Sulfonylimide Battery Electrolyte With Dissolved CO2 for Low Impedance
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Solution Overview
Problem
Non-aqueous electrolyte solutions containing sulfonylimide compounds, such as lithium bis(fluorosulfonyl)imide, in lithium ion secondary batteries experience increased self-discharge and impedance, which affects battery performance, particularly at high temperatures and during charge/discharge cycles, and existing solutions like vinylene carbonate can worsen these issues.
Innovation Solution
A non-aqueous electrolyte solution with a sulfonylimide compound, specifically lithium bis(fluorosulfonyl)imide, is formulated with dissolved carbon dioxide, bicarbonate, or carbonate ions, along with suitable solvents like carbonates and nitriles, to reduce self-discharge and improve battery performance by maintaining low impedance and enhancing charge/discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylene carbonate is added to the non-aqueous electrolyte solution to improve storage characteristics, then storage characteristics are improved, but direct current resistance and impedance increase, making battery performance insufficient
Solution Approach 1:
The invention removes vinylene carbonate from the electrolyte solution composition while maintaining storage characteristics through alternative means (CO2 saturation and specific solvent ratios), thereby eliminating the harmful increase in resistance and impedance
Solution Approach 2:
The invention changes the chemical composition parameters by saturating the electrolyte solution with CO2 and optimizing the ratio of cyclic carbonate to chain carbonate solvents, achieving improved storage characteristics without the harmful effects of vinylene carbonate
2Quantity of substance
If the concentration of electrolyte salt is increased to 1.2 mol/L to improve dissolution of CO2, then CO2 dissolution capacity increases, but the amount of CO2 dissolved remains less than 5 ppm, making the improvement ineffective
Solution Approach 1:
The invention changes the physical state parameters of the electrolyte solution by saturating it with CO2 under pressure and optimizing temperature conditions, achieving significantly higher CO2 dissolution (exceeding 5 ppm) that effectively improves input/output characteristics and high-temperature durability
3Reliability
If room temperature molten salt is used to improve battery safety, then battery safety is improved, but it is extremely difficult to impregnate the positive electrode, negative electrode, and separator with the room temperature molten salt
Solution Approach 1:
The invention removes room temperature molten salt from the electrolyte composition and replaces it with a conventional organic electrolyte solution containing cyclic and chain carbonates, thereby eliminating the impregnation difficulty while maintaining battery safety through alternative means
Solution Approach 2:
The invention changes the electrolyte composition parameters to use volatile organic solvents with appropriate viscosity and wetting properties, enabling easy impregnation of electrodes and separator while maintaining safety through controlled CO2 saturation
4Reliability
If high vapor pressure solvent such as carbon dioxide is used to improve electrolyte performance, then electrolyte performance is improved, but the solvent is volatile with vapor pressure of 1 kPa or higher at 20°C, creating handling and safety challenges
Solution Approach 1:
The invention creates a composite electrolyte system by saturating a conventional organic electrolyte solution with CO2, combining the benefits of CO2 (performance improvement) with the stability of organic solvents (reduced volatility), achieving electrolyte performance enhancement without excessive vapor pressure issues
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 effectively reduces self-discharge and impedance, improves low-temperature charge-discharge capabilities, and maintains battery performance by dissolving carbon dioxide or carbonate ions in the electrolyte solution, addressing the limitations of existing sulfonylimide-based electrolytes.
Implementation Method 1
contains at least one of carbon dioxide (CO2), carbon monoxide (CO), a bicarbonate ion (HCO3−), or a carbonate ion (CO32−) dissolved therein
Data Source
AI summary
A non-aqueous electrolyte solution contains a sulfonylimide compound represented by the general formula (1): LiN(R1SO2)(R2SO2) (wherein R1 and R2 are identical or different from each other and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms) as an electrolyte salt, an electrolyte solution solvent, and at least one of carbon dioxide (CO2), carbon monoxide (CO), a bicarbonate ion (HCO3−), or a carbonate ion (CO32−) dissolved therein. The electrolyte solution solvent includes at least one selected from the group consisting of a carbonate solvent, a lactone solvent, an ether solvent, a nitrile solvent, and a chain ester solvent, and a total amount of the at least one of CO2, CO, HCO3−, or CO32− dissolved is 20 ppm by mass or more.