Sodium-Ion Battery Electrolyte for Stable SEI and First-Cycle Efficiency
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Solution Overview
Problem
Sodium-ion batteries suffer from low cycle performance and first-cycle efficiency due to the larger radius of sodium ions, which leads to poor migration and diffusion properties, resulting in high insertion barriers and unstable performance.
Innovation Solution
A sodium-ion secondary battery design incorporating a fluoroether solvent represented by Structural Formula 1 and a cyclic sulfate ester in the electrolyte, with specific mass percentages and surface area constraints, forms stable SEI and CEI films, reducing side reactions and optimizing electrolyte consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hard carbon prepared by low-temperature carbonization is used as negative electrode material, then ionic conductivity is improved, but first-cycle efficiency and cycle performance deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a cyclic sulfate ester additive and a fluoroether solvent with specific molecular structure (x/(2n+1)≤0.8). This parameter change modifies the electrolyte's interaction with sodium ions and electrode surfaces, enabling stable SEI formation that improves cycle performance while maintaining ionic conductivity.
Solution Approach 2:
The patent creates a composite electrolyte system combining cyclic sulfate ester, fluoroether solvent, and conventional carbonate solvents. This composite approach leverages the unique properties of each component: the cyclic sulfate ester forms protective films, the fluoroether solvent enhances stability, and the carbonate solvents provide ionic conductivity, achieving synergistic improvement in both ionic conductivity and cycle performance.
2Quantity of substance
If sodium ions are used instead of lithium ions, then resource abundance and cost are improved, but migration and diffusion properties deteriorate due to larger ion radius
Solution Approach 1:
The cyclic sulfate ester acts as an intermediary substance that mediates between the sodium ions and the electrode surfaces. It facilitates sodium ion transport by forming a conductive interface layer that reduces the energy barrier for ion insertion and extraction, thereby improving migration speed without compromising the resource abundance advantage of sodium-ion batteries.
Solution Approach 2:
The patent modifies the electrolyte's physical and chemical parameters by incorporating fluoroether solvent with specific molecular weight and structure (x/(2n+1)≤0.8). These parameter changes optimize the electrolyte's viscosity and dielectric constant, enhancing sodium ion solvation and mobility, thus improving ion migration speed while maintaining the cost and resource advantages of sodium-ion systems.
3Ease of manufacture
If conventional electrolytes are used, then manufacturing simplicity is maintained, but interfacial stability and first-cycle efficiency deteriorate
Solution Approach 1:
The cyclic sulfate ester performs a preliminary action by reacting with the electrode surfaces during the first charge cycle to form stable solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) films. This preliminary film formation prevents subsequent side reactions, improves interfacial stability, and enhances first-cycle efficiency, while the overall manufacturing process remains simple and compatible with existing production lines.
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 solution enhances both the cycle performance and first-cycle efficiency of sodium-ion batteries by improving interfacial stability and reducing irreversible capacity loss, while maintaining effective electrolyte conductivity and capacity utilization.
Implementation Method 1
the fluoroether solvent of structural formula 1 can participate in the ion solvation structure, forming a structurally stable SEI and CEI film on the surface of the electrode material
Implementation Method 2
the fluoroether solvent of structural formula 1 can participate in the ion solvation structure, forming a structurally stable SEI and CEI film on the surface of the electrode material
Implementation Method 3
The cyclic sulfate ester compound can suppress side reactions during the formation stage of the battery, reducing irreversible capacity loss
Implementation Method 4
sodium-ion batteries have a cost advantage. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, utilizing the intercalation and de-intercalation processes of sodium ions between the positive and negative electrodes for charging and discharging
Implementation Method 5
sodium-ion batteries have a cost advantage. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, utilizing the intercalation and de-intercalation processes of sodium ions between the positive and negative electrodes for charging and discharging
Data Source
AI summary
Provided is a sodium-ion secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode active material, the electrolyte comprises a sodium salt, an additive, and a non-aqueous organic solvent, the additive comprises a cyclic sulfate ester, and the non-aqueous organic solvent comprises a fluoroether solvent represented by Structural Formula 1:FxCnH2n+1-xOCmH2m+1 Structural Formula 1wherein x/(2n+1)<0.8, n/m>1.5; 4≤n≤10, 1≤m≤5;the sodium-ion secondary battery satisfies the following relational expression:0.9≤(a•d)/(b•c)≤20;wherein, 8%≤a≤25%, 0.5%≤b≤3%, 4 m2/g≤c≤7 m2/g.The sodium-ion secondary battery provided by the present application can improve the cycle performance and first-cycle efficiency of the sodium-ion secondary battery.