Electric vehicles are an important part of the next steps in global personal transportation, but there are still plenty of challenges to overcome. Range anxiety, charging infrastructure, and everyday charging time are three of the most pressing concerns that make potential riders and drivers hesitant. Higher initial cost of ownership is another hurdle before mass adoption can happen, too. Various groups are working on all these problems, but solutions take time.  

Take dendrites. No, really, please, take them far away. They’re a big pain, and they arise at random from normal charging/discharging cycles in lithium-ion batteries, potentially leading to short-circuits and totally ruining your batteries. Dendrites have been a major problem that scientists have been attempting to overcome by various means for years. In May, 2021, one Harvard research team thinks that it’s found a viable, scalable solution.  

That solution is bacon. Well, no, not literally bacon. That’s just how the (knowledge-) hungry researchers opted to illustrate their solution in their exploded diagram. See, half the battle with telling the general public about the exciting and highly technical scientific research you’ve just done is communicating it clearly with the public. Sure, some of the public will be scientific experts who share your specialty, but probably many more won’t be. Hence, the sandwich graphic, which just about everyone can understand. 

So, what’s this delicious sandwich trying to tell us? Harvard John A. Paulson School of Engineering and Applied Science associate professor of materials science Xin Li and his team think they’ve cracked the recipe for stable lithium-metal batteries. This could overcome some of the inherent weaknesses of existing lithium-ion batteries. 

“A lithium-metal battery is considered the holy grail for battery chemistry because of its high capacity and energy density,” said Professor Li in a statement. “But the stability of these batteries has always been poor.” 

In testing, the lithium-metal battery that Li and his team developed was able to be charged and discharged at least 10,000 times, which far exceeds anything previously demonstrated. They also did this at a high current density, and used a high energy density cathode material. If scaled up, the team thinks it could possibly increase the lifetimes of EVs to be more in line with those of piston-powered cars—or about 10 to 15 years, with no need to replace the battery during that time. If this proves to be true, this could be an extremely important breakthrough.  

The sandwich illustrates just how Li and his team worked their magic. By combining a sandwich of different materials with different levels of stability together, the team found that preventing dendritic growth altogether wasn’t necessary. As long as it could control and contain where those dendrites went, the team found that they didn’t necessarily have to be a problem. When a sandwich is assembled in the proper order, it’s delicious and satisfying, and it doesn’t make a mess.  

Full details of the team’s research were published on May 12, 2021 in the peer-reviewed journal Nature, if you’d like to dig deeper. There’s also a paragraph at the bottom of the Harvard Gazette piece, advising that the intellectual property is protected and is already being advanced toward commercial applications. If the team has truly cracked it, the entire EV world will likely benefit. 

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