Non-Aqueous Electrolyte Additives for SEI Protection in Li-Ion Batteries

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Solution Overview

Problem

Lithium-ion batteries face degradation due to the thermal decomposition of lithium salts, leading to the formation of Lewis acids that damage the solid electrolyte interphase (SEI) and increase electrode resistance, causing self-discharge and reduced battery lifespan.

Innovation Solution

A non-aqueous electrolyte solution additive with a zwitterionic compound, represented by Formula 1, is used to scavenge decomposition products and form a stable nitrogen-based film on the electrodes, enhancing the SEI's passivation ability and reducing transition metal dissolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiPF6 is used as lithium salt to achieve suitable battery characteristics, then battery performance is improved, but thermal decomposition occurs at high temperatures generating Lewis acid that damages SEI and increases resistance

Engineering Contradiction:

Improvebattery performanceVSAvoidthermal decomposition damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a nitrogen-containing compound as an intermediary substance that preferentially reacts with Lewis acids (PF5, HF) generated from LiPF6 decomposition. This intermediary captures the harmful decomposition products before they can damage the SEI film, thereby protecting the battery system while allowing LiPF6 to maintain its beneficial electrochemical performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful thermal decomposition of LiPF6 into a beneficial process by having the nitrogen-containing compound react with the generated Lewis acids to form stable complexes. The decomposition products that would normally damage the battery are instead captured and neutralized, transforming a harmful side reaction into a protective mechanism

Inventive Principle:

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

2Duration of action of moving object

If LiPF6 decomposes thermally to generate Lewis acid, then battery operation continues, but SEI film degrades causing self-discharge and reduced lifespan

Engineering Contradiction:

Improvebattery operationVSAvoidbattery lifespan

Core Design Contradiction:

Duration of action of moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent applies beforehand cushioning by pre-introducing the nitrogen-containing compound into the electrolyte system before thermal decomposition occurs. This compound acts as a protective buffer that is already in place to capture Lewis acids when they are generated, preventing SEI degradation and extending battery lifespan throughout its operational duration

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If transition metal ions dissolve in electrolyte solution, then battery continues to operate, but resistance increases and capacity is lost due to SEI destruction and regeneration

Engineering Contradiction:

Improvebattery operationVSAvoidbattery capacity retention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The nitrogen-containing compound serves as an intermediary that captures transition metal ions and Lewis acids in the electrolyte solution, preventing them from reaching and degrading the SEI film. This intermediary action maintains battery operability while preserving capacity by blocking the degradation pathway

Inventive Principle:

Principle #24Intermediary (Mediator)

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 additive improves high-temperature stability and cycle performance by preventing SEI decomposition and reducing resistance, thereby extending the battery's lifespan and maintaining capacity.

Implementation Method 1

the nitrogen atom-based cationic moiety may have a strong binding force with a Lewis acid material generated as a decomposition product of the lithium salt, and thus, may easily scavenge a by-product

Methodology Applied

Scientific EffectLewis base-Lewis acid reaction:

Implementation Method 2

the compound of Formula 1 may form a stable film on a surface of an electrode while being electrochemically reductively decomposed

Methodology Applied

Scientific EffectElectrochemical reduction:

Data Source

PatentUS11916197B2Electrolyte additives for secondary battery, non-aqueous electrolyte for secondary battery comprising same and secondary battery

Publication Date: 2024.02.27 LG ENERGY SOLUTION LTD

AI summary

An electrolyte solution additive for a secondary battery, a non-aqueous electrolyte solution including the same, and a lithium secondary battery including the same are disclosed herein. To be specific, the above non-aqueous electrolyte solution includes the electrolyte solution additive comprising the compound represented by Formula 1:wherein, in Formula 1, R1 and R2 are each independently an unsubstituted or substituted alkylene group having 1 to 5 carbon atoms, and L is a direct bond, —O—, —COO—, —RO—, or —R′COO—, wherein R and R′ are each independently an alkylene group having 1 to 10 carbon atoms. The additive has an excellent effect of scavenging a decomposition product generated from a lithium salt.