[FoRK] Redox battery for EVs is recharged in minutes through electrolyte exchange

Stephen Williams sdw at lig.net
Wed Oct 21 17:52:23 PDT 2009

Cool.  As long as we don't get exploding / lightning-capable liquid at 


Redox battery for EVs is recharged in minutes through electrolyte exchange

Oct 15 2009 4:37PM | Permalink |Comments (7) |

In general, batteries are good at storing energy and not so good at 
charging or discharging rapidly. Supercaps, on the other hand, are 
excellent at fast charging/discharging, but not so good at storing 
energy over a period of days or months. Ideally, for energy storage and 
delivery for the next generation of electric vehicles, you need both 
characteristics. After all, it takes just 5 minutes to gas (or diesel) 
up a conventional car. The 4 – 10 hours it takes to re-charge today’s 
batteries is a sticking point for EVs of the future.

Frounhofer prototype EV w/redox batteryThe redox battery (which is 
shorthand for reduction-oxidation flow battery) offers a novel solution 
to the problem of charging times: Replace the discharged electrolyte 
with a fully-charged electrolyte much as you’d fill up an empty tank 
with more gasoline. Here’s the Wikipeida description:

“A flow battery is a form of rechargeable battery in which electrolyte 
containing one or more dissolved electroactive species flows through an 
electrochemical cell that converts chemical energy directly to 
electricity… Flow batteries can be rapidly "recharged" by replacing the 
electrolyte liquid (in a similar way to refilling fuel tanks for 
internal combustion engines) while simultaneously recovering the spent 
material for re-energization.”

The problem with redox batteries is that they can’t store as much energy 
as, say, a lithium ion battery –only a quarter as much. However, 
researchers at the Fraunhofer Institute for Chemical Technology ICT have 
refined the process for a redox cell that allows a four-to five-fold 
increase in energy storage, making it on par with lithium ion batteries. 
(No details so far on the exact refinements.)

The German government is aiming for one million electric cars being sold 
in Germany by the year 2020.

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