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These are batteries based on the element Sodium (Na) and sulfur (S) or molten chloroaluminate (AlCl4).

See also:

NOTE: is should be emphasized that the sodium-nickel-chloride (Zebra) battery is *VERY* different than the sodium-sulfur battery: it is *MUCH* safer than the sodium-sulfur battery (which really has no realistic application to vehicles) whereas the sodium-nickel-chloride (Zebra) is a very definite contender.

Information from Larry

This part was contributed by Larry Gales.

Normally we prefer non-pov, third person, or matter of fact content, but we sure do appreciate any help that we get no matter the form.

Feb 2009 Info

An Argument for Switching from LiIon to Molten Salt Batteries

I have long been concerned by the exclusive concentration of effort on Lithium batteries, as they appear to lead to a very high cost and unsustainable future for EVs. In contrast, two of the molten salt batteries, the sodium nickel chloride (Zebra) and its nearly identical cousin, the sodium iron chloride battery appear far more affordable and sustainable.

Below are some web sites and reasons for believing that the concerns are real. It appears that a major part of the problem is that very few people, especially in this country, and even those who have a great deal of technical experience with EVs are simply unaware of the virtues of these batteries. So I hope that making their properties more widely known will influence those people who control the research into EVs.

Here are three web sites that address the problem:

  • First, these molten salt batteries are equal (or slightly superior to) the safe type LiIon batteries in terms of:
    1. Maintainability: all 3 are sealed zero-maintenance batteries
    2. Durability and long life: these salt batteries have a proven (not simulated) 10 year calendar life, a 1000-1500 deep (%80) discharge cycle life, and unlike LiIon, a nearly unlimited shelf life.
    3. Safety: as far as I know, these salt batteries may be the only advanced batteries that have passed all European safety tests: wrapped around a pole, roasted in a petro fire for 30 minutes, submerged in water, over-charged, and over-discharged
    4. Energy density: this controls the driving range of an EV. The Zebra in the Th!nk EV has an energy density of 114 wh/kg, some Zebra's are 120 wh/kg, and the sodium iron chloride battery is only 9% less, so it is well over 100 wh/kg. In comparison, the safe LiIon batteries typically range between 80 and 110 wh/kg.
  • Second, the salt batteries are definitely superior to LiIon in terms of:
    1. All weather capabilities: they are virtually unaffected by the most extreme climates/temperatures anywhere in the world
    2. Practical experience: these batteries have been in production for over 10 years. For the last 18 months Zebra powered delivery vans from Smith Electric and Modec in England have been rolling off regular production lines.
  • Third these salt batteries are *dramatically* superior to LiIon batteries in these ways:
    1. Dramatically lower cost. The lowest estimate that I have seen for the cost of safe LiIon batteries, expected between 2011 and 2015 and in large scale production, is $350/KWH. In contrast, without any real R&D, the Zebra in large scale production should cost $130/KWH and the sodium iron chloride battery should cost well under $100/KWH. Note that when Lithium becomes scarce, the cost of safe LiIon batteries will significantly rise, whereas there will never be any scarcity of salt and iron for sodium iron chloride batteries. So there is about a factor of four cost difference which favors the sodium iron chloride battery.
    2. Resource limits: there are about 1 billion cars, trucks, buses, etc. in the world today. At 0.3 kg/kwh, 1 billion 40 KHW would require about 13 million tons of Lithium, which equals the entire world's estimated reserve base. But soon, India, China, and other countries will shoot the number of vehicles to 2 billion. For a single application to consume the entire world's supply of a valuable resource should raise major alarm flags.

