Over the last 15 years the whole battery community has slowly starting looking at one single system: the lithium battery. I remember going to an Electrochemical Society meeting in 1996 to present a paper on Ni-MH batteries. My talk was scheduled for Monday AM (read prime time). By 1997, I was down to Wednesday, and by 1999, I was talking Friday PM with 3 people in the room (yours faithfully, the presenter before me, and the one after me. Even the session chair was missing!). If one was looking to read the signs, this was it.
This week I was talking to someone who was interested in electrochemical capacitors (more on this later) and he asked if all the research was only on lithium batteries or do we do anything else? I had to admit that there was very little that goes on other than lithium. Since that conversation, I've been thinking about the effectiveness of having all our eggs in the lithium basket and wondering if this is a good thing.
First off, I should note that when it comes to batteries, lithium has a lot more energy per weight or volume compared to the other batteries we have been looking at in the past. Its got 4-5 times the energy per mass as a lead-acid battery and 2-3 times that for a Ni-MH battery. There is still a lot more that can be done with this chemistry and so there is a reason for us to obsess about this. When it comes to batteries for a plug-in or an electric car, we need all the energy we can get and working on lithium does make a lot of sense.
But does this mean that there are no advances that can be made in other energy-storage technologies? And even if we do make advances in these other areas, does it really have any impact in the world? Let's look at the second question first.
Remember that we have argued that batteries for plug-in and EVs are going to very expensive and that they may not last very long either. Its far from given that we will indeed be driving in these battery-powered cars. We may not be cost competitive with gasoline for a while, and we may end up seeing that these cars as a niche market. Maybe hydrogen will take off as a carrier and batteries as a primary energy source will not be the future. The future is far from clear, but it is possible that we may end up finding out that hybrid vehicles (like your out-of-control Prius) may be the most common vehicle on the road for a decade. But even your Prius is not as popular as it could be because its expensive.
But when it comes to hybrids, its not energy that is critical, but the power. Many batteries, including the lead-acid and the Ni-MH batteries have the power capability to satisfy the requirements for a hybrid. The cheapest battery we know of is the lead-acid battery. So if we can get the power with a lead-acid battery and if its the cheapest battery we know of, why don't we use this for hybrids?
Remember the post on battery rules where we asked you to "keep you lead-acid charged"? You may also remember that this was important because if the lead-acid is ever discharged, it sulfates and causes capacity loss. In a hybrid, the battery is always sitting partially discharged. This is important because if you hit the brakes, you need to be able to accept the juice in your battery. Hybrid batteries operate around 50% state of charge because of this. Try using a lead-acid at a partially discharged state and you will have a dead battery long before the new car smell fades.
But something strange happened to the lead-acid battery when the rest of us were obsessing over the lithium battery. The companies working on this started using activated carbon in their negative plates. Lo and behold!, these companies started seeing much better cycling with this new concept. Some companies are doing variations of this by replacing the negative electrode with activated carbon so that its a hybrid between a battery and a capacitor. Companies doing this are promising all the cycle life you need at 1/4 the cost of the Li-ion for hybrids! The catch: they don't yet know if the batteries will last 10 years. So they can get the cycle life, but its not clear they can get the calendar life.
But that is not the point I want to make. What amazes me is that someone can take a 150 year old technology and show that they can make it better by solving a particular problem that stops it from being used for an application. I'll take a bet that 90% of the researchers in the field of batteries don't know of this advancement (all right, that may be a bit of an overstatement, but you get the point). I had worked on a mathematical model for a lead-acid battery a few years ago where I had included some features in the model that make it easy to address this advance. A person in the lead-acid industry had sent me a mail when these findings started coming out asking if I was doing anything to address these new findings. I had to (sadly) tell him that although this was interesting, I had no way of doing anything because all my funding is in the area of lithium batteries.
But what if we find out that the new lead-acid batteries do have a calendar life issue. Should we leave it to companies to figure this out by themselves, or should battery researchers be helping with this effort to see if we can find a solution? It seems to me that the answer has to be the latter, but I fear that this will not be the case. The chemistry is considered too "un-sexy" (for want of a better word). Try presenting a paper on this at the Electrochemical Society meeting and you will asked to present on a Saturday morning (after the conference has ended!). To be fair there has recently been government support for these technologies for trying to commercialize them; but I don't see anything happening at the research stage.
The story of the lead-acid is far from unique. The few (very few) folks who continue to work on the Ni-MH system talk about the use of carbon fiber instead of nickel plaques to decrease the weight and cost of the battery and increase its specific energy. The person working on capacitors was telling me that he had ideas for increasing the energy by the factor of 2 (which, as it turns out, could be huge for a hybrid). There are companies working on Ni-Zn batteries that think they can do something better than Li-ion in some applications. But look at research in the US on batteries and there is pretty much zero effort in these areas. None of these ideas may pan out, but the question remains: should battery researchers be looking at these issues along with companies or should we all focus on one system (the lithium system)?
Part of the problem is the amount of funding that is available for battery research. If there was unlimited funding available, all these problems will be looked at. But with funding being tight, one needs to focus on a few problems and not spread one-selves too thin. Another problem is the community. As in any other area, there is a bit of jumping on the bandwagon that happens. Its tough being the only guy doing something, especially when no one cares for what you do.
At LBNL I wear two hats: one as a researcher looking at mathematically modeling batteries and another as the technical manager of the Batteries or Advanced Transportation Technologies (BATT) program. In my latter role, I have a hand at picking the kind of systems we work on. And I know exactly why we have picked to focus on the lithium battery exclusively. But the advances in these less "sexy" fields makes we wonder if this strategy is right. Weigh in with your views.