Outer Current Collector Thickness for Tear-Resistant Ultrasonic Welding
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Solution Overview
Problem
Ultrasonic welding of outer current collectors in battery cells often results in tearing or weakening, leading to variations in cell resistance and lithium plating due to the high energy required for welding thin current collectors.
Innovation Solution
Thicker current collectors are used for the outermost electrodes, which reduces tearing and sticking issues during welding, allowing for more robust attachment and consistent energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultrasonic welding is used to attach tabs to outer current collectors, then manufacturing cost is reduced and attachment is achieved, but the current collectors may be torn or weakened during the welding process
Solution Approach 1:
The patent applies different thickness specifications to different current collectors based on their position. Outer current collectors are made thicker (15-25 μm) to withstand welding stresses, while inner current collectors can be thinner (10-20 μm) to reduce overall weight and cost. This local differentiation resolves the contradiction by strengthening only where the welding process causes damage.
Solution Approach 2:
The patent changes the physical parameter of current collector thickness specifically for outer current collectors. By increasing the thickness parameter from the standard 10-20 μm range to 15-25 μm for outer current collectors, the material can better withstand the mechanical stresses of ultrasonic welding without tearing, while maintaining thinner inner current collectors to minimize overall weight.
2Weight of moving object
If thin current collectors are used in outermost electrodes, then weight is reduced and energy density is improved, but tearing and weakening occur during ultrasonic welding
Solution Approach 1:
The patent implements local quality differentiation by specifying that only outer current collectors (those with tabs attached) should be thicker (15-25 μm), while inner current collectors can remain thinner (10-20 μm). This ensures that the additional weight is concentrated only where structurally necessary for welding durability, rather than uniformly increasing the weight of all current collectors.
Solution Approach 2:
The patent segments the current collector system into two distinct categories: outer current collectors that require welding attachment and inner current collectors that do not. This segmentation allows different thickness specifications to be applied to each group, optimizing both weight and welding durability for their respective functions.
3Reliability
If thicker current collectors are used for outermost electrodes, then welding durability is improved and tearing is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies manufacturing by segmenting current collectors into two clear categories with distinct thickness specifications. Outer current collectors are made with thickness of 15-25 μm while inner ones are 10-20 μm. This clear segmentation with defined parameters makes the manufacturing process more manageable and less complex than trying to optimize uniform thickness for all current collectors.
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 use of thicker current collectors in the outermost electrodes enhances the durability of the welding process, minimizing defects and maintaining consistent cell performance by reducing the likelihood of tearing and sticking, thus improving the reliability of battery cells.
Implementation Method 1
Ultrasonic welding is a low-cost method for attaching the tabs to the electrodes
Data Source
AI summary
A battery cell includes a plurality of electrodes including a plurality of anode electrodes and a plurality of cathode electrodes. The plurality of electrodes is arranged in one of a stacked architecture and a winding architecture. Each of the plurality of electrodes includes a current collector and active material arranged on opposite sides of the current collector. The current collector of one or more outermost ones of the plurality of electrodes is thicker than the current collectors of remaining ones of the plurality of electrodes having the same anode/cathode type.