Lithium Secondary Battery Dinitrile Electrolyte Additive

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Solution Overview

Problem

Lithium secondary batteries with organic-inorganic composite separators face increased side reactions under high-voltage conditions, leading to reduced cycle life and output performance due to thermal shrinkage and rapid dissolution of transition metal ions.

Innovation Solution

Incorporating a dinitrile compound, such as 1,4-dicyano-2-butene, into the non-aqueous electrolyte solution to bond with transition metal ions, preventing their deposition on inorganic particles and reducing side reactions by forming bulkier metallic compounds that impede mobility and increase bonding strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an organic-inorganic composite separator is used to prevent thermal shrinkage, then safety is improved, but side reactions of the electrolyte solution increase under high-voltage conditions

Engineering Contradiction:

ImprovesafetyVSAvoidside reactions of electrolyte solution

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a dinitrile compound as an intermediary substance in the electrolyte solution that mediates between the inorganic particles and the electrolyte. This compound bonds with transition metal ions to form bulkier metallic compounds, preventing direct harmful interactions between the electrolyte and inorganic particles while maintaining the safety benefits of the composite separator

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful effect of transition metal ion dissolution into a beneficial outcome by having the dinitrile compound bond with these ions to form stable metallic compounds. This prevents the ions from catalyzing side reactions while utilizing them as part of the protective mechanism

Inventive Principle:

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

2Use of energy by moving object

If high-voltage operating conditions are applied to increase battery capacity, then energy density is improved, but dissolution of transition metals from cathode increases

Engineering Contradiction:

Improveenergy densityVSAvoiddissolution of transition metals

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

The dinitrile compound acts as an intermediary that captures transition metal ions dissolved from the cathode under high-voltage conditions, forming stable metallic compounds that prevent further degradation and side reactions while allowing high-voltage operation to maintain energy density

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If inorganic particles are used as spacers in the coating layer to maintain physical shape, then thermal shrinkage is inhibited, but side reactions are promoted due to transition metal deposition

Engineering Contradiction:

Improvephysical shape stabilityVSAvoidside reactions

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The dinitrile compound serves as a mediator between the inorganic particles and the electrolyte, bonding with transition metal ions that would otherwise deposit on the inorganic particles and promote side reactions, thus maintaining both structural stability and chemical inertness

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 use of the dinitrile compound effectively inhibits side reactions, enhancing the cycle life and output performance of lithium secondary batteries, especially under high-voltage conditions, while ensuring safety by reducing thermal runaway risks.

Implementation Method 1

Incorporating a dinitrile compound, such as 1,4-dicyano-2-butene, into the non-aqueous electrolyte solution to bond with transition metal ions, preventing their deposition on inorganic particles

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 2

The inorganic particles present in the porous coating layer coated on the porous substrate serve as spacers that can maintain a physical shape of the porous coating layer to inhibit the porous substrate from thermal shrinkage when an electrochemical device overheats

Methodology Applied

Scientific EffectThermal shrinkage resistance: Thermal Expansion

Data Source

PatentEP2648267B1Lithium secondary battery

Publication Date: 2018.01.10 LG CHEM LTD

AI summary

Disclosed is a lithium secondary battery. The lithium secondary battery includes a cathode, an anode, a separator and a non-aqueous electrolyte solution. The separator includes a porous substrate, and a coating layer coated on at least one surface of the porous substrate and including a mixture of inorganic particles and a binder polymer. The non-aqueous electrolyte solution contains an ionizable lithium salt, an organic solvent, and a dinitrile compound having a specific structure. The lithium secondary battery is very safe without side reactions of the electrolyte solution. Therefore, the lithium secondary battery exhibits excellent cycle life and output performance characteristics.