Battery Tab-to-Terminal Welding With Two-Step Laser Defect Repair

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Solution Overview

Problem

Laser welding of external tabs to terminals in battery cells often results in porous welds and detachment issues due to defects at the boundary of fusion, particularly when welding multiple layers in a lap joint, which affects the quality and reliability of the connections.

Innovation Solution

A two-step laser processing method is employed, where a first laser creates a trench and potentially introduces defects, followed by a second laser processing step with different operating parameters to weld and repair defects, using fill material if necessary, to achieve a high-quality weld.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single-step laser welding process is used to join external tabs to terminals, then the manufacturing process is simple and fast, but the weld quality is poor with porous defects and detachment issues

Engineering Contradiction:

Improvewelding speedVSAvoidweld quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The welding process is divided into two distinct steps: first creating a trench to remove contaminants and prepare the interface, then performing the actual welding. This segmentation allows each step to be optimized independently, resolving the contradiction between speed and quality by making the process more structured rather than slower.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The trench creation step is performed as a preliminary action before welding. By pre-preparing the weld interface to remove oxides, contaminants, and uneven surfaces, the subsequent welding step produces higher quality joints without requiring slower welding speeds, thus resolving the quality-speed contradiction.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If laser welding is performed on multiple layers of external tabs in a lap joint, then the connection is achieved, but defects occur at the boundary of fusion reducing reliability

Engineering Contradiction:

Improveconnection reliabilityVSAvoidporous defects

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The trench creation process extracts and removes harmful elements from the weld interface, including oxides, contaminants, and uneven surfaces that would otherwise be trapped in the weld zone. By taking out these harmful factors before welding, the resulting weld has fewer porous defects and higher reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The laser parameters during trench creation are optimized to generate controlled molten material and vapor that carry contaminants away from the weld zone. The plasma and molten flow that could be considered harmful are instead utilized to actively remove impurities, converting a potentially harmful process into a beneficial cleaning mechanism.

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 approach significantly reduces or eliminates defects, improving the weld quality and reliability of connections between external tabs and terminals, enhancing the overall performance and durability of battery cells.

Implementation Method 1

creating a trench in the stack of external tabs of the one of C cathode electrodes and the A anode electrodes at a weld location during a first laser processing step

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

welding the stack of external tabs of the one of C cathode electrodes and the A anode electrodes at the weld location during a second laser processing step

Methodology Applied

Scientific EffectLaser welding: Laser Beam Welding

Implementation Method 3

using a second laser, welding the stack of external tabs... At least some defects created during the first laser processing step are repaired during the second laser processing step

Methodology Applied

Scientific EffectLaser melting: Melting

Data Source

PatentUS20250001522A1Welding of stacks of external tabs of electrodes to terminals with two step laser process that reduces defects

Publication Date: 2025.01.02 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method for joining external tabs of a battery cell to a terminal includes providing a battery cell stack including C cathode electrodes, A anode electrodes, and S separators, where C, S and A are integers greater than one. The method includes arranging a stack of external tabs of one of the C cathode electrodes and the A anode electrodes on a terminal; creating a trench in the stack of external tabs of the one of the C cathode electrodes and the A anode electrodes at a weld location during a first laser processing step; and welding the stack of external tabs of the one of the C cathode electrodes and the A anode electrodes at the weld location during a second laser processing step.