MIT's "Cambridge crude" flowing battery. Photo: Dominick Reuter/MIT News.

As long as electric vehicles (EVs) are stuck with conventional batteries, drivers will either have to park for long periods during recharging or swap out heavy, bulky batteries on the fly.

MIT students Mihai Duduta and Bryan Ho, led by professors Craig Carter and Yet-Ming Chiang and working under DARPA and ARPA-E grants, think they have a third solution: semi-solid flow batteries. MIT’s news office put out a press release about the work yesterday.

The new batteries don’t rely on novel chemistries. Instead, their innovation relies on a new form for conventional chemistries such as lithium-ion batteries. Instead of the more usual solid-form anode and cathode (the electrodes through which current flows into and out of a battery, respectively) the semi-solid battery has an anode and cathode as particles suspended in a liquid electrolyte and separated by a permeable membrane.

This enables the batteries to be pumped in semi-liquid form. Pull your EV up to a pump, the thinking goes, drain out the spent battery, and pump in a freshly charged one, just like gasoline. In fact the new batteries resemble a black, oozing goo, a bit like crude oil. Hence the team’s nickname for the stuff: Cambridge crude, after MIT’s location.

The team promises ARPA-E that they’ll have a prototype ready to scale up for mass production as EV batteries before the close of 2013.