Now these salt batteries do have some disadvantages

  1. The power density is less: a 40 KWH salt battery produces a bit over 80 HP, which is somewhat sluggish for a car (but excellent for commercial vehicles). However, power density can be easily and affordably increased. For example, a small 1 KWH LiIon battery can belt out 40 HP for short periods of time, or you could use ultra-capacitors, or for that matter compressed air or flywheels. Power density is much easier to attain than energy density. Lots of 1 KWH LiIon batteries would not dramatically increase the cost of a vehicle or strain world resources.
  2. Current salt batteries do not charge quickly. However, the great majority of charging will be done at home, where fast charging is not even possible with any battery. Also, rapid battery replacement, being pushed hard by Project Better Place, and small trailer gen-sets sidestep much of the problem.
  3. The need to plug-in the battery at least once/week to avoid freezing (which does not destroy the battery but reduces its life). However, its hard to imagine that if you have a carport or a garage that you would leave it unplugged for an entire week, unless you car is stolen and abandoned (but the battery life may be the least of your worries in that case).
  4. Energy waste: a large 40-50 KWH battery uses 165 watts to keep itself hot, except when in use and for 4 hours afterward. In the worst possible case, where you never ever drove the car but simply kept it ready for use, you would waste $11 or $12 per month, which is a tiny part of the costs of owning a car. In the more usual case, you might waste $0 to $7 dollars a month, if you drove it as most people do, and used the free heat from the battery to provide some or all of your car interior's heat.

So neither individually, or collectively, do these represent major limitations.

Aug 2007 Info

Here is some information about the Zebra battery which was invented nearly 30 years ago in the "Zeolite..." laboratory in South Africa (hence the name Zebra) and developed over a period of over 20 years in Europe.

At the end of this article are links to a number of issues and Zebra powered vehicles.

It seems to me that the obvious solution to the BEV using available technology is to combine a large sodium nickel chloride (Zebra) battery with a small high power density battery, such as the ones from A123 or AltairNano. This should yield a highly affordable, safe, reliable, long range, high performance EV with current technology. So why it is never considered?

The Zebra battery almost has it all:

  • It uses only cheap, abundant, non-toxic materials. The only moderately expensive material is nickel, and it uses only about $17/kwh, perhaps 1/4 that needed by NiMH.
  • Right now it is produced by MEA-DES in Switzerland at a rate of a few thousand batteries/year, but in larger mass production its manufacturing cost would be less than $75/kwh, and could be sold for $110/kwh, far cheaper than any other candidate battery
  • It has a very long storage life, calendar life, and cycle life, good for 200,000 - 300,000 miles in a car.
  • It is the only candidate battery that is immune to the most extreme climates on earth: death valley, northern Siberia, Antarctica, affect it hardly at all.
  • Despite the fact that it is a high temperature battery, around 500-600 degrees F, and uses liquid sodium, it is a very safe battery. A battery contains a large number of cells, each of which contains a thin layer of sodium in an aluminum structure around a nickel chloride core. If the cell is penetrated, it quickly congeals to a solid mixture on mostly aluminum and table salt. It has passed all European auto safety tests: submerged in water, over-charged, over-discharged, roasted in a petroleum fire for 30 minutes, and crashed into a pole at more than 30 mph. In fact, it is the *only* battery that has passed all the Eurocar safety tests.
  • It has more than a million miles of road testing behind it and 3-9 ton delivery vans powered by Zebra batteries with a range of 100-160 miles are rolling off the production lines in England as we speak (Smith Electric and Modec)
  • It has a very high energy density, nearly 50 wh/lb, or well over 100 wh/kg, better than those LiON batteries that are safe enough to be used in a car.

The only not so good features are:

  • While it does not leak electricity like other batteries, it does leak heat, and if you leave it BOTH un-driven AND un-plugged for more than 3 days in a row, you will have to plug it in and spend a day or more heating it up again -- so you don't do that (it does not hurt the battery but it would be inconvenient)
  • Its power density is mediocre: plenty good for cruising at 70-80 mph, but sluggish for acceleration. A 50 KWH battery good for about 220 miles range only produces about 115 HP, so that is why you want to add the small high power LiON batteries, which would be much too expensive for the entire battery pack, but economical in the small size needed.

So why does no one in this country, as opposed to Europe, ever even mention the Zebra battery?

Here are some links to Sodium Nickel Chloride (Zebra) battery vehicles and issues (note that some of the links take up two lines):

See Also