Friday, June 10, 2011

Liquid battery could change the world

Chemical batteries or cells are ubiquitous and for decades, have represented the power source for a huge number of portable consumer electronics devices.

Today, the battery is becoming even more important as we look to ween ourselves off fossil fuels for our transport fleets by way of electric vehicles.

The big problem with all the existing battery technologies however, is the time required for recharging.

Even the most advanced cells, such as the lithium-iron-phosphate types being considered for the next generation of electric vehicles, still have a recharge time that is usually measured in hours, not minutes.

There are two factors which dictate this protracted recharge time:

The first is the amount of electrical power that must be available to replenish the battery. In the case of an EV, this represents many kilowatts and, given that the average wall-socket only supports 2-3KW of load, clearly constitutes a serious bottleneck.

Then there is the battery chemistry itself. The charging process is not a lossless process and therefore a percentage of the power fed into the cell is converted to heat, resulting in a temperature rise that can adversely affect the cells. The rate at which the chemical processes in the cell take place can also limit the recharge speed.

Well imagine a battery that can be recharged just as easily as you currently fill your petrol tank...

That's what researchers at MIT are hinting at with their new liquid-plate battery technology.

Instead of using solid plates separated by an electrolyte, like traditional cells, these new batteries use a suspension of minute particles in a liquid which acts as both the plate and the electrolyte.

Two different fluid suspensions, one for the cathode and one for the anode, are poured into the battery and kept separate by a permeable membrane. This membrane allows the transfer of electrons and ions between the two fluids but does not allow them to actually combine.

When a battery becomes depleted, the cell's contents are drained and then replenished with new liquids in a very quick and efficient process.

It is hoped that, once the right chemistry is developed, the used fluids will then be reconstituted in a separate "recharge" process.

Once (or should I say "if") this technology is perfected, it could be the single largest step in the evolution of electric transport.

When you think about it -- it's obvious, isn't it? But aren't all the good ideas just staring us in the face?

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