The photo is sourced from drive.ru
Lithium metal batteries are batteries that use lithium metal instead of graphite as the anode. Thanks to the use of this material, the batteries weigh less and have an energy density that is ten times higher than that of lithium-ion batteries. However, dendrites (extensions) often emerge on the surface of the anode during the operation of lithium metal batteries. These structures grow into the electrolyte like roots and penetrate the barrier separating the anode and the cathode, prompting a short circuit or even causing the battery to ignite.
The process of dendrite formation is rather simple: lithium ions, which move from the cathode to the anode when the battery is charging, gather and form a metal particle that gradually increases in size. The electrokinetic potential at the interface between the metal and the electrolyte attracts more and more lithium ions, which land on the growing particle, from which a whisker protrudes over time. The dendrites get partially destroyed during battery discharge when lithium ions move from the anode to the cathode, causing dents to form on the surface of the anode, which makes it difficult for the battery to charge further.
The researchers from the Harvard School of Engineering and Applied Sciences attempted to solve this problem by placing micron-sized silicon particles on the anode. This made it possible to narrow the lithiation area: during battery charging, lithium ions would get attached to silicon particles, but would not subside on the base surface of the anode. The interaction of lithium ions with silicon led to the formation of a lithium-metal layer, over the surface of which an electric current was evenly distributed. This helped not only prevent dendrite formation, but also reduce the charging time to 10 minutes.
The authors of the study created and tested a prototype lithium metal battery the size of a postage stamp. The prototype was able to retain 80% of its capacity after 6,000 charge-discharge cycles, showing better results than most batteries available in the market. In the future, the commercialisation of this battery could dramatically increase the driving range of electric vehicles.
