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High-ionicity fluorophosphate lattice via aliovalent substitution as advanced cathode materials in sodium-ion batteries

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InfoMat 2021年第6期3卷 694-704页

作者： Zhen-Yi Gu Jin-Zhi Guo Xin-Xin Zhao Xiao-Tong Wang Dan Xie Zhong-Hui Sun Chen-De Zhao Hao-Jie Liang Wen-Hao Li Xing-Long Wu MOE Key Laboratory for UV Light-Emitting Materials and Technology Northeast Normal UniversityChangchunJilinChina Department of Chemistry Northeast Normal UniversityChangchunJilinChina Center for Advanced Analytical Science School of Chemistry and Chemical EngineeringGuangzhou UniversityGuangzhouGuangdongChina

As a cathode for sodium-ion batteries(SIBs),Na3V2(PO4)2F3(NVPF)with 3D open framework is a promising candidate due to its high working voltage and large theoretical ***,the severe capacity degradation and poor rate capability hinder its practical *** present study demonstrated the optimization of Na-storage performance of NVPF via delicate lattice *** substitution of V^(3^(+))at Na^(+)in NVPF induces the generation of electronic defects and expansion of Na^(+)-migration channels,resulting in the enhancement in electronic conductivity and acceleration of Na^(+)-migration *** is disclosed that the formed stronger Na O bonds with high ionicity than V O bonds lead to the significant increase in structural stability and ionicity in the Na^(+)-substituted NVPF(NVPF-Nax).The aforementioned effects of Na^(+)substitution achieve the unprecedented electrochemical performance in the optimized Na_(3.14)V1.93Na0.07(PO_(4))_(2)F_(3)(NVPF-Na_(0.07)).As a result,NVPF-Na0.07 delivers a high-rate capability(77.5 mAh g^(−1)at 20 C)and ultralong cycle life(only 0.027%capacity decay per cycle over 1000 cycles at 10 C).Sodium-ion full cells are designed using NVPF-Na0.07 as cathode and Se@reduced graphene oxide as *** full cells exhibit excellent wide-temperature electrochemical performance from−25 to 25C with an outstanding rate capability(96.3 mAh g^(−1)at 20 C).Furthermore,it delivered an excellent cycling performance over 300 cycles with a capacity retention exceeding 90%at 0.5 C under different *** study demonstrates a feasible strategy for the development of advanced cathode materials with excellent electrochemical properties to achieve high-efficiency energy storage.

关键词： cathode full cell ionicity Na3V2(PO4)2F3 sodium-ion batteries

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Cation distributions estimated using the magnetic moments of the spinel ferrites Co_(1-x)Cr_xFe_2O_4 at 10K

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Chinese Physics B 2014年第10期23卷 519-528页

作者：尚志丰齐伟华纪登辉徐静唐贵德张晓云李壮志郎莉莉 Hebei Advanced Thin Film Laboratory Department of Physics Hebei Normal University Department of Physics and Electronic Science Liupanshui Normal University

（A）[B]2O4 ferrite samples with the composition COl_xCrxFe204 （0.0 ≤ x ≤1.0） are prepared using a hydrothermal method, and subjected to calcining in a tube furnace with an argon-flow at 1673 K for 2 h. X-ray diffraction patterns indicate that each of all the samples has a single phase cubic spinel structure with a space group of Fd3m. Magnetic measurements show that the saturation magnetization decreases with as the Cr content x increases. The cation distribution of the samples is estimated by fitting the dependence of the magnetic moments on x at l 0 K, using the quantum mechanical model previously proposed by our group. The calculated sum of the content values of the Cr3＋ and Cr2＋ cations occupying the （A） sites increases as the value of x increases. In the fitting process, the magnetic moment directions of the Cr3＋ and Cr2＋ cations are assumed to be antiparallel to those of the Fe and Co cations, respectively, which is in accordance with Hund＇s rules.

关键词： spinel ferrite magnetic property cation distribution ionicity

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Ab initio Valence Bond Study on AB-type Molecules,A Description for XH(X=L,Be,B,C,N,O,F) and XF(X=Li,Be,B)

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Chinese Journal of Chemistry 2003年第3期21卷 225-231页

作者：廖新丽莫亦荣等 DepartmentofChemistry StateKeyLaboratoryforPhysicalChemistryoftheSolidSurfaceCenterforTheoreticalChemistryXiamenuniversityXiamenFujian361005China DepartmentofChemistry StateKe

Ab initio valence bond method is employed to quantitatively study the concepts of ionic resonance energy and ionicity of a chemical bond in the cases of hydrides XH (X = Li, Be, B, C, N, O, F) and fluorides XF (X = Li, Be, B). By establishing the relationship between resonance and stability, and comparing the calculated ionicities with Pauling's earlier estimations in the above diatomic molecules, the merits of Pauling's classical resonance theory were demonstrated at the ab initio level.

关键词： valence bond theory ionicity electronegativity

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Valence electronic structure of tantalum carbide and nitride

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Science China(Physics,Mechanics & Astronomy) 2007年第6期50卷 737-741页

作者： FAN ChangZeng SUN LiLing WEI ZunJie MA MingZhen LIU RiPing ZENG SongYan WANG WenKui Department of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China National Laboratory for Superconductivity Institute of PhysicsChinese Academy of SciencesBeijing 100080China National Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQin-huangdao 066004China

The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.

关键词： TaC TaN valence electronic structure ionicity

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