Sugar may be a human health killer, but it is now used by scientists as a substrate to prevent dendrite formation in lithium metal batteries, and a solution for the next generation of high energy density candidates representing lithium metal batteries is a solution.
Scientists have noticed that dendrites in lithium batteries are similar to whiskers that appear in metals. Dendrites are formed due to uneven deposition of lithium on the surface of the battery electrode, which causes problems such as loss of battery capacity, reduction in charge and discharge efficiency, and short circuit; whiskers are a phenomenon that occurs in electronic components. Vacuum tubes in the early 20th century In the period, scientists used pure tin or alloys close to pure tin as solder, and whiskers on the solder joints caused short spots.
Most importantly, research coordinator/Ming Tang, assistant professor of materials science and nanoengineering at Rice University, said that scientists know that whiskers appear in the presence of compressive stress, but also in the lithium metal coating during battery cycling. The mechanism that causes compressive stress is not well understood, and the compressive stress is irrelevant to the dendritic formation of the anode of the lithium battery. Although the whiskers are straight and the dendrites are more sturdy, the formation mechanism of the two is similar.
Based on this understanding, the researchers first simulated the compressive stress generated during planar plating of soft metals to show how lithium dendrites grow. Experiments have shown that coating lithium metal on a flat substrate leaves lithium with nowhere to go, so it Changed to appear in the form of dendrites.
Compared with tin, lithium has a lower melting point (180.5 °C), which means that lithium atoms are more fluid at room temperature. If there is pressure, the atoms are more willing to move, which is why we can be in hours or even minutes. I saw the reason for the formation of dendrites.
To solve this problem, the team identified a technology that would help inhibit the formation of lithium dendrites, where sugar plays a role. The researchers injected the candy pieces into a substrate with a liquid silicone polydimethyl methoxy alkane (PDMS), which then dissolved the sugar, leaving a three-dimensional porous structure with only soft silica gel, like a sponge that might collapse and deform. It is then covered with a thin layer of copper to conduct electrons, and finally the cavity is filled with lithium metal.