Highly scalable and solvent-free fabrication of a solid polymer electrolyte separator via film casting technology

In order to develop competitive all-solid-state batteries, cost efficient and highly scalable manufacturing methods need to be identified and evaluated. In this work, the scalable production of a polymer solid electrolyte (SPE) separator was investigated to gain deep knowledge on how the process parameters influences product quality and reproducibility. In detail, a sustainable, solvent-free manufacturing route for the fabrication of SPE films based on a PEO based block copolymer through a novel, highly scalable film casting process was developed. The scalability, energy consumption and the SPE separator properties film thickness, density, ionic conductivity, polymer degradation and lithium salt distribution were evaluated in comparison to a reference calendering process. Compared to the considered reference process, the developed film casting process showed improved precision at higher throughputs regarding a constant film thickness below 30 μm and SPE density. The novel film casting process showed a significantly lowered energy consumption, which is of major importance with respect to production costs and sustainability. At the same time, the electrochemical performance was preserved with an ionic conductivity of approx. 0.2 mS cm⁻¹ at 80 °C as well as a rate capability of approx. 60 mAh g_LFP⁻¹ at 1C discharge rate.