EMPT in the battery production

Electromobility and battery technology are placing demands on the materials used, some of which can only be solved with multi-material construction. High-strength joints of thermally sensitive aluminium alloys and copper-aluminium compounds often present great challenges for conventional techniques.

The EMPT, on the other hand, enables intelligent and cost attractive solutions in the following areas of application:

Battery boxes
Bus bars
Packing bracing/tensioning straps for pouch cells
Cell housing for prismatic accumulators

Battery Frame with EMPT Welded Cooling Solution

Particularly in the field of electromobility, the concept of lightweight construction is clearly linked to the vehicle's performance. One option for saving weight and space is provided by battery boxes, some of which are integrated into the vehicle floor and also have to perform load-bearing tasks. These battery boxes are based on lightweight aluminium construction methods that have to meet high strength and tightness requirements.

In terms of manufacturing technology, the major challenge here is the distortion-free welding of the lid and base onto the surrounding frame structure. The EMPT enables a distortion-free welding, because the process does not introduce any significant heat into the workpiece and structure. Thus, it is also possible to weld relatively thin-walled cover plates onto thicker-walled frame structures.

Bus bars

Bus bars provide the power supply between the cells of a battery module or connect one battery module to the next. Hybrid aluminium-copper bus bars place special demands on joining technology. They are used if the cells have copper anodes and aluminium cathodes routed outwards, or if several battery modules are to be screwed together.

Electromagnetic Pulse Technology (EMPT) creates material-locking connections between aluminium and copper or silver-plated or nickel-plated copper, since no thermal energy is introduced. The welds created this way are characterised by a high mechanical strength under static, impact and cyclic loads. In addition, EMPT welded joints exhibit an extremely high electrical conductivity.

Packing bracing/tensioning straps for pouch cells

Lithium-ion pouch cell batteries usually require a housing that encloses and braces the cell stack. These housings often consist of two aluminium pressure plates, which are pre-stressed and connected with two tie rods. The connection of the tie rod and the pressure plates by means of EMPT welding is an advantageous connection option compared to fusion welding process.

This does not produce any heat that could damage the internal temperature-sensitive pouch cells. Another benefit: The EMPT weld seam has a very high strength. There is no thermal distortion as with fusion welding, and no loss of strength. This enables the creation of thin-walled solutions in lightweight design.

Cell housing

Lithium ion accumulators are mainly manufactured in 3 design versions:

  • Round cell
  • Prismatic cell
  • Pouch cell

Prismatic cells combine a high power density with good manageability, and operational safety. The outside of the cell consists of a rectangular cup, which holds the actual cell that is closed with a lid, which usually also contains the battery poles. Welding the cover into the housing, for example, with the aid of laser welding, however, requires very narrow gaps between the cover and the housing.

Electromagnetic pulse technology (EMPT), on the other hand, has very low requirements with regard to housing tolerances. Since EMPT welding does not produce any molten material, leakages are excluded that could develop during thermal welding due to a formation of pores.

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