Polymer Electrolyte Additive for High-Temperature SEI Stability

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Solution Overview

Problem

Lithium secondary batteries face issues with electrode degradation, transition metal ion elution, and swelling due to electrolyte deterioration, especially at high temperatures, leading to reduced stability and performance.

Innovation Solution

A non-aqueous electrolyte with a specific polymer additive containing perfluoroalkyl and nitrile groups is used to form a stable solid electrolyte interphase (SEI) film on the negative electrode, suppressing metal ion elution and enhancing high-temperature stability and cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high-nickel positive electrode active material or high voltage is used to increase capacity, then energy density and output are improved, but transition metal ion elution increases and negative electrode stability deteriorates

Engineering Contradiction:

Improvebattery capacity and outputVSAvoidnegative electrode stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent introduces a polymer additive as an intermediary substance between the positive and negative electrodes. This additive forms a protective interface layer that prevents direct harmful interactions, allowing high-nickel or high-voltage materials to function without causing transition metal ion elution that would deteriorate the negative electrode.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The polymer additive performs preliminary protective action by forming a stable SEI film on the negative electrode surface before harmful elution processes can occur. This pre-formed protective layer actively prevents transition metal ions from eluting from the positive electrode and depositing on the negative electrode, thereby maintaining negative electrode stability under high-capacity operating conditions.

Inventive Principle:

Principle #9Preliminary anti-action

2Use of energy by moving object

If the potential of the positive electrode is increased to improve energy density, then battery capacity increases, but side reactions with electrolyte increase and electrode surface structure deteriorates

Engineering Contradiction:

Improveenergy densityVSAvoidelectrode surface structure stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The polymer additive serves as a mediating layer at the electrode-electrolyte interface, enabling the positive electrode to operate at higher potentials while preventing direct harmful side reactions with the electrolyte. This intermediary layer stabilizes the electrode surface structure even under high-potential operating conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If the battery is operated at high temperatures to improve performance, then output increases, but SEI film stability decreases and swelling phenomenon worsens

Engineering Contradiction:

Improvebattery outputVSAvoidSEI film stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The patent modifies the chemical composition parameters of the electrolyte by incorporating a polymer additive with specific functional groups. This parameter change enables the SEI film to maintain stability at high temperatures, allowing the battery to operate at elevated temperatures without the usual degradation of SEI film and associated swelling problems.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If conventional electrolyte additives are used to suppress metal ion elution, then positive electrode degradation is reduced, but SEI film stability at high temperatures is insufficient and swelling occurs

Engineering Contradiction:

Improvepositive electrode durabilityVSAvoidSEI film high-temperature stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent employs a composite electrolyte system combining conventional additives with a polymer additive containing perfluoroalkyl and nitrile groups. This composite approach synergistically achieves both suppression of metal ion elution from the positive electrode and formation of a thermally stable SEI film on the negative electrode, preventing swelling at high temperatures.

Inventive Principle:

Principle #40Composite materials

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 the durability of the electrode-electrolyte interface, maintaining robust SEI layer stability at high temperatures, resulting in enhanced high-temperature cycle and storage characteristics and overall battery performance.

Implementation Method 1

a polymer which has a repeating unit represented by general formula (1) and general formula (2) below

Methodology Applied

Scientific EffectElectrochemical reaction:

Data Source

PatentUS11881556B2Non-aqueous electrolyte including additive for non-aqueous electrolyte, and lithium secondary battery including the non-aqueous electrolyte

Publication Date: 2024.01.23 LG ENERGY SOLUTION LTD

AI summary

The present disclosure provides a non-aqueous electrolyte including an additive including a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2 below:wherein X, R, R1 and R2 are described herein.