LH2022E093)the Team Program of the Natural Science Foundation of Heilongjiang Province,China(No.TD2021E005)。
文摘Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(Li PSs)undergo notorious shuttle effect,which seriously hinders the commercialization of Li-S batteries.Herein,a unique VSe_(2)/V_(2)C heterostructure with local built-in electric field was rationally engineered from V_(2)C parent via a facile thermal selenization process.It exquisitely synergizes the strong affinity of V_(2)C with the effective electrocatalytic activity of VSe_(2).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 VSe_(2)/V_(2)C-CNTs-PP separator achieved an outstanding initial specific capacity of 1439.1 m A h g^(-1)with a high capacity retention of 73%after 100 cycles at0.1 C.More impressively,a wonderful capacity of 571.6 mA h g^(-1)was effectively maintained after 600cycles at 2 C with a capacity decay rate of 0.07%.Even under a sulfur loading of 4.8 mg cm^(-2),areal capacity still can be up to 5.6 m A h cm^(-2).In-situ Raman tests explicitly illustrate the effectiveness of VSe_(2)/V_(2)C-CNTs modifier in restricting Li PSs shuttle.Combined with density functional theory calculations,the underlying mechanism of VSe_(2)/V_(2)C heterostructure for remedying Li PSs shuttling and conversion kinetics was deciphered.The strategy of constructing VSe_(2)/V_(2)C heterocatalyst in this work proposes a universal 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.
基金This work was supported by the National Key Research and Development Program(2016YFB0901505)the Natural Science Foundation of China(22005190,21938005)+1 种基金the Science&Technology Commission of Shanghai Municipality(19DZ1205500)Zhejiang Key Research and Development Program(2020C01128).
文摘NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is significant for industrial applications.In this work,a porous Na_(3)V_(2)(PO_(4))_(3)/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method.The Na_(3)V_(2)(PO_(4))_(3)/C cathode displayed specific capacities of 113.4 mAh·g^(-1),107.0 mAh·g^(-1) and 87.1 mAh·g^(-1) at 0.1 C,1 C and 10 C,respectively.For the first time,the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C electrodes are successfully fabricated.The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83%at 0℃ owing to the rapid sodium ion migration ability and structural stability of Na_(3)V_(2)(PO_(4))_(3)/C.Moreover,the thermal runaway features are revealed by accelerating rate calorimetry(ARC)test for the first time.Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries.Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C have a prospect of practical application in high safety requirement fields.
基金the National Natural Science Foundation of China (21703217, 11702264, 11702268, 11802276, 11772307) for financial support
文摘MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.
基金supported by National Natural Science Foundation of China(No.52001079)Education Department of Guangxi Zhuang Autonomous Region(No.2019KY0021)the Natural Science Foundation of Guangxi Province(2019GXNSFBA185004,2018GXNSFAA281308,2019GXNSFAA245050)。
文摘Magnesium hydride(MgH_(2))is a potential material for solid-state hydrogen storage.However,the thermodynamic and kinetic properties are far from practical application in the current stage.In this work,two-dimensional vanadium carbide(V_(2)C)MXene with layer thickness of 50−100 nm was fist synthesized by selectively HF-etching the Al layers from V_(2)AlC MAX phase and then introduced into MgH_(2) to improve the hydrogen sorption performances of MgH_(2).The onset hydrogen desorption temperature of MgH_(2) with V_(2)C addition is significantly reduced from 318℃ for pure MgH_(2) to 190℃,with a 128℃ reduction of the onset temperature.The MgH_(2)+10 wt%V_(2)C composite can release 6.4 wt%of H_(2) within 10 min at 300℃ and does not loss any capacity for up to 10 cycles.The activation energy for the hydrogen desorption reaction of MgH_(2) with V_(2)C addition was calculated to be 112 kJ mol^(−1) H_(2) by Arrhenius’s equation and 87.6 kJ mol^(−1) H_(2) by Kissinger’s equation.The hydrogen desorption reaction enthalpy of MgH_(2)+10 wt%V_(2)C was estimated by van’t Hoff equation to be 73.6 kJ mol^(−1) H_(2),which is slightly lower than that of the pure MgH_(2)(77.9 kJ mol^(−1) H_(2)).Microstructure studies by XPS,TEM,and SEM showed that V_(2)C acts as an efficient catalyst for the hydrogen desorption reaction of MgH_(2).The first-principles density functional theory(DFT)calculations demonstrated that the bond length of Mg−H can be reduced from 1.71A for pure MgH_(2) to 2.14A for MgH_(2) with V_(2)C addition,which contributes to the destabilization of MgH_(2).This work provides a method to significantly and simultaneously tailor the hydrogen sorption thermodynamics and kinetics of MgH_(2) by two-dimensional MXene materials.
基金supported by the National Natural Science Foundation of China(51772077)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province(19IRTSTHN027)+5 种基金the Fundamental Research Funds for the Universities of Henan Province(NSFRF200101)the China Postdoctoral Science Foundation(2019M652537)the Henan Postdoctoral Foundation(19030065)the Henan Province Key Science and Tech-nology Research Projects(202102310628)the Foundation of Henan Educational Committee(20B430006)the Doctoral Foundation of Henan Polytechnic University(B2019-41).
文摘The effect of etching environment(opened or closed)on the synthesis and electrochemical properties of V_(2)C MXene was studied.V_(2)C MXene samples were synthesized by selectively etching of V2AlC at 90℃in two different environments:opened environment(OE)in oil bath pans under atmosphere pressure and closed environment(CE)in hydrothermal reaction kettles under higher pressures.In OE,only NaF(sodium fluoride)+HCl(hydrochloric acid)etching solution can be used to synthesize highly pure V_(2)C MXene.However,in CE,both LiF(lithium fluoride)+HCl and NaF+HCl etchant can be used to prepare V_(2)C MXene.Moreover,the V_(2)C MXene samples made in CE had higher purity and better-layered structure than those made in OE.Although the purity of V_(2)C obtained by LiF+HCl is lower than that of V_(2)C obtained using NaF+HCl,it shows better electrochemical performance as anodes of lithium-ion batteries(LIBs).Therefore,etching in CE is a better method for preparing highly pure V_(2)C MXene,which provides a reference for expanding the synthesis methods of V_(2)C with better electrochemical properties.
基金This work was supported by the Ministry of Science and Higher Education of the Russian Federation(State assignment in the field of scientific activity,Southern Federal University,2020).
文摘The structural and electrophysical characteristics of a number of solid solutions of layered oxides of the perovskite-type Bi_(7)Ti_(4+x)WxNb_(1-2x-0.1)V_(0.1)O_(21)(x=0.1-0.4)are studied.According to X-ray powder diffraction data,all the compounds studied are single-phase and have the structure of Aurivillius phases(m=2.5)with a rhombic crystal lattice(space group I2 cm,Z=2).Changes in tetragonal and rhombic distortions of perovskite-like layers in compounds were considered depending on their chemical composition.The temperature dependences of the relative permittivityε(T)were measured.It was shown that the Curie temperature T_(C) of the perovskite-type oxides Bi_(7)Ti_(4+x)WxNb_(1-2x-0.1)V_(0.1)O_(21)(x=0.1-0.4)linearly decreases with increasing parameter x.The activation energies of charge carriers were obtained in different temperature ranges.It was found that there are three temperature regions with very different activation energies due to the different nature of the charge carriers in the studied compounds.The effect of substitution of Nb^(5+) ions by V^(5+) ions is investigated.It was found that for a number of compounds,the substitution of niobium ions by vanadium ions led to an increase in the dielectric constant and a decrease in the dielectric loss tangent.
