Ultrasonic Welding Resin Sheet for Battery Electrode Assembly

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Solution Overview

Problem

Existing methods for producing electrode assemblies in nonaqueous electrolyte secondary batteries face challenges in preventing the ingress of metal powder generated during ultrasonic welding, which can lead to internal short circuits and battery deterioration.

Innovation Solution

The method involves ultrasonic welding with a resin sheet interposed between the ultrasonic horn and the electrode current collector or lead, using a serrated ultrasonic horn to prevent metal powder generation and trapping any generated powder with an adhesive layer, thereby preventing its ingress into the electrode group.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If ultrasonic welding is performed with direct contact between ultrasonic horn and electrode tab/lead, then welding efficiency is improved, but metal powder is generated and may ingress into electrode group causing internal short circuit

Engineering Contradiction:

Improvewelding efficiencyVSAvoidmetal powder ingress

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A resin sheet is introduced as an intermediary between the ultrasonic horn and the electrode tab or lead. The resin sheet includes a sheet base material and an adhesive layer that bonds to the electrode tab or lead. This intermediary prevents direct contact between the ultrasonic horn and the metal surfaces, thereby preventing metal powder generation while still allowing ultrasonic welding to occur through the resin sheet.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If adhesive tape is applied to cover welded portion after ultrasonic welding, then some metal powder detachment is prevented, but metal powder generated during welding still ingresses into electrode group

Engineering Contradiction:

Improvemetal powder detachmentVSAvoidprevention of internal short circuit

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The resin sheet with adhesive layer is applied to the electrode tab or lead before ultrasonic welding takes place. This preliminary action ensures that the adhesive layer is already in position to trap any metal powder that may be generated during the welding process, rather than attempting to cover the welded portion after welding has already occurred.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If resin sheet with adhesive layer is used during ultrasonic welding, then metal powder generation and ingress is prevented, but joining strength may be compromised

Engineering Contradiction:

Improvemetal powder ingress preventionVSAvoidjoining strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The resin sheet is designed with differentiated local qualities: the sheet base material provides mechanical protection and acts as a barrier against metal powder, while the adhesive layer provides bonding strength to the electrode tab or lead. This local quality differentiation ensures that each component of the resin sheet serves its specific function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The resin sheet is constructed as a composite material consisting of a sheet base material and an adhesive layer. This composite structure combines the protective and barrier properties of the base material with the bonding properties of the adhesive layer, achieving both metal powder prevention and adequate joining strength.

Inventive Principle:

Principle #40Composite materials

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 effectively reduces the generation and ingress of metal powder, preventing internal short circuits and maintaining battery performance by ensuring strong welding without compromising joining strength.

Implementation Method 1

a step of ultrasonically welding an exposed portion where a surface of an electrode current collector is exposed and an electrode lead to each other

Methodology Applied

Scientific EffectUltrasonic welding: Ultrasonic Vibration

Implementation Method 2

ultrasonic welding is performed, while the exposed portion and the electrode lead are stacked on each other, with an ultrasonic horn pressed against a resin sheet

Methodology Applied

Scientific EffectFriction heating: Friction

Data Source

PatentUS11075374B2Method for producing electrode assembly and method for producing nonaqueous electrolyte secondary battery

Publication Date: 2021.07.27 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A method for producing an electrode assembly includes a step of ultrasonically welding an exposed portion where the surface of an electrode current collector is exposed and an electrode lead to each other. The ultrasonic welding is performed, while the exposed portion of the electrode current collector and the electrode lead are stacked on each other, with an ultrasonic horn pressed against a resin sheet disposed on the exposed portion or the electrode lead. The resin sheet includes a sheet base material and an adhesive layer formed on one surface of the base material and is bonded to a portion of the exposed portion that is to be in contact with the ultrasonic horn or to a portion of the electrode lead that is to be in contact with the ultrasonic horn.