The new battery could increase the lifetime of electric vehicles by 10 to 15. The lithium battery is made up of multiple levels to protect the inner electrodes. (Photo from Second Bay Studios/Harvard SEAS)
The electric vehicle market is on the rise. We’re starting to see more electric cars on the road, but if the market wants to continue expanding, the cars need better battery power. Currently, lithium-ion batteries are too heavy, too expensive, and take too long to charge. A team from Harvard University recently developed a new lithium-metal battery that can overcome these challenges.
The team, led by Xin Li, Associate Professor of Materials Science, designed a stable, lithium-metal solid-state battery that can be charged and discharged about 10,000 times at a high current density, which is more than standard lithium batteries. With such a high density, electric vehicles could fully charge within 10 to 20 minutes.
“Our research shows that the solid-state battery could be fundamentally different from the commercial liquid electrolyte lithium-ion battery,” said Li. “By studying their fundamental thermodynamics, we can unlock superior performance and harness their abundant opportunities.”
But before they reached this stage, the team had to overcome challenges presented by lithium-metal batteries. During charging, lithium batteries move lithium ions from the cathode to the anode. But when the anode is made of lithium metal, it causes dendrites -a needle-like structure – to form on the surface, which will penetrate the barrier separating the anode and cathode, causing the battery to be short or catch fire.
To address this, the team designed a multilayer battery that places different stable materials between the anode and cathode. It’s kind of like a sandwich: first comes the lithium metal anode followed by a coating of graphite. The electrolytes are next, followed by the final layer, the cathode. This method is meant to control and contain the dendrites, not stop them. Using this method, the dendrites can grow through the graphite and the first electrolyte but are stopped when they reach the second one. The battery can also repair holes created by dendrites.
“This proof-of-concept design shows that lithium-metal solid-state batteries could be competitive with commercial lithium-ion batteries,” said Li. “And the flexibility and versatility of our multilayer design makes it potentially compatible with mass production procedures in the battery industry. Scaling it up to the commercial battery wont’ be easy and there are still some practical challenges, but we believe they will be overcome.”
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