Battery Electrolyte Composition for Stable SEI and High-Temperature Safety
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to the instability of the positive electrode active material at high temperatures, leading to metal ion dissolution, damage to the solid electrolyte interface (SEI) film, increased negative electrode impedance, and potential safety accidents.
Innovation Solution
A battery electrolyte solution comprising an organic solvent with an ethyl group solvent, an additive of fluoroethylene carbonate, and an electrolyte salt of lithium salt, with specific percentage configurations to enhance peeling strength and reduce negative electrode impedance, thereby forming a robust SEI film and improving safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flame retardant is added to the electrolyte solution to improve safety performance at high temperature, then safety performance is improved, but other performance of the battery deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by introducing a specific ethyl group solvent (ethyl methyl carbonate, diethyl carbonate, or ethyl propionate) in controlled proportions (40-85 wt%). This parameter change enables the formation of a stable SEI film that provides both safety improvement and performance maintenance, resolving the contradiction between safety and other battery performance
Solution Approach 2:
The patent creates a composite electrolyte system by combining the ethyl group solvent with fluoroethylene carbonate additive and lithium salt in specific ratios. This composite approach allows the ethyl group solvent to form a protective SEI film while the fluoroethylene carbonate enhances stability, achieving both safety improvement and performance preservation simultaneously
2Stability of the object's composition
If the positive electrode active material is stable at high temperature, then metal ion dissolution is reduced, but the battery cannot effectively handle high temperature conditions without specialized additives
Solution Approach 1:
The patent applies preliminary action by having the ethyl group solvent and fluoroethylene carbonate form a stable SEI film on the negative electrode surface before high temperature conditions cause damage. This pre-formed protective layer prevents metal ion dissolution and maintains battery stability under high temperature stress
Solution Approach 2:
The ethyl group solvent acts as an intermediary substance that mediates between the positive electrode active material and the electrolyte system. It forms a protective interface that prevents direct harmful interactions at high temperature, allowing the battery to maintain stability without requiring the positive electrode material itself to be inherently heat-stable
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 effectively increases the peeling strength of the negative electrode plate, reduces negative electrode impedance and internal resistance, and enhances safety performance by preventing self-heating and self-ignition, while maintaining other battery performance.
Implementation Method 1
A structure of a positive electrode active material in a lithium-ion battery is unstable at a high temperature, and metal ions are easily dissolved and deposited on a surface of a negative electrode plate. This destroys a structure of a solid electrolyte interface (Solid Electrolyte Interface, SEI) film on the surface of the negative electrode plate
Implementation Method 2
a battery electrolyte solution includes an organic solvent, an additive, and an electrolyte salt. The organic solvent includes an ethyl group solvent, the additive includes fluoroethylene carbonate, and the electrolyte salt includes a lithium salt
Data Source
AI summary
Disclosed are a battery electrolyte solution and a battery. The battery electrolyte solution includes an organic solvent, an additive, and an electrolyte salt, and the electrolyte solution is in contact with a negative electrode plate; the organic solvent includes an ethyl group solvent, the additive includes fluoroethylene carbonate, the electrolyte salt includes a lithium salt, and percentages of the ethyl group solvent, the fluoroethylene carbonate, and the lithium salt in a total mass of the electrolyte solution are configured as follows: 0.4−N3≤A+B2+C2≤5.2−N3, where N denotes a peeling strength value of the negative electrode plate, A, B, and C respectively denote a percentage of the mass of the ethyl group solvent, the fluoroethylene carbonate and the lithium salt in the total mass of the electrolyte solution.