TU-TESL

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According to foreign media reports, scientists have discovered the root cause of the growth of needle like structures (dendrites and dendrites) in lithium-ion, which sometimes lead to short circuit, failure or even fire of lithium-ion batteries. A team at the Department of energy's Pacific Northwest National Laboratory (PNNL) found that some compounds in battery electrolytes (liquid materials that cause critical chemical reactions in batteries) promote the growth of dendrites and dendrites. The team hopes that the discovery will facilitate the development of new methods, eventually by controlling the growth of dendrites and dendrites in cell composition. Dendrite is a kind of tiny and hard dendrite structure, which will grow in lithium battery. The needle like part of dendrite is called dendrite. Both can cause great damage and can penetrate the membrane inside the battery, just as weeds can penetrate a concrete terrace or paved road. Moreover, these substances can also increase the adverse reactions between electrolyte and lithium, and accelerate the battery failure. The energy density of lithium metal battery is higher than that of common lithium-ion battery. However, the existence of dendrites and dendrites hinders the popularization of lithium-metal battery. The PNNL team found that the dendrites in lithium metal batteries are derived from the "SEI" film (solid electrolyte mesophase), the film between the anode's solid lithium surface and the liquid electrolyte. In addition, scientists also found that the main culprit of dendrite growth: ethylene carbonate. Ethylene carbonate is an indispensable solvent, which can be added to the electrolyte to improve the performance of the battery. It turns out that it's ethylene carbonate that makes batteries vulnerable to damage. The researchers specially designed lithium metal batteries of nanometer size for the research, and then used the video to show the growth process of dendrites in the batteries step by step. When lithium ions begin to gather or "nucleate" at the anode, dendrites begin to form. At the beginning, particle size indicates the birth of dendrites. As more and more lithium atoms gather together, the structure grows slowly, just as stalagmites grow from the bottom of a cave. The team found that the energy dynamics on the SEI surface push more lithium ions onto the slowly growing dendrites. Then, all of a sudden, a dendrite came out. It's not easy for the team to capture the moment the dendrites grow. To this end, scientists used a combination of atomic force microscopy (AFM) and environmental projection electron microscopy (etem). Etem is a very precious instrument that allows scientists to study the working state of batteries in real conditions. The team used AFM to measure the small force of dendrite growth, and by pressing the cantilever top of AFM downward, measured the force of dendrite growth, and measured the force exerted by dendrites during dendrite growth. The team found a direct relationship between the content of ethylene carbonate and the growth of dendrites and dendrites. The more ethylene carbonate the team added to the electrolyte, the more dendrites they would grow. Using a mixture of electrolytes, the scientists changed its composition to reduce dendrites. For example, the researchers added cyclohexanone to prevent the growth of dendrites and dendrites. Understanding the causes of dendrite generation and growth in batteries can provide new ideas for eliminating dendrite or controlling dendrite, and ultimately preventing battery damage. A deeper understanding of battery dendrites will help clear the way for the wide application of lithium metal batteries in electric vehicles, laptops, mobile phones and other fields, the researchers said.