Battery Cover Welding via Intermediate Plating Layer
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Solution Overview
Problem
The existing methods for welding conductive metal members in secondary battery cells, such as those in lithium ion batteries, face challenges in achieving strong joining strength and low electrical resistance due to material differences in melting points, which can lead to cracking and insufficient bonding.
Innovation Solution
A welded structure is developed where a metal layer with a higher joining force is used, specifically a plating layer on one conductive metal member, and a second conductive metal member with a different material is welded to this layer, forming a melted and elution part that is integrated into the surface layer for enhanced bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal members with different materials are welded directly, then joining strength can be improved, but electrical resistance increases and cracking occurs due to melting point differences
Solution Approach 1:
A metal layer with intermediate melting point is introduced between the first conductive metal member and the second conductive metal member with different materials. This intermediate layer acts as a mediator that bridges the melting point difference, allowing the second metal member to be welded to the metal layer without direct contact with the first metal member, thereby preventing cracking and maintaining low electrical resistance while achieving strong joining strength.
2Strength
If laser irradiation is applied to melt and fuse different metals, then joining strength increases, but electrical resistance reduction is insufficient due to material differences
Solution Approach 1:
The melting point parameter of the joining system is optimized by selecting a metal layer with an intermediate melting point between the two different conductive metal members. This parameter change allows the laser irradiation to effectively melt and fuse the second metal member to the metal layer without excessive temperature differences, achieving both strong joining strength and low electrical resistance.
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 results in a welded structure with low electrical resistance, high bonding force, and high reliability, maintaining the protective functions of the plating layer while increasing the joining area and adhesion strength.
Implementation Method 1
a laser is irradiated to an end of the safety valve unit, and the safety valve unit is welded to the battery cover
Implementation Method 2
the safety valve unit is melted by the laser irradiation, and flowing aluminum-based metal and iron-based metal are fused
Implementation Method 3
the first conductive metal member and the second conductive metal member are joined through the metal layer
Data Source
AI summary
A plating layer 4 is formed on a surface of a battery cover 3, and a peripheral edge part 37b of a cover case 37 is arranged on an upper surface of the plating layer 4. A welding part 40 is formed at a tip part of the peripheral edge part 37b. The welding part 40 includes a melted part 41 in which the tip of the peripheral edge part 37b is melted, and an elution part 42 flowing from the tip onto the plating layer 4, and the melted part 41 and the elution part 42 are welded to the plating layer 4 in the upper surface of the plating layer 4.