Monday, September 6, 2010

A Brief History of Batteries- Part 2

Last week I posted on the need to understand the history of battery development and how this will influence the future of batteries.  We conclude today with Part 2 of this series. 

Chapter 3:  If it is sparingly soluble, then lets talk. 

The lead acid battery is the first rechargeable battery ever made.  Its endurance over 150 years is a testimony to its robustness (or to the fact that battery researchers can’t seem to find anything better even after 150 years.  It is all a point of view!). 

The lead acid battery undergoes what is called dissolution-precipitation.  This is the mechanism by which charge/discharge occurs in the battery.  Basically, you dissolve the compound in solution and then it precipitates out.

The behavior of the lead-acid battery is remarkably similar to that of the zinc electrode in a Zn-manganese oxide alkaline battery or for that matter to the lithium thionyl chloride battery.

But if the lithium thionyl chloride is not a rechargeable battery and the zinc-manganese oxide is not a rechargeable battery, then why is the lead acid a rechargeable battery? 

This is because the lead sulfate is soluble in sulfuric acid (which is the electrolyte) unlike the lithium chloride.  But it’s not as soluble as the zinc oxide in potassium hydroxide.  

Its solubility is not too much, nor too little.  It’s just right!  It’s referred to as a sparingly soluble salt. 

This feature of having sparing solubility is critical in making a battery that undergoes dissolution-precipitation recharge. 

This occurs because the reactants and the products are right next to each other.  This means that when you go in reverse, there is a high probability that things go back to the same place where they came from.  Not having something move around is a great way to prevent shape change.

Once you understand that solubility is key you begin to understand the decades that were spent on trying to change the solubility of zinc oxide in electrolyte using various techniques.  And you begin to start thinking about ways to encapsulate the zinc.  And you begin to wonder if you should never let the zinc precipitate as zinc oxide and if you should just keep it as zincate by, say, flowing it. 

All these perfectly valid ideas start to make a lot of sense.  What you can’t answer is if these ideas will succeed in solving the fundamental problem with the zinc electrode. 

But we should remember that in general, the lead-acid is not the greatest battery in the world when it comes to recharging.  Think sulfation.   Remember the blog post on battery rules where I Haiku-ed my way to better battery life?  Remember that sulfation occurs in the discharged state. 

The reason for this is also fundamentally connected to this dissolution-precipitation mechanism.  On the one hand, this mechanism allows you to make a good rechargeable battery, on the other hand, it also causes it to die in time. 

Moral of this story:   If you want good rechargebility, dissolution-precipitation is not a good idea, although we may be able to live with it.    

Chapter 4:  And you thought electroplating was easy.

Electroplating has been a gift that has been giving for decades.  Probably the last big development was the via-hole plating of copper for making semiconductor chip interconnects. 

In general, plating something uniformly is not easy, but it’s not an unsolvable problem either.  We do have a lot of smoothly plated stuff all over the place. 

This is until you try plating lithium (and a few other metals, including zinc).   Plating lithium is sort of important because this would be the charging reaction if you want to make your watch battery a rechargeable battery or if you want to make a Li-sulfur or Li-air battery rechargeable. 

People spent much of the 2-3 decades of the last century trying to make a rechargeable lithium (watch) battery.  The last time I check, I was asked to buy a new watch battery and not try to recharge it. 

This is because, in the case of lithium, the plating results in dendrites and lead to shorting of the battery. 

The reason for this starts with surface inhomogeneities that lead to nucleation of the deposition process in one spot, after which ohmic and transport effects lead to further amplification of this inhomogeneity.

That complicated paragraph is tying to tell you that it plates out like a needle sticking out of the electrode.  The needle can puncture through the separator and short to the cathode.  As I keep mentioning in these blog posts, shorting a battery is not a good idea.  Really, it is not.

Same problem happens in the zinc electrode.  Zinc wants to plate out as a dendrite instead of a smooth surface.  Same reasons as above. 

Every electrochemist that learns of this issue immediately thinks of 10 things to try that could solve the problem.   Turns out all 10 ideas probably don’t work.

There have been, literarily, thousands of studies on trying to solve this issue.  The most promising appears to be using a separator that is hard and prevents the dendrite from growing. 

But as of today, we do not have a method to prevent lithium dendrites at room temperature and give us good power capability.  It’s a problem that is still around. 

The moral of this story:  If your battery requires you to plate out a metal, it is probably going to be an issue achieving good rechargebility. 

And if you want to make a rechargeable Li-air or Li-S electrode, getting the lithium to recharge is, I’m pretty confident, a pre-requisite. 

Epilogue:  Rules to live by. 

So how do we make a rechargeable Li-S and Li-air (or zinc-air) battery?

If I knew that I would not be writing blog posts!

But we need to beat three things that history has taught us: 

1.     Avoid electrodes that require a plating reaction. 
2.     If you have a product that is highly soluble, you are in trouble
3.     If you don’t have any solubility, its worse

One can avoid all this by finding systems where no structural changes happen.  Thus were born systems like Ni-MH, Li-ion, and Ni-hydrogen.  These systems have their own problems, but atleast we are starting with something that has certain inherent advantage.   I will elaborate on these problems in the very near future when I delve into the present-day developments in batteries. 

But suffice to say, if you want to make the battery of the future, then you have to beat the three issues listed above. 

Along the way, you may make the batteries of the past also work.  



  1. Venkat, I have been following your blog for about a year now and your latest Part I and Part 2 Brief History inspired me to respond.

