Non-Aqueous Lithium Battery Electrolyte for PF5 Scavenging and SEI Protection

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Solution Overview

Problem

Lithium ion batteries face performance degradation at high temperatures due to the decomposition of lithium salts, leading to increased resistance and reduced capacity, primarily caused by the deterioration of the electrolyte solution and the destruction of the solid electrolyte interphase (SEI) on the electrode surfaces.

Innovation Solution

A non-aqueous electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, an organic solvent, a compound represented by Formula 1 as a first additive, and lithium difluorophosphate (LiPO2F2) as a second additive, along with optional additional compounds, which scavenge decomposition products and enhance the stability of the SEI, thereby improving high-temperature durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiPF6-based lithium salt is used to obtain suitable battery characteristics, then electrochemical performance is improved, but decomposition products (PF5) are generated at high temperatures that destroy the SEI and increase resistance

Engineering Contradiction:

Improveelectrochemical performanceVSAvoiddecomposition product damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a scavenger compound as an intermediary substance that selectively reacts with and neutralizes PF5 decomposition products. This mediator prevents PF5 from damaging the SEI and electrodes, while allowing LiPF6 to maintain its electrochemical function. The scavenger acts as a buffer between the lithium salt and the vulnerable components.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful PF5 decomposition product into a beneficial effect by using the scavenger to transform PF5 into harmless substances. The harmful fluorophosphoric acid is converted into stable compounds that actually contribute to SEI stabilization and protect the battery from degradation.

Inventive Principle:

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

2Power

If high-temperature operation is performed, then power delivery is improved, but electrolyte solution deteriorates and SEI is destroyed leading to increased resistance

Engineering Contradiction:

Improvepower deliveryVSAvoidhigh-temperature stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by pre-introducing the scavenger compound into the electrolyte solution before high-temperature operation begins. This scavenger creates a protective chemical environment that cushions against the formation of harmful decomposition products, allowing the battery to withstand high-temperature conditions without SEI destruction or resistance increase.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If organic solvent is used as electrolyte medium, then lithium ion transfer is enabled, but decomposition reactions occur at high temperatures causing capacity loss

Engineering Contradiction:

Improveion transfer capabilityVSAvoidelectrolyte decomposition

Core Design Contradiction:

Ease of operationVSLoss of substance

Solution Approach 1:

The scavenger compound serves as an intermediary that protects the organic solvent from thermal decomposition. It reacts with decomposition products and stabilizes the electrolyte environment, enabling the organic solvent to maintain its ion transfer capability while resisting decomposition at high temperatures.

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 solution effectively forms a robust film on the electrodes, preventing acid-induced degradation and maintaining electrochemical stability, resulting in improved high-temperature storage characteristics and extended battery life.

Implementation Method 1

scavenging PF5 which is formed by the pyrolysis of the LiPF6-based salt

Methodology Applied

Scientific EffectScavenging: Absorption (physical)

Implementation Method 2

PF5 which is formed by the pyrolysis of the LiPF6-based salt

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Implementation Method 3

forming a film having passivation ability on surfaces of a positive electrode and a negative electrode

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Implementation Method 4

an electrolyte solution that becomes a medium for transferring lithium ions

Methodology Applied

Scientific EffectIon transport: Ion Exchange

Implementation Method 5

maintaining passivation ability of the SEI when exposed to heat

Methodology Applied

Scientific EffectPassivation: Oxidation

Data Source

PatentEP3944392B1Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery comprising same

Publication Date: 2025.01.01 LG ENERGY SOLUTION LTD

Figure 1~2

AI summary

The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery, which includes a lithium salt, an organic solvent, a compound represented by Formula 1 as a first additive, and lithium difluorophosphate as a second additive, wherein a weight ratio of the first additive to the second additive is in a range of 1:2 to 1:10, and a lithium secondary battery including the non-aqueous electrolyte solution.