Lithium Battery Electrolyte Additives for High-Voltage Stability

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Solution Overview

Problem

Existing lithium secondary batteries face issues with electrolyte decomposition and side reactions at high voltages and temperatures, leading to performance deterioration and safety concerns due to oxidation and gas generation, which are exacerbated by LiPF6 decomposition products like HF and PF5.

Innovation Solution

An electrolyte composition for lithium secondary batteries comprising a non-aqueous organic solvent, lithium salt, and additives including trispentafluorophenyl borane (TPFPB), tris(2,2,2-trifluoroethyl) phosphite (TTFP), and fluoroethylene carbonate, which suppress electrolyte decomposition and stabilize the system at high voltages and temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiPF6 is used as lithium salt in electrolyte, then ion conductivity is improved, but decomposition occurs at high voltage generating HF and PF5 that deteriorate battery performance and safety

Engineering Contradiction:

Improveion conductivityVSAvoiddecomposition products (HF, PF5)

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between LiPF6 and the electrode surface. This compound preferentially decomposes to form a protective fluorinated film layer that prevents direct contact between LiPF6 and the electrode, thereby eliminating the generation of harmful decomposition products like HF and PF5 while maintaining ion conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful decomposition behavior of fluorinated cyclic carbonate into a beneficial protective mechanism. The controlled decomposition of this compound forms a stable fluorinated protective film on the electrode surface, which actually prevents further decomposition of LiPF6 and protects the battery system from the harmful effects of decomposition products.

Inventive Principle:

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

2Quantity of substance

If voltage region is expanded to 4.45 V or higher to increase energy density, then capacity is improved, but electrolyte oxidation is accelerated causing performance deterioration

Engineering Contradiction:

Improveenergy densityVSAvoidelectrolyte stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds with specific molecular structures and fluorine content ratios. This parameter change modifies the electrochemical window and oxidation resistance of the electrolyte, enabling stable operation at voltages of 4.45 V or higher while maintaining high energy density.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite protective interface on the electrode surface consisting of fluorinated cyclic carbonate decomposition products and other electrolyte components. This composite film structure combines the advantages of different materials to provide both high voltage stability and good ion conductivity, enabling the battery to operate at elevated voltages without electrolyte oxidation.

Inventive Principle:

Principle #40Composite materials

3Speed

If temperature is increased to accelerate reaction rate, then charging speed is improved, but side reactions are accelerated generating gas that increases internal pressure and reduces safety

Engineering Contradiction:

Improvecharging rateVSAvoidgas generation

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent converts the temperature-accelerated side reactions into a beneficial protective mechanism. At elevated temperatures, the fluorinated cyclic carbonate compound preferentially decomposes to form a more robust and stable protective film on the electrode surface. This film becomes increasingly effective at higher temperatures, preventing further side reactions and gas generation, thus improving both charging speed and safety simultaneously.

Inventive Principle:

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

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 electrolyte composition prevents oxidative decomposition and improves high-temperature cycle-life characteristics of lithium secondary batteries, maintaining performance and safety even at voltages up to 4.45 V or higher.

Implementation Method 1

there is a problem that an electrolyte may be oxidized and thus deteriorate positive electrode performance

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

these side reactions are much accelerated at a high temperature at which a reaction rate is increased

Methodology Applied

Scientific EffectThermal decomposition: Decomposition (biological)

Data Source

PatentUS12424658B2Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Publication Date: 2025.09.23 SAMSUNG SDI CO LTD

AI summary

Provided is an electrolyte for a lithium secondary battery that comprises a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive includes a mixture of a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 2, and a cyclic carbonate-based compound substituted with a halogen.The details of Chemical Formula 1 and Chemical Formula 2 are as described in the specification.