Cell Joining Techniques

There are many cell joining techniques. When we say joining we mean external electrical cell joints to busbars, some of these will be specific to certain cell formats. Firstly though it is good practice to think about the properties and features of these joints:

• electrical
  • low electrical resistance of the joint
  • low resistance maintained over lifetime
• mechanical
  • appropriate pull strength
  • intermetallic and material corrosion resistance
  • vibration durability
  • low mechanical input to cell during joining process
• thermal
  • low thermal resistance
  • low heat input into cell during joining process

The selection of the process will also be dependent on the design and layout of the cells and busbars.

Busbar to Cell Connectors

The busbar to cell connectors need to have:

• low electrical resistance
• mechanical integrity

For some applications they need to also have good thermal conductivity.

The joining options are:

• Soldered
• Welded – see also Cleaning Battery Terminals before Welding
  • resistance weld
    • Anti-Shunt Tab Design – there to enable a better resistance micro spot weld.
  • laser weld
    • atmosphere
    • vacuum
  • ultrasonic bonding
  • micro tig welding
  • electron beam welding
  • friction stir welding
• Mechanical
  • bolted
  • sprung
  • micro-clinching

For each of these techniques it is important to understand how they work, the properties of the joints and examples of their application in battery cell to busbar assembly.

Cylindrical Cell Joining Methods

Cylindrical cells are commonly joined using several methods, each with distinct advantages and disadvantages depending on the application. Here are the most popular methods.

References

• Das, A., Li, D., Williams, D., & Greenwood, D., Joining Technologies for Automotive Battery Systems Manufacturing, World Electric Vehicle
• Y. Zhou, S. J. Dong & K. J. Ely, Weldability of thin sheet metals during small-scale resistance spot welding using an alternating- current power supply, Journal of electronic materials 29, 1090-1099.
• Zhijia Du, D. L. Wood III, C. Daniel, S. Kalnaus & Jianlin Li, Understanding limiting factors in thick electrode performance as applied to high energy density Li-ion batteries, Journal of Applied Electrochemistry 47, 405-415.
• Martin J. Brand, Philipp A. Schmidt, Michael F. Zaeh, Andreas Jossen, Welding techniques for battery cells and resulting electrical contact resistances, Journal of Energy Storage, 7-14.

Note: we are always interested in posting articles from research teams and companies with a depth of knowledge in the subject. Please contact us if you would like to contribute to this section.

See also

• Welding – the broader set of joining processes used across cell, module and pack assembly
• Manufacturing – where cell-to-busbar joining fits within module and pack assembly