A New Fast-Charging Solid-State Battery Designed Like a "Chocolate Truffle" Shows Serious Longevity

A team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has come up with a new solid-state lithium metal battery which, they say, can survive at least 6,000 charge-discharge cycles — and yet can be charged in just minutes.

"Lithium metal anode batteries are considered the holy grail of batteries because they have ten times the capacity of commercial graphite anodes and could drastically increase the driving distance of electric vehicles," says senior author Xin Li, associate professor of materials science, of the team's work. "Our research is an important step toward more practical solid state batteries for industrial and commercial applications."

High-capacity, high-current batteries based on lithium metal anodes have one big problem: the formation of small spikes, called dendrites, on the anode. As these grow, they can pierce the battier between the anode and the cathode — creating a short which, at best, destroys the battery and at worst starts a hard-to-extinguish lithium fire. Slower charging is one approach, but not one which gels well with the need to top up an electric vehicle's battery during a journey.

The battery proposed by the researchers takes a different approach: the inclusion of micron-sized silicon particles within the anode, which allows for a smoother lithium metal plating and the avoidance of dendrite growth. "In our design," Li analogizes, "lithium metal gets wrapped around the silicon particle, like a hard chocolate shell around a hazelnut core in a chocolate truffle."

The result is a battery which can be charged from empty in as little as ten minutes, yet which retains 80 per cent of its original capacity after an impressive 6,000 charge-discharge cycles — and which is far less likely than the competition to suddenly burst into flames. The team's prototype, though, isn't quite ready for use in electric vehicles: despite being an order of magnitude larger than rival designs, it's roughly the size of a postage stamp.

The team's work has been published in the journal Nature Materials under closed-access terms; the core technology has already been licensed by Adden Energy, a spin-off from Harvard co-founded by Li, which has successfully scaled the technology to a battery the size of a smartphone.