Layered Sodium-Ion Battery Anode for Higher Initial Efficiency
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Solution Overview
Problem
The initial charge-discharge efficiency of sodium-ion secondary batteries is low due to undesirable side reactions and irreversible capacity issues, particularly when using carbon materials as negative-electrode active materials, leading to decreased efficiency and cycle characteristics.
Innovation Solution
A negative electrode for sodium-ion secondary batteries comprising a first layer of carbon material and a second layer of sodium-containing alloy, with the alloy layer also serving as a current collector, enhances ion supply and reduces irreversible capacity, improving efficiency and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon materials are used as negative-electrode active materials in sodium-ion secondary batteries, then the batteries can operate with stable structure, but undesirable side reactions occur during initial charge causing sodium ions to be trapped and initial charge-discharge efficiency to decrease
Solution Approach 1:
The negative electrode is segmented into multiple layers: a first negative electrode layer containing carbon material and a second negative electrode layer containing sodium-containing alloy. This segmentation allows each layer to perform its specialized function - the carbon layer provides structural stability while the alloy layer supplies sodium ions, thereby resolving the contradiction between structural stability and initial charge-discharge efficiency
Solution Approach 2:
The first negative electrode layer containing carbon material acts as an intermediary between the solid electrolyte and the sodium-containing alloy in the second layer. This intermediary structure prevents direct contact between the alloy and electrolyte, reducing side reactions while still allowing efficient sodium ion transfer, thus improving initial charge-discharge efficiency without compromising structural stability
2Productivity
If sodium-containing alloy is used as negative-electrode active material, then ion supply is improved, but the material requires protection to prevent side reactions with electrolyte
Solution Approach 1:
The first negative electrode layer containing carbon material serves as a protective intermediary layer between the solid electrolyte and the sodium-containing alloy in the second layer. This intermediary structure allows sodium ions to pass through while preventing direct chemical reactions between the alloy and electrolyte, thus maintaining both ion supply capability and chemical stability
Solution Approach 2:
The first negative electrode layer is positioned in advance to prevent side reactions between the sodium-containing alloy and the solid electrolyte. This preliminary protective structure prevents harmful chemical interactions before they can occur, ensuring the alloy maintains its high ion supply capability without degradation from side reactions
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 proposed structure improves initial charge-discharge efficiency and cycle characteristics by ensuring sodium ions are effectively supplied between layers, reducing irreversible capacity and preventing dendrite formation, while maintaining high electronic conductivity and reducing production costs.
Implementation Method 1
a first negative-electrode active material containing a carbon material; and a second negative-electrode active material containing a sodium-containing alloy
Data Source
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AI summary
Provided is a negative electrode for a sodium-ion secondary battery that can improve the initial charge-discharge efficiency of the secondary battery. A negative electrode for a sodium-ion secondary battery contains: a first negative-electrode active material containing a carbon material; and a second negative-electrode active material containing a sodium-containing alloy.