Saturday, April 28th, 2012 01:02 pm GMT -6 Saturday, April 28th, 2012 01:02 pm GMT -6Saturday, April 28th, 2012 01:02 pm GMT -6
 
Lithium-air battery schematic diagram by Na9234

4x and 10x better batteries will be here sooner than you think.

 

 

 

Lithium Ion Batteries

The current high performance battery of choice is lithium ion. There are several variations on the market, including our familiar LiPo or lithium ion polymer cells. Unfortunately, they are far from an ideal solution.

Electric Cars

The biggest technology purchase that most of us make are cars. The auto manufacturers are always working very hard to bring to market the products that we want to buy. The auto industry spends about $17 billion dollars a year in research and new product development.

With the high cost of gasoline and better awareness of environmental issues, electric cars are in the spotlight. Problem is, the energy density (watt-hour/kilogram) of present day lithium ion batteries is not quite good enough.

A recent survey of electric car owners discovered that only about a third (33%) of them would buy an electric car again. If you take out the loyal Toyota Prius owners out of the equation, the number of happy owners drops to just a quarter (25%). Yes, there are a lot of unhappy electric car owners out there.

Electric motor technology is excellent, so the fault for all that dissatisfaction must be the batteries. They are simply too heavy, too big, and too expensive.

Performance Criteria

Designing a new battery is a very challenging problem. First, it must not cost too much. Right now it costs about $500 to manufacture a lithium ion battery that can store one kilowatt-hour of energy. We need to do better than that.

It must not be too big or weigh too much. This is the critical energy density measure. Lithium ion has been improving at about 10% a year. Right now, they can store about 150 watt-hours per kilogram.

The battery must be able to handle relatively fast charge and discharge rates. A battery that takes a month to charge up is no good, for example.

A car that is driven every day will probably be plugged-in every night. That’s 1,000 partial charge cycles over a period of three years. If the battery cannot support at least hundreds of full discharge cycles, then it will just not be practical.

It also must be relatively safe to operate. As I’ll explain in a moment, this might be the hardest criteria to fully satisfy.

Lithium

The element lithium appears to be a key component of every promising new battery technology. It is not hard to see why.

Lithium is the lightest metal and the third lightest element. Only hydrogen and helium are lighter. In fact, it is the lightest element that is a solid at room temperature.

It is also highly reactive, easily entering into chemical reactions. Lithium will spontaneously self-igniting when exposed to the moisture in the air. Lithium is so light that it floats in water, but it also reacts violently with it. A piece of lithium weighs about the same as a piece of pine wood.

It is this light weight, electrical conductivity, and ease of creating chemical reactions with other compounds that puts it at the top of the list of desirable battery materials.

Lithium Sulfur Batteries

Sulfur is another lightweight element that freely enters into chemical reactions with other compounds. It is also inexpensive. A very promising battery technology that is very close to being practical is lithium sulfur.

Lithium sulfur batteries have about the same density as water. They also have about four times the energy density of lithium ion. In other words, using this technology in your model airplane will let you use a battery pack that is four times lighter. Good times!

The main challenge with this technology has been the number of discharge cycles. The batteries on the market right now are useless after about 30-50 cycles. Not very practical.

But the latest research samples in the laboratory are showing much higher numbers of usable discharge cycles. We might be just a couple of years away from practical lithium sulfur batteries hitting the market.

Lithium Air Future?

If you talk to the research scientists, the holy grail of battery technology is lithium air. Lithium is a very light material, and stuff does not get any lighter than air! Actually, the lithium is reacting with the oxygen in the air, so a more technically accurate name for them would be lithium oxygen.

Advantages

Lithium air has the potential to have ten times the energy density of lithium ion. In fact, it could match the energy density of gasoline, which is really amazing. In other words, a battery pack would weigh no more than an equivalent gas tank.

A battery works by using a chemical reaction to generate electricity. An internal combustion engine creates kinetic energy by burning gasoline, also a chemical reaction. The key difference is that the chemical reaction in a battery is reversible. Batteries also directly generate electricity, a clean source of energy.

Air is cheap, so eventually these batteries could be quite inexpensive. They also promise to be able to handle five times the number of charge cycles as lithium ion batteries.

Challenges

There are many technical problems that need to be solved before these batteries are practical. The problems are many and very technical in nature, so I won’t go into their details here.

Any battery with this high an energy density will need to be protected against accidental physical damage. We are all well aware of the safety hazards that lithium poses. All of these issues would need to be carefully addressed.

IBM

Many excellent scientists around the world are working to solve these problems. In fact, there are about thirty labs around the world focused on lithium air battery research.

About three years ago IBM made a big splash with the announcement of a large research project to make lithium air batteries practical. They are calling it the Battery 500 Project, because their stated goal is to have a battery that can drive a practical car for 500 miles (800 km). Today’s lithium ion technology is not capable of doing this.

Even with the massive amounts of resources being devoted to solving the problems with the technology, even IBM says that a practical lithium air battery won’t be sold commercially at least until 2020.

I don’t know about you, but I cannot wait for these technologies to hit the market!

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