External Laser Welding of Electrode Tabs in High Power Cells

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Solution Overview

Problem

Conventional methods for joining electrode tabs in electrochemical cells require significant vertical space and can result in internal gaps, leading to risks from free metallic particles and reduced battery capacity.

Innovation Solution

An end-cap insert design that allows penetration of laser energy to electrode tabs, creating a weld that extends from the external surface of the end cap insert to the core insert, ensuring complete overlap and containment of the weld within the cell, thereby eliminating internal gaps and spatter risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional welding methods (ultrasonic, resistance welding) are used to join electrode tabs, then the tabs can be connected to the central terminal, but significant vertical space is required and internal gaps are created leading to spatter risks

Engineering Contradiction:

Improveweld reliabilityVSAvoidcell volume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent replaces conventional mechanical welding methods (ultrasonic welding, resistance welding requiring weld anvils) with laser beam welding. The laser beam penetrates through the end cap insert to directly weld the electrode tabs to the core insert, eliminating the need for mechanical contact from external welding equipment and reducing the vertical space required for welding operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a new dimensional approach by applying laser welding from the external surface of the end cap insert through its thickness to reach the electrode tabs. This external-to-internal welding path through the end cap insert eliminates the need for internal access to tabs, allowing welding without compromising cell volume while maintaining weld reliability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If electrode tabs are oriented parallel to the longitudinal axis of the cell, then connection to the central terminal is achieved, but considerable vertical space is consumed in the cell

Engineering Contradiction:

Improveconnection easeVSAvoidcell volume

Core Design Contradiction:

Ease of manufactureVSVolume of moving object

Solution Approach 1:

Instead of accessing electrode tabs from the internal side of the cell (which requires vertical space), the patent inverts the welding approach by accessing the tabs through the external surface of the end cap insert. The laser beam travels from outside the cell through the end cap insert to weld the tabs, effectively reversing the traditional internal access method and preserving cell volume.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If internal welding is performed without proper containment, then electrode tabs can be joined, but free metallic particles (spatter) are generated creating safety risks

Engineering Contradiction:

Improvewelding efficiencyVSAvoidspatter risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The end cap insert serves as an intermediary structure that contains the welding process. The laser beam welds through the end cap insert material itself, which acts as a containment barrier. Spatter generated during welding is trapped within the end cap insert rather than being released into the cell interior, thus maintaining welding efficiency while eliminating spatter risks.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potentially harmful spatter into a beneficial contained feature. The end cap insert design allows the welding process to generate spatter that is immediately contained within the insert structure. The spatter that would normally be a hazard is instead used to fill and seal the keyhole, creating a hermetic seal while the outer surface of the end cap insert prevents any release of particles.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design enhances the volumetric and gravimetric efficiency of the electrochemical cell by reducing internal gaps and spatter risks, allowing for a more compact and reliable high-strength, low-impedance electrical connection, which increases the battery's capacity and operational stability.

Implementation Method 1

At least one electrode tab is disposed between the end cap insert and the core insert. The end cap insert, the at least one electrode tab, and the core insert are electrically coupled by a weld provided by an external laser beam.

Methodology Applied

Scientific EffectLaser beam welding: Laser Beam Welding

Data Source

PatentUS8632907B2Method and design for externally applied laser welding of internal connections in a high power electrochemical cell

Publication Date: 2014.01.21 A123 SYSTEMS LLC

AI summary

An electrochemical cell includes components that are welded from an external source after the components are assembled in a cell canister. The cell canister houses electrode tabs and a core insert. An end cap insert is disposed opposite the core insert. An external weld source, such as a laser beam, is applied to the end cap insert, such that the end cap insert, the electrode tabs, and the core insert are electrically coupled by a weld which extends from the end cap insert to the core insert.