Flow batteries are based on the electro-chemical reaction produced by the interaction between two fluid electrolytes. The two electrolyte solutions are generally stored in separate external tanks and pumped through the battery cell. Energy storage capacity is largely governed by the size of the tank. This would make them ideal for smoothing out the energy from intermittent power sources such as wind, wave and solar. A quick way to recharge the battery is to just to replace the electrolyte; this property makes them attractive for use in electric vehicles.
Conventional flow batteries use a special (expensive) membrane to separate the two electrolytes but a team at MIT headed by Cullen Buie have produced a practical membrane-less design that relies on the laminar-flow effect produced by the two liquids flowing past each other in a channel to ensure there is little mixing between the two electrolytes.
Other research groups have already produced membrane-less flow battery designs but the MIT battery is the first to demonstrate one that can be recharged. The new design produces up to 0.795 W/cm2; three times more than other membrane-less designs and about 10 times better than Lithium-ion batteries.