Cylindrical Battery Protective Layer for Laser Welding Heat Management

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Solution Overview

Problem

Cylindrical secondary batteries face safety risks due to overheating and potential electrolyte leakage during laser welding, as existing technologies do not effectively prevent welding heat from damaging the battery case and electrode assembly when connecting battery cells.

Innovation Solution

A cylindrical secondary battery design featuring a protective layer with high thermal conductivity on the inner surface of the battery case, including the crimping part, which disperses welding heat and prevents concentration of energy during laser welding, using materials like copper or copper alloys, and forming irregularities on the surface to scatter laser beams.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If laser welding is used to connect battery cells, then welding efficiency and connection strength are improved, but overheating and electrolyte leakage occur due to concentrated energy

Engineering Contradiction:

Improvewelding efficiencyVSAvoidoverheating and electrolyte leakage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A protective layer made of aluminum foil is introduced as an intermediary between the laser beam and the battery case. This protective layer absorbs and disperses the laser energy, preventing direct concentration of heat on the battery case and electrode assembly, thereby eliminating overheating and electrolyte leakage while maintaining welding efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective layer converts the harmful concentrated laser energy into beneficial dispersed heat distribution. By intentionally placing a material that interacts with laser energy (aluminum foil with specific reflectivity and thermal conductivity), the harmful overheating effect is transformed into controlled heat distribution that protects critical components while still enabling effective welding

Inventive Principle:

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

2Temperature

If a protective layer is formed on the inner surface of the battery case, then heat dissipation is improved, but the battery case structure becomes more complex

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidbattery case structure

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The protective layer is implemented as a thin aluminum foil film rather than a thick rigid structure. This thin film provides effective thermal protection and heat dissipation while adding minimal structural complexity and maintaining the simplicity of the battery case design

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The protective layer uses aluminum foil, a material that combines high thermal conductivity for heat dissipation with high laser reflectivity for energy protection. This composite approach integrates multiple protective functions (thermal management and laser protection) in a single material layer, avoiding the need for multiple separate components

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

The protective layer effectively disperses welding heat, preventing damage to the battery case and electrode assembly, and reducing the risk of electrolyte leakage, while maintaining weld integrity and enhancing heat dissipation efficiency.

Implementation Method 1

a protective layer, made of a material that exhibits high thermal conductivity, is formed on at least a portion of the inner surface of the cylindrical battery case

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

configured to have a structure in which a protective layer, made of a material that exhibits high thermal conductivity, is formed on at least a portion of the inner surface of a cylindrical battery case

Methodology Applied

Scientific EffectLaser reflection: Reflection

Implementation Method 3

forming irregularities on the surface to scatter laser beams

Methodology Applied

Scientific EffectLaser scattering: Scattering

Data Source

PatentUS11171371B2Cylindrical secondary battery including structure configured to block laser beam for welding and battery pack including the same

Publication Date: 2021.11.09 LG ENERGY SOLUTION LTD

AI summary

A cylindrical secondary battery including a cylindrical battery case configured to receive an electrode assembly and an electrolytic solution, a cap assembly located on the open upper end of the cylindrical battery case, and a jelly-roll type electrode assembly configured to have a structure in which a positive electrode sheet and a negative electrode sheet are wound in the state in which a separator is interposed therebetween, wherein a protective layer, made of a material that exhibits high thermal conductivity, is formed on at least a portion of the inner surface of the cylindrical battery case, including a crimping part is provided.