Sodium-ion intercalation oxides generally possess high compositional diversity according to their different stacking sequences.The sodium diffusion pathway in layered P-type materials used in sodium-ion batteries is o...Sodium-ion intercalation oxides generally possess high compositional diversity according to their different stacking sequences.The sodium diffusion pathway in layered P-type materials used in sodium-ion batteries is open,which can increase their rate capability by directly transmitting Na+between adjacent triangular prismatic channels,rather than passing through an intermediate tetrahedral site in O-type structure.However,how the structure chemistry of the P-type oxides determines their electrochemical properties has not been fully understood yet.Herein,by comparing the crystalline structures,electrochemical behaviors,ion/electron transport dynamics of a couple of P-type intercalation cathodes,P2-Na_(2/3)Ni1/3Mn_(2/3)O_(2)and P3-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)with the same compositions,we demonstrate experimentally and computationally that the P2 phase delivers better cycling stability and rate capability than the P3 counterpart due to the predominant contribution of the faster intrinsic Na diffusion kinetics in the P2 bulk.We also point out that it is the electronic conductivity that captures the key electrochemistry of layered P3-type materials and makes them possible to enhance the sodium storage performance.The results reveal that the correlation between stacking structure and functional properties in two typical layered P-type cathodes,providing new guidelines for preparing and designing alkali-metal layered oxide materials with improved battery performance.展开更多
NiFe_(2)O_(4) nanoparticles(<10 nm)embedded in a NiO matrix have been fabricated by calcining the corresponding Ni^(Ⅱ)Fe^(Ⅲ)-layered double hydroxide(LDH)precursors at high temperature(500℃).Compared with the Ni...NiFe_(2)O_(4) nanoparticles(<10 nm)embedded in a NiO matrix have been fabricated by calcining the corresponding Ni^(Ⅱ)Fe^(Ⅲ)-layered double hydroxide(LDH)precursors at high temperature(500℃).Compared with the NiFe_(2)O_(4)/NiO nanocomposite obtained by calcination of a precursor prepared by a traditional chemical coprecipitation method,those derived from NiFe-LDH precursors show much higher blocking temperatures(TB)(~380 K).The enhanced magnetic stability can be ascribed to the much stronger interfacial interaction between NiFe_(2)O_(4) and NiO phases due to the topotactic nature of the transformation of the LDH precursor to the NiFe_(2)O_(4)/NiO composite material.Through tuning the Ni^(Ⅱ)/Fe^(Ⅲ) molar ratio of the NiFe-LDH precursor,the NiFe_(2)O_(4) concentration can be precisely controlled,and the TB value as well as the magnetic properties of the final material can also be regulated.This work represents a successful example of the fabrication of ferro(ferri)magnetic(FM)/antiferrimagnetic(AFM)systems with high magnetic stability from LDH precursors.This method is general and may be readily extended to other FM/AFM systems due to the wide range of available LDH precursors.展开更多
The self-assemblies of 4-hexadecyloxybenzoic acid and 3,4,5-trihexadecyloxybenzoic acid have been studied by using scanning tunneling microscopy (STM). The well-ordered assemblies with different arrangement have been ...The self-assemblies of 4-hexadecyloxybenzoic acid and 3,4,5-trihexadecyloxybenzoic acid have been studied by using scanning tunneling microscopy (STM). The well-ordered assemblies with different arrangement have been investigated. The structural change is attributed to the different number of substituted alkyl chains on periphery.展开更多
Cobalt ferrite CoxNi1-xFe2O4 （x = 0, 0.5, 1 ） particles with controllable magnetic properties have been prepared by calcination of co-substituted NiFe^2＋Fe^3＋ -layered double hydroxide （NiFe^2＋Fe^3＋-LDH） precu...Cobalt ferrite CoxNi1-xFe2O4 （x = 0, 0.5, 1 ） particles with controllable magnetic properties have been prepared by calcination of co-substituted NiFe^2＋Fe^3＋ -layered double hydroxide （NiFe^2＋Fe^3＋-LDH） precursors prepared via a scalable method involving separate nucleation and aging steps （SNAS）. Their structural and magnetic characteristics were investigated by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） and vibrating sample magnetometry （VSM）. Measurements of magnetic properties show that the saturation magnetization （Ms） and coercivity （He） of the calcined products increased with increasing cobalt content. The LDH precursor-based product obtained by calcination of a mixture of CoFe^2＋Fe3^＋-LDH and NiFe^2＋Fe^3＋ -LDH powders with a Co/Ni molar ratio of 1：1, exhibits a moderate value of Ms and an increased value of He compared to the corresponding values for an Ni0.5Co0.5Fe2O4 material prepared by calcination of a Co0.5Ni0.5Fe^2＋Fe^3＋-LDH precursor, and a physical mixture of CoFe2O4 and NiFe2O4 with a Co/Ni molar ratio of 1 ： 1. These results may provide a way to regulate magnetic anisotropy of ferrite spinels by varying the composition of the LDH precursors.展开更多
