Internal Laser Welding of Battery Lower Cans Without Exterior Traces

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Solution Overview

Problem

Existing welding methods for secondary batteries leave welding traces on the exterior of the lower can, limiting material properties and commercial value, and lack effective monitoring of the welding process.

Innovation Solution

A welding method and apparatus that emit a laser beam inside the lower can to weld the electrode tab to its inner surface, using a jig with a pipe-shaped insertion portion and a disk-shaped seating portion to prevent deformation and enhance welding strength, while a monitoring system uses illumination and welding laser beams to verify the welded state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If welding is performed from the outside of the lower can, then welding can be completed, but welding traces are left on the outer surface and material properties are limited

Engineering Contradiction:

Improvewelding process simplicityVSAvoidouter surface quality

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The patent inverts the conventional welding approach by performing welding from the inside of the lower can rather than from the outside. The laser beam is irradiated through the center hole of the electrode assembly to weld the electrode tab to the inner bottom surface of the lower can, which eliminates welding traces on the outer surface while maintaining welding effectiveness.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent uses a jig with an insertion portion that is inserted into the center hole of the electrode assembly. The electrode tab is positioned between the jig and the lower can, and welding is performed through the nested structure of the jig inside the electrode assembly inside the lower can, enabling internal welding without affecting the outer surface.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Strength

If laser beam is focused tightly at the welding point, then welding strength is maximized, but deformation occurs in the exterior of the lower can

Engineering Contradiction:

Improvewelding strengthVSAvoidexterior deformation

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The patent changes the focusing parameter of the laser beam by using defocusing instead of tight focusing. The laser beam is deliberately defocused during welding, which reduces the peak temperature at the welding point and minimizes heat-affected zone, thereby preventing deformation of the lower can exterior while still achieving adequate welding strength.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If welding is performed from the outside, then process is simple, but welding efficiency is limited by material properties and thickness

Engineering Contradiction:

Improvewelding setup simplicityVSAvoidwelding efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent inverts the welding direction to perform welding from the inside of the lower can through the electrode assembly center hole. This approach improves welding efficiency by allowing the laser beam to directly weld the electrode tab to the lower can inner surface without being constrained by the thickness or material properties of the lower can wall, enabling more consistent and efficient welding across different can specifications.

Inventive Principle:

Principle #13The other way round (Inversion)

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 eliminates exterior welding traces, enhances welding efficiency and strength, and allows for precise monitoring of the welding process, improving the commercial value and performance of secondary batteries.

Implementation Method 1

an electrode tab of an electrode assembly is welded to an inner bottom surface of a lower can... a laser beam is emitted into a hole inside an insertion portion

Methodology Applied

Scientific EffectLaser beam welding: Laser Beam Welding

Implementation Method 2

the bonding is made as the lower can relatively greater than the negative electrode tab is melted

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

emitting the laser beam such that defocusing is made, thereby preventing deformation in the exterior of the lower can and increasing welding strength

Methodology Applied

Scientific EffectDefocusing: Focusing

Implementation Method 4

an illumination laser beam is emitted into the hole inside the insertion portion... an image sensor receives the reflected illumination laser beam

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS20230356327A1Welding method and welding apparatus for secondary battery, and monitoring method and monitoring apparatus for secondary battery welding process

Publication Date: 2023.11.09 LG ENERGY SOLUTION LTD

AI summary

A welding apparatus is provided for a secondary battery having an electrode assembly with a center hole seated on a lower can. The welding apparatus includes a jig which includes an insertion portion that has a pipe shape and a diameter enabling entry into the center hole of the electrode assembly and a seating portion that has an enlarged diameter of a disk shape on an end of the insertion portion; and a laser irradiation apparatus to emit a laser beam into a hole of the insertion portion. When the electrode assembly is seated on the lower can such that an electrode tab of the electrode assembly is placed within the center hole, the laser irradiation apparatus performs a weld between the inner bottom surface of the lower can and the electrode tab after passing through the hole of the insertion portion of the jig.