A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal...A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal fiber is measured to be 14 times as low as that of the undadded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of lattice distortion are analyzed and discussed. It is found by X-ray diffraction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structure of a new compound from the Li-Mg-Nb-O ternary system. It is proposed, for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.展开更多
Rechargeable Mg-ion batteries(MIBs)have attracted much more attentions by virtue of the high capacity from the two electrons chemistry.However,the reversible Mg^(2+)diffusion in cathode materials is restricted by the ...Rechargeable Mg-ion batteries(MIBs)have attracted much more attentions by virtue of the high capacity from the two electrons chemistry.However,the reversible Mg^(2+)diffusion in cathode materials is restricted by the strong interactions between the high-polarized bivalent Mg^(2+)ions and anionic lattice.Herein,we design and propose a hetero-structural VO_(2)(R)-VS_(4)cathode,in which the re-delocalized d-electrons can effectively shield the polarity of Mg^(2+)ions.Theoretically,the electrons should spontaneously transfer from VS_(4)to VO_(2)(R)through the interfaces of hetero-structure due to the lower work function value of VS_(4).Furthermore,the internal electrons transfer lead to the electronic injection into VO_(2)(R)from VS_(4)and the partially broken V-V dimers,indicating the presence of lone pair electrons and charge re-delocalization.Benefiting from the shield effect of re-delocalized electrons,and the weakened attraction between cations and O/S anions enables more S^(2-)-S_(2)^(2-)redox groups to participate the electrochemical reactions and compensate the double charge of Mg^(2+)ions.Accordingly,VO_(2)(R)-VS_(4)hetero-structure exhibits a high specific capacity of 554 mA h g^(-1)at 50 mA g^(-1).It is believed that the charge re-delocalization of cathode extremely boost the Mg^(2+)ions migration for the high-capacity of MIBs.展开更多
Owing to the features(high safety,inexpensive and environmental friendliness)of aqueous rechargeable Mg-ion batteries(ARMIBs),they have drawn extensive attention in the future energy storage systems.However,the poor M...Owing to the features(high safety,inexpensive and environmental friendliness)of aqueous rechargeable Mg-ion batteries(ARMIBs),they have drawn extensive attention in the future energy storage systems.However,the poor Mg^(2+)migration kinetics during the Mg^(2+)intercalation/extraction still hinders the progress of developing suitable cathode materials.Herein,a layered buserite Mg-Mn oxide(MMO)material with large interlayer space(~9.70A)and low-crystalline structure is studied as a high-performance cathode in ARMIBs.Compared with the counterpart,the Mg^(2+)migration kinetics of the MMO cathode can be enhanced by its unique structure(bigger interlayer spacing and low-crystalline structure).The layered buserite MMO as a high-performance ARMIBs cathode exhibits high Mg storage capacity(50 mAg^(-1):169.3 mAh g^(-1)),excellent rate capability(1000 mAg^(-1):98.3 mAh g^(-1)),and fast Mg^(2+)migration(an average diffusion coefficient:~4.21×10-^(10)cm^(2)s^(-1))in 0.5 M MgCl_(2)aqueous electrolyte.Moreover,the MMO-1//AC full battery achieved a high discharge capacity(100 mAg^(-1):111 mAh g^(-1)),and an ignored fading over 5000 cycles(1000 mAg^(-1)).Therefore,layered Mg-Mn oxide with large interlayer space may break a new path to develop the promising ARMIBs.展开更多
The selection of the most suitable crystal structure for ions storage and the investigation of the corresponding reaction mechanism is still an ongoing challenge for the development of Mg-based batteries.In this artic...The selection of the most suitable crystal structure for ions storage and the investigation of the corresponding reaction mechanism is still an ongoing challenge for the development of Mg-based batteries.In this article,high flexible graphene network supporting different crystal structures of Nb2 O5(TTNb_(2)O_(5)@rGO and T-Nb_(2)O_(5)@rGO) are successfully synthesized by a spray-drying-assisted approach.The three-dimensional graphene framework provides high conductivity and avoids the aggregation of Nb2 O5 nanoparticles.When employed as electrode materials for energy storage applications,TT-Nb_(2)O_(5) delivers a higher discharge capacity of 129.5 mAh g^(-1), about twice that of T-Nb_(2)O_(5) for Mg-storage,whereas,T-Nb_(2)O_(5) delivers a much higher capacity(162 mAh g^(-1)) compared with TT-Nb_(2)O_(5)(129 mAh g^(-1)) for Li-storage.Detailed investigations reveal the Mg intercalation mechanism and lower Mg^(2+) migration barriers,faster Mg^(2+) diffusion kinetics of TT-Nb_(2)O_(5) as cathode material for Mg-storage,and the faster Li+ diffusion kinetics,shorter diffusion distance of T-Nb_(2)O_(5) as cathode material for Li-storage.Our work demonstrates that exploring the proper crystal structure of Nb2 O5 for different ions storage is necessary.展开更多
Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Exper...Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.展开更多
Rechargeable Mg batteries have attracted much attention in the past decade due to their high theoretical energy density and low production cost,in which the electrolyte is the key component that determines the overall...Rechargeable Mg batteries have attracted much attention in the past decade due to their high theoretical energy density and low production cost,in which the electrolyte is the key component that determines the overall performance.Applying solid Mg-ion electrolytes brings many benefits to rechargeable Mg bat-teries,which can improve safety under aggressive conditions and open opportunities for new electrode applications.After extensive investigations,researchers make major breakthroughs in the solid Mg-ion electrolyte field,especially in terms of Mg-ion conductivities.However,the development of solid-state Mg batteries is still at the early stage since their stable cycling has not been achieved yet.In this review,we introduce the Mg-ion conducting properties of current solid Mg-ion electrolytes,and then summarize the performances of corresponding solid-state Mg batteries.In addition,we provide a discussion on the application potentials and future directions of each type of solid Mg-ion electrolytes that are applied in solid-state Mg batteries.展开更多
Rechargeable magnesium batteries are identified as a promising next-generation energy storage system,but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium me...Rechargeable magnesium batteries are identified as a promising next-generation energy storage system,but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium metal anode.To avoid or alleviate these problems,the exploitation of alternative anode materials is a promising choice.Herein,we present titanium pyrophosphate(TiP_(2)O_(7))as anode materials for magnesium-ion batteries(MIBs)and investigate the effect of the crystal phase on its magnesium storage performance.Compared with the me-tastable layered TiP_(2)O_(7),the thermodynamically stable cubic TiP_(2)O_(7) displays a better rate capability of 72 mAh g^(−1) at 5000 mA g^(−1).Moreover,cubic TiP_(2)O_(7) exhibits excellent cycling stability with the capacity of 60 mAh g^(−1) after 5000 cycles at 1000 mA g^(−1),which are better than pre-viously reported Ti-based anode materials for MIBs.In situ X-ray diffraction technology confirms the single-phase magnesiumion inter-calation/deintercalation reaction mechanism of cubic TiP_(2)O_(7) with a low volume change of 3.2%.In addition,the density functional theory calcu-lation results demonstrate that three-dimensional magnesiumion diffu-sion can be allowed in cubic TiP_(2)O_(7) with a low migration energy barrier of 0.62 eV.Our work demonstrates the promise of TiP_(2)O_(7) as high-rate and long-life anode materials for MIBs and may pave the way for further development of MIBs.展开更多
Based on the report given by J. E. Midwinter that the refractive indices n<sub>o</sub> and n<sub>e</sub> oflithium niobate doped with magnesium （MgO:LiNbo<sub>3</sub>） are lower t...Based on the report given by J. E. Midwinter that the refractive indices n<sub>o</sub> and n<sub>e</sub> oflithium niobate doped with magnesium （MgO:LiNbo<sub>3</sub>） are lower than those of LiNbO<sub>3</sub>,S.Sudo et al. achieved for the first time the core-cladding wave guide structure of LiNbO<sub>3</sub>展开更多
An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupl...An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupled waveguides is proposed and its parameters are determined using the variational method. The results calculated using this method agree well with those obtained using the finite-element method. The present method has been used to check the accuracy of the effective index method as well as a quasi-analytical technique based on the effective index method. The results show that the effective index method is generally accurate for the fundamental mode and becomes less accurate for higher-order vertical modes.展开更多
基金the Fund of Electronic Materials Research Laboratory, Xi'an Jiaotong University
文摘A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal fiber is measured to be 14 times as low as that of the undadded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of lattice distortion are analyzed and discussed. It is found by X-ray diffraction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structure of a new compound from the Li-Mg-Nb-O ternary system. It is proposed, for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.
