This scanning electron microscope image shows large, uniform crystals of lithium metal growing on a lithiophobic surface. Image: Zhaohui Wu and Zeyu Hui/UC San Diego.A team of engineers has found a way to create lithium-metal batteries that charge fast – in just an hour. This fast charging is thanks to lithium-metal crystals that can be seeded and grown – quickly and uniformly – on a surface that lithium officially doesn't ‘like’. Dense layers of uniform lithium metal can then grow from these seed crystals.
Uniform layers of lithium metal are of great interest to battery researchers because they prevent the formation of battery-performance-degrading crystal spikes known as dendrites. The formation of these dendrites in battery anodes is a longstanding roadblock to fast-charging, ultra-energy-dense lithium-metal batteries.
This new approach, developed by a team led by engineers at the University of California (UC) San Diego, allows lithium-metal batteries to be charged in about an hour, a speed that is competitive with today’s lithium-ion batteries. The UC San Diego engineers, in collaboration with UC Irvine imaging researchers, report this advance in a paper in Nature Energy.
To grow the lithium metal crystals, the researchers replaced the ubiquitous copper surfaces on the anodes of lithium-metal batteries with a lithiophobic (lithium-hating) nanocomposite surface made of lithium fluoride (LiF) and iron (Fe). Depositing lithium on this lithiophobic surface causes lithium crystal seeds to form, and from these seeds dense lithium metal layers can grow – even at high-charging rates. The result is long-cycle-life lithium-metal batteries that can be charged quickly.
"The special nanocomposite surface is the discovery," explained Ping Liu, a nanoengineering professor at UC San Diego and senior author of the paper. "We challenged the traditional notion of what kind of surface is needed to grow lithium crystals. The prevailing wisdom is that lithium grows better on surfaces that it likes, surfaces that are lithiophilic. In this work, we show that is not always true. The substrate we use does not like lithium. However, it provides abundant nucleation sites along with fast surface lithium movement. These two factors lead to the growth of these beautiful crystals. This is a nice example of a scientific insight solving a technical problem."
This advance could eliminate a significant roadblock that is holding back the widespread use of energy-dense lithium-metal batteries for applications like electric vehicles (EVs) and portable electronics. While lithium-metal batteries hold great potential for EVs and portable electronics because of their high charge density, today's lithium-metal batteries must be charged extremely slowly in order to maintain battery performance and avoid safety problems.
The slow charging is necessary to minimize the formation of battery-performance-wrecking lithium dendrites, which form as a result of lithium ions joining with electrons to form lithium crystals on the anode side of the battery. These crystals build up as the battery charges, and then dissolve as the battery discharges.
This story is adapted from material from University of California, San Diego, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.