Bi-based transition metal oxide(Bi_(5)Nb_(3)O_(15))has become a highly hopeful anode material for lithium-ion batteries(LIBs)due to its large theoretical capacity and affordable availability.Unfortunately,poor conduct...Bi-based transition metal oxide(Bi_(5)Nb_(3)O_(15))has become a highly hopeful anode material for lithium-ion batteries(LIBs)due to its large theoretical capacity and affordable availability.Unfortunately,poor conductivity,as well as volume expansion and pulverization during repeated reactions will result in bad specific capacity and inferior cycling stability.Hence,Bi_(5)Nb_(3)O_(15)@C anode materials for LIBs were successfully synthesized using sucrose as a carbon source through a two-step high-temperature solid-phase method.Physical characterizations and electrochemical tests suggest that the highly conductive carbon shell derived from sucrose provides fast channels for Li^(+)transport and greatly reduces the charge transfer resistance.Moreover,ex situ scanning electron microscopy(SEM)indicates that the presence of carbon effectively suppresses the aggregation and pulverization of Bi_(5)Nb_(3)O_(15) particles in the reaction process,effectively ensuring the integrity of Bi_(5)Nb_(3)O_(15) particles.Benefiting from the above merits,the C-modified Bi_(5)Nb_(3)O_(15),especially Bi_(5)Nb_(3)O_(15)@8%C(BNO-C3),holds charge capacity of 414.6 and 281.4 mAh·g^(−1) at 0.1 and 0.5 A·g^(−1),respectively.Additionally,the high specific capacity of 379.5 mAh·g^(−1) is much greater than that of the bare Bi_(5)Nb_(3)O_(15)(only 158.7 mAh·g^(−1))after 200 cycles.Importantly,cyclic voltammetry(CV)combined with ex situ X-ray diffraction(XRD)confirms the conversion reaction between Bi_(5)Nb_(3)O_(15) and Bi during cycling.This work provides a method for suppressing volume expansion and pulverization during cycling of Bi-based transition metal oxides and constructing high-performance LIBs anode materials.展开更多
TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,exce...TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,excellent safety and relatively high specific capacity.Nonetheless,the inferior electronic conductivity and poor ion diffusion coefficients are the biggest bottlenecks that restrict the popular application.Much effort has been focused on resolving these problems toward large-scale applications,and numerous significant advances have been accomplished.In the present work,a comprehensive overview of structure characteristics,electrochemical reaction mechanism and modification strategies of TiO_(2)-based materials was presented.The recent advances of various efficient ways for improving conductivity,Li(Na)storage capacity,rate capability and cycle stability are systematically summarized,including surface engineering,constructing composite and element doping,etc.Constructing TiO_(2)-based materials with novel porous heterogeneous core-shell structures have been regarded as one of the most effective ways to resolve these challenges.Finally,the future research directions and development prospects of TiO_(2)-based anode materials used in the manufacture of high-performance Li(Na)-ion batteries are prospected.This review can provide important comprehension for the construction and optimization of highperformance of TiO_(2)-based anode materials.展开更多
In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The i...In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The introduction of CNTs does not change the structure of the Bi_(5) Nb_(3) O_(15) materials,the Bi_(5) Nb_(3) O_(15) particles are decorated on a three-dimensional CNTs network,and the high conductive network promotes transfer of electron/ion and relieve the volume change of Bi_(5) Nb_(3) O_(15).The Bi_(5) Nb_(3) O_(15)@CNTs(8 wt%) electrode shows a superior rate capability with charge(discharge) capacities of 490(898.7),379.1(401.6),311.3(326.9),276.5(285.5) and 243.4(252)mAh·g^(-1) at 50,100,200,300 and 500 mA·g^(-1),respectively.However,the Bi_(5) Nb_(3) O_(15) only shows charge(discharge) capacities of 431(772.6),278.6(309.9),193.1(213.7),160.8(171.1),129.9(139.1) mAh·g^(-1) at the corresponding rates,respectively.The excellent rate capability of Bi_(5) Nb_(3) O_(15)@CNTs can be ascribed to the homogeneous distribution of Bi_(5) Nb_(3) O_(15) particles in the CNTs conductive network and the enhancement of conductivity.Hence,the CNTs modulation can be considered as an effective strategy to enhance electrochemical performances of Bi_(5) Nb_(3) O_(15) materials.展开更多
The superfluid states of attractive Hubbard model in α–T_(3) lattice are investigated. It is found that one usual needs three non-zero superfluid order parameters to describe the superfluid states due to three subla...The superfluid states of attractive Hubbard model in α–T_(3) lattice are investigated. It is found that one usual needs three non-zero superfluid order parameters to describe the superfluid states due to three sublattices. When two hopping amplitudes are equal, the system has particle–hole symmetry. The flat band plays an important role in superfluid pairing near half filling. For example, when the filling factor falls into the flat band, the large density of states in the flat band favors superfluid pairing and the superfluid order parameters reach relatively large values. When the filling factor is in the gap between the flat band and upper band, the superfluid order parameters take small values due to the vanishing of density of states. The superfluid order parameters show nonmonotonic behaviors with the increase of filling factor. At last, we also investigate the edge states with open boundary conditions. It is shown that there exist some interesting edge states in the middle of quasi-particle bands.展开更多
基金supported by the National Natural Science Foundation of China(No.52374301)Hebei Provincial Natural Science Foundation(No.E2024501010)+2 种基金Shijiazhuang Basic Research Project(No.241790667A)the Fundamental Research Funds for the Central Universities(No.N2423054)the Performance Subsidy Fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province(No.22567627H).
