Darwinism is alive and kicking in the battery world (despite the threat the theory faces in other spheres).
Let me elaborate.
The Bible (or Koran, or Gita or… take your pick) for most battery-related topics is the book “Handbook of Batteries” by David Linden. It’s page after page of different chemistries that allow us to store charge. Some of these are primary batteries (not rechargeable) and others are secondary (rechargeable). Some operate at high voltages, others at low. Some are water-based, others are non-aqueous. Some operate at room temperature, others at higher (much higher) temperatures.
What is not listed in the book are a bunch of chemistries that can still be made into a battery but are not worth listing because no one is interested in using them.
One can (literally) go to the periodic table, pick up two elements from it, and make a battery from these elements. In all probability the resulting battery will not be very good, but you can certainly make something (think lemon battery).
Of these numerous combinations of anodes, cathodes, and electrolytes that make a battery, natural selection kicks in and we identify the ones that give us favorable performance. From this Darwinian process we end up with the batteries that we all know and love (although love may be too strong a word to describe our relationship with our energy storage device!).
Volta and Daniell could be playing with the Zn electrode, but it took putting it with a MnO2 electrode to make it a commercial success that endures to this day. Similarly, we could play all we want with a Li metal anode but it took pairing an oxide cathode with a graphite anode to make, what is come to be called, a lithium-ion battery for this concept to be a successful rechargeable battery.
Along the way, we have relegated a bunch of batteries to niche applications. No one has heard about a lithium-thionyl chloride battery because it’s used in obscure military applications involving missiles, nuclear bombs, remote launching, and a button in the White House (or so I’m told. Who knows). Similarly no one knows about the nickel-hydrogen battery, despite it being the chemistry that has the highest cycle/calendar life of all batteries we know of (the catch: it costs 100 times that of lithium-ion batteries. And you thought lithium-ion was expensive!). But it sits quietly in space powering our satellites day in and day out.
But natural selection does not happen overnight. There is a period of instability where it is not clear if a particular species (or battery chemistry) will make it or if it will left to the ash heap of history (being dodo-ed, so to speak). And similar to evolution, in battery chemistries, there is also such a thing as relegation to a niche (I will not give any examples from the animal kingdom because of the risk of offending someone). To survive you don’t have to be the fittest, you only need to be fit enough to have a market share, however small the share may be!
But let us stop this history lesson and get back to the modern day where I believe we are in the cusp of one (or two) such evolutionary change(s).
One is in the area of lithium batteries for vehicles.
The class of batteries that we have come to call lithium batteries is unlike the previous battery chemistries that we have encountered in that it does not represent a single anode/cathode/electrolyte combination.
When someone refers to a lead acid battery, they are talking about a battery that has a lead dioxide positive electrode and a lead negative electrode with sulfuric acid electrolyte. You may be using some carbon in the plate, or using a different current collector grid, but fundamentally you have not changed the voltage or capacity of this battery. In the same way a Ni-Cd or Ni-MH battery has a clear meaning in defining the anode/cathode/electrolyte.
When someone says they are using a lithium-ion battery that only tells you that the class of battery where the charge is carried by a lithium ion. The anode, cathode and (to a lesser extent) electrolyte are not specified. It could be a graphite/cobalt oxide battery that your cell phone uses or a graphite/lithium manganese oxide battery that your powertool uses. Both are called lithium-ion batteries.
In what I consider to be a public-relation disaster, the lithium battery community decided to club all these chemistries into one term, lithium-ion. If, instead of calling the graphite/cobalt oxide battery a lithium-ion battery, they had called it a, say, carbon-cobalt battery, today we would be talking about a carbon-manganese battery, a carbon-iron battery, a carbon-nickel battery, a titanate-nickel battery and so on and so forth.
If we had the foresight to do that (I use “we” to refer to the royal pronoun. I should not blame myself for this because I was but only a teenager when this happened) then it would seem like batteries are changing all the time. Instead, we get asked uncomfortable questions like “Lithium batteries have been around for 20 years. So… are you guys doing anything new?”. Not that I’m bitter or anything.
But let’s get back to the topic at hand.
Its becoming increasing clear that lithium-ion will be the choice for PHEVs in the near-term. What is not clear is which of these numerous chemistries will ultimately be the winner.
Would the low-cost, safe manganese system (the chemistry picked by LG Chem/CPI and Dow Kokam) win over the longer-life (presumably, although I have not seen such data) safe iron phosphate system (A123)? Would the higher energy nickelate system (Johnson Control and Saft) be the choice because of its higher energy despite its safety issues? Would the fast-charge capability of the titanate anode (Enerdel and Altair nano) be of any use in a world where even slow charging could be an infrastructure nightmare?
Each chemistry has its pros and cons. There are four criteria one looks for in a battery: Cost, life, performance, and safety. No one chemistry is the magic bullet that satisfies all these criteria. Each choice leads to a compromise. As of today, it appears hard to predict the winner.
We the consumer may be the ultimate deciding authority.
Will we choose a car with more trunk space and decide that we need to use the highest energy density battery we can get our hands on even if its only lasts 4-5 years or would we prefer something that may be a bit cheaper but that may be a small car that is only useful for a short commute?
Or maybe we will end up saying that gasoline is fine and that all this battery technology stuff is hype with no substance (now, that’s a blog post that is well worth making!).
We are at a time when we are unable to clearly see which one (or two or three…or maybe even none!) of these will be our future. GM and Nissan have chosen the manganese oxide system for the Volt and the Leaf, respectively, but this does not mean the race is finished. We live in interesting times, indeed.
Something similar is happening in the emerging market for grid-level electricity storage. With applications ranging from frequency regulation to storage of renewable applications, the time of discharge can range from less than a second all the ways to hours to days. It is clear that one battery will not serve as the solution for all these applications.
There are already many systems that are in various stages of deployment for grid applications. Lead-acid, sodium-sulfur, Ni-Cd, and Ni-MH are being deployed along with lithium-ion. And flow batteries are trying to make inroads. And similar to lithium batteries, flow batteries are a class and can represent anything from vanadium-based, halogen-based, or iron-based (I wonder if we are repeating our mistake with the lithium-ion by calling something a flow battery as opposed to, say, a hydrogen-halogen battery). Some of these systems have been around for a decades, while others are being developed as we speak.
And it’s not just batteries that compete in this application. Flywheels, capacitors, compressed air, and superconductors are jostling for space. Over the next decade, systems will be narrowed down and down-selected to ones that make sense. Something similar happened in the 90’s and in the early 2000’s in the vehicle space and technologies like electrochemical capacitors (or supercaps or pseudocaps) were slowly deemphasized. This is bound to happen in the grid storage space.
50 years from now, when we open the Handbook of Batteries (in whatever form we may be reading at that time), all these chemistries will be in the book. Question is, which chemistries will have the biggest chapters.