Much of our world runs on batteries.

Heck, you’re probably watching this video on a battery-powered device! The world has been transformed by the innovations in battery tech  over the last 150 years or so.

Whether it’s the lead-acid  batteries that start our cars, or the lithium-ion batteries  powering our portables, batteries help get us where we want to go. But it’s more than just our personal devices. A reliable grid powered by green  energy is going to need batteries, too.

Not just electric cars—think  solar power on a cloudy day. You need batteries to store  energy for when the grid needs it. Lucky for us, there’s an old  battery showing new promise for long-duration energy storage.

And its secret is rust. [ INTRO MUSIC ] Let’s start with a quick  refresher on modern battery tech, just in case you are like me, you’re a little rusty on your electrochemistry. Today we’re talking about chemical batteries, which use the power of chemistry to store energy that can later be released as electrical energy. Electrical energy, or electricity, is the thing you get when charged particles, like electrons, move around.

The flow of those charges is called a current, and while batteries can’t store electricity, they can store chemicals that produce current during a series of reactions. To do this, they need three components: an anode to release electrons,  a cathode to accept electrons, and in the middle: an electrolyte, a substance capable of conducting  all those moving charges. Lithium-ion batteries are probably  the ones you’ve heard most about.

They’re in cell phones and electric cars, and they changed the game in terms  of rechargeability and portability. But before them, there were lead-acid batteries. The OG rechargeable  batteries, first invented in 1859.

If you drive a gas-powered car, you still probably have one  of these under your hood. They’re heavy and they take a long  time to power back up when they die. Which if you've ever had to jumpstart your car you're probably very familiar with Lead-acid batteries have a negative lead anode and a positive lead dioxide cathode, separated by a aqueous solution  of sulfuric acid and water.

And, that’s why they’re so heavy! Lead is not known for being lightweight, and quite frankly, water isn’t either. You get power from the battery when the  lead plates react with the sulfuric acid, causing charges to move around in the process.

Eventually, everything that can react has reacted and both plates are electrically neutral. That’s when your battery is dead. You can recharge it by slowly putting  electricity back into the battery, which causes the anode to  return to being lead oxide and the cathode to becoming lead.

The problem is that as these materials redeposit, it changes their microscopic structure, ultimately degrading the battery’s efficiency. Of course, other kinds of  chemical batteries came to market after the invention of lead-acid batteries. You might also be familiar  with alkaline batteries, named for the alkaline, or  basic, electrolyte inside.

These are the batteries that go in your TV remote or your cat’s laser pointer , and they’re typically designed to be disposable. Some can be recharged, but degrade  after just a few recharging cycles. Their limited rechargeability  means they’re not a good option for variable power storage, like the kind we'd need to  stabilize an entire power grid.

In comparison, lithium-ion batteries were like a popstar double threat  of rechargeability and portability. They hit the market in the early 1990s, just in time to help miniaturize portable  cell phones at the turn of the century. Lithium-ion batteries are way  lighter than lead-acid batteries, partly because lithium ions are  tiny compared to lead atoms!

This lets the battery pack way  more charge into a small volume. The electrolyte also doesn’t get consumed during the discharging or charging process, enabling the battery to operate  with less electrolyte overall. These batteries charge relatively fast  and hold onto that charge decently well.

When not in use, they lose less  than 2% of their charge per month. They can also be drained and  recharged hundreds of times before degrading a noticeable amount! And in the battery world, those  kinds of stats are just- MUAH!

Many of these benefits are possible because of the unique  arrangement of the lithium ions within the anode and cathode layers. On the anode side, the lithium ions  are shuffled between layers of carbon in the form of graphite. When they escape the graphite, they’re transported through the electrolyte over to the cathode side, which is usually made of something  like lithium cobalt oxide.

Recharging reverses that process, detaching some lithium ions from the cathode and sticking them back between  the layers of the carbon anode. But as miraculous as these batteries  have been, they have some problems. They’re made with rare minerals  that are expensive, dangerous, and environmentally harmful to mine.

You should really be recycling  your batteries, by the way! And companies you should  be designing stuff to be reusable, don’t think you weren’t going to get  out of some B Camera finger wagging Until then, we’re relying on fossil  fuels like coal and natural gas for our energy needs. These resources can be burned at any time  of the day or night to generate electricity.