    I like reading your posts because they are so very interesting, clear and understandable. An inspiration to anyone who would want to write a technical article. Your writing style may seem lite, so as to now loose your readers, but you still manage to cover the topic in such fine detail that nothing is lost. Well done!

    From your Feb 28, 2010 post: "And if you are one of those using the lead-acid battery for deep discharge-cycling then you are in real trouble."...

    As it turns out, that's exactly what I use to run my home! I have a small bank of AGM batteries (6-210Ah 12v) connected to 700 watts of solar panels. I understand your toung-in-cheek statement but couldn't resist commenting.

    I look forward to each new post on your blog. Please, don't stop.

  2. For the dentrites problem: is not possible to restore the battery every x cycles?
    If the battery is configured in a roll, shouldn't be possible to mechanically unroll it, and press/heat the layers separately to flat the dentrites? Or maybe use some chemical treatment?

    I understand this is probably unpractical for some reason, but I would like to know why...

  3. Gregg- Thanks for the encouraging words.
    Luis- Most Li-metal batteries will be stacked flat cells. However, to open the cell and do what you are suggesting, you need a dry room (to keep the moisture out). And this is a manual (read expensive) process. Moreover, the lithium deposits not just in dendritic form, but also in a type of mossy deposit. This mossy lithium is very high in surface area and can be explosive. Best not to handle it.

    But before we even get to these solutions, I think the "restoring" of batteries by doing it an aftermarket treatment is a non starter. Too many liability issues for the person doing it and too much of a hassle for the consumer. Most Ni-MH cells fail because the electrolytes dries out. One could restore it by adding back water (like the old lead-acid batteries), but there is no consumer pull for doing this; hence its a nonexistent business.


  4. Another interesting post. When you posted about the three things that battery makers will need to overcome it got me wondering. Is this what hydrogen fuel cell makers are trying to avoid altogether? It sounds like there are unique problems with those, but that the interest in fuel cells is that they hope to avoid these 3 problems all together. No need to respond. I'm just following along and learning as I go. Thanks!

  5. Venkat

    Plate thru hole - when I did stuff like that about a decade and half ago, I would surface prepare drilled holes and deposit palladium, a very thin film as a chemical method, which would then bridge the two faces and in the inner layers in the case of Multi-layered board. Clip the board and then plate copper on the hole ...

    I was fascinated to say the least as to how a non-conductor could be made conductor by deposting a few micron thin stuff on the laminate ... the palladium bath could be a moody animal. It could dump stuff / precipitate and that was really costly ... I fell in love with a handbook (can't remember the name though) ....

    Another "bath" I loved to hate was the stripper. That which would strip the tin plated on the copper after stripping out the photofilm and the rest of the bare copper on the board to leave the circuit on. The vendor supplied tin stripper was of inconsistent quality, which would frustrate us ... the tin plated on would not fully strip off. I dug into our 7th sem corrosion handbooks and discovered hydrazine (I think so .. but my memory can be weak). Mixed it with potent nitric acid and after a few trials had my own stripper that worked well ... I was a bit cautious in using it on production line though for the fear that it may etch out fine lines

    People don't appreciate chemistry no more :) ...

    Good work da, as always .. but to quote Alice (in Wonderland), "what's a book without pictures?" ... TIP: use some pictures / graphs ... and keep it going


  6. The concept of periodical treatment of batteries looks interesting to me, but just for traction batteries. Moving your car/truck/bus to a service center each 100 cycle's or equivalent seems a workable solution for EVs.
    Some lead-acid battery restoring kits are on the market, and seems to be popular, so I just wonder if batteries can be designed with serviceability in mind.
    I was thinking in nickel based chemistries anyway, I understand Lithium is difficult to work with.

  7. Like reading your blog, please keep it up.

    Reading about the dendrite problem, I thought of of one of old time washing machines, the kind with two pinch rollers on top to squeeze the water out of the rollers? Now make the zinc or lead in a little continuous loop and keep squeezing in flat with the rollers.

    Kind of silly, but fun to think about.

  8. Maams- Good to see that you actually remember what you did last decade. As for me: the 90's were a blur! :-)
    As for the Alice in Wonderland problem: I spent 1 hour a week writing this blog. Getting a bit more professional will take more time which means less time to watch dogs on skateboards. Can't let that happen :-)
    But point taken. Will see what I can do.

    Luis- Its an interesting thought. It was not long ago that we were adding DI water in our lead acid batteries. We have gotten used to the luxury of not worrying about our batteries. I remember in India in the 80's where you take the battery that is dead to this dude who would open the top, check the voltage of each cell, and find the one that sulfated and replace that plate. Kept your battery running for many many years before you had to get a new one. For the Ni-MH, we can atleast start by adding some water!


  9. Hello Venkat. i like your blog very much .i am just wondering does anyone still working in the strange nickel electrode batteries?.why so many unresolved problem such as memory effect,secondary discharge, structural change in that material?what you think of that electrode's future ?

  10. Electrotherm India is acquiring Firefly Energy. Firefly developed a carbon graphite foam lead-acid battery. Electrotherm developed the alpha-weave technology based batteries. Could you share with us your thoughts on these two batteries, as well as on the bi-polar lead-acid batteries and on the bi-polar NiMH batteries?

    Thanks -- Arnold in marvelous Marin

  11. Venkat,

    I just came across this press release on a zinc-air fuel cell, and wonder if you might be willing to comment:

  12. As batteries play a key role in our day today life, it is important to know more explanation brief history about batteries. Thanks for posting the history and future about batteries

  13. Hi Venkat - saw this on the net today - anything to it?