As renewable energy technology like wind and solar become cheaper, energy storage is becoming increasingly vital. Right now, Lithium Ion is the king of the hill due to its relatively low cost and high energy density. But we can’t just rely on one technology to meet all our energy needs.
What if there was a battery technology that was cheaper than lithium-ion and didn’t use any metal at all? What if we could have a battery that used… plastic? That’s what one company, along with a team of MIT researchers are exploring in Boston.
So how does this new technology stack up to current battery technology? Will it be the energy storage solution we’ve been waiting for? What are its pros and cons, how might it be used, and just how far along are they?
I’m Ricky, welcome to Two Bit da Vinci.
A typical battery configuration has three main components — two terminals made of different chemicals — the anode, the cathode, and a liquid electrolyte between them.
Primary cells are batteries that can’t be recharged, like the alkaline batteries in your remote, or the aluminum air battery we’ve covered in the past. While those have their place, for obvious reasons, secondary cells are much more interested, because they can be charged and discharged many times. So good news the plastic polymer battery is a rechargeable secondary cell. LINK LINK
Typically, metals like lithium are used for the cathode, because it is very light, and has 1 valence electron that it’s happy to donate. Other metals like nickel and cobalt is also added for other characteristics like safety, and stability. Graphite is typically used for the anode, due to its high conductivity, and ability to wedge in and hold lithium ions.
But the key, of course, is not just finding the material that is the most conductive or has the highest capacity — cost is also a major factor.
Right now lithium is king because It boasts a high energy density, it can undergo multiple charges and discharge cycles, AND it’s relatively low cost compared to other battery chemistries. LINK
While the energy world wouldn’t be where it is today without Lithium Ion batteries, there’s good reason to continue exploring new battery chemistries. Mainly because while Lithium ion battery prices have fallen over the past few decades, recent years have seen dramatic increases in the price of raw lithium and other metals, a lagging indicator of how lithium ion battery prices might fair in the future. December 2021 saw lithium prices leap a jaw-dropping 485% year over year, according to S&P Global. LINK
Not to mention the fact that some of the materials in Lithium Ion batteries, including cobalt, manganese, and lithium itself, carry some environmental and supply chain question marks. It wouldn’t be such a big deal, 20 years ago, but if we’re planning GWhs of grid storage, and a billion EVs in the next few decades, this question mark is of the utmost importance.
[Insert Ad]
This is where Boston-based energy storage company PolyJoule comes in. This company is pioneering a brand new battery technology that doesn’t use any metals at all. Instead, they use something called conductive polymers.
And if you’re thinking wait a minute don’t we already have lithium polymer or li-po batteries? Yes but li-po batteries have a polymer electrolyte instead of a liquid electrolyte. They still have metal cathodes, and graphite anodes.
We’ve covered polymers on our channel before — they’re very large molecules consisting of many repeating subunits, basically long chains linked together. Essentially, it’s plastics. I know, I know — aren’t we trying to get rid of plastics? Now you want to put them in batteries?!? LINK LINK
Stick with me, I’ll dive into that in just a bit.
But essentially, these properties allow these materials to be incredibly strong and conductive, which means they can act like metals even though they are entirely organic-based materials. There are quite a few polymers that are electrically conductive when linked with conjugated double bonds that run along their backbones. LINK LINK
I know — that word conjugation might give you flashbacks to your high school Spanish class. But here it means alternating single and double bonds. This lets the electrons become delocalized — meaning they can move over the whole system and be shared by many atoms. LINK LINK
Novel research into conductive polymers isn’t new, in fact the Nobel Prize for Chemistry was awarded to a group of 3 researchers for the discovery and development of conductive polymers all the way back in 2000 (link).
So what does this look like in a battery — and why does it matter?
PolyJoule’s cells are essentially constructed the same way as any other traditional battery. But instead of lithium or cobalt, they use conductive polymers as a cathode, a carbon-graphene hybrid anode, and a non-flammable liquid electrolyte. LINK LINK
During charging, ions are stored in the electrode bulk through a Faradaic process known as oxidation… essentially rusting when talking about iron. During discharging the process is reversed, and the ions are expelled from the electrodes through a process called reduction. LINK LINK
So what makes this new technology so important?
Well, compared to lithium-ion, PolyJoule’s battery has several advantages. For one, it works around some of the supply chain issues that other battery materials face. The materials inside these batteries are far more abundant than lithium or cobalt and can be easily synthesized with widely available industrial chemicals — which means no mining. LINK LINK
Because these batteries don’t contain a flammable electrolyte or use highly reactive materials like lithium, they can forgo the temperature management and fire suppressant systems other batteries require (LINK). Or at the the very least, they require much less stuff for thermal and fire management. Remember every pound of stuff that’s needed for things like this, is a pound of stuff that adds weight, but not energy storage. This factors huge, in the energy density of an individual cell, vs the density of an entire pack.
Also they can tolerate much colder temperatures than lithium ion batteries can. While an EV today parked in -30C climates, would have to actively heat the battery pack and lose range slowly even while parked, this might not be the case this the polymer battery.
