Welded Rivet Connections Stabilize Contact Resistance in Energy Storage Devices

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Solution Overview

Problem

Conductive connections in energy storage devices, such as lithium ion secondary batteries, experience varying contact resistance due to vibration and material creep, leading to heat generation and potential defects like melting of conductive members at connection points between conductive members.

Innovation Solution

The implementation of welded connections using aluminum solder at contact points between the current collector, rivet, and external terminal, which reduces contact resistance and prevents heat generation by melting at a predetermined temperature, acting as a fuse to prevent further current flow and heat buildup.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductive connections are made using conventional methods (rivets, pressure connections), then the device structure is simple and easy to manufacture, but contact resistance varies due to vibration and material creep, leading to heat generation and potential melting of conductive members

Engineering Contradiction:

Improvecontact resistance stabilityVSAvoidconnection manufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies welding technology to change the connection method from mechanical (rivets, pressure) to metallurgical bonding. This parameter change in the connection process ensures stable contact resistance by creating a permanent, vibration-resistant weld joint between conductive members, directly resolving the reliability issue while accepting increased manufacturing complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces mechanical connection systems (rivets, pressure connections) with a welding system. This substitution eliminates the problems of material creep and vibration-induced contact resistance variation inherent in mechanical connections, achieving stable electrical contact through metallurgical bonding.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If welded connections are implemented to reduce contact resistance, then heat generation is reduced and reliability is improved, but manufacturing complexity and production time increase

Engineering Contradiction:

Improveconnection durabilityVSAvoidconnection process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the connection parameter from mechanical assembly to welding process, which inherently provides more durable and reliable joints. The welding process creates metallurgical bonds that resist vibration and material creep, directly improving connection durability despite the increased process complexity.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If aluminum solder is used for welding to prevent heat generation, then contact resistance is stabilized and heat buildup is prevented, but the manufacturing process becomes more complex and time-consuming

Engineering Contradiction:

Improveheat generation controlVSAvoidmanufacturing efficiency

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The patent introduces aluminum solder as an intermediary material in the welding process. This intermediary enables reliable welding between aluminum conductive members by facilitating metallurgical bonding, thereby stabilizing contact resistance and controlling heat generation during operation, though it adds steps to the manufacturing process.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively reduces heat generation and enhances the durability and reliability of energy storage devices by stabilizing contact resistance and preventing defects, even under conditions of large current flow or external vibrations.

Implementation Method 1

at least one of a contact portion between a casing inner portion of the rivet and the current collector, a contact portion between a casing outer portion of the rivet and the connection conductor, and a contact portion between the connection conductor and the external terminal has a welded portion

Methodology Applied

Scientific EffectWelding: Welding

Implementation Method 2

prevents heat generation by melting at a predetermined temperature, acting as a fuse to prevent further current flow and heat buildup

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS9472798B2Energy storage device

Publication Date: 2016.10.18 GS YUASA INT LTD

AI summary

An energy storage device includes a casing, a power generating element, a current collector, a connection conductor, an external terminal, and a rivet. The energy storage device further includes a welded portion where at least one of a contact portion between a casing inner portion of the rivet and the current collector, a contact portion between a casing outer portion of the rivet and the connection conductor, and a contact portion between the connection conductor and the external terminal is welded at least partially.