Why your iPhone isn't powered by a solid-state battery yet – even though it beats lithium-ion

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ZDNET’s key takeaways

• Solid-state batteries have significant advantages over lithium-ion.
• At the top of the advantages list are increased safety and improved lifespan.
• The tech isn’t ready for the billions of batteries the industry would need.

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The other day, I reviewed a power bank with a solid-state battery at its core, rather than a lithium-ion battery. Solid-state batteries offer increased energy density, improved safety, and a longer lifespan. To demonstrate the improved safety profile, I opened the power bank and stabbed a screwdriver into a fully charged battery; apart from a few wisps of smoke, nothing happened.

So, why aren’t our iPhones and other gadgets and gizmos powered by solid-state batteries?

Also: I tested a solid-state portable battery for a week – now lithium-ion feels old school

Before we answer that question, let’s look at what a solid-state battery is and how it differs from a lithium-ion battery. 

Solid-state versus lithium-ion

Solid-state batteries are next-generation rechargeable batteries that use solid materials for the electrolyte (the material that carries the electric charge between the battery’s anode and cathode), rather than the typical liquid or gel electrolytes found in lithium-ion batteries. The electrolytes in lithium-ion batteries are typically lithium salts dissolved in a cocktail of noxious and flammable organic solvents, whereas in solid-state batteries, various dry ceramics are used. This dry electrolyte is not only non-flammable and significantly safer but also paves the way for batteries with significantly higher energy densities. 

On top of that, these solid-state batteries charge faster than equivalent lithium-ion batteries and offer more recharge cycles. 

In almost every way, solid-state beats lithium-ion. 

So why isn’t all our portable tech powered by solid-state batteries?

Billions of batteries every year 

Ultimately, it comes down to cost. We’ve been using lithium-ion batteries for over 30 years, and we’ve got mass production figured out, churning out billions of them every year. 

Think that’s an exaggeration? Apple alone is estimated to have sold close to 250 million iPhones last year, all of which need a cheap yet reliable battery. In all, the global smartphone market last year was in the region of 1.25 billion to 1.6 billion, so once you throw in the laptops, earbuds, smartwatches, power banks, e-cigarettes (yes, even disposable non-rechargeable units still contained a rechargeable battery), not to mention electric cars (modern electric vehicles have around 6,000 18650 or 21700 cells in every power pack). 

The supply chain for solid-state batteries is nowhere near ready for this level of output.

Also: Why phone and laptop batteries explode – and 6 ways to protect yourself

Add to that the technical issues. 

Solid-state batteries are more complex to manufacture, which, in turn, leads to lower yields. When you need billions made, this is a problem. Solid-state batteries are also more sensitive to vibrations and swell slightly in use, and neither is great when you consider how we expect modern tech to work and the abuse we expect it to withstand.

And low yields mean that the solid-state batteries that do roll off the production line are some four to eight times more expensive than conventional lithium-ion batteries of similar capacity. 

ETA for large-scale production?

But these are likely issues that will be overcome in time. 

Finally, and this is a big one, is the fact that lithium-ion batteries are so good in every way — from safety to recharge speed to lifespan —  that there isn’t any real rush on the part of manufacturers or consumers to upgrade to the newer tech.

People in the industry tell me that large-scale production of solid-state batteries is expected to happen by the early 2030s. Then, and only then, are we likely to see lithium-ion being phased out in favor of the newer tech.