Electrochemical characterisation was performed in Li + and Na + salt solutions to provide useful insight into the performance of CEMs for LiOH production after water splitting and electrodialysis of common Li2SO4 leachates. The electrochemical transport properties of the selected membranes were characterised by the Li-ion conductivity measured by PEIS (Figures S3) and their transport numbers measured by the Hittorf method, using aqueous LiCl solutions in both characterisations (Figure ). The transport properties at 25 o C show that membranes based on the LiSTFSI monomer possess a Liion conductivity of 3  1 mS cm -1 , which is approximately half of that of P(LiMTFSI-IBMA) membrane (for example, the conductivity of the LiMTFSI-based membrane with 10%wt EGDMA is 6.2  0.8 mS cm - 1 ). The higher conductivity of the P(LiMTFSI-IBMA) 2.5%wt EGDMA membrane could arise from a more uniform distribution of the aqueous solution across the membranes, compared to the LiSTFSI-based CEM where clustering of ionic groups is suspected due to π-π interaction of the styrene moieties, as previously mentioned. These bulk conductivity values are close to that of 0.1 M LiCl (ca. 8 mS cm -1 ) , indicating the low additional resistance introduced by these membranes towards ion transport in aqueous solutions. These are also in line with the measured values for the benchmark Nafion TM 117 perfluorinated membrane (Figure ) of 6  1 mS cm -1 . The conductivity of P(LiMTFSI-IBMA) 2.5%wt EGDMA (6  1 mS cm -1 ) remains nearly identical to that of the analogous LiMTFSI-based membrane with higher crosslinker content.