Because of these features, PolyJoule claims that their LCOE is about 30% less than lithium-ion — with a target price point of around $65 per kilowatt hour. While this is still quite a bit higher than the $20/ kWh that some researchers point to as the critical price point for energy storage, it’s still significantly less than Lithium Ion which hovers somewhere between $143 and $250 / kWh. And, PolyJoule batteries could potentially last longer than lithium-ion batteries. LINK LINK
Currently, Lithium-ion batteries have lifespans of around 15–20 years PolyJoule claims that their technology could nearly double that, with projected lifespans between 20 and 30 years! LINK LINK
In the lab, PolyJoule’s team performed 12,000 charge cycles at 100% depth of discharge. So in terms of cost, PolyJoule Batteries could be cheaper to build, last longer, AND degrade less over time than their competitors. LINK
Now, as we mentioned above, the polymers used in these batteries are essentially plastics. And, of course, we all know plastic is pretty terrible for the environment. Fortunately, according to the company, their batteries are 95% recyclable. And, using polymers for these types of batteries could create a whole new market for recyclable materials — which would be a major win! But there’s little info available on just how much recycled plastics could be used. So yes after end of life its recyclable, but could we use the tons of waste plastic already in existence today? LINK
What about battery performance?
PolyJoule batteries boast power densities 10X higher than lithium-ion! Rember, power density is a measure of power output per unit volume. If electricity is water, power density is the size of your hose. A larger hose can put out more water at once. This was a major feature I mentioned in my “Graphene Supercapacitor” video. The products under development can rapidly discharge up to 1 mWh in less than 10 seconds, then recharge to full capacity in under 5 minutes! Compare that to a tesla battery that requires 30 minutes or more to recharge typically to 80%. LINK
Now, here’s where the reality check comes in. While these batteries have many advantages over lithium-ion like greater power density, where they simply cannot compete is in energy density — the amount of electricity they can hold per unit volume. Remember that water analogy? Well, if power density is the size of your hose nozzle, energy density is the size of your tank.
According to the MIT researchers behind PolyJoule’s technology, lithium-ion batteries have energy densities up to five times greater than the polymer batteries under development. That means PolyJoule would need a battery five times as big to store the same amount of energy. So, yeah… not ideal for, say, your phone or laptop. But the abundance, safety and longevity might make it an excellent candidate for stationary grid storage. LINK LINK
When we report on a new battery chemistry or breakthrough, the goal isn’t to replace today’s lithium ion batteries. Because while all this research is going on, the lithium ion tech isn’t just standing still. Today’s lithium ion batteries have less cobalt than ever, some have none at all. Plus solid state batteries are ever on the horizon. This polyjoule battery isn’t a replacement, its a supplement.
Current tesla powerwalls, while beautiful and compact, do use that precious lithium ion battery material for stationary applications. For every 5.5 powerwalls Tesla makes, they could make a long range Model Y, and while lower energy densities are a no go for EVs they might be just fine for home storage. Would you buy a powerwall equivalent battery that was 5x as big, but lasted 2 to 3 times as long? And cost quite a bit less?
Don’t forget they have 5x the power density, which would be great for power surges for larger appliances like ACs and heaters, and at a grid level, hugely beneficial for grid balancing, power conditioning, peak shaving, and more. LINK
According to Polyjoule CEO Eli Paster, in 2021, “The ideas that we work on in the lab, you’ll see turned into products three to four years from now, and they will still be innovative and well ahead of the curve when they get to market.” (link).
But for all we know about Polyjoule and their battery, there’s just as much we don’t. For example, efficiency, I couldn’t find data on this anywhere. This is again where lithium ion reigns supreme, and other batteries we’ve covered like cryogenic air, or pumped hydro lags behind. Based on the fact that this data isn’t highlighted, I’m guess it’s not as good as lithium ion.
Also nearly all of the plastic in the world comes from fossil fuels, so when it comes to this battery, there are two ways this can go. This could be finally be the solution to the massive mess of plastic we’ve made over the past 70 years. While it was first invented in 1862 by Alexander Parkes and showcased at the London International Exhibition, it wouldn’t flood our lives until the 1950s. In 1988 the Society of Plastics Industry established a system for categorizing many recyclable plastics into groups numbered 1 through 7 shown here:
- Polyethylene Terephthalate (PET, PETE). PET is clear, tough, and has good gas and moisture barrier properties. Commonly used in soft drink bottles
- High Density Polyethylene (HDPE). HDPE is used to make bottles for milk, juice, water and laundry products.
- Vinyl (Polyvinyl Chloride or PVC). The diverse slate of vinyl products can be broadly divided into rigid and flexible materials. Bottles and packaging sheet are major rigid markets, but it is also widely used in the construction market for such applications as pipes and fittings
- Low Density Polyethylene (LDPE). Used predominately in film applications due to its toughness, flexibility and relative transparency.
- Polypropylene (PP). Polypropylene has good chemical resistance, is strong, and has a high melting point making it good for hot-fill liquids, and packaging for catsup and margarine.
- Polystyrene is a versatile plastic that can be rigid or foamed. General purpose polystyrene is clear, hard and brittle. It has a relatively low melting point. Typical applications include protective packaging, containers, lids, cups, bottles and trays.
- Other. Use of this code indicates that the package in question is made with a resin other than the six listed above.
If the polyjoule battery requires very specific types of plastics, then very little recycling will be possible, but if they could develop their chemistry to work with a wide range of existing plastics, this could be huge. There’s so little incentive to do the right thing in our world. Recycling is largely, and sadly, a sham, because it’s almost always cheaper for companies to just buy new plastic than to actually recycle it.
If we can better standardize new plastic for recyclability, and companies like Polyjoule can find novel ways of using it for energy storage, this could be a game changer.
I am going to try to reach out to polyjoule for an onsite, or interview, and i’ll do a follow up video if that happens. At this point, i have a ton of questions, but color me intrigued.
By the way we talked a little about graphene in this video, but if you want to learn a whole lot more about this wonder material, check out this video next!
