According to foreign media reports, scientists have discovered the root cause of the growth of needle-like structures (ie, dendrites and dendrites) in lithium-ion batteries. Such structures sometimes cause short-circuits, failures, and even fires in lithium-ion batteries.
(Source: Northwest Pacific National Laboratory)
A research team from the Department of Energy's Pacific Northwest National Laboratory (PNNL) found that certain compounds in battery electrolytes (liquid materials that enable batteries to undergo critical chemical reactions) promote the growth of dendrites and dendrites . The research team hopes that this discovery will facilitate the development of new methods, and ultimately organize the growth of dendrites and dendrites by controlling the components of the battery.
A dendrite is a tiny, hard tree-like structure that grows in a lithium battery. The needle-like protrusions are called dendrites. Both things can cause huge damage, and can penetrate the membrane inside the battery, just like weeds can penetrate a concrete terrace or paved road. Moreover, such substances will increase the adverse reaction between the electrolyte and lithium, and accelerate battery failure. The energy density of lithium metal batteries is higher than that of commonly used lithium ion batteries. However, the presence of dendrites and dendrites hinders the popularity of lithium metal batteries.
The PNNL team found that the dendrites in lithium metal batteries originate from the "SEI" film (solid electrolyte intermediate phase), which is the thin film between the anode solid lithium surface and the liquid electrolyte. In addition, scientists have discovered the culprit of dendrite growth: ethylene carbonate. Ethylene carbonate is an indispensable solvent that can be added to the electrolyte to improve battery performance. The results prove that it is ethylene carbonate that makes the battery easy to damage.
The researchers specifically designed a nano-sized lithium metal battery for the study, and then used the video to show the growth process of the dendrites in the battery step by step.
When lithium ions begin to accumulate or "nucleate" at the anode, dendrites begin to form, initially at the particle size, indicating the birth of dendrites. As more and more lithium atoms gather, the structure will slowly grow as if stalagmites have grown from the bottom of the cave. The research team found that the energy dynamics on the surface of the SEI will push more lithium ions onto the slowly growing dendritic column. Then, suddenly, a dendrite grew out.
It was not easy for the team to capture the moment when dendrites grew. To this end, the 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 under real conditions.
The team used AFM to measure the tiny force during dendrite growth, and measured the strength of dendrite growth by pressing down the top of the cantilever of AFM, and measured the force exerted by dendrites during dendrite growth.
The research team found that the content of ethylene carbonate is directly related to the growth of dendrites and dendrites. The more ethylene carbonate the team added to the electrolyte, the more dendrites it grew. Scientists use electrolyte mixtures to experiment and change their composition to reduce dendrites. For example, the researchers added cyclohexanone to prevent the growth of dendrites and dendrites.
Understanding the reasons for the generation and growth of dendrites in batteries can provide new ideas for eliminating dendrites or controlling dendrites and ultimately preventing battery damage. Researchers say that a deeper understanding of battery dendrites will help clear the way for the widespread application of lithium metal batteries in electric vehicles, laptop computers, mobile phones and other fields. (Author: Yuqiu Yun)
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