Fluorinated Carbonate Electrolyte for Thermal Runaway Suppression
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Solution Overview
Problem
Lithium-ion secondary batteries are prone to thermal runaway and ignition due to heat generation reactions, particularly when the temperature exceeds 100°C, leading to the risk of internal short circuits and gas generation, which can cause ignition.
Innovation Solution
The use of an electrolyte solution comprising a mixed solvent of fluorinated linear and cyclic carbonates with a high concentration of lithium salt, along with a separator containing an imide compound, to inhibit heat generation and gas production, thereby enhancing thermal stability and preventing thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used, then the battery can operate at normal temperatures, but thermal runaway and ignition occur when temperature exceeds 100°C
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by using fluorinated cyclic carbonate and fluorinated linear carbonate with specific fluorine substitution patterns. This parameter change results in electrolyte components that do not undergo exothermic decomposition reactions at elevated temperatures, thereby suppressing heat generation and preventing thermal runaway while maintaining operational functionality.
Solution Approach 2:
The patent employs a composite electrolyte system combining fluorinated cyclic carbonate and fluorinated linear carbonate components. This composite material approach creates an electrolyte solution where the fluorinated structures work synergistically to provide both functional performance at operating temperatures and thermal stability at elevated temperatures, resolving the contradiction between normal operation and thermal safety.
2Reliability
If conventional electrolyte solutions are used, then the battery functions normally, but gas is generated at high temperatures leading to ignition risk
Solution Approach 1:
The patent modifies the chemical parameters of the electrolyte by incorporating fluorinated carbonate structures where fluorine atoms replace hydrogen atoms at specific positions. This parameter change alters the thermal decomposition behavior of the electrolyte, preventing the formation of flammable gases at elevated temperatures while maintaining the electrolyte's ionic conductivity and functional properties.
3Reliability
If nonflammable agents are mixed into electrodes (Patent Document 1), then thermal runaway is inhibited, but electrode structure and performance may be affected
Solution Approach 1:
The patent extracts the thermal stability function from the electrode components and relocates it to the electrolyte solution. Instead of modifying electrodes with nonflammable agents, the invention places thermally stable fluorinated carbonate components in the electrolyte, which suppresses heat generation and prevents thermal runaway without altering electrode structure or complexity.
Solution Approach 2:
The patent uses the electrolyte solution as an intermediary medium to achieve thermal stability. The fluorinated carbonate electrolyte acts as a mediator between the electrodes, providing thermal protection and preventing heat generation reactions without requiring modifications to the electrode structures themselves, thus avoiding increased device complexity.
4Temperature
If high thermal conductivity gas is used to fill container (Patent Document 2), then heat dissipation is improved, but container structure and gas management complexity increase
Solution Approach 1:
The patent extracts the heat management function from the container system and relocates it to the electrolyte solution. The fluorinated carbonate electrolyte inherently suppresses exothermic reactions and stabilizes temperature through its chemical composition, eliminating the need for complex container structures filled with high thermal conductivity gases.
Solution Approach 2:
The fluorinated carbonate electrolyte serves as a thermal management intermediary that prevents heat generation at the source through its chemically stable fluorinated structure. This intermediary approach provides passive thermal stability without requiring active cooling systems or complex container modifications, simplifying the overall device structure.
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 electrolyte solution and separator design significantly reduce heat generation and gas production, inhibiting thermal runaway and ignition, even at elevated temperatures, thus improving the safety and reliability of lithium-ion secondary batteries.
Implementation Method 1
the concentration of the lithium salt is higher than 1 mol per liter of the mixed solvent... In a differential scanning calorimetry (DSC) measurement of the electrolyte solution, a peak of heat flow of a heat generation reaction in a range higher than or equal to 180° C. and lower than or equal to 300° is less than or equal to 200 mW/g
Data Source
AI summary
To provide an electrolyte solution capable of inhibiting ignition or the like and a secondary battery including the electrolyte solution. The secondary battery includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution. The electrolyte solution includes a mixed solvent and a lithium salt. In the electrolyte solution, a concentration of the lithium salt is higher than 1 mol per liter of the mixed solvent. The mixed solvent includes a fluorinated linear carbonate and a fluorinated cyclic carbonate. In a DSC measurement of the electrolyte solution, a peak of heat flow of a heat generation reaction in a range higher than or equal to 180° C. and lower than or equal to 300° C. is less than or equal to 200 mW/g.