SOLiD was launched with the aim of bringing scalable manufacturing, recycling-ready design, and digital quality control into the DNA of solid-state batteries. Meanwhile, the solid polymer electrolyte (SPE) itself is being reinvented. This battery production line digital twin could become a template for future gigafactories, seeking to minimise waste and maximise efficiency. Pilot-scale slot-die coating of solid polymer electrolytes on a separator with a cross-linking capability. However, as the SOLiD project demonstrates, it is possible to integrate cutting-edge materials science, innovative production methods, and sustainability principles into a coherent roadmap.