Wound Electrode Flat-Surface Welding for Low-Resistance Li-Ion Batteries
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Solution Overview
Problem
High-rate discharge in lithium ion batteries faces challenges due to high internal resistance, which is exacerbated by defective welding and instability in laser welding processes caused by the thickness of current-collecting plates and protruded parts on the electrode foils.
Innovation Solution
A secondary battery design featuring a current-collecting plate structure with band-shaped and plate-shaped parts, including a positive electrode and negative electrode with non-covered active material parts that are bent and overlapped to form a flat surface for stable laser welding, reducing internal resistance and enabling high-power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the current-collecting plate is increased to reduce internal resistance, then the internal resistance decreases and high-power characteristics improve, but defective welding occurs due to separator damage by laser welding heat or holes in electrode foils
Solution Approach 1:
The current-collecting plate has different thicknesses in different regions: a first thickness in the welding region and a second thickness in non-welding regions. This local variation allows the welding area to have lower thickness for better laser welding quality and reduced heat penetration, while other regions maintain greater thickness for low internal resistance and high-power characteristics.
Solution Approach 2:
The current-collecting plate is divided into multiple regions with different thickness characteristics. The plate includes a welding region with first thickness and non-welding regions with second thickness, creating segmented functional zones that optimize both welding quality and electrical performance.
2Power
If the thickness of the current-collecting plate is increased to reduce internal resistance, then high-power characteristics improve, but laser welding becomes complicated and unstable
Solution Approach 1:
The current-collecting plate has different thicknesses in different regions: a first thickness in the welding region and a second thickness in non-welding regions. This local variation allows the welding area to have lower thickness for better laser welding quality and reduced heat penetration, while other regions maintain greater thickness for low internal resistance and high-power characteristics.
3Power
If high-rate discharge is implemented to achieve high-power characteristics, then power output increases, but internal resistance becomes problematic due to resistance between electrode foils and current-collecting plate
Solution Approach 1:
The current-collecting plate has different thicknesses in different regions: a first thickness in the welding region and a second thickness in non-welding regions. This local variation allows the welding area to have lower thickness for better laser welding quality and reduced heat penetration, while other regions maintain greater thickness for low internal resistance and high-power characteristics.
Solution Approach 2:
The thickness parameter of the current-collecting plate is changed spatially to optimize performance. By varying the thickness from the first value in welding regions to the second value in non-welding regions, the plate achieves both good weldability and low internal resistance for high-rate discharge capability.
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 battery achieves reduced internal resistance and stable production, facilitating high-power performance while ensuring stable welding processes, thus addressing the issues of defective welding and instability in high-rate discharge applications.
Implementation Method 1
there is the problem of defective welding due to a separator damaged by the heat of laser welding
Data Source
AI summary
Provided is a secondary battery. The secondary battery includes a positive electrode includes a first covered part covered with a positive electrode active material layer and a positive electrode active material non-covered part on a positive electrode foil, and a negative electrode includes a second covered part covered with a negative electrode active material layer and a negative electrode active material non-covered part on a negative electrode foil, an electrode wound body includes: a flat surface formed by bending each of the positive electrode active material non-covered part and the negative electrode active material non-covered part toward the central axis of the electrode wound body to have an overlap with each other; and a groove formed in the flat surface.