Sodium-magnesium-manganese-based layered oxide material having variable-valence anions, preparation method and use

Abstract

The invention discloses a sodium-magnesium-manganese-based layered oxide material having variable-valence anions, a preparation method and a use. The material has a chemical formula of Naa[MgbMnc]O2+[beta], wherein a, b, c, and [beta] are the mole percentages of the corresponding elements respectively and satisfy a relationship of b + c = 1 and a + b + 4c = 2 * (2 + [beta]), wherein 0.5 <= a <= 0.85; 0.25 <= b <= 0.425; 0.575 <= c <= 0.75; and -0.02 <= [beta] <= 0.02. The layered oxide material has a space group of P63 / mmc or P63 / mcm or R-3m, and a corresponding structure of P2 phase or P3 phase. An anionic variable-valence layered oxide material is used as a positive electrode active material of a sodium ion secondary battery. When the material is charged in the first cycle, oxygen ions in a crystal lattice lose electrons, and have an average valence increasing from -2 to a valence state between -2 and -1. When the material is discharged in the first cycle, oxygen ions with high valences regain electrons, and as the discharge progresses, some manganese ions obtain electrons and have an average valence state changing from tetravalent to trivalent. From the second cycle, during thecharge and discharge processes, oxygen ions and manganese ions jointly participate in reversible electron gain and loss processes.

Description

technical field [0001] The invention relates to the field of material technology, in particular to a sodium-magnesium-manganese-based layered oxide material with variable anion valence, a preparation method and an application. Background technique [0002] With the development and progress of society, human beings have an increasing demand for energy. However, due to the depletion of traditional fossil energy such as coal, oil, and natural gas, coupled with the increasingly severe problems of urban environmental pollution and greenhouse effect, Its application is gradually restricted in many ways, so the development of sustainable clean energy has always been the direction of attention of all countries. However, in the process of converting wind energy, solar energy, and tidal energy into electrical energy, these renewable energy sources are greatly restricted by natural conditions, and have the characteristics of obvious time discontinuity and spatial distribution, which le...

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Problems solved by technology

[0006] However, sodium-ion batteries are still in the research stage at present, and there is no commercial sodium-ion battery cathode material. Now researchers focus on the layered structure oxide cathode material Na x MO 2 (M represents 3d transition metal elements, which can contain one or more, such as Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Nb, Ru, Mo, Zn, etc.)

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