How would you broadly define the importance of the design of these cells and why NEXTCELL’s innovation is the key to transformation in the battery world?  What are the main activities performed during the scale-up and optimisation of electrode/separator formulations, compositions and interfaces?

In solid state batteries, the design of the solid-solid interfaces is the most efficient way to improve the electrochemical properties of electrodes and separators. So far, the most popular strategy to improve these interfaces is to in situ cross-link polymer structures with high conductivity. However, this strategy includes the use of complicated monomers and initiators that do not permeate well into the pores of the cathode particles and still need a separator to avoid short circuit of the anode and cathode materials.

The NEXTCELL strategy, is an integrated electrode/gel polymer electrolyte will be designed by using a crosslinked polymer network that will replace the cathode binder, the liquid electrolyte, and the commercial separator. To achieve this, we need to precisely design the properties of the electrodes (loading, percentage of active material, porosity, etc.) and the separator (stability, homogeneity, thickness, electrolyte retention, ionic conductivity, etc.) to obtain an integrated design that is low-cost and more environment friendly compared with the in-situ polymerisation method.

On the other hand, the manufacturing of high-quality cathodes and membranes requires the optimisation of the formulation and the mixing and coating protocol. In addition, the particle size distribution of the components, the amount and the type of the conductive binder and plasticizers must be adjusted, and their compatibility must be proven to avoid potential issues between the components during extrusion and coating. Apart from the impact of the extrusion during the kneading of the materials, the coating of the current collector, the calendaring and the application of the membrane onto the electrodes will have also an important impact on the quality of the electrode since the contact area between the separator and the electrode must be maximized by compacting both elements. In this regard, the calendaring temperatures, and density and porosity of the electrodes, before and after calendaring, must be studied.

Finally, the minimisation of unwanted reactions between the electrode and the separator and the achievement of favorable interface characteristics must also be addressed.