Lithium Battery Electrolyte Additives for SEI Stability

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Solution Overview

Problem

Lithium secondary batteries face challenges in improving output and life characteristics due to sub-reactions between active materials and electrolytes, leading to increased resistance and deterioration, especially with high-temperature preservation, which affects the performance and energy density.

Innovation Solution

An electrolyte composite for lithium secondary batteries is developed, incorporating lithium salt, solvents, and additives such as bis(trimethylsilyl)fumarate, bis(trimethylsilyl)thiophene-2,5-dicarboxylate, trimethyl(phenyl)silane, and vinylene carbonate, which form stable solid electrolyte interface (SEI) films to reduce resistance and enhance ion conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional electrolyte composites are used, then the battery can operate, but the resistance increases and performance deteriorates after multiple cycles and high-temperature storage

Engineering Contradiction:

Improvebattery life characteristicsVSAvoidresistance increase

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the chemical composition parameters of the electrolyte by introducing specific additives (vinylene carbonate at 0.1-5 wt%, trimethyl(phenyl)silane at 0.1-5 wt%, and bis(trimethylsilyl) fumarate or bis(trimethylsilyl)thiophene-2,5-dicarboxylate at 0.1-5 wt%). These parameter changes enable the formation of stable SEI films that prevent resistance increase during cycling and high-temperature storage, thereby improving reliability without sacrificing performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces intermediary substances (additives) that mediate between the electrodes and the bulk electrolyte. These additives form protective SEI films on the electrode surfaces, which act as intermediaries to prevent direct harmful interactions between the electrodes and electrolyte, thus preventing resistance increase while maintaining ionic conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of stationary object

If high-temperature preservation is performed, then the battery can be stored, but the active materials and electrolytes undergo sub-reactions leading to increased resistance

Engineering Contradiction:

Improvestorage stabilityVSAvoidsub-reactions between active materials and electrolytes

Core Design Contradiction:

Duration of action of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by having the additives react first during initial cycles to form stable SEI films on the electrode surfaces. These pre-formed protective films prevent subsequent sub-reactions between the active materials and electrolyte during high-temperature storage, thereby maintaining storage stability without generating harmful effects.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The additives serve as intermediaries that form protective barriers between the active materials and electrolyte. During high-temperature storage, these intermediary SEI films prevent direct contact and sub-reactions between the reactive components, thereby eliminating the harmful effects while maintaining storage capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the electrolyte composition is modified to improve output characteristics, then the energy density increases, but the complexity of electrolyte formulation increases

Engineering Contradiction:

Improveoutput characteristicsVSAvoidelectrolyte formulation

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs composite electrolyte formulation by combining multiple additives (vinylene carbonate, trimethyl(phenyl)silane, and bis(trimethylsilyl) fumarate or bis(trimethylsilyl)thiophene-2,5-dicarboxylate) with conventional electrolyte components. This composite approach synergistically improves output characteristics and energy density, while the systematic formulation methodology manages the complexity through defined concentration ranges and compatible material selection.

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 electrolyte composite significantly improves the output and life characteristics of lithium secondary batteries by maintaining high capacity retention and reducing resistance, even after multiple cycles and high-temperature storage, thereby enhancing the battery's energy density and cycle life.

Implementation Method 1

incorporating lithium salt, solvents, and additives such as bis(trimethylsilyl)fumarate, bis(trimethylsilyl)thiophene-2,5-dicarboxylate, trimethyl(phenyl)silane, and vinylene carbonate, which form stable solid electrolyte interface (SEI) films to reduce resistance and enhance ion conductivity

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) film formation:

Implementation Method 2

enhance ion conductivity

Methodology Applied

Scientific EffectIon conductivity: Conduction (electrical)

Data Source

PatentUS11024880B2Electrolyte for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2021.06.01 HYUNDAI MOTOR CO LTD

AI summary

Disclose are an electrolyte composite for a lithium secondary battery having an improved output; a cathode including a protective film on its surface; and a lithium secondary battery comprising the same.