Negative Electrode Binder Swelling for Battery Contact

Solution Overview

Problem

Non-aqueous electrolyte secondary batteries face challenges in maintaining electrical contact between the negative electrode current collector and the exterior housing can due to the expansion and contraction of negative electrode active materials, leading to issues with clearance and insertion during battery assembly.

Innovation Solution

A non-aqueous electrolyte secondary battery design where the negative electrode mixture layer is formed on both surfaces and one surface of the negative electrode current collector, with the one-surface coated portion having a binder with a higher degree of swelling than the both-surface coated portion, ensuring consistent contact with the exterior housing can.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a negative electrode active material with large expansion with charge is used, then the electrode assembly expands to allow sufficient contact between the negative electrode current collector and the exterior housing can during charge, but the negative electrode current collector and exterior housing can cannot be sufficiently contacted during discharge due to large contraction

Engineering Contradiction:

Improveelectrical contact reliabilityVSAvoidcontact loss during discharge

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies different binder materials with different swelling characteristics to different regions of the negative electrode mixture layer. Specifically, a first binder material is used in a first region and a second binder material with different swelling properties is used in a second region. This local differentiation allows the electrode to maintain contact with the exterior housing can during both charge and discharge states by having different expansion/contraction behaviors in different areas.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical and chemical parameters of the binder material by selecting materials with different swelling ratios. The first binder material has a first swelling ratio and the second binder material has a second swelling ratio that differs from the first. This parameter change enables the electrode assembly to maintain appropriate contact pressure with the exterior housing can across different charge states.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a negative electrode active material with small expansion with charge is used, then the clearance between the electrode assembly and the exterior housing can must be reduced to ensure contact, but insertion of the electrode assembly into the exterior housing can fails during battery assembly

Engineering Contradiction:

Improveelectrical contact reliabilityVSAvoidassembly ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies different binder materials with different swelling characteristics to different regions of the negative electrode mixture layer. Specifically, a first binder material is used in a first region and a second binder material with different swelling properties is used in a second region. This local differentiation allows the electrode to maintain contact with the exterior housing can during both charge and discharge states by having different expansion/contraction behaviors in different areas.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical and chemical parameters of the binder material by selecting materials with different swelling ratios. The first binder material has a first swelling ratio and the second binder material has a second swelling ratio that differs from the first. This parameter change enables the electrode assembly to maintain appropriate contact pressure with the exterior housing can across different charge states.

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

This configuration maintains electrical contact and improves output characteristics by ensuring the negative electrode current collector remains in contact with the exterior housing can even during discharge, enhancing the battery's performance and assembly efficiency.

Implementation Method 1

a degree of swelling of the binder by an electrolyte liquid in the one-surface coated portion is larger than a degree of swelling of the binder by an electrolyte liquid in the both-surface coated portion

Methodology Applied

Scientific EffectSwelling: Absorption (physical)

Data Source

PatentUS20230080854A1Non-aqueous electrolyte secondary battery

Publication Date: 2023.03.16 PANASONIC ENERGY CO LTD

AI summary

The non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure comprises a wound-type electrode body. A negative electrode has: a negative electrode current collector; a double-sided coated part in which a negative electrode mixture layer including a negative electrode active material and a binder is formed on the surface of the negative electrode current collector, and a negative electrode mixture layer is formed on both surfaces of the negative electrode current collector; and a one-sided coated part in which a negative electrode mixture layer is formed on one outer-periphery-side surface of the negative electrode current collector. At least a portion of the one-sided coated part is positioned on the outermost periphery of the electrode body. The swelling degree of the binder in the one-sided coated part is higher than the swelling degree of the binder in the double-sided coated part.