Electrode Unit Corner Geometry for Separator Integrity

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Solution Overview

Problem

The structural configuration of electrode units in electric storage devices, where the separator is stretched and torn at the corner of the active material layer, leading to potential internal short-circuits due to applied loads during lamination.

Innovation Solution

The electrode units are designed with a first face tapered section and a first face curved section formed by melting the surface of the active material layer, preventing the separator from being torn and ensuring a smooth surface without burrs, and the second face active material layer is configured with a second face orthogonal section to maintain volume and prevent contact with the first separator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the active material layer is cut with a blade to form a right-angled corner, then the manufacturing process is simple, but the separator may be stretched and torn at the corner under applied load

Engineering Contradiction:

Improvecutting processVSAvoidseparator integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The corner shape of the active material layer is changed from a right-angled corner (90-degree angle) to an obtuse-angled corner (greater than 90 degrees). This parameter change in the geometric angle reduces the stress concentration on the separator at the corner, preventing the separator from being stretched and torn while maintaining manufacturing simplicity through laser cutting

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The corner of the active material layer is formed with a curved surface instead of a sharp right angle. This curvature distributes the stress more evenly across the separator contact area, eliminating the stress concentration point that would cause separator tearing under applied load during lamination

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Device complexity

If the separator is positioned close to the active material layer edge, then the device structure is compact, but the separator may contact the opposite electrode causing internal short-circuit

Engineering Contradiction:

Improvestructure compactnessVSAvoidinternal short-circuit risk

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The separator is positioned asymmetrically relative to the active material layer, with different distances from the separator to the active material layer edges on opposite sides. This asymmetric positioning, combined with the obtuse-angled corner design, ensures adequate clearance between the separator and the opposite electrode while maintaining compact overall structure

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The obtuse-angled corner configuration acts as a preventive measure that beforehand prevents the separator from being torn and contacting the opposite electrode. By designing the corner geometry to reduce stress concentration, the structure preemptively eliminates the risk of separator failure and internal short-circuit under applied load

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 reduces the rate of extraction in discharge tests and enhances safety by preventing internal short-circuits and ensuring the integrity of the separator, thereby improving the reliability and safety of the electric storage device.

Implementation Method 1

a first face tapered section provided between a tapered side corresponding to one side of the first face at the current collector and the first face parallel section, the first face tapered section being inclined to an inner side of the current collector relative to a thickness direction of the first face active material layer, and a first face curved section continuously extending to form a curved surface between and across the first face parallel section and the first face tapered section

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS11302968B2Electric storage device and method of manufacturing electrode unit

Publication Date: 2022.04.12 TOYOTA INDUSTRIES CORP

AI summary

A first electrode sheet includes respective active material layers on a first face of a positive electrode metal foil and an opposing second face. The first face active material layer includes a parallel section along the first face, a tapered section between a positive electrode first lateral side of the first face and a first face parallel section and inclined inward towards a current collector inner region relative to a thickness direction of the first face active material layer, and a curved section forming a curved surface between and across the first face parallel and the first face tapered sections. A separator includes a first separator covering the side of the positive electrode metal foil first face, and a second separator covering the side of the second face. A first separator part lying flush against and contacting the first face tapered section arranged along the first face tapered section.