What is a solid state battery for EVs?

Electric car technology is moving at a dizzying pace. The first Nissan Leaf, launched in 2011 had a range of 109 miles, cost a third more than an equivalent petrol hatchback and took almost an hour to recharge, even on the fastest points. Now an equivalent car such as an MG4 is cheaper than the Leaf was in 2011, has double the range and charges in half the time.

But the biggest revolution in electric car technology is still to come. Solid state batteries are set to be a real game changer, making electric cars cheaper, safer, quicker to charge, longer lasting and with much more range.

Car makers say they will offer at least twice the energy density of the current lithium-ion battery technology, significantly shorter charging times, and all at a lower cost.

What is a solid-state battery?

Before talking about solid state, it’s important to understand the limitations of the current technology. The most common type of battery used in electric cars at the moment is called lithium-ion. It’s similar to the packs found in laptops and mobile phones and uses a liquid as the electrolyte between the anode and cathode. When it is charged, lithium ions which hold the energy move from the cathode to the anode through a liquid called an electrolyte. This is reversed when the motor is driven, and the battery is discharged. Bigger, high-capacity batteries contain more lithium and therefore offer more range.

However, the liquid used as the electrolyte limits the speed at which the lithium ions move as it gets hot when it is charged or discharged quickly. This is why most modern electric vehicles use a cooling system to keep them at a safe operating temperature of below 60°C.

If the electrolyte does get too hot, it will gradually damage the battery and reduce its capacity – this is known as degradation. This is why our phones and other devices lose capacity as they get older, although the loss of capacity is far slower in cars as they have more protection from overheating.

It’s also an issue if the liquid electrolyte gets too cold in extreme weather, as it will hurt the delicate chemicals and cause slower movement of the energy.

There’s another problem too – the solvent used in the electrolyte is highly flammable which means the cells need to be protected with armour to stop them being damaged in an accident.

Solid state batteries do away with the liquid electrolyte, which is replaced with a solid material between the anode and cathode. This means it does not boil or freeze, allowing the batteries to be used in extremes of temperature.

As there is less chance of adverse chemical reactions, the battery makers can also use different materials inside the battery. This makes it possible to select cathodes with fewer precious metals to lower costs, and anode materials with higher energy density. The eventual plan is to take out the minerals such as cobalt which are expensive and scarce.

Why are solid state batteries better in electric cars?

There are a host of reasons. For example:

They will be cheaper: As the electrolyte is more stable, battery makers can use different materials inside the cells. These include minerals which are far less costly than the precious metals used in lithium-ion packs. Also, there is less protection needed for the solid-state cells so they don’t need cooling hardware or as much protection from accident damage.

They are smaller: The change in the ingredients inside the battery allows them to be made more energy dense – that is they can hold more power in a smaller space. More room is saved by removing the cooling systems and thick armoured battery case, allowing electric cars to be made lighter and more spacious for passengers. Toyota says its prototypes are no thicker than a small notebook. Having more energy density, lower costs and faster charge times also means battery electric powertrains will start to become practical for larger vehicles such as trucks, vans and pick-ups.

They offer more range and faster charging: Toyota says its solid-state batteries will offer a range of 700km in an average size car – that’s almost 440 miles, which equals the cars with the longest range currently on sale. They will also be able to charge much faster, with times cut from 30 minutes to just 10 to top up from 10-80%. With a top up taking only a little longer than filling with fuel, it’s expected drivers won’t feel they need longer range cars and the battery can be made even smaller.

They’re safer: As these is no solvent-based liquid in a solid-state battery, the electrolyte is said to be much safer as it is not nearly as flammable.

When will I see solid state batteries in cars?

The manufacturers are frantically racing to be first to market. Nissan together with its partners Renault and Mitsubishi have promised a car on the market “by fiscal year 2028”, which means it has given itself a deadline of April 2029. Toyota has been working in a joint venture with Panasonic since 2020 and claims to be “on track for limited production by 2025”. Hyundai is also busily working on the technology but has yet to promise a date for production. Volkswagen battery company PowerCo announced it would ‘industrialise’ solid-state battery production with QuantumScape but put no date on when this would happen.

What is the hold up?

The makers need to finalise a way of making the batteries to very precise tolerances. They’re also testing them continuously to ensure they will work reliably over the lifetime of a car – and beyond as storage devices for renewable power. There are already hundreds of prototypes testing around the world.

Ironically the drop in the price of the older lithium-ion technology is also making car makers less desperate to push solid-state research along.

Does this mean my electric car will be obsolete?

Experts think lithium-ion and the alternative lithium iron phosphate (LFP) batteries currently used in electric vehicles will co-exist with the new solid-state cells for some time as the market evolves and the cost of all the technology comes down. It will take some time for the car makers to ramp up production and change the vehicle designs to match the latest power packs.

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