Some Purdue scientists have developed a flow battery which does not require membranes to function:
Flow batteries are batteries whose internal contents are liquid electrolytes. They can be charged up the regular way via plug-in, or alternatively the liquid contents can be drained and re-filled with fresh electrolytes which are already charged up. This would allow an electric vehicle to have 2 different alternatives for recharging: using the plug-in way (eg. at home in the driveway), or else do a liquid refill for immediate full recharge (eg. at a pumping station).
The main limitation on such flow batteries, is that they use a membrane which can get clogged up and has to be changed fairly often. The new design from the Purdue researchers does not use a membrane, and removes that limitation.