Non-aqueous Battery Electrolyte Conductivity and Layer Thickness

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Solution Overview

Problem

Existing non-aqueous secondary batteries face issues with high-temperature durability and internal resistance increase when using nitrile-based solvents, leading to degradation and reduced capacity, especially when used in vehicles and household storage systems, and there is a need for improved rate performance and stability at high and low temperatures.

Innovation Solution

A non-aqueous secondary battery design utilizing a specific electrolyte solution with an ion conductivity of 15 mS/cm or more, featuring a lithium salt, acetonitrile as a solvent, and optimized electrode active material layers with controlled porosity and thickness, along with the use of metal oxide and carbon materials, to achieve high rate performance even with high volumetric energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the basis weight of the positive electrode active material layer is increased to achieve higher capacity, then the volumetric energy density improves, but the diffusion pathway for lithium ions becomes longer and internal resistance increases

Engineering Contradiction:

Improvevolumetric energy densityVSAvoidrate performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the basis weight of the positive electrode active material layer within the range of 20-60 mg/cm². This optimization balances the volumetric energy density and rate performance by adjusting the thickness and density parameters of the electrode layer, ensuring sufficient lithium ion diffusion pathways while maintaining high capacity.

Inventive Principle:

Principle #35Parameter changes

2Speed

If nitrile-based solvents are used to improve ion conductivity and rate characteristic, then the low-temperature performance improves, but the solvent undergoes electrochemical reduction and decomposition at high temperatures

Engineering Contradiction:

Improveion conductivityVSAvoidhigh-temperature durability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent uses a composite electrolyte system combining nitrile-based solvent (acetonitrile) with cyclic carbonate solvents (EC, PC) and chain carbonate solvents (DMC, DEC). This composite approach leverages the high ion conductivity and low-temperature performance of nitrile-based solvents while the carbonate components provide thermal stability and suppress decomposition, achieving both high rate characteristic and high-temperature durability.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If the electrode active material layer is pressed at high pressure to reduce porosity and increase capacity, then the volumetric energy density improves, but the lithium ion diffusion becomes more difficult

Engineering Contradiction:

Improveelectrode active material mass per unit volumeVSAvoidlithium ion diffusion rate

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The patent optimizes the porosity parameter of the positive electrode active material layer to within 20-40%, balancing the volumetric energy density and lithium ion diffusion rate. This controlled porosity ensures sufficient pathways for lithium ion transport while maintaining high packing density of the active material.

Inventive Principle:

Principle #35Parameter changes

4Speed

If the basis weight of the positive electrode active material layer is reduced to shorten lithium ion diffusion pathway, then the rate performance improves, but the volumetric energy density decreases

Engineering Contradiction:

Improverate performanceVSAvoidvolumetric energy density

Core Design Contradiction:

SpeedVSQuantity of substance

Solution Approach 1:

The patent determines the optimal basis weight range of 20-60 mg/cm² for the positive electrode active material layer, which balances the lithium ion diffusion pathway length and volumetric energy density. This parameter optimization ensures practical rate performance while maintaining sufficiently high capacity for vehicle and household storage system applications.

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 enables a non-aqueous secondary battery to maintain high rate performance and stability across various temperatures, reducing internal resistance and degradation, thus enhancing its practical application in vehicles and storage systems.

Implementation Method 1

an electrolyte solution that contains a lithium salt and a non-aqueous solvent... having an ion conductivity at 25° C. of 15 mS/cm or more

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

the diffusion pathway for the lithium ions becomes longer, which means that internal resistance resulting from the insertion and desorption of lithium ions increases

Methodology Applied

Scientific EffectLithium ion insertion and desorption: Absorption (physical)

Data Source

PatentEP2772981B1Non-aqueous secondary battery

Publication Date: 2020.10.21 ASAHI KASEI KOGYO KABUSHIKI KAISHA

Figure 1

AI summary

A non-aqueous secondary battery including an electrolyte solution that contains a lithium salt and a non-aqueous solvent, a positive electrode, and a negative electrode, wherein a basis weight of a positive-electrode active material layer included in the positive electrode is 8 to 100 mg/cm2, and/or, a basis weight of a negative-electrode active material layer included in the negative electrode is 3 to 46 mg/cm2, and wherein the electrolyte solution has an ion conductivity at 25°C of 15 mS/cm or more.