Electric vehicles are great, but they would be even better if they didn’t have to lug around a big and very heavy battery pack. Making EV batteries smaller, safer, and more power-dense are top priorities for all manufacturers, but each is a challenge in its own right, and we’ve only seen incremental advancements over the last decade or more.

The lithium-ion batteries that are in most EVs today can be traced back to a concept introduced in 1991, and they were developed primarily for use in consumer electronics such as laptops. Through incremental improvements, they became good and cheap enough to be the go-to solution for automotive traction batteries. However, even though billions are being poured into battery research today, the limitations aren’t easy to overcome, and automakers are looking for a breakthrough solution that will fix all the problems of lithium-ion or the newer lithium polymer (LFP) batteries.

Solid-state batteries might be the breakthrough that the industry is looking for, but it’s still unclear when they will reach production vehicles. They are already used in small devices such as smartwatches and even medical implants, but we’ve not seen them used in many larger applications yet.

But even once the technical issues are ironed out, there will still be the issue of solid-state battery cost. They are expected to be around three or four times more expensive than lithium-ion batteries.

Why Are Solid-State Better EVs Than Lithium-Ion Or LFP?

Unlike current EV batteries, which use either a liquid or a gel electrolyte, solid-state batteries use a solid electrolyte. In a current-gen lithium-ion battery, lithium salts are dissolved in a solvent, resulting in a volatile liquid that floods the entire cell, while in solid-state batteries, the electrolyte can be either a ceramic, a sulfide, or some other type of solid-state material. It serves the same purpose of allowing electrons to flow between a battery’s cathode and anode.

By eliminating the flammable liquid electrolyte, solid-state batteries are made much safer in the event of an accident. Solid-state cells will not only be able to hold their shape better, but even if they are breached, the chance that it will result in a massive battery pack fire is much lower thanks to their higher tolerance to high temperatures. As a result, the chance of a cell short circuit is also much lower.

This also reduces the chance of thermal runaway, which is a chain reaction where battery cells will overheat and potentially combust, and this will spread from one cell to another, eventually consuming the entire pack.

Solid-state batteries can be over twice as energy-dense as current lithium-ion batteries. This means an EV’s battery pack would require fewer battery cells for the same capacity, and the pack would be lighter, thus improving the vehicle’s range, performance, and handling. The pack would also be physically smaller, so it wouldn’t have to take up the entire bottom of the car, thus allowing for improved interior use of space and more room for passengers or cargo.

With designs like the solid-state lithium-metal battery, the cells themselves are shorter, so even in a battery pack where the cells are placed vertically, you can still make the pack thinner.

Electrolyte degradation due to repeated thermal cycles caused by charging a lithium-ion battery pack is one way current EV batteries lose capacity over time. Solid-state batteries have a much more stable electrolyte, so they should last much longer while maintaining more capacity.

Another advantage of solid-state batteries is that they can potentially charge quicker and not get damaged when regularly fast-charged to 100 percent. Current lithium-ion batteries like to be kept between 20 and 80 percent state of charge for the longest possible life, but this would not be a requirement with solid-state.

Improved cold weather performance is another area where solid-state is better. Solid-state batteries can withstand a wider range of temperatures, and they should be less affected by outside temperatures. This means they would retain more charge in freezing temperatures and also allow for higher charging speeds under the same conditions.

Toyota, the automaker with the most advanced in-house solid-state battery research project, says that it should offer 20 percent more range compared to its still unreleased next-gen lithium-ion and lithium iron phosphate batteries. It should allow EVs to exceed 620 miles of range, and charge from 10 to 80 percent in about 10 minutes.

When Are Solid-State Batteries Coming To EVs?

Mercedes-Benz eCitaro

Toyota has been somewhat cryptic when it comes to revealing its solid-state battery plans. In its battery-powered vehicle rollout roadmap, Toyota revealed it aimed to have solid-state batteries ready for commercial use by 2028 (although a recent report suggests they may arrive even sooner). The manufacturer confirmed that the first solid-state batteries will be introduced in its hybrid vehicles, not full EVs.

Just like Toyota, Nissan has also vowed to launch a solid-state EV by 2028, and it already has a prototype production facility up and running capable of making the batteries in-house. Hyundai recently filed a patent for an all-solid-state battery in the US, and it plans to put these batteries into production EVs before 2030.

BMW is working with Solid Power to develop solid-state batteries, but its goal is to eventually move development in-house and not rely on a third party. The Bavarian automaker will launch a brand new bespoke EV platform called Neue Klasse in 2025, but it won’t feature solid-state cells until closer to the end of the decade.

Mercedes-Benz eCitaro Uses All-Solid-State Batteries From BlueSolutions

Dongfeng is an automaker working on solid-state batteries, and its Nammi 01, a new electric city car introduced in China in 2023, was designed to support a solid-state battery, and it initially sounded like it was going to launch with it. However, the finished production car has two available battery packs, but neither is solid-state.

Mercedes-Benz equipped a few dozen eCitaro electric city buses destined for the German city of Bremen with solid-state battery packs in 2021 and 2022. They feature 441 kWh lithium polymer batteries with a solid electrolyte produced by Blue Solutions in France. These buses are still in use in Bremen today, and Mercedes notes that even though it still offers a solid-state eCitaro, it’s seen more demand for its new generation NMC batteries.

The time frame for solid-state battery rollout is unclear, but there should be a handful of commercially available models by this decade's end. The process of solid-state adoption will be spurred by potential breakthroughs that we can’t anticipate. There’s also a chance that the constant incremental improvements and lowering of costs brought to liquid electrolyte batteries will keep them relevant even once a viable solid-state battery solution hits the market. It will be a question of cost more than anything else.

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