Lithium-silicon smartphone batteries explained

Research on the lithium-ion battery began back in the 1960s and matured into a commercially viable product around the 1990s. The earliest prototype was developed by NASA in 1965, and the first commercial product appeared on the shelves in 1991. It was made by Sony.

This type of battery follows the above mechanism, using lithium as a main chemical element. Why lithium? While there has been extensive research on a multitude of materials for potential use in lithium-ion batteries, the actual chemistry space that has been successfully incorporated into commercial applications within this technology is quite limited. To put it simply, lithium works best.

In lithium-ion batteries, the cathode is commonly composed of a lithium metal oxide, such as lithium cobalt oxide or lithium iron phosphate. The anode is made from some type of carbon, such as graphite, and the electrolyte is a lithium salt. What's the deal with the silicon, then?

Lithium-silicon batteries

Lithium-silicon batteries use a tiny tweak to the anode that results in a substantial improvement in capacity. Graphite has an upper limit in capacity of 372 mAh/g. On the other hand, pure crystalline silicone has a theoretical capacity of 3600 mAh/g, roughly ten times that of graphite.

Where are our 50 000 mAh smartphone batteries then? Well, pure silicon crystals have a nasty property to change their volume when charged and discharged, by as much as 300%. This means that the battery will swell, break and catch fire or explode.

In order to prevent that while still reap some benefits from silicon, scientist have made a composite silicon-carbon material. It uses silicon nanoparticles to increase the capacity of the graphene anode. Currently, commercial silicon-carbon batteries have a capacity of around 550 mAh/g. Tesla uses this technology in its car batteries, and Honor also employs it in the Honor Magic 5 Pro, the foldable Magic V2, and the upcoming Magic 6 Pro.

What's next?

Let's get one thing straight. Lithium-silicon batteries are not solid-state batteries. You may have heard a ton about the latter, with promises for increased capacity and super-fast charging. This type of battery deserves a separate article, and indeed the potential there is huge but there are difficulties that need to be overcome, and they are huge too.

Is there a future for lithium silicon-carbon batteries? Absolutely! Expect more smartphone manufacturers to try and facilitate this technology. The most important factor here is that the materials and processes used to create such batteries are not radically different from conventional lithium-ion batteries. And this means scalability and commercially acceptable cost.

At their current state, lithium silicon batteries offer a modest 20% bump in capacity but advancements in this technology could increase this number tenfold. So, 10 000mAh iPhones and Galaxies might not be that far away.