03 October 2010

New Nickel-Lithium Battery Has “Ultrahigh” Energy Storage Capacity

Lithium-ion batteries are great and allhaving heralded in a new age of portable electronics and allowed for the possibility of mass-market electric carsbut they have a few major drawbacks. For instance, they have a propensity to catch fire and explode and, although they have a much better energy storage capacity than say lead-acid or nickel metal hydride (NiMH) batteries, they still weigh too much to packmore than a couple hundred miles of range into a passenger car.

Your standard issue Li-ion battery can hold about 55 watt hours of energy per pound of battery. Todays modern electric cars need about 25 kilowatt hours (kWh) of power to go 100 miles. As an example, TheTesla Roadster has a 53 kWh Li-ion battery pack and goes just a bit more than 200 miles on a fullcharge.

Doing some calculations, youll find that the weight of a Li-ion battery quickly becomes the limiting factor in increasing the driving range of an electric caryou need roughly 500 pounds of Li-ion battery for every 100 miles or range, give or take. Taking the Roadster as an example again, its battery pack weighs about 1000 poundsjust a bit more than 1/3 of the entire cars weight.

Taking this dilemma head-on, Researchers at Japans National Institute of Advanced Industrial Science and Technology (AIST) have combined the recent discovery of a special glass ceramic film called LISICON with what would normally be two incompatible battery materialsNickel and Lithiumand have succeeded in making the worlds first Ni-Li battery. It can hold more than 3.5 times the energy of Li-ion batteries and doesnt run the risk of catching fire.

How Did They Do It?

A typical battery works by separating a cathode (positively charged) and an anode (negatively charged) in some sort of electrolyte. The difference in charge between the cathode and anode is what generates electricity. In a Li-ion battery the electrolyte is an organic solid substance (part of what makes it prone to catching fire), whereas in both lead-acid and NiMH batteries the electrolyte is a liquid (much less prone to catching fire).

Usually the electrolyte separating the cathode and anode has to be the same substance. Because of this, the cathode and anode materials both need to be compatible with the same electrolyte, which has restricted the choice of cathode and anode materialsup till now.

By separating the cathode and anode with the special LISICON material, the AIST researchers have found that the cathode and anode can be placed in two completely different electrolytesallowing for much greater flexibility in the choice of cathode and anode materials.

Further reasoning that by combining the best properties of NiMH batteries with those of a Li-ion battery they could obtain an ultrahigh energy density, they placed a nickel hydroxide cathode in a liquid electrolyte and the lithium metal anode in an organic electrolyte separated by the LISICON glass.

And voila! The worlds first Ni-Li battery was born. Their experimental battery cell has already obtained a practical energy density of about 194 watt hours per pound of battery material.

Imagine if that Tesla Roadster had 1000 pounds of Ni-Li batteries in itthats a 700 mile range. Certainly an improvement, no? Now we just need to figure out how to fully charge it in a reasonable timeon a standard household outlet it would take the better part of three days.

Granted the Ni-Li battery has some hurdles to overcome, namely that is an incredibly complex battery and manufacturing it may be difficult. Also, the LISICON glass would need to be durable enough to resist breakage over the expected life of the battery. But humans have figured other more complicated things outlike thisso its really just a matter of time.

No comments:

Post a Comment

All comments are welcome!
Please use the Name/URL option (you don't have to register, just enter a screen-name) or sign your anonymous post at the bottom.