Background: Pouch cells are widely used in lithium-ion battery applications due to their high energy density and flexible design. Lead tabs play a crucial role in connecting the electrode layers within pouch cells, providing electrical conductivity and mechanical stability. Avocet Research Centre (ARC) was approached by a leading engineering company seeking to improve the performance and reliability at a pack level by utilising bimetallic lead tabs.
Challenge: A bimetallic tab is manufactured in a different orientation to standard tab materials. The challenge was to develop a new edge preparation method that would enhance the bonding strength of the polymer strip to the tab, minimising the risk of delamination and failure during pouch cell assembly and operation. The method needed to be scalable, cost-effective, and compatible with high-volume production processes.
Solution: ARC’s team of battery materials experts and engineers conducted extensive research and experimentation to develop an innovative edge preparation method for bimetallic lead tabs. The new method involved a mechanical punch process – designed, built and commissioned in-house at ARC – to force the required geometry on the edge of the tabs in a reproducible method. Key steps in the edge preparation process included:
1. Mechanical tooling design: Precision mechanical machining techniques were employed to tooling at the exact geometry required to achieve good sealing of the polymer strip, this was based on Avocet’s extensive knowledge of battery components.
2. Quality control and optimisation: ARC implemented rigorous quality control measures to ensure consistency and repeatability of the edge preparation process. Tooling was tested and several hundred parts were produced to validate a full Gage R&R study.
3. Semi-automatic press design: Following the validation of the tooling in a static process, ARC have designed and built a semi-automatic press with the edge-preparation built-in to reliably produce 1000s of parts that meet our partner’s requirements.
Results: The development of the new edge preparation method resulted in several significant improvements in performance at a pack level:
- Weight reduction: The integration of bimetallic tabs to the cell resulted in a significant reduction in weight due to replacing a portion of the copper tab with aluminium.
- Pack integration: Bimetallic tabs ensure that busbar welding is seamless, with all cell terminals being aluminium at the exterior of the cell, resulting in low electrical resistance and so cooler pack temperatures.
- Scalability and Cost-Effectiveness: The new edge preparation method is readily scalable and compatible with customer requirements. Minimising implementation costs and ensuring seamless integration into high-volume manufacturing operations was a key focus for this operation and the resultant products.
Conclusion: The successful development of the innovative edge preparation method for bimetallic lead tabs represents a significant advancement in pack level assembly and integration. ARC’s expertise in battery materials, mechanical design and process optimisation has enabled our partner to achieve higher performance, reliability, and cost-effectiveness in their pouch cell products. By continuously innovating and optimising battery components and manufacturing processes, ARC remains at the forefront of the energy storage industry, driving progress and enabling the widespread adoption of advanced battery technologies.