Lithium-Sulfur Electrolyte Balancing Dendrite Control and Capacity

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Solution Overview

Problem

Lithium polysulfide and lithium bis(fluorosulfonyl)imide, when used individually in lithium sulfur batteries, degrade the performance of either the negative or positive electrodes, leading to reduced cycle performance and stability issues.

Innovation Solution

A combination of lithium polysulfide and lithium bis(fluorosulfonyl)imide within specific concentration ranges in the electrolyte, along with additional lithium salts and solvents, is used to enhance the performance of both electrodes, stabilizing the lithium metal negative electrode and sulfur positive electrode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lithium polysulfide is added to the electrolyte to suppress dissolution, then capacity retention is improved, but dendrite formation is promoted

Engineering Contradiction:

Improvecapacity retentionVSAvoiddendrite formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Lithium bis(fluorosulfonyl)imide acts as an intermediary substance that mediates between lithium polysulfide and the lithium metal negative electrode. It forms a stable decomposition product film that prevents direct contact and harmful reactions between lithium polysulfide and lithium metal, thereby suppressing dendrite formation while maintaining capacity retention

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful effect of lithium polysulfide (which promotes dendrite formation) into a beneficial effect by controlling its concentration within 0.01-2.0 mol/dm³. At this optimized concentration, lithium polysulfide suppresses dissolution of intermediate active materials while lithium bis(fluorosulfonyl)imide prevents dendrite formation, transforming a potentially harmful substance into a beneficial component

Inventive Principle:

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

2Reliability

If lithium bis(fluorosulfonyl)imide is used to form stable decomposition product film, then negative electrode performance is improved, but positive electrode capacity decreases

Engineering Contradiction:

Improvenegative electrode stabilityVSAvoidpositive electrode capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention optimizes the concentration parameters of both lithium polysulfide (0.01-2.0 mol/dm³) and lithium bis(fluorosulfonyl)imide (0.001-0.15 mol/dm³) to achieve the best balance. By precisely controlling these concentration parameters, the electrolyte formulation maximizes negative electrode stability while minimizing negative impact on positive electrode capacity

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If higher concentration of lithium bis(fluorosulfonyl)imide is used, then dendrite suppression is improved, but positive electrode performance degradation increases

Engineering Contradiction:

Improvedendrite suppressionVSAvoidpositive electrode performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The invention establishes an optimized concentration range for lithium bis(fluorosulfonyl)imide (0.001-0.15 mol/dm³) that balances dendrite suppression with positive electrode performance. This parameter optimization ensures sufficient dendrite protection while avoiding excessive concentration that would accelerate positive electrode degradation

Inventive Principle:

Principle #35Parameter changes

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 achieves high cycle performance and stability in lithium sulfur batteries by suppressing dendrite formation and maintaining capacity retention.

Implementation Method 1

lithium polysulfide serving as an intermediate active material dissolves in an electrolyte

Methodology Applied

Scientific EffectDissolution: Solvation

Implementation Method 2

polysulfide ions are excessively reduced and decomposed on a lithium negative electrode during charging

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 3

polysulfide ions are excessively reduced and decomposed on a lithium negative electrode during charging

Methodology Applied

Scientific EffectDecomposition: Decomposition (biological)

Implementation Method 4

promotes the precipitation of needle-like crystals (dendrite) of lithium metal

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Implementation Method 5

lithium bis(fluorosulfonyl)imide is a suitable material to form a stable decomposition product film

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Data Source

PatentUS20250329782A1Electrolyte for lithium sulfur battery and lithium sulfur battery

Publication Date: 2025.10.23 THE FURUKAWA BATTERY CO LTD

AI summary

An electrolyte, the electrolyte including: a first component; a second component; and a solvent, where the first component includes lithium polysulfide, the second component includes lithium bis(fluorosulfonyl)imide, and a concentration A of the lithium bis(fluorosulfonyl)imide satisfies 0.001 mol/dm3≤A≤0.15 mol/dm3.