The diffusion of metal ions in polymer electrolyte membranes is an important parameter for aging and capacity loss in elec-trochemical cells. Here, the diffusion coefficients of vanadium ions in Nafion membranes are studied. These are important todescribe transportation of the ions through the membrane separator in vanadium redox flow batteries. Commonly, the concen-tration change in dialysis cells is used for this purpose. They yield an average value on all influencing factors. For a better under-standing of ion mobility in these membranes, a direct study of ion transport in the membranes is a highly valuable addition. Thiscan be done by obtaining concentration profiles. Here, we have applied laboratory based mXRF, as it is excellently suited to probevanadium in hydrated membranes. Two processing methods were compared. It was determined that the diffusion coefficientsdecrease from V3+ > VO2+ > VO+2 , with values of 22 × 10−11, 16 × 10−12, and 8 × 10−12 m 2 /s.
Mahler et al. (Wed,) studied this question.