Non-Aqueous Battery Electrolyte Additives for Stable High-Temperature SEI
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high-temperature stability and lifespan due to decomposition of lithium salts, leading to the formation of Lewis acids that deteriorate the solid electrolyte interphase (SEI) and increase internal resistance.
Innovation Solution
A non-aqueous electrolyte for lithium secondary batteries is developed, incorporating a compound with an imidazole group and a pyridine group as an additive, which effectively removes Lewis acids such as HF and PF5, stabilizes the SEI, and suppresses self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte additives are added to form SEI on the negative electrode, then the SEI formation is improved, but the lifespan performance and high-temperature stability deteriorate
Solution Approach 1:
The patent introduces a dual-functional additive (containing both imidazole and pyridine groups) that acts as an intermediary substance. The imidazole group specifically targets and removes PF5 Lewis acid, while the pyridine group facilitates stable SEI formation. This intermediary additive mediates between the conflicting requirements of SEI formation and lifespan stability, eliminating the need for multiple separate additives that cause side reactions.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte additive by incorporating specific functional groups (imidazole and pyridine) with defined chemical properties. The imidazole group provides Lewis base characteristics to neutralize PF5, while the pyridine group contributes to SEI stability. This parameter change in additive composition resolves the contradiction by enabling both SEI formation and high-temperature stability simultaneously.
2Ease of operation
If LiPF6 is used as lithium salt to achieve suitable battery characteristics, then the battery performance is improved, but thermal decomposition occurs at high temperature generating Lewis acid and HF
Solution Approach 1:
The patent converts the harmful effect of PF5 generation into a beneficial one by introducing the imidazole group as a Lewis base that specifically captures PF5. The harmful Lewis acid that would otherwise decompose the electrolyte and SEI is now utilized to form a protective complex with the imidazole group, thereby protecting the battery system while maintaining the performance benefits of LiPF6.
Solution Approach 2:
The imidazole group acts as an intermediary that mediates between LiPF6 and the electrolyte/SEI system. It intercepts the harmful PF5 generated from LiPF6 decomposition and converts it into a less harmful complex, preventing the cascade of detrimental reactions while preserving the advantageous electrical characteristics provided by LiPF6.
3Stability of the object's composition
If electrolyte additives are added to remove decomposition products, then the SEI stability is improved, but other side effects occur such as deterioration in lifespan and high-temperature stability
Solution Approach 1:
The patent achieves universality by designing a single additive molecule that performs multiple functions: the imidazole group removes PF5 Lewis acid, the pyridine group stabilizes SEI formation, and the overall structure provides high-temperature stability. This multi-functional additive eliminates the need for separate additives that would cause side reactions, resolving the contradiction between SEI stability and high-temperature reliability.
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 enhances the high-temperature stability and lifespan of lithium secondary batteries by preventing SEI deterioration, reducing internal resistance, and minimizing volume expansion, thereby maintaining excellent performance even at elevated temperatures.
Implementation Method 1
the nitrogen atom in the imidazole group acts as a Lewis base, thereby removing Lewis acids such as PF5
Implementation Method 2
forming a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode
Implementation Method 3
the lithium ions cross the non-aqueous electrolyte and the separator to move to the negative electrode part
Implementation Method 4
the electrons move to the positive electrode through the external circuit
Data Source
AI summary
The present invention relates to a novel electrolyte additive, a non-aqueous electrolyte for a lithium secondary battery comprising the novel electrolyte additive, and a lithium secondary battery comprising the non-aqueous electrolyte. More specifically, the present invention relates to a non-aqueous electrolyte for a lithium secondary battery comprising an additive capable of forming a stable film on an electrode surface. The present invention also relates to a lithium secondary battery comprising such a non-aqueous electrolyte, thereby, a high temperature lifespan of the lithium secondary battery is not deteriorated, resistance does not increase when the lithium secondary battery is stored at a high temperature, and expansion of a volume (thickness) of the lithium secondary battery is suppressed when the lithium secondary battery is stored at a high temperature.