Lithium Battery Electrolyte Additive for PF5 Capture and SEI Stability
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining high-temperature stability and cycle life due to increased battery resistance and capacity reduction, primarily caused by acid decomposition products from lithium salts, which deteriorate the solid-electrolyte-interface (SEI) film and lead to irreversible capacity loss.
Innovation Solution
Incorporating a specific additive, represented by Chemical Formula 1, which includes pyridine or pyrimidine groups that capture PF5− and provide unshared electron pairs to stabilize the SEI film, combined with a non-aqueous organic solvent and lithium salt, and using cobalt-free lithium nickel manganese oxide as the positive electrode active material to enhance cycle life and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte with lithium salt is used, then high energy density is achieved, but battery resistance increases and cycle life decreases at high temperature
Solution Approach 1:
The patent introduces a specific additive compound (with pyridine or pyrimidine ring structure containing unshared electron pairs) as an intermediary substance between the lithium salt and the SEI film. This additive captures PF5− decomposition products and donates electron pairs to stabilize the SEI film, preventing acid-induced deterioration without interfering with normal battery operation, thus resolving the contradiction between maintaining high energy density and preventing resistance increase.
Solution Approach 2:
The patent converts the harmful acid decomposition products (PF5−) generated by lithium salt into beneficial effects. The additive captures these harmful decomposition products and transforms them into stable complexes, while the unshared electron pairs from the additive actively stabilize the SEI film. This converts the harmful acidification process into a beneficial stabilization process, improving cycle life while maintaining high energy density.
2Power
If high-temperature storage is performed, then battery output is improved, but capacity reduction and resistance increase occur
Solution Approach 1:
The patent applies beforehand cushioning by pre-stabilizing the SEI film with the additive compound before high-temperature storage conditions cause deterioration. The additive is incorporated into the electrolyte in advance, where it proactively captures PF5− and donates electron pairs to the SEI film, creating a protective effect that cushions against the harmful effects of high-temperature storage, thus maintaining capacity retention while allowing high output performance.
3Use of energy by moving object
If lithium salt concentration is increased to improve energy density, then acid decomposition products increase, but SEI film deterioration accelerates
Solution Approach 1:
The additive compound serves as a mediator that decouples the relationship between lithium salt concentration and SEI film stability. By introducing this intermediary substance with unshared electron pairs, the system can tolerate higher lithium salt concentrations (maintaining high energy density) because the additive actively neutralizes the harmful acid decomposition products, thus preventing SEI film deterioration even at elevated salt concentrations.
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 suppresses the increase in battery resistance and improves cycle life and high-temperature storage characteristics by stabilizing the SEI film and preventing acid-induced deterioration, resulting in enhanced performance and capacity retention.
Implementation Method 1
provide unshared electron pairs to stabilize the SEI film
Implementation Method 2
capture PF5−
Data Source
AI summary
An additive for an electrolyte represented by Chemical Formula 1, and an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. The details of Chemical Formula 1 are as described in the specification.