文摘Bi-based transition metal oxide(Bi_(5)Nb_(3)O_(15))has become a highly hopeful anode material for lithium-ion batteries(LIBs)due to its large theoretical capacity and affordable availability.Unfortunately,poor conductivity,as well as volume expansion and pulverization during repeated reactions will result in bad specific capacity and inferior cycling stability.Hence,Bi_(5)Nb_(3)O_(15)@C anode materials for LIBs were successfully synthesized using sucrose as a carbon source through a two-step high-temperature solid-phase method.Physical characterizations and electrochemical tests suggest that the highly conductive carbon shell derived from sucrose provides fast channels for Li^(+)transport and greatly reduces the charge transfer resistance.Moreover,ex situ scanning electron microscopy(SEM)indicates that the presence of carbon effectively suppresses the aggregation and pulverization of Bi_(5)Nb_(3)O_(15) particles in the reaction process,effectively ensuring the integrity of Bi_(5)Nb_(3)O_(15) particles.Benefiting from the above merits,the C-modified Bi_(5)Nb_(3)O_(15),especially Bi_(5)Nb_(3)O_(15)@8%C(BNO-C3),holds charge capacity of 414.6 and 281.4 mAh·g^(−1) at 0.1 and 0.5 A·g^(−1),respectively.Additionally,the high specific capacity of 379.5 mAh·g^(−1) is much greater than that of the bare Bi_(5)Nb_(3)O_(15)(only 158.7 mAh·g^(−1))after 200 cycles.Importantly,cyclic voltammetry(CV)combined with ex situ X-ray diffraction(XRD)confirms the conversion reaction between Bi_(5)Nb_(3)O_(15) and Bi during cycling.This work provides a method for suppressing volume expansion and pulverization during cycling of Bi-based transition metal oxides and constructing high-performance LIBs anode materials.
基金financially supported by the National Natural Science Foundation of China(No.51774002)the Key Program for International S&T Cooperation Projects of China(No.2017YFE0124300)the“333 Talent Project”of Hebei Province(No.A202005018)。
文摘TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,excellent safety and relatively high specific capacity.Nonetheless,the inferior electronic conductivity and poor ion diffusion coefficients are the biggest bottlenecks that restrict the popular application.Much effort has been focused on resolving these problems toward large-scale applications,and numerous significant advances have been accomplished.In the present work,a comprehensive overview of structure characteristics,electrochemical reaction mechanism and modification strategies of TiO_(2)-based materials was presented.The recent advances of various efficient ways for improving conductivity,Li(Na)storage capacity,rate capability and cycle stability are systematically summarized,including surface engineering,constructing composite and element doping,etc.Constructing TiO_(2)-based materials with novel porous heterogeneous core-shell structures have been regarded as one of the most effective ways to resolve these challenges.Finally,the future research directions and development prospects of TiO_(2)-based anode materials used in the manufacture of high-performance Li(Na)-ion batteries are prospected.This review can provide important comprehension for the construction and optimization of highperformance of TiO_(2)-based anode materials.
基金financially supported by the Key Program for International S&T Cooperation Projects of China (No.2017YFE0124300)the National Natural Science Foundation of China (Nos.U1960107 and 22179019)+2 种基金the "333" Talent Project of Hebei Province (No.A202005018)the Fundamental Research Funds for the Central Universities (No.N2123001)the Natural Science Foundation of Hebei Province of China (No.B2020501003)。
文摘In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The introduction of CNTs does not change the structure of the Bi_(5) Nb_(3) O_(15) materials,the Bi_(5) Nb_(3) O_(15) particles are decorated on a three-dimensional CNTs network,and the high conductive network promotes transfer of electron/ion and relieve the volume change of Bi_(5) Nb_(3) O_(15).The Bi_(5) Nb_(3) O_(15)@CNTs(8 wt%) electrode shows a superior rate capability with charge(discharge) capacities of 490(898.7),379.1(401.6),311.3(326.9),276.5(285.5) and 243.4(252)mAh·g^(-1) at 50,100,200,300 and 500 mA·g^(-1),respectively.However,the Bi_(5) Nb_(3) O_(15) only shows charge(discharge) capacities of 431(772.6),278.6(309.9),193.1(213.7),160.8(171.1),129.9(139.1) mAh·g^(-1) at the corresponding rates,respectively.The excellent rate capability of Bi_(5) Nb_(3) O_(15)@CNTs can be ascribed to the homogeneous distribution of Bi_(5) Nb_(3) O_(15) particles in the CNTs conductive network and the enhancement of conductivity.Hence,the CNTs modulation can be considered as an effective strategy to enhance electrochemical performances of Bi_(5) Nb_(3) O_(15) materials.
基金supported by the National Natural Science Foundation of China (Grant No. 11874127)the startup grant from Guangzhou University。
文摘The superfluid states of attractive Hubbard model in α–T_(3) lattice are investigated. It is found that one usual needs three non-zero superfluid order parameters to describe the superfluid states due to three sublattices. When two hopping amplitudes are equal, the system has particle–hole symmetry. The flat band plays an important role in superfluid pairing near half filling. For example, when the filling factor falls into the flat band, the large density of states in the flat band favors superfluid pairing and the superfluid order parameters reach relatively large values. When the filling factor is in the gap between the flat band and upper band, the superfluid order parameters take small values due to the vanishing of density of states. The superfluid order parameters show nonmonotonic behaviors with the increase of filling factor. At last, we also investigate the edge states with open boundary conditions. It is shown that there exist some interesting edge states in the middle of quasi-particle bands.
