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Fraunhofer ICT Working on New Redox Flow Batteries with Improved Capacity for EV Applications

15 October 2009

Redoxflow
Working principle of a redox flow battery. Source: Jens Noack, Fraunhofer ICT. Click to enlarge.

Researchers from the Fraunhofer Institute for Chemical Technology ICT in Pfinztal near Karlsruhe are developing improved redox flow batteries for automotive applications in an attempt to address storage capacity and charging time limitations of current Li-ion battery solutions for electric vehicles.

Redox flow batteries (RFB) are chemical energy storage devices, and use dissolved redox couples (an oxidizing agent and a reducing agent in an electron transfer process) held in separate external tanks; electricity is converted in a separate power module. The two fluid electrolytes containing metal ions flow through porous graphite felt electrodes, separated by a membrane which allows protons to pass through it. During this exchange of charge a current flows over the electrodes, which can be used by a battery-powered device.

Rfb
Experimental cell design for a Vanadium Redox Flow Cell. Source: Jens Noack. Click to enlarge.

During discharge the electrodes are continually supplied with the dissolved substances from the tanks; once they are converted the resulting product is removed to the same or another tank. The devices could theoretically be recharged at a station in a few minutes. “The discharged electrolyte is simply pumped out and replaced with recharged fluid. The pumped-off electrolyte can be recharged at the gas station, for example, using a wind turbine or solar plant,” says engineer Jens Noack from ICT.

A number of different redox couples are possible; Fraunhofer has been doing some detailed work with conventional vanadium redox flow batteries for a number of years. For the new system, Noack says, “We are using different redox couples than in well-known redox flow batteries, but at this moment we can’t say what it is in detail.” Noack presented Fraunhofer’s work on conventional vanadium redox flow batteries at the just-completed 216th meeting of the Electrochemical Society in Vienna, Austria.

Redox flow batteries theoretically offer a number of advantages:

  • high energy efficiency >75 % (> 95% found on lab scale)
  • long calendar life, excellent cycle ability (> 10,000)
  • flexible design
  • fast response time
  • overcharge and over discharge tolerant
  • low maintenance costs
  • low self discharge or no discharge depending on pumping of electrolyte

Up to now, however, redox flow batteries have had the disadvantage of storing significantly less energy than lithium-ion batteries. The vehicles would only be able to cover about a quarter of the distance—around 25 kilometers (15 miles)—which means the driver would have to recharge the batteries four times as often.

The Fraunhofer team has increased the capacity four or fivefold, to approximately that of lithium-ion batteries, according to Noack. The team has already produced the prototype of a cell, and is in the process of assembling several cells into a larger unit and optimizing them.

This work is being carried out with colleagues from the University of Applied Sciences, Ostphalia, in Wolfenbüttel and Braunschweig. They are testing electric drives and energy storage units on model vehicles that are only a tenth of the size of normal vehicles. The research team has already built a traditional redox flow battery into a model vehicle. A vehicle on a scale of 1:5 is on display on a test rig set up at the eCarTech in Munich (Hall C3, Stand 424) from 13 to 15 October.

In the coming year the researchers also want to integrate the new battery, with four times greater mileage, into a model vehicle.

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October 15, 2009 in Batteries | Permalink | Comments (14) | TrackBack (0)

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Comments

That might be the answer to all pending issues including recharging speed and cycle number.
Remaining issue - price.

$1000/Kwh for lithium batteries just isn't going to cut it.

The original designs from ~30 years ago vanadium *.*.
were a great idea, that has'nt changed.
except:
In the coming year the researchers also want to integrate the new battery, with four times greater mileage, into a model vehicle.

A game changing improvement, if they can do it.

Zn air non rechargeable battery can potentially provide a huge energy density, just just need to recycle the ZnO at the station

Automotive Li-ion mass production costs will be <$150 KW/h

Plug in hybrids are more than sufficient for cutting automobile operation cost. Automobile fuel use per mile could be cut very usefully just be reducing road speed limits.

Flow batteries are very useful they could be used for faster recharging of cars and save wind or off peak power to do this. VRB went bankrupt because of the greed of speculators, so did other flow battery companies.

REVOLT claims to have a rechargeable zink air. Battery improvement is not necessary for plug in hybrids. The thought that electric cars must be very high powered is the biggest barrier. How many horsepower do you need in the garage(Personenkraftwagenabstellgebaeude) or stopped in traffic or parked at work; none. Home and office Combined heat and power is a fantastic use for flow batteries. ..HG..

I thought the Vanadium-Lithium-ion battery (as in the Subaru Ge4 - which has 5 times the range of Li-ion alone) was a good reason to get excited about vanadium, but this research is leading to a 100% vanadium redox battery for cars. The VRB will be the battery of choice for load-leveling renewable energy output for the power grid which will get a huge boost from our friends on Capital Hill. And now that the patent restricting VRB development/use has expired... watch out lithium here comes vanadium.

To learn all the latest about vanadium follow my tweets @VanadiumJoe. For now, read this: http://www.energydigital.com/Magazine.aspx?id=1728

Present cost of Lithium batteries is $1000 per Kwh energy storage < $150 per Kwh is pie in the sky.

Ah..but people with large egos typing it want you to believe it is true, because they said so, they can see the future, they are omnipotent and they can walk on water.

@Mannstien,
Check out the Thundersky site. Anyone can order $350/kWh batteries right now...with no volumes.

http://www.thunder-sky.com/home_en.asp

Imagine what you could get three years from now with some major volume commitments. Maybe $150 is very possible.

The AIST researchers who recently made the breakthrough with the Li-Air battery also proposed a redox-like operation.

They suggested that the aqueous electrolite and the metallic lithium be simply replaced at the refueling station and regenerated separately.

Li-air chemistry has HUGE energy density, with redox-like operation, cars could easily have a thousand mile range and 5 minute refueling times.

Vanadium-redox is an already well-developed technology (e.g.: you can buy 5kw - 25kwh units for powering your home). However, its energy density is not very high and its recharge efficiency is only ~70%. At least, the current products seem to offer these parameters.

May the best technology win.

By 2020/2025 the world needs much lower cost, higher energy density batteries or e-storage units.

The 2020/2025 mass production goals should be 500 to 1000Wh/Kg at a cost of $150 to $250/Kwh.

In the coming year the researchers also want to integrate the new battery, with four times greater mileage, into a model vehicle.
club penguin cheats

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