基金the financial support of this work by the National Natural Science Foundation of China(No.52034011)the Key R&D Program of Shanxi(No.2019ZDLGY04-05)+2 种基金the National Natural Science Foundation of Shaanxi(No.2019JLZ-01)the Fundamental Research Funds for the Central Universities(No.G2020KY05129)the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2020-BJ-03)。
文摘Rechargeable Mg-ion batteries(MIBs)have attracted much more attentions by virtue of the high capacity from the two electrons chemistry.However,the reversible Mg^(2+)diffusion in cathode materials is restricted by the strong interactions between the high-polarized bivalent Mg^(2+)ions and anionic lattice.Herein,we design and propose a hetero-structural VO_(2)(R)-VS_(4)cathode,in which the re-delocalized d-electrons can effectively shield the polarity of Mg^(2+)ions.Theoretically,the electrons should spontaneously transfer from VS_(4)to VO_(2)(R)through the interfaces of hetero-structure due to the lower work function value of VS_(4).Furthermore,the internal electrons transfer lead to the electronic injection into VO_(2)(R)from VS_(4)and the partially broken V-V dimers,indicating the presence of lone pair electrons and charge re-delocalization.Benefiting from the shield effect of re-delocalized electrons,and the weakened attraction between cations and O/S anions enables more S^(2-)-S_(2)^(2-)redox groups to participate the electrochemical reactions and compensate the double charge of Mg^(2+)ions.Accordingly,VO_(2)(R)-VS_(4)hetero-structure exhibits a high specific capacity of 554 mA h g^(-1)at 50 mA g^(-1).It is believed that the charge re-delocalization of cathode extremely boost the Mg^(2+)ions migration for the high-capacity of MIBs.
基金financially supported by the Fundamental Research Funds for the Central Universities(NO.2021CDJXDJH003)Guangdong National Technology Co.,Ltd.
文摘Owing to the features(high safety,inexpensive and environmental friendliness)of aqueous rechargeable Mg-ion batteries(ARMIBs),they have drawn extensive attention in the future energy storage systems.However,the poor Mg^(2+)migration kinetics during the Mg^(2+)intercalation/extraction still hinders the progress of developing suitable cathode materials.Herein,a layered buserite Mg-Mn oxide(MMO)material with large interlayer space(~9.70A)and low-crystalline structure is studied as a high-performance cathode in ARMIBs.Compared with the counterpart,the Mg^(2+)migration kinetics of the MMO cathode can be enhanced by its unique structure(bigger interlayer spacing and low-crystalline structure).The layered buserite MMO as a high-performance ARMIBs cathode exhibits high Mg storage capacity(50 mAg^(-1):169.3 mAh g^(-1)),excellent rate capability(1000 mAg^(-1):98.3 mAh g^(-1)),and fast Mg^(2+)migration(an average diffusion coefficient:~4.21×10-^(10)cm^(2)s^(-1))in 0.5 M MgCl_(2)aqueous electrolyte.Moreover,the MMO-1//AC full battery achieved a high discharge capacity(100 mAg^(-1):111 mAh g^(-1)),and an ignored fading over 5000 cycles(1000 mAg^(-1)).Therefore,layered Mg-Mn oxide with large interlayer space may break a new path to develop the promising ARMIBs.
基金supported by the National Natural Science Foundation of China(51972259,51832004,51521001)the Fundamental Research Funds for the Central Universities(WUT:2020III043GX,2020III015GX)+2 种基金Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003)the National Key Research and Development Program of China(2016YFA0202601)the Hubei Provincial Natural Science Foundation of China(2019CFB519)。
文摘The selection of the most suitable crystal structure for ions storage and the investigation of the corresponding reaction mechanism is still an ongoing challenge for the development of Mg-based batteries.In this article,high flexible graphene network supporting different crystal structures of Nb2 O5(TTNb_(2)O_(5)@rGO and T-Nb_(2)O_(5)@rGO) are successfully synthesized by a spray-drying-assisted approach.The three-dimensional graphene framework provides high conductivity and avoids the aggregation of Nb2 O5 nanoparticles.When employed as electrode materials for energy storage applications,TT-Nb_(2)O_(5) delivers a higher discharge capacity of 129.5 mAh g^(-1), about twice that of T-Nb_(2)O_(5) for Mg-storage,whereas,T-Nb_(2)O_(5) delivers a much higher capacity(162 mAh g^(-1)) compared with TT-Nb_(2)O_(5)(129 mAh g^(-1)) for Li-storage.Detailed investigations reveal the Mg intercalation mechanism and lower Mg^(2+) migration barriers,faster Mg^(2+) diffusion kinetics of TT-Nb_(2)O_(5) as cathode material for Mg-storage,and the faster Li+ diffusion kinetics,shorter diffusion distance of T-Nb_(2)O_(5) as cathode material for Li-storage.Our work demonstrates that exploring the proper crystal structure of Nb2 O5 for different ions storage is necessary.
