Chapter 380 Brick Throwing
There are still nearly two months before New Year's Day. Wu Tong feels that there is still plenty of time. He can slow down and take it easy, and even take a vacation to do research and development!
Her research team has been preparing for this project for more than a year. Although not all their efforts have been put into this project, at least more than half of it has been put into it.
Therefore, this time Wu Tong changed her style and prepared to work with the team. She would provide inspiring guidance, while the team would do the actual operations, which would also further enhance their scientific research capabilities.
The growth and cultivation of the team is also an important issue. She can take on all the R&D work, but in this case, her team will be meaningless. The team is full of excellent talents, so Wu Tong will not waste them like this! The future of this group of people is promising!
Therefore, Wu Tong wants to use the project to give team members enough opportunities to gain experience and learn!
The news that Wu Tong wanted to bring the research team to work on this project naturally made the research team happy. After working on new energy batteries for so long, it would be a lie to say that they didn't want to make a qualitative breakthrough in this area. However, compared with President Wu, their speed was lagging behind, and for a moment, they were ashamed to mention it.
However, now, Mr. Wu is willing to take them to do it together, which is equivalent to them asking for personal guidance from a top mentor. If they cannot seize and make good use of this opportunity, it would be a real waste!
Wu Tong organized an initial project seminar, and several core team members seized the opportunity to speak freely.
"...Lithium is the most ideal negative electrode material, but it also poses a fatal threat. When charging, the lithium ions that return to the negative electrode will never be as obedient as people wish and turn back into a lithium metal layer. Instead, they will form a beautiful but deadly branch like a flower." Thinking of the obstacles encountered in this year's experiment, Tao Ran couldn't help but feel a toothache.
The dendritic lithium metal formed when lithium ions are reduced during the charging process of this lithium battery is called lithium dendrites by scientific researchers, but the form of lithium when it appears on the negative electrode side is not necessarily lithium dendrites, which are collectively referred to as lithium plating.
"Lithium dendrite growth is one of the fundamental problems that affect the safety and stability of lithium-ion batteries. The growth of lithium dendrites will lead to instability of the electrode and electrolyte interface during the cycle of lithium-ion batteries, destroying the generated solid electrolyte interface (SEI) film. During the growth process, lithium dendrites will continuously consume electrolyte and cause irreversible deposition of metallic lithium, forming dead lithium and causing low coulombic efficiency.
Once this thing is formed, it will continue to grow unstoppably with continuous charging, and will eventually pierce the diaphragm and contact the positive electrode like a sharp fork. In this state, it is no different from a wire together with the positive and negative poles of the battery. A direct short circuit is a minor problem.
Organic electrolytes are flammable. The formation of lithium dendrites will pierce the diaphragm and cause a short circuit inside the lithium-ion battery, resulting in thermal runaway of the battery and causing combustion and explosion. "Ruan Chengxu cooperated well and analyzed the problem carefully.
"The classic case of lithium dendrites is not to mention the distant past. The product of Moli Company almost made history, but because it used lithium as the negative electrode, a major safety accident occurred, which led to the recall of NTT mobile phones and the downfall of Moli Company. Later, it declared bankruptcy and was acquired, which was also closely related to this!
For this reason, lithium metal was abandoned as a negative electrode by the industry. The short circuit problem caused by dendrite growth turned the battery into a burning bomb, "blowing down" a listed company with a market value of tens of billions. A fatal defect led to the decline of a large company, which is really fierce! "
In contrast, Sony was very smart. It used graphite as the negative electrode and launched lithium-ion batteries, which quickly occupied the market and led to the rise of Sony! However, substitutes are substitutes after all, and there is an upper limit.
"Currently, lithium-ion batteries are mainly based on graphite negative electrodes. We calculated through the product LiC6 that the theoretical specific capacity of graphite is 372mAh/g. If we don't consider the cost, we can use graphene technology in the laboratory to turn this number into 747mAh/g.
However, compared to the capacity of lithium, which is 3860mAh/g, the difference is ten times. We can intuitively feel from the numbers that if we can make a breakthrough in this field, the future prospects will be so broad! "
This gap is what attracts countless scientific researchers and material research laboratories to rush into the field of lithium batteries, investing heavily in experiments. The reason is that it represents a huge temptation of hundreds of billions of market prospects.
Internationally, both the private company sector and the international sector have not stopped the research and development of lithium metal negative electrode materials.
"Our initial experiments were also arranged in a similar way. We started with 95.7% graphite as the negative electrode material, the binder was sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and the current collector was copper foil.
The graphite layer gradually tends to be preferred at different thicknesses. At 90 microns, LiFePO4 is used as the positive electrode active material and aluminum foil is used as the current collector.
As for the diaphragm, we use a three-layer Celgard2325 diaphragm, and the thickness is also the best choice tested in the experiment, 25 microns. This is also the current mainstream! "
“So, we still have to find a way out in the negative electrode material coating film!” Their research over the past year has not been in vain. “We have also made many attempts here…”
Since it was a brainstorming session, no one was afraid of making a fool of themselves. Various ideas were reported one by one and everyone spoke freely. The young people's active thinking and various unique perspectives made Wu Tong and Mr. Cheng, who was also participating in the meeting, smile.
Scientific research requires such brainstorming and active thinking. To use the brain scientifically, one must learn scientific thinking. This will not only achieve twice the result with half the effort, but also lead to creativity. Scientific research is an extremely difficult and complex creative mental work.
Of course, on the other hand, it also requires scientific researchers to work conscientiously and earnestly, without any hypocrisy. Scientific research cannot tolerate fraud and recklessness! Because recklessness will pay a high price!
"Lithium-ion batteries are afraid of water and oxygen, and the commonly used technical means to characterize SEI are very limited!"
"What about conventional transmission electron microscopy?" Someone raised his hand and tried to ask, "Let me throw out some ideas!"
Wu Tong nodded slightly. She remembered this student recommended by senior brother Zhang Shaoming. Although he was still a little green, according to the observation reports of Tao Ran and the junior brother, his learning attitude was correct and serious, and his talent was also good. He was worth cultivating. Not long ago, he was absorbed into the core team.
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