Electrostatic Granule Transfer for Battery Electrode Coating

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Solution Overview

Problem

The existing methods for producing electrodes using electrostatic coating face challenges with nonuniformity due to varying adhering forces between electrode material and magnetic particles, leading to issues with coating uniformity and yield loss when transferring powder without magnetic force, especially when gravity affects the powder transfer.

Innovation Solution

A method involving the use of granules with a solid fraction of 70 to 100% and a D50 size of 100 to 200 μm, which are electrostatically charged and transferred across multiple electric fields to adhere to a substrate, reducing nonuniformity and yield loss by utilizing a two-step electrostatic coating process and adjusting electric field strengths to counteract gravity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If magnetic particles are used to transfer electrode material, then powder can be transferred against gravity, but adhering force varies greatly causing nonuniform coating

Engineering Contradiction:

Improvecoating uniformityVSAvoidadhering force consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The invention removes magnetic particles from the system entirely. Instead of using magnetic force to transfer powder, the patent employs electrostatic charging of the powder itself, eliminating the source of variable adhering force while maintaining the ability to transfer powder against gravity through electric field control.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the physical state of the powder by electrostatically charging the granules. This parameter change allows the powder to be controlled by electric fields rather than magnetic fields, providing more consistent and controllable transfer characteristics without the variability inherent in magnetic particle adhesion.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If powder is transferred without magnetic force, then coating uniformity may improve, but gravity causes powder to fall from roller

Engineering Contradiction:

Improvecoating uniformityVSAvoidpowder transfer efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The invention replaces the mechanical/gravitational transfer system with an electrostatic system. By charging the granules and using electric fields, the powder can be transferred against gravity without relying on magnetic force, maintaining both coating uniformity and transfer efficiency through electric field control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If electrostatic coating is used, then uniform composition can be achieved, but yield loss occurs during powder transfer

Engineering Contradiction:

Improvecomposition uniformityVSAvoidpowder yield loss

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The invention optimizes the electrostatic parameters by controlling the charging level of granules and the strength of electric fields in different regions. This parameter control ensures that powder is transferred efficiently without excessive loss, while maintaining uniform composition through consistent electrostatic deposition.

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 approach enhances coating uniformity and reduces yield loss by ensuring granules adhere firmly to the substrate, improving the fluidity and angle of repose of the granules, and minimizing solvent usage, thereby reducing production costs and environmental impact.

Implementation Method 1

electrically charging the granules

Methodology Applied

Scientific EffectElectrostatic charging: Electrostatic Induction

Implementation Method 2

forming a first electric field between the second region and a third region to allow the granules to fly from the second region toward the third region

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 3

forming a second electric field between the third region and a substrate to allow the granules to fly from the third region toward the substrate

Methodology Applied

Scientific EffectElectrostatic deposition: Electrostatic Deposition

Implementation Method 4

The second region is positioned lower in a vertical direction than the first region

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS20230027943A1Method of producing electrode, and electrode production apparatus

Publication Date: 2023.01.26 TOYOTA JIDOSHA KK

AI summary

Granules including an active material powder and a binder are prepared. The granules are supplied onto a surface of a roller. The granules are electrically charged. The granules are transferred from a first region to a second region by way of rotation of the roller. A first electric field is formed between the second region and a third region to allow the granules to fly from the second region toward the third region. A second electric field is formed between the third region and a substrate to allow the granules to fly from the third region toward the substrate.