They’re like nature’s battery, it just takes millions of years to recharge them. The good news is that renewable energy sources like wind and solar are getting cheaper and being deployed at greater volumes every year. But a reliable grid needs  more than just generation, it needs the ability to store energy and deploy it whenever and it's needed most.

The sun doesn't always shine and  the wind doesn't always blow- Electricity demand is at historically high levels, extreme weather events are becoming more frequent stressing the grid for days at a time- and transmission lines can only move so much power from where it's generated to where it's needed. So we need capacity that's able to  store many days worth of energy, enough to prevent outages through any period of grid stress  weather that's a cloudy week, a demand surge or a severe weather event. And the solution might be rust.

It turns out that rust is not always synonymous with being useless or bound for the scrap heap. In this case, rust is literally powerful. See there’s a whole class of batteries  that use a pure metal as an anode, and air as the cathode.

And iron happens to be a  really abundant, non-toxic, pure affordable metal that we  could use for exactly this purpose. These appropriately named Iron-air batteries basically work by rusting to release energy, and un-rusting to recharge the battery. And all it takes is iron, air, and water!

These batteries are built from sheets  of iron surrounded by an electrolyte, with thin channels of air to provide oxygen. When the battery “breathes in”, it draws positive ions from  the air to oxidize the metal. Which, in the case of iron,  is also known as rusting.

The oxygen from the air first  reacts with the electrolytes, which then reacts in several  stages with the metallic iron, The orange red-compound you get if you run your cast  iron through the dishwasher, is called Hematite. And that's what we normally think of as rust And although in most Iron Air batteries  the chemistry is slightly different- the idea of oxidizing the iron is the same. And it's this flow of electrons generated  from the reaction of iron with oxygen that creates a current in the battery.

It can then be recharged by  applying electricity to the rust, which separates the oxygen  molecules from the metallic iron. The oxygen dissolves back into the electrolyte, and then is “breathed out”  into the air by the battery. The greatest advantage of iron-air batteries is that they’re built from  incredibly abundant resources.

They also have a higher capacity  than lithium ion batteries, at about 110th the cost. They’re safe, as none of the  components are toxic or as fire prone, and they should last a long  time without degrading. The kicker is that this tech isn’t new Rust-based batteries were first  investigated in the 1960s by NASA. and then continued to be explored  by researchers in the 70s Early results were positive, especially given how cost-effective  these batteries can be.

An early target application at the  time was battery-powered electric cars… a hot topic around then due to concerns  about oil availabilities in the 1970s. It turns out though that iron air  batteries weren't the right fit for cars, they were too heavy and they're  slow and steady discharge isn't exactly what you want when you  need to quickly merge onto a highway. And since grid scale storage  wasn't really on the table as an application back then research  largely fell by the wayside.

But as the need for long duration grid storage started heating up researchers started  dusting them off for a second look - and they might be just what we need  to stabilize a sustainable energy grid One US-based company called Form Energy is working on deploying these batteries to power grids over the coming years. Their batteries can store about  100 hours’ worth of energy that can be slowly discharged  over the course of several days. This could provide stable  energy throughout cloudy days, cold winter storms and more Iron-air batteries do still have some downsides: they recharge pretty slowly, their power output tends to be  on the slow-and-steady side, and that water makes them  a heavy load to transport.

But in the context of stabilizing a power  grid, these are basically non-issues. We want slow, steady, and stationary. Most of the time we wouldn’t  need them to discharge quickly, and we could always supplement  with lithium-ion batteries for the cases when we do need quick power.

Form energy has conducted  tens of thousands of tests on it's iron air battery systems, begun commercial manufacturing and is just starting to  deploy them at utility scale - that said like any new energy technology there's still plenty of work ahead  to discover problems and solve them. And luckily, they aren’t the only researchers  dedicated to helping these batteries meet their full potential. This is pretty promising tech  that proves it can really pay off to occasionally dip into the archives!

The future of green energy may actually  end up being a more rusty orange color. Support for this Episode was  provided by breakthrough Energy [ outro ]