基金supported by the National Natural Science Foundation of China (U1607128,52102302 and 21521005)Natural Science Foundation of Beijing (2222020)+1 种基金the Young Talent Support Plan and Siyuan Scholar of Xi’an Jiaotong University (DQ6J011 and DQ1J009)State Key Laboratory of Electrical Insulation and Power Equipment (EIPE23313)
文摘Sodium-ion intercalation oxides generally possess high compositional diversity according to their different stacking sequences.The sodium diffusion pathway in layered P-type materials used in sodium-ion batteries is open,which can increase their rate capability by directly transmitting Na+between adjacent triangular prismatic channels,rather than passing through an intermediate tetrahedral site in O-type structure.However,how the structure chemistry of the P-type oxides determines their electrochemical properties has not been fully understood yet.Herein,by comparing the crystalline structures,electrochemical behaviors,ion/electron transport dynamics of a couple of P-type intercalation cathodes,P2-Na_(2/3)Ni1/3Mn_(2/3)O_(2)and P3-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)with the same compositions,we demonstrate experimentally and computationally that the P2 phase delivers better cycling stability and rate capability than the P3 counterpart due to the predominant contribution of the faster intrinsic Na diffusion kinetics in the P2 bulk.We also point out that it is the electronic conductivity that captures the key electrochemistry of layered P3-type materials and makes them possible to enhance the sodium storage performance.The results reveal that the correlation between stacking structure and functional properties in two typical layered P-type cathodes,providing new guidelines for preparing and designing alkali-metal layered oxide materials with improved battery performance.
基金This work was supported by the National Natural Science Foundation of China,the 111 Project(No.B07004)the 973 Program(No.2009CB939802)+1 种基金the Program for New Century Excellent Talents in Universities(No.NCET-07-0055)the Beijing Nova Program(No.2007B021).
文摘NiFe_(2)O_(4) nanoparticles(<10 nm)embedded in a NiO matrix have been fabricated by calcining the corresponding Ni^(Ⅱ)Fe^(Ⅲ)-layered double hydroxide(LDH)precursors at high temperature(500℃).Compared with the NiFe_(2)O_(4)/NiO nanocomposite obtained by calcination of a precursor prepared by a traditional chemical coprecipitation method,those derived from NiFe-LDH precursors show much higher blocking temperatures(TB)(~380 K).The enhanced magnetic stability can be ascribed to the much stronger interfacial interaction between NiFe_(2)O_(4) and NiO phases due to the topotactic nature of the transformation of the LDH precursor to the NiFe_(2)O_(4)/NiO composite material.Through tuning the Ni^(Ⅱ)/Fe^(Ⅲ) molar ratio of the NiFe-LDH precursor,the NiFe_(2)O_(4) concentration can be precisely controlled,and the TB value as well as the magnetic properties of the final material can also be regulated.This work represents a successful example of the fabrication of ferro(ferri)magnetic(FM)/antiferrimagnetic(AFM)systems with high magnetic stability from LDH precursors.This method is general and may be readily extended to other FM/AFM systems due to the wide range of available LDH precursors.
基金This work was supported by the National Natural Science Foundation of China (Grant No. G2000077501) the Foundation of the Chinese Academy of Sciences.
文摘The self-assemblies of 4-hexadecyloxybenzoic acid and 3,4,5-trihexadecyloxybenzoic acid have been studied by using scanning tunneling microscopy (STM). The well-ordered assemblies with different arrangement have been investigated. The structural change is attributed to the different number of substituted alkyl chains on periphery.
基金supported by the National Natural Science Foundation of China, the 111 Project (B07004)the Program for New Century Excellent Talents in Universities, the Beijing Nova Program (2007B021)the Natural Science Foundation for Young Teachers of Beijing University of Chemical Technology
文摘Cobalt ferrite CoxNi1-xFe2O4 （x = 0, 0.5, 1 ） particles with controllable magnetic properties have been prepared by calcination of co-substituted NiFe^2＋Fe^3＋ -layered double hydroxide （NiFe^2＋Fe^3＋-LDH） precursors prepared via a scalable method involving separate nucleation and aging steps （SNAS）. Their structural and magnetic characteristics were investigated by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） and vibrating sample magnetometry （VSM）. Measurements of magnetic properties show that the saturation magnetization （Ms） and coercivity （He） of the calcined products increased with increasing cobalt content. The LDH precursor-based product obtained by calcination of a mixture of CoFe^2＋Fe3^＋-LDH and NiFe^2＋Fe^3＋ -LDH powders with a Co/Ni molar ratio of 1：1, exhibits a moderate value of Ms and an increased value of He compared to the corresponding values for an Ni0.5Co0.5Fe2O4 material prepared by calcination of a Co0.5Ni0.5Fe^2＋Fe^3＋-LDH precursor, and a physical mixture of CoFe2O4 and NiFe2O4 with a Co/Ni molar ratio of 1 ： 1. These results may provide a way to regulate magnetic anisotropy of ferrite spinels by varying the composition of the LDH precursors.