文摘Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(Nos.51971146,51971147,52171218,and 52271222)the Shanghai Municipal Science and Technology Commission(No.21010503100)+2 种基金the Major Program for the Scientific Research Innovation Plan of Shanghai Education Com-mission(No.2019-01-07-00-07-E00015)the Shanghai Outstand-ing Academic Leaders Plan,the Shanghai Rising-Star Program(No.20QA1407100)the General Program of Natural Science Foun-dation of Shanghai(No.20ZR1438400).
文摘Rechargeable Mg batteries have attracted much attention in the past decade due to their high theoretical energy density and low production cost,in which the electrolyte is the key component that determines the overall performance.Applying solid Mg-ion electrolytes brings many benefits to rechargeable Mg bat-teries,which can improve safety under aggressive conditions and open opportunities for new electrode applications.After extensive investigations,researchers make major breakthroughs in the solid Mg-ion electrolyte field,especially in terms of Mg-ion conductivities.However,the development of solid-state Mg batteries is still at the early stage since their stable cycling has not been achieved yet.In this review,we introduce the Mg-ion conducting properties of current solid Mg-ion electrolytes,and then summarize the performances of corresponding solid-state Mg batteries.In addition,we provide a discussion on the application potentials and future directions of each type of solid Mg-ion electrolytes that are applied in solid-state Mg batteries.
基金This study was supported by the National Natural Science Foundation of China(51832004,U1804253,and 51972259)Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003).
文摘Rechargeable magnesium batteries are identified as a promising next-generation energy storage system,but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium metal anode.To avoid or alleviate these problems,the exploitation of alternative anode materials is a promising choice.Herein,we present titanium pyrophosphate(TiP_(2)O_(7))as anode materials for magnesium-ion batteries(MIBs)and investigate the effect of the crystal phase on its magnesium storage performance.Compared with the me-tastable layered TiP_(2)O_(7),the thermodynamically stable cubic TiP_(2)O_(7) displays a better rate capability of 72 mAh g^(−1) at 5000 mA g^(−1).Moreover,cubic TiP_(2)O_(7) exhibits excellent cycling stability with the capacity of 60 mAh g^(−1) after 5000 cycles at 1000 mA g^(−1),which are better than pre-viously reported Ti-based anode materials for MIBs.In situ X-ray diffraction technology confirms the single-phase magnesiumion inter-calation/deintercalation reaction mechanism of cubic TiP_(2)O_(7) with a low volume change of 3.2%.In addition,the density functional theory calcu-lation results demonstrate that three-dimensional magnesiumion diffu-sion can be allowed in cubic TiP_(2)O_(7) with a low migration energy barrier of 0.62 eV.Our work demonstrates the promise of TiP_(2)O_(7) as high-rate and long-life anode materials for MIBs and may pave the way for further development of MIBs.
基金Project supported by the Foundation of Electronic Materials Research Laboratory,Xi'an Jiaotong University.
文摘Based on the report given by J. E. Midwinter that the refractive indices n<sub>o</sub> and n<sub>e</sub> oflithium niobate doped with magnesium （MgO:LiNbo<sub>3</sub>） are lower than those of LiNbO<sub>3</sub>,S.Sudo et al. achieved for the first time the core-cladding wave guide structure of LiNbO<sub>3</sub>
基金Project supported in part by the National Natural Science Foundation of China,Science Foundation of Guangdong Province,Zhongshan University,Chinese Post-doctoral Committee.
文摘An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupled waveguides is proposed and its parameters are determined using the variational method. The results calculated using this method agree well with those obtained using the finite-element method. The present method has been used to check the accuracy of the effective index method as well as a quasi-analytical technique based on the effective index method. The results show that the effective index method is generally accurate for the fundamental mode and becomes less accurate for higher-order vertical modes.
