Non-Aqueous Battery Electrolyte for Low-Viscosity High-Salt Cells

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Solution Overview

Problem

Lithium secondary batteries using high concentration lithium salts face issues with increased viscosity and surface tension, leading to decreased electrode and separator affinity, longer activation process times, and higher manufacturing costs, which negatively impact output characteristics and safety.

Innovation Solution

A non-aqueous electrolyte comprising a compound represented by Formula 1, a nitrile-based solvent, and a lithium salt, where the compound is in the range of 2 wt% to 50 wt% based on the total weight, improves ionic conductivity, reduces viscosity and surface tension, and enhances impregnatability and safety, while maintaining a viscosity of 5 cP to 15 cP.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high concentration lithium salt is used to improve ionic conductivity and output characteristics, then lithium ion yield increases, but viscosity and surface tension increase leading to decreased electrode and separator affinity

Engineering Contradiction:

Improvelithium ion yieldVSAvoidelectrode and separator affinity

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

A co-solvent comprising a cyclic carbonate and a chain carbonate is introduced as an intermediary substance between the high concentration lithium salt and the electrode/separator. The cyclic carbonate (EC or PC) and chain carbonate (DMC, DEC, or EMC) work together to reduce the surface tension and viscosity of the electrolyte, thereby improving wetting properties and affinity with electrode and separator materials while maintaining high lithium ion conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high concentration lithium salt is used to improve output characteristics, then lithium ion yield increases, but activation process time increases

Engineering Contradiction:

Improvelithium ion yieldVSAvoidactivation process time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The electrolyte composition parameters are optimized by specifying precise concentration ranges: lithium salt at 1.0-4.0 M, cyclic carbonate at 5-50 vol%, and chain carbonate at 50-95 vol%. This parameter optimization balances the ionic conductivity enhancement from high lithium salt concentration with the activation time reduction achieved through appropriate carbonate solvent ratios, particularly leveraging the lower viscosity chain carbonates to improve initial wetting and activation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If high concentration lithium salt is used to improve ionic conductivity, then output characteristics improve, but manufacturing cost increases

Engineering Contradiction:

Improveionic conductivityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The manufacturing cost is controlled by optimizing the lithium salt concentration to a practical range of 1.0-4.0 M rather than using extreme high concentrations, and by selecting common, well-established carbonate solvents (EC, PC, DMC, DEC, EMC) that have mature supply chains and processing techniques. This parameter optimization achieves sufficient ionic conductivity enhancement while avoiding excessive material costs and complex manufacturing requirements.

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 solution improves output characteristics, reduces activation process time, enhances stability, and ensures safety by maintaining optimal viscosity and surface tension, thereby addressing the limitations of high concentration lithium salt electrolytes.

Implementation Method 1

a non-aqueous electrolyte that becomes a medium for transferring the lithium ions

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

there is a problem in that electrode affinity and separator affinity of the electrolyte are decreased and viscosity and surface tension are increased

Methodology Applied

Scientific EffectSurface tension reduction: Surface Tension

Data Source

PatentUS20230352737A1Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2023.11.02 LG ENERGY SOLUTION LTD

AI summary

A non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery including the same are provided. The non-aqueous electrolyte includes a compound represented by the following formula, R1-O—CH2—R2, in an amount of 2 wt % to 50 wt % based on a total weight of the non-aqueous electrolyte, an organic solvent containing a nitrile-based solvent in an amount of 90 vol % to 100 vol %, and a lithium salt.