Production of hydrogen and solid lithium hydroxide

The problem addressed by the invention is that of specifying a process for producing lithium hydroxide that is very energy-efficient. The process should in particular manage without using thermal energy. As a raw material, the process should be able to process Li-containing waters that arise when used lithium-ion batteries are digested. The LiOH produced by the process should be of sufficiently high purity that it can be used directly for the production of new LIBs. The process should achieve a high throughput and have a low space requirement so that it can be combined with existing processes for reprocessing used LIBs or for producing new LIBs to form a closed, continuous production cycle. The process according to the invention is an electrolytic membrane process that is operated using an LiSICon membrane. A particular aspect of the process is that the electrolysis is operated up to the precipitation limit of the lithium hydroxide.