Non-Aqueous Electrolyte Additives for LiPF6 High-Temperature Stability
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Solution Overview
Problem
Lithium ion batteries face performance degradation and increased resistance at high temperatures due to the decomposition of lithium salts, particularly LiPF6, which leads to the formation of Lewis acids that damage the solid electrolyte interphase (SEI) and reduce battery capacity and lifespan.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, incorporating a lithium salt, an organic solvent, a Lewis base compound as a first additive, and lithium difluorophosphate (LiDFP) as a second additive, which scavenges decomposition products and forms a robust SEI to enhance high-temperature durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt to obtain suitable battery characteristics, then the battery achieves good electrochemical performance, but at high temperatures the PF6- anion decomposes to form Lewis acids that damage the SEI and increase resistance
Solution Approach 1:
A compound of Formula 1 acts as an intermediary substance between the LiPF6 decomposition and the SEI layer. It preferentially reacts with the generated PF5 to form stable complexes, preventing PF5 from attacking and destroying the SEI layer. This mediator approach allows LiPF6 to maintain its electrochemical benefits while eliminating its harmful high-temperature decomposition effects.
Solution Approach 2:
The invention converts the harmful decomposition product PF5 into a beneficial substance by having it react with the compound of Formula 1 to form stable complexes. The decomposition reaction that was previously harmful is redirected to produce a protective effect, as the compound of Formula 1 scavenges PF5 and prevents SEI destruction while maintaining battery performance.
2Power
If the battery is operated or stored at high temperatures to meet performance demands, then power delivery is improved, but resistance increases and capacity decreases due to electrolyte solution deterioration
Solution Approach 1:
The compound of Formula 1 is pre-added to the electrolyte solution to perform preliminary protection before high-temperature damage occurs. It proactively scavenges PF5 as soon as it is generated from LiPF6 decomposition, preventing the subsequent destruction of the SEI layer and avoiding the chain reactions that lead to resistance increase and capacity loss.
Solution Approach 2:
The compound of Formula 1 provides beforehand cushioning by creating a protective chemical environment in the electrolyte solution. It cushions against the harmful effects of PF5 by being present in advance and ready to react, thereby protecting the SEI layer and maintaining battery stability during high-temperature operation and storage.
3Stability of the object's composition
If conventional electrolyte additives are used to protect the SEI, then some passivation ability is maintained, but they are insufficient to effectively scavenge PF5 and suppress battery degradation at high temperatures
Solution Approach 1:
The invention changes the chemical parameters of the electrolyte additive by using a compound of Formula 1 with specific molecular structure and Lewis base properties. This parameter change enables the additive to have enhanced PF5 scavenging capability compared to conventional additives, allowing it to effectively protect the SEI layer and suppress battery degradation at high temperatures.
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 scavenges decomposition products, reduces initial resistance, and improves high-temperature storage characteristics by forming a stable SEI, thereby enhancing the battery's long-term life and capacity retention.
Implementation Method 1
a compound represented by Formula 1... having an excellent effect of scavenging a decomposition product generated from a lithium salt... PF5 which is formed by the pyrolysis of the LiPF6-based salt
Implementation Method 2
lithium difluorophosphate (LiDFP)... forms a desired film on surfaces of a positive electrode and a negative electrode... forming a stable SEI
Implementation Method 3
a Lewis acid, such as PF5−, is generated due to pyrolysis when the battery is exposed to high temperatures
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, a non-aqueous electrolyte solution includes a compound represented by Formula 1 having an excellent effect of scavenging a decomposition product generated from a lithium salt in the electrolyte solution, as a first additive, and lithium difluorophosphate as a second additive. The lithium secondary battery include the non-aqueous electrolyte solution has improved high-temperature durability.