Chapter 154 The Beautiful and Deadly Dendrite

Lu Zhou replied, "I'll do it."

The system does not stipulate who must operate the experiment, as long as the experiment is done once, and then the data that needs to be collected is collected. But not for the purpose of learning, Lu Zhou still wants to do it himself.

After all, what comes on paper is always shallow, and the books handed over to him are all theories. Only when it is put into practice can the legendary black technology be turned into a real thing.

Changing into a white coat with a sense of ritual, Lu Zhou showed a bit of a scientist's momentum, took a deep breath, and reached for the sample box containing the experimental materials.

However, before he could touch his hand, he was snatched away by Senior Brother Qian, who had quick eyesight and quick hands.

"Let me come and watch."

Without further ado, Senior Brother Qian took over the initiative of the experiment, leaving Lu Zhou with a confused face aside.

Looking at senior brother Liu, who folded his arms, he shrugged helplessly.

"Don't mind, Lao Qian is like this. The equipment here is like his wife, more important than his life... You should watch him do it for the first time."

Senior Brother Qian didn't turn his head back, and then said: "Doing experiments is not doing mathematics. If you make a mistake in a decimal point, you can continue to calculate it. If you make a small mistake in the experiment, it may lead to the failure of the whole experiment. Of course, I am more afraid of it." It was you who abolished the experimental equipment...show me the experimental process of your design."

"Here." Lu Zhou quickly took out the A4 paper.

He wrote the experimental steps required by the system and the experimental data to be collected.

Brother Qian took the A4 paper and glanced at it, then nodded: "The design is quite professional."

emmm...

After all, it is designed by the system.

Lu Zhou had a subtle expression and did not speak.

...

The process of the experiment is very simple, from making the battery to observing the phenomenon.

95.7% graphite is used as the negative electrode material, the binder is sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and the current collector is copper foil. The thickness of the graphite layer is 90 μm, the positive electrode active material is LiFePO4, and the current collector is aluminum foil.

As for the diaphragm, a three-layer diaphragm of Celgard2325 with a thickness of about 25 μm is used.

In order to prevent material oxidation, all operations were carried out in a glove box filled with argon.

Of course, not only to prevent the material from oxidizing, but also to prevent the LiPF6 component in the electrolyte from reacting with water in the air to generate hydrofluoric acid.

Anyone who has studied high school chemistry knows about hydrofluoric acid.

Anyone who has worked in a silicon-based microelectronics laboratory should know how dangerous this thing is. Put a little on which hand, and this hand is basically invisible.

Judging from Senior Brother Qian's operation process, it is obvious that he is more professional than Lu Zhou, a theoretician.

In no time, the samples were produced.

In order to prevent the sample from being damaged, an edge-to-edge assembly is used. Brother Qian completely covered the LiFePO4 material with a layer of separator in the glove box, and carefully left a 2mm gap between the free ends of the positive and negative electrodes.

This step is critical and concerns the safety of the experiment.

After taking the sample out of the glove box, Senior Brother Qian closed the various air valves, and heaved a sigh of relief.

"Done."

Looking at the sample in Senior Brother Qian's hand, Lu Zhou asked, "Is this a battery?"

"A simple and unsafe lithium-ion battery," Mr. Qian briefly introduced.

Lu Zhou was nervous for a moment: "Will it explode?"

Senior Brother Qian shook his head: "It will not explode, but if it is not operated properly, it may cause a fire."

And, it's fire on a digital microscope.

Burning out the sample is a trivial matter, but burning the lens of a digital microscope is a big problem.

Lu Zhou reckoned that this was one of the reasons why Senior Brother Qian didn't let himself, a novice, touch the experiment.

Connect the sample to the BK-6808 rechargeable battery performance tester, and then put it on the digital microscope. Brother Qian set up a few parameters in front of the computer, while repeating the steps on the paper in a low voice as if talking to himself: "2min Collect an image once, the data collection frequency is 1Hz, the battery is charged to 400min for the first time and then discharged to the cut-off voltage...OK."

