Borate-Nitrile Electrolyte Additives for Stable SEI Formation

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Solution Overview

Problem

Lithium secondary batteries face challenges in high-rate charge and discharge characteristics, high-temperature performance, and life characteristics due to non-uniform solid electrolyte interface (SEI) formation and irreversible capacity issues caused by poor electrolyte additives.

Innovation Solution

A novel electrolyte additive composition combining a borate-based lithium compound and a nitrile-based compound, excluding phosphate-based compounds, to form a robust SEI, improving durability and ion mobility, and stabilizing electrode films for enhanced performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional electrolyte additives are used, then the battery can operate, but the SEI formed is non-uniform leading to poor low-temperature output characteristics

Engineering Contradiction:

Improvelow-temperature output characteristicsVSAvoiduniformity of SEI

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent uses a composite electrolyte additive system combining a borate-based compound (Formula 1) and a nitrile-based compound (Formula 2). This composite approach creates a synergistic effect where the borate compound forms the primary SEI structure while the nitrile compound enhances uniformity and stability, resolving the contradiction between operational functionality and SEI uniformity for improved low-temperature performance

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the concentration ratio of the borate-based compound to the nitrile-based compound within a specific range (0.1:1 to 10:1). By adjusting these compositional parameters, the SEI formation process is controlled to achieve both uniformity and functionality, thereby improving low-temperature output characteristics while maintaining stable composition

Inventive Principle:

Principle #35Parameter changes

2Reliability

If electrolyte additive is included to improve SEI formation, then low-temperature output may improve, but at high temperature the additive decomposes or causes oxidation reaction reducing battery life

Engineering Contradiction:

Improvelow-temperature output characteristicsVSAvoidbattery life at high temperature

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent carefully controls the concentration parameters of both additives and their ratio to each other. The borate-based compound is maintained at 0.01-5 wt% while the nitrile-based compound is kept at 0.01-1 wt%, with their ratio optimized. This parameter optimization ensures sufficient SEI formation for low-temperature performance while preventing excessive reactivity that would cause decomposition or oxidation at high temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The borate-based compound acts as a primary SEI-forming agent that creates a stable protective layer, while the nitrile-based compound serves as a secondary additive that enhances and stabilizes this SEI structure. This intermediary relationship allows the system to achieve low-temperature improvement through controlled SEI formation while the synergistic combination prevents high-temperature decomposition and oxidation reactions

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If more electrolyte additive is added to improve SEI robustness, then high-rate charge and discharge characteristics improve, but irreversible capacity increases and output characteristics reduce

Engineering Contradiction:

Improvehigh-rate charge and discharge characteristicsVSAvoidirreversible capacity

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent optimizes the concentration parameters of both additives and their ratio to each other. The borate-based compound is maintained at 0.01-5 wt% while the nitrile-based compound is kept at 0.01-1 wt%, with their ratio optimized. This parameter optimization ensures sufficient SEI formation for low-temperature performance while preventing excessive reactivity that would cause decomposition or oxidation at high temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

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 additive composition enhances high-rate charge and discharge capabilities, suppresses gas generation at high temperatures, and extends battery life by forming a stable SEI, reducing irreversible capacity and improving capacity retention.

Implementation Method 1

a film may be formed on the surface of the negative electrode. The film is referred to as 'solid electrolyte interface (SEI)'

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) formation:

Implementation Method 2

The SEI only passes the lithium ions by acting as an ion tunnel

Methodology Applied

Scientific EffectIon tunneling:

Implementation Method 3

the electrolyte causes an oxidation reaction during a high-temperature reaction

Methodology Applied

Scientific EffectOxidation reaction: Oxidation

Data Source

PatentUS11476499B2Electrolyte additive and electrolyte for lithium secondary battery including the same

Publication Date: 2022.10.18 LG ENERGY SOLUTION LTD

AI summary

An electrolyte additive composition of the present invention may improve high-rate charge and discharge characteristics and high-temperature storage and life characteristics of a lithium secondary battery when the electrolyte additive composition is used in an electrolyte while including a novel borate-based lithium compound as well as a nitrile-based compound.