Lithium Battery Electrolyte Suppressing Gas Generation

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Solution Overview

Problem

Lithium secondary batteries face issues with internal pressure increase due to gas generation during the formation of the solid electrolyte interface (SEI) film, leading to swelling and decomposition at high temperatures, which affects capacity retention and safety.

Innovation Solution

An electrolyte composition is developed using a non-aqueous organic solvent blend, including a branched ester-based solvent, a carbonate-based solvent, and specific electrolyte additives like fluoroethylene carbonate and 1,3-propanesultone, which reduces side reactions and internal resistance, enhancing high-voltage and high-temperature performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a carbonate-based organic solvent is used in the electrolyte, then the battery achieves high energy density and good ion conductivity, but gas is generated during SEI film formation causing internal pressure increase and battery swelling

Engineering Contradiction:

Improveion conductivityVSAvoidgas generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a fluorinated cyclic carbonate compound (VEC or FMC) as an intermediary substance that mediates between the lithium ions and the carbonate-based solvent. This intermediary forms a stable SEI film first, preventing direct reaction between the carbonate solvent and carbon negative electrode, thereby suppressing gas generation while maintaining ion conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the electrolyte by incorporating specific fluorinated cyclic carbonate compounds at controlled concentrations (0.1-10 wt%). This parameter change modifies the SEI film formation process, reducing gas-generating side reactions while preserving the beneficial properties of carbonate-based solvents.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the battery is kept at high temperature for extended periods, then thermal energy increases which can improve reaction kinetics, but the SEI film decomposes continuously causing renewed reactions and increased internal pressure

Engineering Contradiction:

Improvereaction kineticsVSAvoidSEI film stability

Core Design Contradiction:

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

Solution Approach 1:

The patent applies preliminary action by forming a robust, stable SEI film during initial charging cycles using fluorinated cyclic carbonate compounds. This pre-formed SEI film acts as a protective barrier that remains stable at high temperatures, preventing continuous decomposition and renewed reactions that would otherwise occur with conventional electrolytes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful effect of high temperature into a benefit by using fluorinated cyclic carbonate compounds that form SEI films with higher thermal stability. The high temperature that would normally cause SEI decomposition instead helps form an even more stable and protective SEI layer, improving overall battery performance and safety.

Inventive Principle:

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

3Reliability

If organic solvents with high molecular weight are used to improve ion transport, then ion conductivity increases, but co-intercalation into the carbon negative electrode causes structure disintegration

Engineering Contradiction:

Improveion transportVSAvoidelectrode structure integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The fluorinated cyclic carbonate compound acts as an intermediary that forms a protective SEI film on the carbon negative electrode surface. This SEI film allows lithium ions to pass through while blocking larger organic solvent molecules, preventing co-intercalation and structure disintegration while maintaining effective ion transport.

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 new electrolyte composition effectively suppresses thickness expansion and internal resistance increase, improving capacity retention and cycle-life characteristics of lithium secondary batteries, especially at high charge voltages and elevated temperatures.

Implementation Method 1

lithium reacts with the carbon negative electrode to produce Li2CO3, LiO, LiOH, etc., thereby forming a thin film on the surface of the negative electrode. This film is referred to as a solid electrolyte interface (SEI) film.

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) film formation:

Implementation Method 2

it also acts as an ion tunnel, allowing the passage of lithium ions

Methodology Applied

Scientific EffectIon transport through SEI film:

Implementation Method 3

gases are generated inside a battery using a carbonate-based organic solvent due to decomposition of a carbonate-based organic solvent during the SEI film-forming reaction

Methodology Applied

Scientific EffectDecomposition reaction suppression:

Data Source

PatentUS11424485B2Lithium secondary battery electrolyte and lithium secondary battery comprising same

Publication Date: 2022.08.23 SAMSUNG SDI CO LTD

AI summary

The present disclosure relates to a lithium secondary battery electrolyte and a lithium secondary battery comprising the lithium secondary battery electrolyte, which comprises: a non-aqueous organic solvent including a branched ester-based solvent represented by formula 1; and a lithium salt.