Phosphonium Salt Electrolyte for Low-Temperature Lithium Batteries

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Solution Overview

Problem

Lithium secondary batteries face limitations in low-temperature performance due to the high melting point of ethylene carbonate, which leads to degradation in battery performance, and they also generate excessive gas during high-temperature storage, affecting their reliability.

Innovation Solution

A non-aqueous electrolyte solution for lithium secondary batteries is developed, which includes a phosphonium salt additive. This additive reduces gas generation at high temperatures, enhances fast charging performance, and improves low-temperature output characteristics by modifying the electrode film and interacting with the solvent.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ethylene carbonate is used as the organic solvent, then the limitation of propylene carbonate causing irreversible decomposition reaction with graphite material is solved, but the temperature of use is limited due to the high melting point of ethylene carbonate and significant degradation in battery performance at low temperatures occurs

Engineering Contradiction:

Improvestability with graphite materialVSAvoidlow-temperature performance

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent introduces a phosphonium salt compound with specific molecular structure parameters (Formula 1 with defined R1-R4 groups and L1 linkage) to modify the electrolyte solution's physical and chemical parameters. This enables the electrolyte to maintain liquid state and ionic conductivity at low temperatures while preserving stability with graphite electrodes, thus resolving the contradiction between material stability and temperature adaptability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrolyte system by combining ethylene carbonate base solvent with phosphonium salt additive (Formula 1 compound). This composite formulation leverages the electrochemical stability of ethylene carbonate while the phosphonium salt component provides low-temperature fluidity and ionic mobility, achieving both reliability and low-temperature performance simultaneously.

Inventive Principle:

Principle #40Composite materials

2Productivity

If conventional electrolyte solutions are used, then the battery can operate normally, but excessive gas is generated during high-temperature storage affecting reliability

Engineering Contradiction:

Improvenormal operationVSAvoidgas generation at high temperature

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The phosphonium salt compound in the electrolyte solution preferentially reacts with trace water and impurities at high temperatures to form stable byproducts, preventing these substances from causing harmful gas generation through unwanted side reactions. The additive sacrifices itself to convert potentially harmful reactions into benign processes, eliminating gas generation while maintaining normal battery operation.

Inventive Principle:

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

Solution Approach 2:

The phosphonium salt acts as an intermediary substance between the electrolyte components and electrode materials at high temperatures. It mediates the chemical interactions by providing a stable interface that prevents direct harmful reactions that would generate gas, thus maintaining normal battery function while eliminating the harmful gas generation effect.

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 phosphonium salt additive in the non-aqueous electrolyte solution significantly improves the battery's capacity retention during fast charging, maintains excellent output at low temperatures, and reduces gas generation during high-temperature storage, thereby enhancing the overall performance and reliability of the lithium secondary battery.

Implementation Method 1

including a phosphonium salt additive to improve bulk properties through the interaction with a solvent

Methodology Applied

Scientific EffectFilm formation:

Implementation Method 2

a compound represented by Formula 1 as follows... A− is (CF3SO2)2N−, (FSO)2N−, PF6−, PO2F2−, BF4−, ClO4−, (C2O4)BF2−, HSO4−, CF3SO3−, (C2F5SO2)2N−, C(CF2SO2)3−, AsF6−, SbF6−, AlCl4−, NbF6−, or CF3CO2−

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 3

a non-aqueous electrolyte solution, which becomes a medium for transferring the lithium ions

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 4

a negative electrode including a negative electrode active material capable of storing lithium ions

Methodology Applied

Scientific EffectLithium ion intercalation:

Data Source

PatentUS12283663B2Non-aqueous electrolyte solution for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2025.04.22 LG ENERGY SOLUTION LTD

AI summary

A non-aqueous electrolyte solution for a lithium secondary battery includes a compound represented by Formula 1 as follows, a lithium salt, and an organic solvent; and a lithium secondary battery including the same:wherein R1 to R3, L1 and A− are described herein.