What you need to know about solid-state batteries

How are you reading this article? Most likely with a smartphone, a tablet or a laptop. 

What do they all have in common? Batteries.

Lithium-ion rechargeable batteries

Yep. Invaluable, rechargeable, lithium-based batteries that allow you to use devices for hours or even days at a time, carrying millions of times more computing power in your pocket than what landed the Apollo 11 astronauts on the moon’s surface in July 1969. 

These convenient pieces of technology — first made commercially available in 1991 by Japanese firms Sony and Asahi Kasei — completely revolutionized the world.  

Lithium-ion batteries are a very efficient way to store energy. Compared to predecessors, they have a high energy density, which means that they can store a lot of energy in a small space. They also have a long lifespan and can be recharged many times. But even better, next-gen ones are under development. 

Rechargeable batteries are also playing a key role in the fight against climate change by powering e-vehicles. That’s why more and more countries — among them Canada, the UK, the EU, China and India — are planning bans on selling new fossil-fuel-powered vehicles. In some places, like Norway, the bans begin as soon as 2030. 

And as Germany’s annual IAA car show kicks off in Munich on Tuesday  — one of the world's biggest — electric cars and  batteries are among the protagonists. 

This follows huge breakthroughs in the battery world announced in the last few months by big companies and giant car manufacturers like Samsung, Toyota, Ford and Honda.  

Much of the buzz is about solid-state batteries. They promise to be longer-lived, smaller, faster to charge and pack more of a power punch. Some companies claim they want to start mass production as early as 2024. 

What are solid-state batteries? 

Short answer: They’re like regular lithium batteries, but better.

They work according to the same principles, just without any liquid components inside. That battery on your smartphone has a fluid component called an electrolyte, which allows lithium ions to flow freely. And that ultimately powers your devices. 

Why do we need them? 

Conventional liquid-electrolyte lithium batteries need to be pretty large to power something the size of a car. They have safety issues and can swell due to changes in temperature or leak when squeezed too hard. The liquid inside is also flammable. 

As you probably know, your phone’s battery usually doesn’t last too long. Everyone has felt "my-phone-battery-is-dying" anxiety. Though better than their forebears, conventional lithium-ion batteries’ energy density could be improved. They also charge slowly and have a limited lifespan. This makes them less than ideal for many applications, among them e-vehicles, along with medical devices like pacemakers or electric planes. 

How are solid-state batteries better? 

Solid-state batteries have a higher energy density than standard lithium-ion counterparts, which means they can store more energy in the same volume. This can translate into longer-range electric vehicles or smartphones that can go for days on a single charge, as well as smaller, lighter batteries for portable devices. And who knows? They might even one day make electric flight a feasible scenario. 

Solid-state batteries can also charge faster than liquid-electrolyte ones, making them more suitable for electric vehicles and other applications where fast charging is important. No more waiting five hours to get back on the road! 

Solid-state batteries are also safer. Because they’re less likely to catch fire or explode than liquid batteries, they’re better suited for use in applications where safety is a concern, such as electric vehicles and drones. 

At least, that’s according to theory. Making an actual commercially available solid-state battery at an affordable price is a whole different matter. 

But to understand what that means and why a commercially available solid-state battery would be a breakthrough, let’s quickly go over the battery basics you learned back in school.  

How do lithium batteries work? 

The basic elements in a lithium-ion battery are a side with a positive electrode, a side with a negative electrode, and a separator layer in-between that prevents any direct contact. All that is submerged in a liquid electrolyte. 

The key to lithium-based batteries is that lithium atoms are very good electron donors. They really want to get rid of the single electron they have on their outer shell. The flow of these electrons is the electric current that comes out of the battery.  

And by the way, when a lithium atom loses that outer electron, it becomes a positively charged ion. That’s where the name "lithium-ion battery" comes from. 

The separator layer we mentioned earlier allows lithium ions to pass through, but not electrons. So it also acts like an insulator. 

The negative electrode side of the battery contains graphite that stores lithium atoms when the battery is charged. When you plug in the device, the battery begins to discharge. The lithium loses an electron to electrical flow — turning it into an ion — and the ion travels through the liquid electrolyte and through the separator into the positive electrode side. The positive side is usually made of compounds that also have downsides and limitations. Not to mention that the use of liquid electrolytes has several drawbacks. 

So how does a solid-state battery work? 

Solid-state batteries work pretty much like a conventional lithium-ion one, just that they have a solid electrolyte instead of the liquid one through which the lithium ions flow. The basic principle, however, is the same. A big plus is they don’t have the safety issues a liquid electrolyte brings. 

On the positive side, instead of containing a metal oxide electrode like standard liquid-electrolyte batteries, pure lithium accumulates in metal form as it flows from the negative to the positive side during discharge. This saves a lot of space. 

Why are they not in every e-device? 

Well, because they are still under development, and some challenges still have to be overcome before they see wide use. 

Cost is a major factor here. Solid-state batteries right now are more expensive to produce than regular lithium-ion batteries because solid-state batteries use materials that are more expensive and complex to produce. 

Many of the potential advantages discussed earlier, such as longer lifespan, faster charging, and higher energy density, have not yet been fully transferred into commercial products. 

Safety is also an issue. Although solid-state batteries are considered safer than conventional ones, there are still safety concerns, especially short circuits that can be caused by needle-like growths of lithium metal. 

Most of the developments in solid-state batteries so far have remained at the laboratory level, and it’s unclear how difficult it might prove to scale them up.  

However, there is a lot of research and development being done in the field, and many experts believe that solid-state batteries will eventually become the standard in areas like the electric vehicles segment.