Wound Secondary Battery Bead Welding for Low Internal Resistance
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Solution Overview
Problem
Existing lithium ion batteries face high internal resistance due to welding failures, which hinder their suitability for high rate discharge applications.
Innovation Solution
A secondary battery design featuring strip-shaped positive and negative electrodes with non-covered portions that are stacked and wound around a central axis, where these non-covered portions are bent and overlapped to form a flat surface, and joined to current collector plates via laser welding, with specific dimensions and overlaps to reduce internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active material non-covered portion is joined to the current collector plate using conventional welding methods, then the battery can be assembled, but welding failures occur resulting in high internal resistance
Solution Approach 1:
The patent replaces conventional mechanical welding methods with laser welding technology. The laser beam melts and fuses the active material non-covered portion to the current collector plate, creating a more reliable electrical connection with lower resistance compared to traditional welding methods.
Solution Approach 2:
The patent optimizes specific parameters including the width of the active material non-covered portion (0.03mm to 0.12mm), the width of the bead (0.05mm to 0.18mm), and the thickness of the current collector plate (0.07mm to 0.20mm). These parameter changes ensure proper laser welding penetration and connection strength, resolving the welding reliability issue.
2Ease of manufacture
If the electrode structure is simplified to reduce manufacturing complexity, then ease of manufacture improves, but internal resistance increases due to insufficient welding
Solution Approach 1:
The patent designs the active material non-covered portion with predetermined dimensions and positioning before the welding process. This preliminary preparation ensures that the laser welding can be performed efficiently with consistent results, maintaining low internal resistance while keeping the manufacturing process simple and straightforward.
3Power
If the battery is designed for high rate discharge capability, then power output increases, but heat generation becomes excessive
Solution Approach 1:
The laser welding creates a more efficient electrical connection with lower contact resistance compared to conventional welding. This reduced resistance minimizes heat generation during high rate discharge operations, allowing the battery to deliver high power without excessive temperature rise.
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 design achieves low internal resistance, making the battery suitable for high rate discharge and reducing heat generation during discharge.
Implementation Method 1
a surface of a current collector plate disposed on the end portion is irradiated with a laser to join the active material non-covered portion and the current collector plate
Data Source
AI summary
Disclosed is a secondary battery in which a positive electrode active material non-covered portion is joined to a positive electrode current collector plate at one end portion of an electrode winding body, a negative electrode active material non-covered portion is joined to a negative electrode current collector plate at the other end portion of the electrode winding body, the positive electrode current collector plate has a positive electrode bead on a surface thereof, the negative electrode current collector plate has a negative electrode bead on a surface thereof, a width of the positive electrode bead is 0.05 mm or more and 0.18 mm or less, a width of the negative electrode bead is 0.03 mm or more and 0.12 mm or less.