Coated Sodium-Ion Cathode Material for Stable Cycling
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Solution Overview
Problem
The cathode material of sodium ion batteries is prone to lattice distortion and phase change during charging and discharging, hindering sodium ion transport and diffusion, leading to irreversible capacity loss and performance degradation.
Innovation Solution
A cathode material with a chemical formula of Na1+aNixMnyFezAmBnO2 is developed, where elements A and B form a modified structure and coating layer, respectively, enhancing structural stability and forming a protective layer to inhibit side reactions with the electrolyte, improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layered oxide cathode material is used for sodium ion battery, then high specific capacity and high voltage are achieved, but lattice distortion and phase transformation occur during charge and discharge, hindering sodium ion transport and diffusion
Solution Approach 1:
The patent applies local quality by introducing different elements (Al, Ti, Zr, B, F) at specific positions in the crystal structure (A and B sites) to locally stabilize the lattice and prevent distortion during sodium ion insertion/extraction, while maintaining the overall layered oxide structure for high capacity
Solution Approach 2:
The patent creates composite materials by combining multiple transition metal elements (Ni, Mn, Fe) with stabilizing elements (Al, Ti, Zr, B, F) in a layered oxide structure, achieving both high specific capacity from the transition metals and structural stability from the composite formulation
2Quantity of substance
If excessive sodium salt is added in material production process, then sodium element loss is compensated, but residue of sodium salt (free sodium) remains after sintering, causing high alkalinity
Solution Approach 1:
The patent applies parameter changes by optimizing the sodium salt addition amount and sintering temperature (800-900°C) to achieve complete reaction of excess sodium salt, transforming residual sodium carbonate and sodium hydroxide into stable phases or removing them, thereby controlling the free sodium content and alkalinity of the final product
3Speed
If free sodium is present on the surface of the material, then sodium ion transport is facilitated, but sodium reacts with electrolyte to form irreversible capacity loss and deteriorate cycling performance
Solution Approach 1:
The patent introduces an intermediary protective coating layer on the surface of the cathode material that acts as a barrier between the reactive free sodium and the electrolyte, preventing harmful side reactions and irreversible capacity loss while allowing sodium ion transport through the coating
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 modified cathode material ensures complete occupation of sodium ions within the material, reduces irreversible capacity loss, and enhances cycling performance by facilitating sodium ion transport and forming a protective layer against electrolyte reactions.
Implementation Method 1
the surface of the material is modified by coating the material, thereby forming an effective protective layer on the surface of the material
Implementation Method 2
hinders the transport and diffusion of sodium ions
Data Source
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AI summary
The present disclosure is in the technical field of sodium ion batteries, and particularly relates to a cathode material for a sodium ion battery having a coating structure and a preparation method and use thereof. The general chemical formula of the cathode material for a sodium ion battery having a coating structure is Na1+aNixMnyFezAmBnO2, where -0.35≤ a ≤ 0.20, 0.08 < x ≤ 0.5, 0.05 <y≤ 0.48, 0.03 <z< 0.4, 0.03 < m < 0.24, 0.001 < n < 0.06, x+y+z+m+n=1. A preparation method of a cathode material for a sodium ion battery comprises the steps of: firstly, mixing a sodium source, a nickel source, a manganese source, an iron source and an A source uniformly, and then performing a first sintering, cooling and crushing to obtain a semi-finished product; then, after mixing the semi-finished product with a B source uniformly, performing a second sintering, cooling and crushing to obtain the cathode material for a sodium ion battery . The cathode material for a sodium ion battery according to the present disclosure is structurally stable, and a surface coating layer thereof inhibits side reactions with an electrolyte, so that the cycling performance is significantly improved.