Electrode Plate Binder Distribution for Battery Bond Strength

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Solution Overview

Problem

Conventional electrode plates for secondary batteries face issues with uneven binder distribution, leading to reduced bond strength between the active material layer and the current collector plate, and increased production costs due to multiple coating and drying steps.

Innovation Solution

An electrode plate design featuring a current collector plate with an active material layer containing multiple binders having different glass transition points, where the binder ratio between the surface and current collector sections is optimized (1.0 to 1.2), with a lower glass transition point binder on the surface and a higher on the current collector, enhancing bond strength without requiring multiple drying steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single binder is used in the active material layer, then the manufacturing process is simple, but the bond strength between the active material layer and current collector plate is reduced due to uneven binder distribution

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidbond strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent applies local quality by using different binders with different glass transition points in different regions of the active material layer. Specifically, a first binder with a higher glass transition point is used near the current collector plate to provide strong adhesion, while a second binder with a lower glass transition point is used toward the surface to maintain flexibility and prevent cracking. This regional differentiation of binder properties optimizes both bond strength and overall electrode performance without requiring multiple coating steps.

Inventive Principle:

Principle #3Local quality

2Strength

If multiple coating and drying steps are performed to improve binder distribution, then the bond strength is improved, but the number of production steps increases and costs rise

Engineering Contradiction:

Improvebond strengthVSAvoidnumber of production steps

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-mixing both binders (with different glass transition points) into a single active material paste before coating. This preliminary preparation ensures that both binders are present in the coating layer from the start, and during the single drying process, they naturally distribute to appropriate regions based on their different glass transition points and migration behaviors. This eliminates the need for multiple sequential coating and drying steps while achieving the desired binder distribution and bond strength.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If binder migrates toward the surface during drying, then the surface section contains more binder, but the bond strength at the current collector plate interface is reduced

Engineering Contradiction:

Improvebinder distribution controlVSAvoidbond strength at interface

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies parameter changes by selecting binders with specifically different glass transition points. The first binder has a higher glass transition point (providing stronger adhesion near the current collector), while the second binder has a lower glass transition point (allowing it to migrate more easily toward the surface during drying). This parameter differentiation controls the binder distribution pattern during drying, ensuring that the interface region maintains sufficient binder for strong bonding while the surface region also receives adequate binder coverage.

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 improves the bond strength between the active material layer and the current collector plate, reduces internal resistance, and simplifies the production process by minimizing the number of drying steps, resulting in higher-performing and more durable secondary batteries.

Implementation Method 1

the active material layer includes a plurality of binders having glass transition points Tg different from each other... the binder contained in the surface section has an average glass transition point Tgu lower than an average glass transition point Tgd of the binder contained in the current collector plate section

Methodology Applied

Scientific EffectGlass transition:

Data Source

PatentUS8574763B2Electrode plate with a binder in a surface section with a lower glass transition point than a binder in a current collector plate section, secondary battery, and method for producing the electrode plate

Publication Date: 2013.11.05 TOYOTA JIDOSHA KK

AI summary

An electrode plate includes a current collector plate and an active material layer formed thereon. The active material layer includes, as a binder, a plurality of binders having different glass transition points (Tg) from each other. A ratio (A2/A1) between the amount of a binder contained in a surface section and the amount of a binder contained in a current collector plate section is 1.0 to 1.2. Further, an average glass transition point (Tgu) of the binder in the surface section is lower than an average glass transition point (Tgd) of the binder in the current collector plate section (Tgu<Tgd).