Enhanced Material Properties in joints in Li-ion batteries (EMPIRE)

Purpose and goal:

The goal of the project was to find material concepts/solutions that would increase the quality of the joints in lithium-ion batteries. The objective is to improve operational stability in battery systems and avoid unplanned downtime or, in worst cases, fires.. Through the work towards the goal, the project has delivered the following:

- A report describing the modern assembly of Li-ion battery modules - Group and individual meetings with partners - Characterised intermetallic compounds (IMC) of joined samples, assessment of joint quality, and joint properties - Strategies for ductility enhancement and brittle IMCs reduction - Material concepts that can minimise the brittle IMCs

- Report on optimised joining process (laser welding and brazing) for tabs onto busbars - Documentation of the final properties of the chosen joints - Guidelines for joints in Li-ion batteries Expected results and effects:

The project results are foreseen to be applied widely during the electrification of society and industry. The project results will improve the reliability of electrical joints in EVs and battery systems. The results are easily implementable in a wide variety of industries, from automotive to marine and aerospace industries.

The optimised joining processes will enhance the quality of the joint, but also shorten cycle times in production which is beneficial for environment (reduced consumption of resources) and lead to increased competitiveness and profitability. Approach and implementation:

The study was conducted to find suitable patterns, suitable power, and suitable scanning speed to produce defect-free laser welding joints between Al/Al Al/Cu with a minimum joint width of 1 mm and minimum penetration of 0.2 mm. To find out that, an experiment plan was designed and conducted with two different laser beam patterns such as i) Zigzag pattern, ii) Hourglass pattern.

The input power was changed between 1300W to 3600W, and the scanning speed was changed between 60mm/s and 240 mm/s. Circular welds and straight welds were tried out with single and double beads.