Stop the formation of harmful crystals in lithium metal batteries

　　Now, an international research team led by Wei Bingqing, professor of mechanical engineering at the University of Delaware and director of the Fuel Cell and Battery Center, is working to lay the foundation for the wider use of lithium metal batteries, which will be more common than lithium-ion batteries currently used in consumer electronics. Larger capacity.

　　From smart phones to electric cars, many technologies today use lithium-ion batteries. This means that consumers must maintain the convenience of chargers. The iPhoneX battery only lasts for 21 hours of talk time, while Tesla’s S model has a range of 335 miles-which means you can travel from Newark, Delaware to Providence, Rhode Island City, but not all ways to go to Boston, one charge.

　　Scientists all over the world-even John Goodenough, the inventor of lithium-ion batteries-are looking for ways to make rechargeable batteries safer, lighter, and more powerful.

　　Now, an international research team led by Wei Bingqing, professor of mechanical engineering at the University of Delaware and director of the Fuel Cell and Battery Center, is working to lay the foundation for the wider use of lithium metal batteries, which will be more common than lithium-ion batteries currently used in consumer electronics. Larger capacity. The team developed a method to alleviate dendrite formation in lithium metal batteries, which they described in a paper published on NanoLetters.

　　The promise (and trap) of lithium metal batteries

　　"" In a lithium ion battery, the anode or current generating side is made of a material such as graphite, with lithium ions bound to it. Lithium ions flow to the cathode or current collecting side.

　　In lithium metal batteries, the anode is made of lithium metal. Electrons flow from the anode to the cathode to generate electricity. Rechargeable batteries made of lithium metal have many promises because lithium is the metal with the most electrical properties and has a very high capacity.

　　"In theory, lithium metal is one of the best choices for batteries, but it is difficult to handle in practice," Wei said.

　　Lithium metal batteries have so far been inefficient, unstable, and even have fire hazards. Their performance is hindered by lithium dendrites, which look like small stalagmites made from lithium deposits. As the battery is used, lithium ions will accumulate on the anode. Over time, lithium deposits become uneven, leading to the formation of these dendrites, which can cause the battery to short circuit.

　　new understanding

　　Research groups around the world have tried various techniques to inhibit the formation and growth of these dendrites. After studying the literature, Wei found that almost all applied technologies can be understood under an umbrella: introducing a layer of porous material into the system can prevent dendrites from accumulating on the anode.

　　The 　　 research team used mathematical modeling to find that porous materials inhibited the initiation and growth of dendrites. The dendrites that do form are 75% shorter than those formed in systems lacking a porous membrane. To further prove this discovery, the team created a diaphragm made of porous silicon nitride filaments, each of which is less than one-hundredths of a millionth. Then they integrated the membrane into the lithium metal battery in the battery and ran it for 3,000 hours. No dendrites grow up.

　　"This basic understanding may not be limited to the silicon nitride we use," Wei said. "Other porous structures may also do this."

　　More importantly, this principle can also be extended to other battery systems, such as zinc or potassium-based batteries, he said.

　　"In this field of metal batteries, this is the latest understanding," he said. "This is a job that can have a significant impact."