Non-Aqueous Electrolyte Composition for High-Temperature SEI Protection

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Solution Overview

Problem

Lithium secondary batteries face performance degradation and increased resistance at high temperatures due to the decomposition of the solid electrolyte interphase (SEI) caused by Lewis acids like PF5, which damages the SEI and degrades battery life.

Innovation Solution

A non-aqueous electrolyte containing a compound with nitrogen, fluorine, and a propargyl group is used as an additive, acting as a Lewis base to scavenge Lewis acids and promote polymerization of the SEI, forming a stable passivation layer on the electrode surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If LiPF6 is used as the lithium salt in the non-aqueous electrolyte, then high ionic conductivity and good electrochemical performance are achieved, but at high temperatures the PF6- anion thermally decomposes to generate Lewis acid (PF5) which destroys the SEI and increases battery resistance

Engineering Contradiction:

Improveionic conductivityVSAvoidhigh-temperature stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a compound containing a propargyl group as an intermediary substance in the electrolyte. This compound acts as a mediator that reacts with PF5 to form a stable complex, preventing PF5 from attacking and destroying the SEI. The propargyl group-containing compound serves as a protective intermediary between the Lewis acid and the SEI, resolving the contradiction between maintaining ionic conductivity and ensuring high-temperature stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful effect of PF5 decomposition into a beneficial outcome. Instead of allowing PF5 to destroy the SEI, the system allows controlled reaction of PF5 with the propargyl group-containing compound to form a stable complex. This transforms the harmful Lewis acid into a beneficial protective mechanism, where the decomposition product is neutralized and even contributes to forming a more stable SEI structure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Temperature

If the battery is exposed to high temperatures, then thermal energy is available to enhance reaction rates, but the SEI decomposes due to Lewis acid generation, causing resistance increase and performance degradation

Engineering Contradiction:

Improveoperating temperatureVSAvoidbattery performance

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent applies preliminary anti-action by pre-introducing the propargyl group-containing compound into the electrolyte system before thermal decomposition occurs. This compound is positioned in advance to counteract the harmful effects of high-temperature decomposition. When PF5 is generated at elevated temperatures, it immediately reacts with the pre-present propargyl compound, preventing SEI destruction before it can occur.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent changes the chemical composition parameters of the electrolyte by adding a compound with specific functional groups (propargyl group). This parameter change modifies the chemical behavior of the system at high temperatures, altering the decomposition pathway and reaction products. The added compound changes the thermal stability parameter of the electrolyte system, enabling it to maintain performance at elevated temperatures.

Inventive Principle:

Principle #35Parameter changes

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

This approach effectively suppresses SEI damage and gas generation during high-temperature exposure, thereby preventing battery performance degradation and enhancing high-temperature stability and cycle characteristics.

Implementation Method 1

an N atom in the compound acts as a Lewis base to scavenge a Lewis acid generated as an electrolyte decomposition product

Methodology Applied

Scientific EffectLewis base-Lewis acid interaction:

Implementation Method 2

the propargyl group included in the additive of Formula 1 induces polymerization of a solid electrolyte interphase (SEI) by being decomposed on a surface of an electrode

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 3

since a F atom included in the additive of Formula 1 is separated from the compound to form LiF as a component of a negative electrode SEI

Methodology Applied

Scientific EffectDecomposition:

Data Source

PatentUS12148886B2Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2024.11.19 LG ENERGY SOLUTION LTD

AI summary

A non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, a non-aqueous electrolyte for a lithium secondary battery includes an organic solvent, a lithium salt, and a compound represented by Formula 1. In some embodiments, the compound represented by Formula 1 is present in an amount of 0.1 part by weight to 3 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.