Laser Welding Separator to Anode Foil for Battery Cells

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Solution Overview

Problem

Existing methods for producing lithium ion battery electrode assemblies, such as gluing or welding, can lead to increased lithium ion diffusion resistance and potential electrolyte contamination, affecting long-term cycling performance and requiring extensive surface coverage.

Innovation Solution

A method involving a laser beam to heat the anode composite material, causing the polymer layer of the separator foil to melt and integrate into the anode's micro pores, effectively welding the separator to the anode foil without large-scale surface coverage, and subsequently joining the second separator to the cathode foil using an adhesive, allowing for efficient electrode assembly formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional gluing or welding methods are used to join separator to electrodes, then mechanical attachment is achieved, but lithium ion diffusion resistance increases and electrolyte contamination occurs

Engineering Contradiction:

Improvelong-term cycling performanceVSAvoidlithium ion diffusion resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces mechanical joining methods (gluing, welding) with a thermal bonding process where laser energy heats the polymer separator to melt it and integrate it into the anode's micro pores. This substitution eliminates the harmful effects of conventional mechanical/chemical joining methods while achieving secure mechanical attachment through material integration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes the phase transition of the polymer separator material from solid to melted state through laser heating, allowing the separator to flow into and integrate with the anode's micro pore structure. Upon cooling, the material solidifies, creating a strong mechanical bond without requiring additional adhesives or welding processes.

Inventive Principle:

Principle #36Phase transitions

2Strength

If large-scale surface coverage is used to ensure adequate joining, then mechanical stability is improved, but material usage increases and diffusion resistance increases

Engineering Contradiction:

Improvemechanical stabilityVSAvoidseparator material usage

Core Design Contradiction:

StrengthVSLoss of substance

Solution Approach 1:

The patent applies localized heating through laser energy to specific regions where joining is required, rather than heating or bonding large-scale surface areas. The laser beam is directed at specific locations on the separator, melting the polymer locally to integrate it into the anode's micro pores only where mechanical attachment is needed, thus reducing overall material usage while maintaining mechanical stability.

Inventive Principle:

Principle #3Local quality

3Productivity

If conventional welding methods are used to join separator to electrode, then joining speed is improved, but electrolyte contamination occurs affecting long-term performance

Engineering Contradiction:

Improvejoining speedVSAvoidelectrolyte contamination

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces conventional welding methods with a laser-based thermal bonding process that melts the polymer separator material directly. This substitution eliminates the need for external welding tools that could introduce contaminants into the electrolyte, while maintaining high joining speed through rapid laser heating and cooling cycles.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method enhances lithium ion diffusion rates, reduces material usage, and allows for easier assembly and stacking of electrode sub-stacks, improving the mechanical stability and performance of lithium ion battery cells.

Implementation Method 1

a laser beam is directed onto the first separator foil such that energy of the laser beam largely penetrates the first separator foil and such that the anode composite material of the anode foil largely absorbs the energy of the laser beam. By absorbing said energy of the laser beam, the temperature of the anode composite material is rising.

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

the anode composite material of the anode foil largely absorbs the energy of the laser beam

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 3

the energy of the laser beam is applied such that the anode composite material is heated to a temperature below a melting point or below a decomposition temperature of the anode composite material and above or near to a melting point or a softening point of the polymer layer of the first separator foil

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP3401978B1Method for producing an electrode assembly for a battery cell

Publication Date: 2022.06.08 ROBERT BOSCH GMBH

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AI summary

The invention relates to a method for producing an electrode assembly for a battery cell, whereat an anode foil (31) is provided, a first separator foil (41) is placed on the anode foil (31), the first separator foil (41) is welded to the anode foil (31) by dint of a laser beam (80), a cathode foil is placed on the first separator foil (41) and a second separator foil is placed on the cathode foil whereby the cathode foil can be fixed within the two separator foils as well. The invention also relates to a battery cell, comprising at least one electrode assembly produced using the method according the invention.