The geometry and performance of lithium-ion batteries (LIBs) are significantly influenced by the electrode arrangement. Established industrial processes encompass coiling (round or prismatic) and Z-folding, for example. In addition, greater focus continues to shift to individual sheet stacking. Radii-dependent drawbacks such as uneven mechanical stresses on the electrode and inhomogeneous heat distribution are consequently reduced. This creates the potential to increase power densities, cyclic stabilities, longevity and safety. Furthermore, non-linear ageing mechanisms such as occur during coiling are minimised. However, systems currently available for ultra-rapid stacking processes are more sufficient so for laboratory requirements than for those in mass production.
This is where ZSW comes into play, focussing together with industry partners in the STACK project funded by the German Federal Ministry of Education and Research on developing an ultra-rapid “stacker” for the high-precision individual sheet stacking of electrodes. The flexibility of individual sheets represents a major challenge. Development of a non-woven material-based full ceramic separator with laminating capability is planned to compensate, which will prove an important technical innovation. Initial successes with laminating capable separators have been achieved with the ZSW research platform FPL’s “electrode winder”. For instance, lithium-ion cells with laminating capable separators demonstrate reduced coiling thickness (see fig. below). This allows a greater number of electrode layers to be incorporated per cell and thus the energy density to be increased.