Sodium-Ion Anode Material Using Fe-Sn Alloy to Buffer Volume Change
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Solution Overview
Problem
The volume change during charge and discharge cycles in sodium-ion secondary batteries using metal Sn as a negative electrode material leads to unstable battery characteristics due to insufficient mitigation by amorphous components in the glass matrix.
Innovation Solution
A negative electrode active material for sodium-ion secondary batteries containing an amorphous phase with SiO2 and a Fe—Sn-based alloy, such as FeSn2, which mitigates volume change through alloying, ensuring stable battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal Sn is used as negative electrode material to achieve high theoretical capacity, then capacity is improved, but volume change during charge and discharge increases leading to electrode breakage
Solution Approach 1:
The invention uses a composite structure consisting of Fe-Sn-based alloy particles embedded in a glass matrix. The glass matrix comprises specific ratios of SiO2 (40-70 wt%), B2O3 (10-30 wt%), and other oxides, forming a composite material that combines the high capacity of Sn with the structural stability of glass, thereby maintaining electrode integrity during volume changes
2Stability of the object's composition
If amorphous components in glass matrix are used to mitigate volume change, then structural stability is improved, but volume change mitigation is insufficient leading to unstable battery characteristics
Solution Approach 1:
The invention optimizes the chemical composition parameters of the glass matrix, specifically setting SiO2 content at 40-70 wt%, B2O3 at 10-30 wt%, and controlling the ratio of network formers to modifiers. This parameter optimization enhances the glass matrix's ability to buffer volume changes, ensuring stable battery characteristics during repeated charge-discharge cycles
3Stability of the object's composition
If FeSn2 alloy is used instead of pure Sn to reduce volume change, then volume stability is improved, but capacity may be reduced
Solution Approach 1:
The invention creates local quality differentiation by having Fe-Sn-based alloy particles (providing high capacity regions) distributed within the glass matrix (providing structural stability regions). This spatial distribution allows different parts of the composite to fulfill different functions, achieving both high capacity and volume stability simultaneously
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 material exhibits stable battery characteristics with improved cycle life and capacity retention due to the amorphous phase acting as a buffer for volume changes during charge and discharge.
Implementation Method 1
The amorphous phase acts as a buffer that mitigates expansion and contraction of a Fe—Sn-based alloy, such as FeSn2
Implementation Method 2
FeSn2, a type of Fe—Sn-based alloy, repeats a reaction of 2FeSn2+15Na++15e−←→2Fe+Na15Sn4 upon charge and discharge. Compared to metal Sn, FeSn2 exhibits a small volume change due to alloying during charge and discharge
Data Source
AI summary
Provided is a negative electrode active material for a sodium-ion secondary battery that exhibits stable battery characteristics when repeatedly charged and discharged. A negative electrode active material for a sodium-ion secondary battery contains: an amorphous phase containing SiO2 and a Fe—Sn-based alloy.