Mar 05 2020

Organic and Flow Batteries – Hype or Promise

It’s important to recognize that we currently do not know with any confidence the path forward that our energy infrastructure will take. This is why we have to spread our bets out on as many technologies as possible – we don’t know which ones will be the most successful. Many people place their hopes on battery technology, and there is no doubt that batteries are a great energy storage medium and will play a critical role in our energy future. But batteries are not a simple panacea, and we may run into important limits. This is why we need new battery technology.

The demand for batteries is likely to increase significantly. Electric cars depend on batteries, and therefore putting millions of EVs onto the road means necessarily putting millions of batteries on the road as well. Also, batteries are one possible solution to home and grid energy storage, which will be necessary if we want to maximize renewable energy sources like wind and solar. Current lithium-ion battery tech is great, and is getting incrementally better all the time, but it has limitations. One significant limitation is the availability of lithium and cobalt which are necessary for their manufacture.

Cobalt, for example, comes mostly from the DRC, an unstable country, and it comes mostly as a byproduct of copper and nickle mining. Global supplies are expected to fall short of global demand, and if there is a surge in Li-ion batteries this will only get worse. Lithium is more complicated, and we are not really sure what the worldwide supply is. For now there is no problem, but there is widespread concern that lithium supply will not keep up with demand as EVs take to the streets. We also do not currently have the ability to recycle lithium into a pure enough state to reuse in batteries.

What battery tech is on the horizon that will potentially change the game for batteries? For now, continued incremental improvements in Li-ion battery technology are important. We need to squeeze as much function out of the raw materials as possible, with greater capacity, and longer charge-discharge lifespans. Right now Tesla boasts million-mile batteries for its EVs. Increasing the lifespan further will decrease the need for new batteries as replacements. Batteries from retired EVs can also be repurposed for grid storage, where it wont’ matter if their range has decreased.

Better still would be an entirely new kind of battery that uses less toxic, cheaper, and more abundant raw materials. Ideally we would develop a battery tech that is completely sustainable, which means they don’t use any limited resource. That is the promise of organic batteries, that use proteins or other organic materials for their electrodes. Batteries that can be “grown” essentially could be entirely sustainable.

There are already organic prototype batteries in existence. Most of these are better for grid storage, where size and energy density are not as much of an issue as batteries for EVs. Perhaps the biggest issue for grid storage is charge-dicharge cycles, because the batteries will be used daily. The ones referenced above claim 5,000 cycles, which is about a 15 year lifespan.

A recent study also presents positive results for an organic Li-ion battery that replaces the cobalt electrode with a protein. This could be useful in EVs. The trick with organic electrodes is that they get hot and are therefore unstable. The researchers in the new study claim to have solved that issue, while maintaining current Li-ion battery performance. Always the key question with such laboratory breakthroughs is – can this technology be scaled up to industrial production? If not, then it is nothing but a lab curiosity. It may improve our knowledge, but is not directly applicable.

There has also been a lot of hype surrounding flow batteries. Flow batteries use large containers of liquid electrolyte solution to store charge. One example is the vanadium flow battery, which stores charge in the different valence states of vanadium: “Fewer electrons gives a higher positive charge. Energy is stored by providing electrons making V(2+,3+), and energy is released by losing electrons to form V(4+,5+).”

The advantage of flow batteries is that they are easily scalable – just make bigger tanks for more solution. They also have long lifespans, >20 years, and can be cost-effective. However, they are only useful for grid storage. They are too big for EVs. Still, even just a grid storage solution would be a huge benefit in planning our energy future. The bigger problem, however, is that they generally use rare, expensive, and toxic metals. But again, research is ongoing to develop flow batteries that are cheaper, more environmentally friendly, and more sustainable. So flow batteries have great potential, but there is no killer tech available right now.

Overall – that is where I think we are. We have good batteries for EVs, that are slowly improving, but we may run into limits if we try to increase the number of EVs by orders of magnitude. We don’t really have any great grid storage solution, but we do have lots of possibilities. We cannot currently map out our energy future because we are still researching battery options that are good enough to be the clear winner.

The challenge with battery tech, as I have pointed out before, is that a good battery needs to have a suite of characteristics all at the same time, and any one can be a deal-killer. Ideally we want a batter with high energy density, able to charge and discharge quickly, stable and efficient under a variety of operating and environmental conditions, long charge-discharge lifespan, that uses abundant, cheap, and environmentally friendly materials, and can be recycled and/or produced sustainable. EVs have more strict criteria than grid storage, because these batteries need to be driven around in a car at high speed, but even with grid storage we need most of these characteristics. The need for sustainability becomes greater the more we want to deploy these batteries.

In fact, we can’t even be sure that batteries are going to be the primary solution. I would bet on batteries, mostly because they are making early gains in infrastructure, and if history is any guide, infrastructure usually wins the day. But hydrogen fuel cells may turn out to the the better overall solution. Hydrogen is a good energy storage medium, and the only byproduct of combustion is water. We need to improve our ability to make hydrogen from water using renewable energy, and then we need a vast infrastructure of storage and distribution. For current hydrogen fuel cell cars, range is also an issue. We never really found the perfect material for storing hydrogen for use in cars, which is what ultimately stalled the “hydrogen revolution.” Now, lack of filling stations is a huge problem.

But right now we do not know what grid storage will look like in 30-50 years. This is also why we need to spread our bets to energy solutions that don’t require grid storage at all, like nuclear.

I am encouraged, however, by the amount of research being done and the steady report of incremental progress. However, we have to understand that most of this progress does not directly translate into a battery product. Many will be blind ends. But cumulatively, they are grinding the battery technology forward. I do wish it would be faster, because batteries are likely going to be an increasingly critical component of our energy infrastructure and an important part of reducing our carbon footprint.



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