All that's left is a long wait.

Looking at the unchanged instrument, Lu Zhou couldn't help asking, "Do you all have to wait so long for battery material tests?"

Four hundred minutes, almost seven hours.

Brother Qian pushed his glasses and said: "Seven hours is the basic operation, and sometimes you have to wait for a few days to see the results. Generally, someone will be left on duty in the laboratory. Basically, Liu Bo and I will take turns to do it. "

"That's right," Liu Bo said with a smile, "I watched more than forty dramas last year, and I watched them when I was on duty in the laboratory. Do you want me to recommend something to you?"

Lu Zhou: "This, it's better not to use it."

Even if it is recommended, he probably doesn't have much time to watch it.

After finishing all the necessary operations, Senior Brother Qian briefly taught Lu Zhou how to deal with emergencies.

For example, if you see smoke from the sample, smell something wrong, how to clean up the damaged sample, how to protect the instrument, and most importantly, how to protect yourself.

No matter how expensive the instrument is, it is not as important as the person.

Of course, this experiment was not that dangerous, so Senior Brother Qian threw the key into Lu Zhou's hands with confidence.

He and Senior Brother Liu still have something to do, it is impossible to stay here all the time, and Lu Zhou is embarrassed to bother him so much. After all, doing this experiment has already delayed them a lot of time.

Taking out the book on Quantum Chromodynamics, Lu Zhou sat next to the digital microscope, while supplementing his knowledge of theoretical physics, while glancing at the situation on the digital microscope from time to time.

Later, he found that he didn't need to be so cautious at all, so the product stayed under the microscope for so long, and the outside didn't look changed at all.

It can be seen that Senior Brother Qian's experimental skills are quite reliable.

From ten o'clock in the morning, he stayed in the laboratory until almost six o'clock in the evening. During this period, Lu Zhou ordered a takeaway and had lunch.

Finally, when the set time came, and the charge and discharge were over, Lu Zhou followed what Senior Brother Qian said, kept the circuit open and waited for 10 minutes before cutting off the power.

Almost right after he finished the finishing work, footsteps came from outside the laboratory. Brother Liu, who had just had dinner in the cafeteria, almost stepped onto the laboratory.

"Finished?" After looking at the sample, Senior Brother Liu skillfully operated the computer and clicked the print button, "Then let's collect the data."

The printer hums.

Soon, Lu Zhou got what he wanted.

A set of pictures that record the growth of lithium dendrites under the microscopic, as well as graphs such as cycle voltage curves that the system requires to collect, and so on.

While collecting these data, Brother Liu said in a chatty tone.

"...Lithium is the most ideal negative electrode material, but it is also the most difficult to serve. When charging, the lithium ions returning to the negative electrode will never change back to a flat lithium metal layer as you wish, but instead It will form a beautiful but deadly twig, just like the blossoms."

Waiting for the printer to finish printing the chart, Lu Zhou asked casually, "Fatal?"

"Yes, once this kind of dendrite is formed, it will continue to grow irresistibly with continuous charging, and eventually it will pierce the separator like a fork and contact the positive electrode."

Having said that, Brother Liu paused for a moment, and said in a joking tone: "Imagine, what would happen if a wire was used to connect the positive and negative electrodes of the battery? That's right, it's a short circuit. And organic electrolytes are easy to Burning things, have you heard of Moli company?"

"no, what happened?"

Brother Liu shrugged, and handed the printed A4 paper to Lu Zhou, "Their products almost made history, but because of the use of lithium as the negative electrode, a major safety accident occurred, resulting in the NTT mobile phone It was recalled, and finally the company went bankrupt and was acquired. In contrast, Sony was very smart, directly used graphite as the negative electrode, and launched lithium-ion batteries to quickly occupy the market.”

Lu Zhou couldn't help asking: "Didn't they do a safety test?"

Brother Liu sighed: "Yeah, everyone would ask this question, but things may be far from that simple. Maybe they didn't find the problem after doing it? Maybe they thought they found the perfect solution? Who knows? Sometimes , reality is so magical.”