Non-aqueous Battery Peel Strength Control

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Solution Overview

Problem

Non-aqueous electrolyte secondary batteries face the challenge of short-circuiting when a nail penetrates the battery, primarily due to detachment between the electrode and separator, leading to potential contact between the positive and negative electrodes and the nail, causing heat generation and short-circuit currents.

Innovation Solution

Incorporating cellulose nanofibers into the electrode composite material layers and separator, with a specific peel strength configuration to ensure that detachment occurs at the interface with the lowest bonding strength, thereby minimizing contact between both electrodes and the nail, and using an ionic liquid to enhance bonding between the electrode composite material layers and the separator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If cellulose nanofibers are used as a binder to strengthen adhesion between electrode particles and current collector, then bonding strength is improved, but detachment between electrode and separator may occur during nail penetration leading to short-circuit

Engineering Contradiction:

Improveadhesion between electrode particles and current collectorVSAvoidresistance to short-circuit during nail penetration

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies different peel strength characteristics to different interfaces: the interface between separator and electrode composite material layer is designed to have higher peel strength than the interface between current collector and electrode composite material layer. This local differentiation ensures that during nail penetration, detachment occurs preferentially at the current collector interface, preventing short-circuit between electrodes.

Inventive Principle:

Principle #3Local quality

2Strength

If strong adhesion is achieved between separator and electrode composite material layer, then electrode detachment is prevented, but the complexity of controlling peel strength ratios increases

Engineering Contradiction:

Improvepeel strength between separator and electrode composite material layerVSAvoidcontrol of peel strength ratios

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent controls the peel strength parameter by adjusting the cellulose nanofiber content in the electrode composite material layer. By varying the concentration of cellulose nanofibers, the peel strength between separator and electrode composite material layer can be optimized to be higher than the peel strength between current collector and electrode composite material layer, thereby preventing short-circuit during nail penetration.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the greater peel strength is at least 1.5 times the smaller peel strength, then short-circuit current is mitigated, but manufacturing precision requirements increase

Engineering Contradiction:

Improvemitigation of short-circuit currentVSAvoidpeel strength ratio control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent utilizes the self-assembling properties of cellulose nanofibers to achieve the desired peel strength ratio. The cellulose nanofibers automatically form a network structure within the electrode composite material layer that provides the required adhesion characteristics, reducing the need for precise external control of peel strength ratios during manufacturing.

Inventive Principle:

Principle #25Self-service

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 use of cellulose nanofibers with controlled peel strengths and ionic liquid impregnation effectively mitigates short-circuit currents by ensuring that only one electrode comes into contact with the nail upon penetration, reducing the likelihood of heat generation and maintaining battery integrity.

Implementation Method 1

cellulose nanofibers as a binder for an electrode composite material in a non-aqueous electrolyte secondary battery enables strong adhesion between the particles of the electrode active material and also between the electrode active material and the current collector

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS11223047B2Non-aqueous electrolyte secondary battery, and method of producing non-aqueous electrolyte secondary battery

Publication Date: 2022.01.11 TOYOTA JIDOSHA KK

AI summary

A non-aqueous electrolyte secondary battery includes an electrode array and an electrolyte solution. The electrode array includes a positive electrode that includes a positive electrode current collector and a positive electrode composite material layer; a negative electrode that includes a negative electrode current collector and a negative electrode composite material layer; and a separator. The electrode array includes cellulose nanofibers. At least one of the peel strength between the positive electrode current collector and the positive electrode composite material layer and the peel strength between the negative electrode current collector and the negative electrode composite material layer is smaller than both the peel strength between the separator and the positive electrode composite material layer and the peel strength between the separator and the negative electrode composite material layer. The greater of the two peel strengths is at least 1.5 times greater than the smaller of the two.