Batteries for Static Applications

 To my way of thinking, we should try very hard to discontinue the use of batteries based on Li chemistry for static applications such as home batteries and grid storage.  One reason for this is that doing so would reduce the demand for Li and reduce its price.  This would bring down the price of Li batteries for mobile applications, reduce the price of EVs (Electric Vehicles) and hence widen the market for these cars and increase how fast we shift away from fossil fuels. 

 

Better still, some of the alternate chemistries produce batteries that are superior to Li batteries for static applications.  The reason we stick with Li for mobile applications is weight.  I'm not aware of any other battery that holds more power per kg(Kilogram) of battery than Li batteries.   Weight is of very little significance for batteries which are used for static applications.  So what other possibilities are there and how are they superior to Li batteries.

 

Liquid metal batteries

Conceptually one of my favorite types is the liquid metal battery.  These were developed by professor Sadoway and his team at MIT.  His favorite comment when he is talking about his battery is that if you want a battery that is dirt cheap, make it from dirt.  OK, it is not exactly dirt that is used but fairly close.  His batteries are based on Ca(Calcium), Sb(Antimony) and a calcium chloride salt.  They operate at about 500 degrees C(centigrade).  And, many experiments are ongoing to use different chemistries that need lower temperatures.

These batteries are kept molten by the electric current flowing through them during charging and discharging so there is some waste of power.  The effectiveness of the insulation is of primary importance.  When shipped the chemicals are simply dumped into the battery and the battery sealed.  When they arrive at their destination, the chemicals are heated up until they melt, separate into their layers and the battery is ready to go.  This sort of battery works well under heavy use but if left unused for some time, the components will eventually solidify and have to be melted again to regain function.  If left fully charged, when the components solidify, the battery is fully charged and ready to go when melted.  So what are the characteristics of these batteries.

They can be cycled between 0 and 100% charge with no damage.  This has a lot to do with their liquid nature.  Because all the components are liquid, they can't form spicules which in other batteries, grow and short out the plates.

They last far longer than Li batteries with no fade.  In fact I am not sure if they have even found a limit to the number of times they can be cycled from 0 to 100% and back again, before they show some fade.

They are completely safe to ship and so can be shipped by air, sea or land.  Ingredients are solid, mixed and you could short out the terminals with no effect.

They are made from elements which are readily available and cheap from multiple sources.  Antimony is mainly from the sulfide mineral known as stibnite.  It is not particularly expensive, ranging from US$2 to US$6 per pound at various times in the past.  Calcium metal is obtained from the electrolysis of a calcium salt such a Calcium cloride.

Liquid metal batteries operate under a wider range of external temperatures than Li batteries

ZnBr Batteries

There are two types of ZnBr batteries.  On is the flow/plating batteries.  It is essentially a Zn electroplating unit.   Zinc Bromide is dissolved in an aqueous solution and there are plastic horizontal 'shelves' in the battery dosed with C to make them conductive.  Under charging, the Zinc comes out of solution and electro-plates the plastic shelves.  The bromine which is heavier than the solution accumulates at the bottom of the battery.  Under discharge, the Zn and the Br recombine and zinc bromide dissolves into the solution.  It is not only possible but is recommended that the battery be discharged completely from time to time as this eliminates any build up of dendrites (spicules) that could short out the battery.  Thus it is useful to have your battery pack operate in multiple stacks.  One stack is completely discharged into the other pack on an established schedule.

The other type of ZnBr battery is the gel battery.  Instead of a solution, the electrolyte is in the form of a gel.  From the outside, these batteries look very much like a Lead-Acid battery and in fact the manufacturing process is very similar.  Apparently a Lead-Acid battery manufacturing plant can be converted to making ZnBr gel batteries with only modest modifications.  Gel batteries also need to be completely discharged from time to time.  To me they sound like a real winner since you simply stack them in series and parallel to get the voltage and capacity that you need. And there are no moving parts.  It remains to be seen what their cost per kWh stored will be and what their working life will be.

For their advantages, look back at the advantages of liquid metal batteries.  They are the same.

Redox Batteries

These batteries are based on elements with two or more valence states.  For instance Fe (iron) compounds exists in the Ferric (+3) state and the Ferrous (+2) state.  You have two tanks, one with an iron salt in the +3 state and one in the +2 state.  And you have a reactor through which these solutions flow separated by a membrane.  What is notable about such batteries is that if there is a small amount of leakage through the membrane, it is of little consequence.  It is still an Iron salt.  If you were using two different elements, you could quickly contaminate your solution.  If you want more capacity you simply need bigger tanks.  If you want more power you need more reactors.  I don't know how they get around the solubility problem.  The ferric state is far less soluble than the ferrous state*.

The other element used so far is V(Vanadium) which has multiple valence states.

*By the way, this is why there are huge deposits of iron in some parts of the world.  In the early years of the world there was no oxygen.  The oceans were anaerobic.  Iron was dissolved in the oceans in the soluble ferrous state.  Then stromatolites  developed.  These are sort of like reef building algae that take in Carbon dioxide and put out oxygen.  Apparently the oceans were full of ferrous iron.  As oxygen was produced, the ferrous iron used up the oxygen, converting it to ferric iron which precipitated.  Western Australia is a region where you can see this and in the shallow water there are still some living stromatolites.

Iron oxygen Batteries

These are also being worked on and apparently a very large one is about to be built.  As they discharge, iron is combined with oxygen producing rust.  When charging the rust is converted back into Iron and Oxygen.  An interesting aside here is that this is a way to produce iron from Iron ore which is essentially rust.  This would be a carbon free method of refining iron ore.  I have read speculation that you could put the oxides of other metals into the retort and produce alloys of iron such as stainless steel.

I'll add more batteries as they are shown and described.  So far it is hard to get reliable data on the longevity and other characteristics of these alternate batteries.