As for the separator, a three-layer separator of Celgard2325 is used, with a thickness of about 25 μm.
The printer buzzed.
Almost as soon as he finished the finishing work, footsteps were heard outside the laboratory. Senior Brother Liu, who had just had dinner in the cafeteria, almost stomped to the laboratory.
"That's right," Liu Bo said with a smile, "I watched more than 40 dramas last year, while I was on duty in the laboratory. Do you want me to recommend some to you?"
After taking out the sample from the glove box, Senior Brother Qian closed all the air valves and let out a sigh of relief.
Later, he discovered that there was no need to be so cautious. This sample had been under the microscope for so long, and it looked unchanged on the outside.
The system does not stipulate who must perform the experiment. It only needs to be done once and then collect the data that needs to be collected. But not for the purpose of learning, Lu Zhou still wanted to do it himself.
Everyone who has studied high school chemistry knows about hydrofluoric acid.
Lu Zhou was nervous: "Will it explode?"
Of course, it is 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.
"Yes, once this kind of thing called dendrite is formed, it will continue to grow uncontrollably as it is continuously charged, and eventually it will be like a fork, piercing the separator and contacting the positive electrode."
No matter how valuable the instrument is, it is not as important as people.
Anyone who has spent time in a silicon-based microelectronics laboratory should also know how dangerous this thing is. If you apply a little bit on either hand, that hand will basically be invisible to others.
A set of pictures recording the microscopic growth of lithium dendrites, as well as charts such as cycle voltage curves that the system requires to collect, etc.
Moreover, it was a fire on the digital microscope.
"A simple and unsafe lithium-ion battery." Senior Brother Qian introduced it concisely and comprehensively.
The experimental process is very simple, starting from making the battery to observing the phenomenon.
Soon, the samples were produced.
Lu Zhou couldn't help but ask: "Didn't they do safety testing?"
He and Senior Brother Liu had something to do, so they couldn't stay here forever, and Lu Zhou was too embarrassed to bother him so much. After all, doing this experiment has already taken them a lot of time.
It can be seen that Senior Brother Qian's experimental skills are quite reliable.
Lu Zhou's expression was subtle and he said nothing.
Senior Brother Qian took the A4 paper, glanced at it, and nodded: "The design is quite professional."
After all the required operations were completed, Senior Brother Qian briefly taught Lu Zhou some methods of dealing with emergencies.
Lu Zhou replied: "I'll do it."
Soon, Lu Zhou got what he wanted.
"I'll do it and watch."
"Here." Lu Zhou quickly took out the A4 paper.
Finally, the set time came and charging and discharging ended. Lu Zhou followed Brother Qian's instructions and kept the circuit open for 10 minutes, then cut off the power.
Taking out the book on quantum chromodynamics, Lu Zhou sat next to the digital microscope, supplementing his knowledge of theoretical physics while glancing at the situation on the digital microscope from time to time.
Judging from Senior Brother Qian's operating procedures, he is obviously much more professional than the theorist Lu Zhou.
Senior Brother Qian pushed up his glasses and said: "Seven hours is a basic operation. Sometimes you have to wait a few days to see the results. Under normal circumstances, someone will be left on duty in the laboratory. Basically, Liu Bo and I take turns. "
However, before his hand could touch it, he was snatched away by Senior Brother Qian who had quick eyes and quick hands.
This step is critical and is related to the safety of the experiment.
He wrote down the experimental steps required by the system and the experimental data that needed to be collected.
For example, if you see smoke coming from a sample or smell something wrong, how to clean the damaged sample, how to protect the instrument, and most importantly, how to protect yourself.
Senior Brother Qian didn't look back, and then said: "Doing experiments is not mathematics. If you make a mistake in calculating a decimal point, you can still continue to calculate if you correct it. If you make a mistake in a small detail of the experiment, the entire experiment may be ruined. Of course, I am more afraid. It was you who destroyed the experimental equipment... show me the experimental process you designed."
Senior Brother Liu sighed: "Yes, everyone will ask this, but things may be far from that simple. Maybe they didn't find the problem at all? Maybe they thought they found the perfect solution? Who knows? Sometimes , reality is so magical.”
Looking at the sample in Brother Qian's hand, Lu Zhou asked, "Is this a battery?"
"Done."
"...Lithium is the most ideal anode material, but it is also the most difficult to maintain. When charging, the lithium ions returning to the anode will never return to the flat lithium metal layer as you wish, but will Like a flower, it forms a beautiful but deadly branch."
After all, it is designed by the system.
Even if it was recommended, he probably wouldn't have time to look at it.
In order to prevent the sample from being damaged, 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.
After all, what he learned on paper was shallow. The books handed to him were just theories. Only by putting them into practice could he turn the legendary black technology into a real thing.
Without saying a word, Senior Brother Qian took over the initiative of the experiment, leaving the confused Lu Zhou aside.
The rest is a long wait.
Looking at the unchanged instrument, Lu Zhou couldn't help but ask, "Do you have to wait so long for battery material testing?"
Waiting for the printer to finish printing the chart, Lu Zhou asked casually: "Fatal?"
"Done?" After looking at the condition of the samples, Senior Brother Liu skillfully operated the computer and clicked the print button, "Then let's collect the data."
emmm…
He started at around ten in the morning and stayed in the laboratory until almost six in the evening. During this period, Lu Zhou also ordered takeout and had lunch.
At this point, Brother Liu paused 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? Yes, it would be a short circuit. And organic electrolytes are easy to Burning things, have you ever heard of Moli Company?”
"no, what happened?"
Brother Liu shrugged and handed the printed A4 paper to Lu Zhou, "Their product almost made history, but because it used lithium as the negative electrode, a major safety accident occurred, which resulted in the NTT mobile phone It was recalled, and eventually the company went bankrupt and was acquired. In contrast, Sony was very smart, directly using graphite as the negative electrode, launching lithium-ion batteries and quickly occupying the market."
After connecting the sample to the BK-6808 rechargeable battery tester and placing it on the digital microscope, Brother Qian set several parameters on the computer while repeating the steps on the paper in a low voice as if talking to himself: "2min Collect images once, the data collection frequency is 1Hz, charge the battery for the first time to 400 minutes and then discharge it to the cut-off voltage... OK."
…
Lu Zhou: "It's better not to use this."
Senior Brother Qian shook his head: "It won't explode, but improper operation may cause a fire."
Four hundred minutes, that's almost seven hours.
To prevent material oxidation, all operations were performed in an argon-filled glove box.
While collecting these data, Senior Brother Liu said in a casual tone.
Looking at Senior Brother Liu, Senior Brother Liu crossed his arms and shrugged helplessly.
95.7% graphite is used as the negative electrode material, the binder is sodium carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR), and the current collector is copper foil. The thickness of the graphite layer is 90 μm, LiFePO4 is used as the positive active material, and aluminum foil is used as the current collector.
Lu Zhou estimated that this was one of the reasons why Senior Brother Qian did not allow him, a novice, to experiment.
"Don't mind, that's how old Qian is. The instruments here are like his wife, more important than his life... You should watch him do it for the first time."
After putting on his white coat in a ceremonial manner, Lu Zhou showed off a little bit of the aura of a scientist, took a deep breath, and reached for the sample box containing the experimental materials.
It is a trivial matter to burn the sample, but it is a big trouble if the lens of the digital microscope is burned.
Of course, this experiment was not that dangerous, so Senior Brother Zai Qian threw the key into Lu Zhou's hand with confidence.