Non-Aqueous Battery Electrolyte for PF5 Suppression and Stable SEI
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Solution Overview
Problem
Lithium secondary batteries face performance degradation and gas generation issues at high temperatures due to the thermal decomposition of PF5 and subsequent reactions, leading to increased resistance and reduced lifespan.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries incorporating vinylene carbonate, vinyl ethylene carbonate, and a specific compound (represented by chemical formula 1) is used, along with a lithium salt like LiPF6, to form a stable SEI film and remove Lewis acids, thereby suppressing gas generation and improving high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the electrolyte solution, then electrochemical characteristics of the battery are improved, but thermal decomposition occurs at high temperature generating PF5 which decomposes the carbonate-based organic solvent and accelerates elution of transition metal
Solution Approach 1:
The patent introduces a cyclic carboxylate compound as an intermediary substance that reacts with PF5 to form a stable complex. This intermediary approach prevents PF5 from directly decomposing the carbonate solvent and eluting transition metals, thereby resolving the contradiction between maintaining electrochemical performance and preventing thermal decomposition.
Solution Approach 2:
The patent converts the harmful PF5 byproduct into a beneficial complex through reaction with the cyclic carboxylate compound. The PF5 that would otherwise cause decomposition is transformed into a stable species that does not harm the electrolyte system, thus converting a harmful factor into a benign state.
2Reliability
If the SEI film does not have sufficient passivation capability, then additional decomposition of the electrolyte solution occurs during storage, but forming a robust SEI film requires stable electrolyte composition
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by introducing a cyclic carboxylate compound with specific molecular structure and properties. This parameter change enables the formation of an SEI film with enhanced passivation capability while maintaining electrolyte stability through the unique chemical characteristics of the cyclic carboxylate.
Solution Approach 2:
The patent creates a composite SEI film structure formed by the interaction of cyclic carbonate, chain carbonate, and cyclic carboxylate compounds. This composite approach combines the benefits of different molecular components to achieve both superior passivation capability and electrolyte stability simultaneously.
3Object-affected harmful factors
If the battery is exposed to high temperature, then PF5 is generated which causes decomposition of the electrolyte solution and elution of transition metal, but preventing PF5 generation requires alternative lithium salts that may reduce performance
Solution Approach 1:
The patent extracts and removes PF5 from the harmful byproducts through chemical reaction with the cyclic carboxylate compound. By taking out PF5 and converting it into a stable complex, the system prevents PF5-induced decomposition and metal elution while maintaining the performance benefits of LiPF6.
Solution Approach 2:
The cyclic carboxylate compound serves as a mediator that intervenes between LiPF6 and the electrolyte components. It captures PF5 through chemical reaction, preventing PF5 from attacking the carbonate solvent and transition metal, thus protecting the system while allowing LiPF6 to maintain its electrochemical benefits.
4Reliability
If side reaction occurs continuously at high temperature, then resistance of the electrolyte solution increases and battery performance deteriorates, but suppressing side reactions requires stable SEI film formation
Solution Approach 1:
The patent employs preliminary action by having the cyclic carboxylate compound pre-react with PF5 to form a stable complex before PF5 can cause harmful decomposition reactions. This preliminary complex formation prevents subsequent side reactions that would increase resistance and degrade performance at high temperatures.
Solution Approach 2:
The patent converts the harmful thermal energy that drives unwanted side reactions into a beneficial effect by using the cyclic carboxylate compound to stabilize the system. The compound's chemical structure and reactivity are designed to withstand and neutralize thermal stress, converting potential harm into system stability.
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 removes by-products and suppresses gas generation, forming a firm SEI film that enhances the battery's high-temperature characteristics while maintaining capacity, thereby improving the battery's performance and lifespan.
Implementation Method 1
a SEI film is formed as side reaction, in which the used electrolyte solution is decomposed
Implementation Method 2
if the SEI film fails to have a passivation capability enough to suppress additional decomposition of the electrolyte solution
Implementation Method 3
Lewis acid such as PF5 is generated due to thermal decomposition when a battery is exposed to a high temperature
Implementation Method 4
anion PF6− is vulnerable to heat, Lewis acid such as PF5 is generated due to thermal decomposition
Implementation Method 5
side reaction, in which the exposed negative electrode active material surface reacts with the solvent of the electrolyte solution to thereby be decomposed, continually occurs
Data Source
AI summary
The present disclosure relates to a non-aqueous electrolyte solution for a lithium secondary battery, and the non-aqueous electrolyte solution includes: a lithium salt; an organic solvent; and an additive including vinylene carbonate, vinyl ethylene carbonate, and a compound represented by chemical formula 1:Herein, each of R1 to R3 is independently hydrogen or an alkyl group having 1 to 3 carbon atoms.