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New lithium metal battery design can be recharged in minutes

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new lithium metal battery that can be charged and discharged at least 6,000 times and can be recharged in a matter of minutes.

While lithium-metal batteries have the potential to hold about double the energy that lithium-ion batteries can, they also present a far greater risk of catching fire or even exploding.

Xin Li, Associate Professor of Materials Science at SEAS and senior author of the paper said: ‘Lithium metal anode batteries are considered the holy grail of batteries because they could drastically increase the driving distance of electric vehicles.’

One of the biggest challenges in the design of these batteries is the formation of dendrites on the surface of the anode which grow like roots into the electrolyte and pierce the barrier separating the anode and cathode, causing the battery to short or even catch fire. 

These dendrites form when lithium ions move from the cathode to the anode during charging, attaching to the surface of the anode in a process called plating. Plating creates an uneven surface which allows dendrites to take root. When discharged, that uneven surface needs to be stripped from the anode and the more uneven the surface is, the longer the stripping takes. 

In this new research, Li and his team have found a way to stop dendrites from forming by using micron-sized silicon particles in the anode to constrict the lithiation reaction.

Li said: ‘In our design, lithium metal gets wrapped around the silicon particle, like a hard chocolate shell around a hazelnut core in a chocolate truffle.’

These coated particles create a homogenous surface across which the current density is evenly distributed, preventing the growth of dendrites. And, because plating and stripping can happen quickly on an even surface, the battery can recharge in only about 10 minutes.

The researchers built a postage stamp-sized pouch cell version of the battery, which is 10 to 20 times larger than the coin cell made in most university labs. The battery retained 80% of its capacity after 6,000 cycles, outperforming other pouch cell batteries on the market today.

The technology has been licensed through Harvard Office of Technology Development to Adden Energy, a Harvard spinoff company cofounded by Li and three Harvard alumni. The company has scaled up the technology to build a smart phone-sized pouch cell battery.

 

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