Ether-Based Sodium Battery Electrolyte for Stable Tin Anodes
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Solution Overview
Problem
Sodium secondary batteries using tin (Sn) as a negative electrode face challenges due to the instability of conventional carbonate-based electrolytes, which lead to severe degradation and capacity loss due to the formation of a solid electrolyte interface (SEI) and poor electrochemical stability, especially with large volume changes during charge and discharge.
Innovation Solution
Employing an ether-based organic liquid electrolyte with specific solvents such as Dimethoxyethane (glyme) and sodium salts like NaPF6, which provides a wider electrochemical stability window and reduces SEI formation on the tin anode, enhancing the stability and performance of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbonate-based electrolytes are used with tin negative electrode, then the battery can operate initially, but the electrolyte becomes unstable and forms SEI layer causing severe degradation and capacity loss
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing carbonate-based solvents with ether-based solvents (such as dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether) and adjusting the sodium salt concentration to 0.5-2.0 M. This parameter change fundamentally alters the electrolyte's interaction with the tin anode, preventing harmful SEI formation while maintaining ionic conductivity, thereby resolving the stability-degradation contradiction.
2Productivity
If tin particles with small size are used, then the surface area increases for better reaction, but the volume change during charge-discharge causes severe degradation
Solution Approach 1:
The patent creates a composite negative electrode structure by combining tin particles (average diameter 1-50 μm) with conductive carbon materials (such as acetylene black, graphite, or carbon nanotubes) and binder resins. The carbon matrix provides structural support and conductivity while accommodating the volume expansion of tin during sodiation, preventing particle degradation and maintaining electrode integrity throughout cycling.
3Quantity of substance
If large amount of tin is used to increase capacity, then the energy density improves, but the volume expansion during charging causes electrolyte consumption and degradation
Solution Approach 1:
The patent converts the harmful volume expansion of tin during charging into a beneficial effect by using ether-based electrolytes that form stable solvated sodium species. The ether molecules coordinate with sodium ions, creating a stable solvation shell that accommodates the volume changes of tin particles. This stabilizes the electrode-electrolyte interface, preventing electrolyte decomposition and consumption even with high tin content (90-99 wt%) in the negative electrode.
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 ether-based electrolyte enables high-capacity utilization of tin, improves ionic conductivity, and extends cycle life, achieving high energy density and safety with reduced sodium inventory loss and electrolyte consumption, thus overcoming the limitations of carbonate-based electrolytes.
Implementation Method 1
an electrolyte in sold or liquid form and an organic or inorganic electrolyte, to ensure sodium ionic conductivity between the positive electrode and the negative electrode
Implementation Method 2
which provides a wider electrochemical stability window and reduces SEI formation on the tin anode, enhancing the stability and performance of the battery
Data Source
AI summary
The present disclosure is related to an electrolyte for a sodium secondary battery, wherein the electrolyte comprises a compound having a chemical structure including an oxygen molecule covalently bound to R1 and R2 groups (R1-O-R2), wherein each of R1 and R2 is an alkyl group or an aryl group.