Before returning to the college entrance examination, I became popular in the science circle

There are still nearly two months before New Year's Day. Wu Tong feels that there is still plenty of time, so he can slow down and take his time, and do research and development as a vacation!

It can be said that her research team has been preparing for this project for more than a year.Although not all the energy is spent on this project, at least more than half.

Therefore, this time Wu Tong changed his style and planned to bring the team together. She would provide inspiring guidance and the actual operation would be done by the team, which would further enhance their scientific research capabilities.

The growth and training of the team is also an important issue. She can do all the research and development things, but in this case, her team will be meaningless, and the team is also full of excellent talents. Wu Tong naturally wouldn't waste it like this!As this group of people grows up, the future is very promising!

Therefore, Wu Tong wants to use the project to give team members the opportunity to experience and learn!
The news that Wu Tong wanted to take the research team to work on this project together, and the instructions were passed on, naturally made the research team happy.Having been working on new energy batteries for so long, it would be false to say that they don’t want to make a qualitative breakthrough in this area.But compared to Mr. Wu, their speed was lagging behind, and for a while, 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 the personal guidance of a peak mentor. If they cannot seize and make good use of this opportunity, it will really be a waste of natural resources!

Wu Tong held an initial seminar on the project, 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. During charging, the lithium ions returned to the negative electrode will never return to the lithium metal layer as expected and return to the lithium metal layer. It will bloom like a flower, forming a beautiful and deadly branch." Tao Ran couldn't help but feel a toothache when he thought of the obstacles he encountered during this year's experiment.

The dendritic metal lithium formed when lithium ions are reduced during the charging process of this lithium battery is called lithium dendrites by troubled scientific researchers. However, when lithium appears on the negative electrode side, the form of lithium is not necessarily lithium dendrites, collectively known as lithium dendrites. To analyze lithium.

"Lithium dendrite growth is one of the fundamental issues affecting the safety and stability of lithium-ion batteries. The growth of lithium dendrites will cause instability at the interface between the electrode and electrolyte during the cycling process of the lithium-ion battery, destroying the generated solid electrolyte interface (SEI) film, lithium dendrites will continuously consume the electrolyte during the growth process and lead to irreversible deposition of metallic lithium, forming dead lithium and causing low Coulombic efficiency;
Once this kind of thing is formed, it will continue to grow uncontrollably as it is continuously charged, and eventually it will be like a sharp fork, piercing the separator and contacting the positive electrode. In this state, it will be connected to a wire together with the positive and negative electrodes of the battery. There is no difference, a direct short circuit is a minor problem.

Organic electrolytes are all flammable. The formation of lithium dendrites will pierce the separator and cause an internal short circuit in the lithium-ion battery, causing thermal runaway of the battery and causing a combustion explosion. "Ruan Chengxu cooperated well and analyzed the problem carefully.

"The classic case of lithium dendrites, not to mention the Moli company, their products almost made history, but because they used lithium as the negative electrode, a major safety accident occurred, which resulted in the recall of NTT mobile phones. It once led to the downfall of Moil Company, which later declared bankruptcy and was acquired. This has a lot to do with it!

For this reason, lithium metal was abandoned by the industry as anode. Because of the short circuit problem caused by dendrite growth, the battery turned into an incendiary bomb and "exploded" a listed company with a market value of tens of billions.How ferocious it is for a fatal flaw to lead to the downfall of a large company! "

In contrast, Sony was very smart. It directly used graphite as the negative electrode, launched lithium-ion batteries and quickly occupied the market, thus leading to the rise of Sony!However, alternatives are alternatives after all, and there is an upper limit.

"Currently lithium-ion batteries are mainly based on graphite anodes. We can calculate from the product LiC6 that the theoretical specific capacity of graphite is 372mAh/g. Regardless of cost, this number can be turned into 747mAh through graphene technology in the laboratory. /g. However, compared to the capacity of lithium, which is 3860mAh/g, the ten-fold difference can be intuitively felt from the numbers. If we can make a breakthrough in this field, the future prospects will be so broad! "

This gap has officially attracted countless scientific researchers and countless materials research laboratories. They are flocking to the flames like moths. In the field of lithium batteries, the reason why they are constantly rushing forward and investing heavily in experiments is that it represents hundreds of billions and a huge market prospect. lure.

Internationally, both private companies and international sectors have not stopped researching and developing lithium metal as anode materials.

"Our initial experiment was also a similar arrangement. Starting from basically using 95.7% graphite as the negative electrode material, the binder was sodium carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR), and the current collector was copper foil .

The graphite layer gradually tends to take priority at different thicknesses. At 90 microns, the positive active material uses LiFePO4 and the current collector is aluminum foil.

As for the separator, the three-layer separator of Celgard2325 is used, and the thickness is also the best tested in the experiment, 25 microns.This is also the current mainstream! "

"So, we still have to find a way out of the negative electrode material coating film!" This more than a year of research is not in vain, "We have 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 they spoke freely. The young people's active thinking and various perspectives made Wu Tong and the adults who participated in the meeting smile.

Scientific research requires such brainstorming and active thinking.To use your brain scientifically, you must learn to think scientifically.This not only gets twice the result with half the effort, but also creates something creative.Scientific research is inherently an extremely arduous and complex creative mental work.

Of course, on the other hand, scientific researchers are also required to work down-to-earth and conscientiously without any hypocrisy. Scientific research does not tolerate fraud and nonsense!Because he acted recklessly, he paid a high price and ended up in the sea!
"Lithium-ion batteries are afraid of water and oxygen, and the commonly used technical means to characterize SEI are very limited!"

"What about the conventional transmission electron microscopy method?" Someone raised his hand and tried to ask, "I'll give you some ideas!"

Wu Tong nodded lightly. She remembered this student recommended by senior brother Zhang Shaoming. Although he was still a little green, according to the observations and reports of Tao Ran and his junior brother, he had a correct and serious attitude towards learning, good talent, and was worth cultivating. , not long ago, was absorbed into the core team.