Layered Sodium-Ion Cathode Doping for Phase-Stable NaMnO2
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Solution Overview
Problem
Layered sodium ion battery positive electrode materials, such as NaMnO2, are unstable in air and prone to structural changes during charging and discharging, leading to poor cycle performance and limited large-scale application due to the difference in ion radii and instability during material synthesis and battery assembly.
Innovation Solution
A positive electrode material with the chemical formula NaxMnO2-a(MO4)a, where 0<x≤1 and 0.01≤a≤0.2, is developed by mixing a manganese salt solution with an alkaline potassium permanganate solution containing molybdate or tungstate, followed by solid-liquid separation, washing, drying, and sintering with a sodium source, enhancing structural stability and specific capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layered NaMnO2 material is used as positive electrode material, then high energy density and high specific capacity are achieved, but structural stability deteriorates due to interphase structural changes during charging and discharging
Solution Approach 1:
The patent introduces a dual-doping strategy where Mn3+ ions and transition metal elements (Fe2+, Co2+, Ni2+) are simultaneously incorporated into the NaMnO2 lattice at specific positions. This local modification of composition creates regions with enhanced structural stability while maintaining the overall high capacity characteristics of the layered structure, directly addressing the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite doped material system by combining multiple elements (Na, Mn, Fe, Co, Ni, O) in a layered perovskite structure. The composite nature of this material allows synergistic effects where different elements contribute different properties: Mn provides high capacity, while Fe, Co, and Ni doping enhance structural stability and electrochemical performance, resolving the contradiction between capacity and stability.
2Quantity of substance
If layered NaMnO2 material is used as positive electrode material, then high energy density is achieved, but electrochemical cycle performance deteriorates due to poor structural stability
Solution Approach 1:
The patent introduces a dual-doping strategy where Mn3+ ions and transition metal elements (Fe2+, Co2+, Ni2+) are simultaneously incorporated into the NaMnO2 lattice at specific positions. This local modification of composition creates regions with enhanced structural stability while maintaining the overall high capacity characteristics of the layered structure, directly addressing the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite doped material system by combining multiple elements (Na, Mn, Fe, Co, Ni, O) in a layered perovskite structure. The composite nature of this material allows synergistic effects where different elements contribute different properties: Mn provides high capacity, while Fe, Co, and Ni doping enhance structural stability and electrochemical performance, resolving the contradiction between capacity and stability.
3Ease of manufacture
If conventional preparation method is used, then material synthesis is achieved, but uneven doping occurs leading to poor material quality
Solution Approach 1:
The patent employs a pre-synthesis approach where the doped MnO2 precursor is prepared first using a solvothermal method with controlled doping during the precursor formation stage. This preliminary doping action ensures uniform distribution of transition metal elements before the final sodium insertion step, achieving both ease of manufacture and high doping uniformity.
Solution Approach 2:
The patent optimizes preparation parameters including solvothermal temperature (100-200°C), reaction time (12-48 hours), and precursor composition ratios to achieve uniform doping. By carefully controlling these parameters during the precursor synthesis stage, the patent ensures homogeneous distribution of dopants throughout the material structure, resolving the contradiction between ease of manufacture and doping precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The doped material improves specific capacity, cycle performance, and rate capability by stabilizing the skeleton structure, overcoming issues of phase changes and uneven doping, resulting in enhanced electrochemical performance.
Implementation Method 1
adding the alkaline potassium permanganate solution to the manganese salt solution, and performing solid-liquid separation after the reaction is finished to obtain a solid material
Implementation Method 2
after washing and drying the solid material, mix the solid material with a sodium source and then sinter to obtain a positive electrode material for layered sodium ion battery
Data Source
AI summary
A layered sodium ion battery positive electrode material and a preparation method therefor. The chemical formula of the layered sodium ion battery positive electrode material is NaxMnO2-a(MO4)a, wherein 0<x≤1, 0.01≤a≤0.2, and M is one or two of W and Mo. The preparation method comprises: preparing a manganese salt solution and a basic potassium permanganate solution mixed with an M element material, wherein the M element material is one or two of molybdate or tungstate; adding the basic potassium permanganate solution to the manganese salt solution, and potassium permanganate solution to the manganese salt solution, and after a reaction is finished, carrying out solid-liquid separation to obtain a solid material; and washing and drying the solid material, mixing the solid material with a sodium source, and then sintering same to obtain a layered sodium ion battery positive electrode material. The layered sodium ion battery positive electrode material of the present invention enhances the framework structure of the material due to the doping of the tungsten or molybdenum element, inhibits the phase change of the material during the charging and discharging process, and can significantly improve the specific capacity, the cycle performance and the rate capability of the material.