The transference number, on the other hand, shows a high value of 0.98  0.02 for the LiSTFSI membrane and 0.98  0.04 LiMTFSI membrane with 10 wt% of crosslinker. The lower crosslinked P(LiMTFSI-IBMA) 2.5%wt EGDMA membrane presents the lowest transport number of 0.91  0.04 in the series. These observed transference numbers can be correlated to the measured water uptake of the membranes. The lowest crosslinked membrane possesses higher water uptake (90%) hence facilitating counter-ion crossover resulting in lower cationic transport number compared to the higher crosslinked membranes with water uptake below 60%, similar to other reports in the literature. In the case of the benchmark Nafion TM 117 membrane, this has a 0.99  0.04 transport number, in line with the higher 10 wt% crosslinked LiTFSI membranes presented here.