Chapter 248 Your complete indifference makes me very hurt
On Friday, Xu Qingzhou came to the Optoelectronics Laboratory of Beijing University after two months of absence.
There is only Gong Yunfei in the office.
“Junior Brother.”
Senior Brother Gong was more enthusiastic than before. He held Xu Qingzhou’s hand and touched it non-stop, causing goosebumps all over his body. The fear of exchanging private messages came back again.
"Senior Brother Gong, you..." Xu Qingzhou took two steps back without leaving a trace, but his hand was still held by Gong Yunfei.
Gong Yunfei chuckled, "I just want to soak up the immortal spirit of the god of learning."
In the past, there was still pressure in front of this junior brother Xu, but now there is no pressure at all, okay? , as long as there is no comparison, there is no harm.
"Okay, Xiao Gong, let go of your junior brother quickly." Professor Zhao walked out of the experiment.
"Professor." Xu Qingzhou finally got rid of Senior Brother Gong.
"Xiao Xu, sit down first. I'll tell you about the experiment."
Professor Zhao first handed Xu Qingzhou a stack of information and said, "You should know that what we chose this time is a new silicon-based The negative electrode materials actually have a common problem in the two months of experiments-too much lithium is released."
Xu Qingzhou nodded slightly. The relatively high lithium insertion potential of silicon is helpful to a certain extent. In order to avoid the formation of lithium dendrites, silicon will undergo huge volume expansion during the charge and discharge process.
This volume change in turn leads to stress accumulation inside the silicon particles, pulverizing the silicon material, which may intensify the formation of lithium dendrites.
“Of course, we have been prepared for this situation, so in subsequent experiments, the silicon particles were nanosized, which effectively alleviated the volume effect of the silicon anode material when deintercalating lithium.”
"Nanoization can be divided into zero-dimensional nanonization, three-dimensional nanonization and two-dimensional nanonization." Xu Qingzhou recalled the information he had seen in the past two days.
Professor Zhao showed admiration, and it could be seen that this young man had carefully consulted the information in this area.
Next, Professor Zhao detailed the progress of the project to Xu Qingzhou.
Xu Qingzhou is also very clear about his work.
Function analysis is required, using linear functions, polynomial functions, etc. to analyze the changing trends of battery performance parameters, such as capacity, voltage, and resistance, with the number of cycles or time.
It is also necessary to establish an electrochemical model, a thermal model, and a mechanical model that describes the stress-strain relationship and mechanical failure mechanism of the material during the charge and discharge process.
At the end, Professor Zhao sighed:
“Data analysis and processing are the bridge connecting experimental data and experimental conclusions. Through effective processing of experimental data, the changing rules of battery performance can be revealed. , to provide data support for further optimization of battery design. ”
“Our research team can actually do this, but due to the wrong direction a few days ago, our progress is much slower than planned. If If we spread our staff further, the progress will be delayed.”
“Besides, I’m definitely not as professional as you in mathematics.”
Xu Qingzhou turned over the information in his hand and smiled: "I will do my best."
"Don't be pressured. Our goal is to improve the thermal stability and energy density of the battery. As long as it can be improved compared to the market Between 2% and 4%, we can solve the problem.”
Professor Zhao chuckled, “Those lithium dendrite problems and diaphragm problems cannot be solved with our limited funds and people. It’s not within the scope of consideration.”
Xu Qingzhou nodded, Professor Zhao’s project was funded by two companies, but the funding seemed to be only about 5 million.
This money seems to be a lot, but once you put aside the purchase of raw materials, equipment purchase, business trips, and labor, it is really not enough to solve big problems like lithium dendrites.
Professor Zhao handed the hard drive to Xu Qingzhou, then handed over the experimental tasks to the three students, and then left the laboratory to do other things.
Xu Qingzhou sat down in front of the computer and opened the hard drive. It contained experimental data from this period. In addition to the experimental data, there was also more comprehensive experimental information.
After 10 minutes, a girl walked in, holding a stack of magazines in her hand, sorting out two books and placing them on the table by the door, "Brother Gong, this is the new issue of "Physics Report" "
"Okay, thank you." Gong Yunfei was processing the data. He looked up and looked at Xu Qingzhou, who was deep in thought in front of the computer. He hesitated, waved his hand and smiled: "Hi. , are you fascinated?”
“Here, there are two papers written by Xu Shen.” The girl’s eyes were full of admiration, and she kept her voice down for fear of disturbing Xu Qingzhou.
Gong Yunfei was stunned for a moment, then opened the latest "Physics Report" and looked down the table of contents. Sure enough, Xu Qingzhou's name was written behind both papers.
"Junior brother, have you written two more sci-fi articles?"
Xu Qingzhou raised his head and took his mind off all kinds of data. He glanced at the journal in Gong Yunfei's hand and then remembered the previous few articles. The editorial office responded to the email the next day, saying it had been published.
"Well, yes, the result of my last experiment."
"." Looking at Xu Qingzhou's calm expression, Gong Yunfei's throat moved, but he hesitated to speak.
No, two top issues.
I'm a little hurt by the way you don't care at all.
If it were him, with two top-notch articles published, he would have already booked a restaurant, called friends, and was ready to have a good time.
Okay, this may be the great god.
Neither of the two top issues could arouse the slightest emotion.
"Senior brother, is there anything else?"
"It's okay."
"Okay, I'll read the information first."
"."
The thousands of words in Gong Yunfei's heart were all condensed into one sentence: Junior brother is awesome.
In the morning, Xu Qingzhou basically read the information. At noon, he went to the cafeteria with Gong Yunfei and the others to eat. In the afternoon, instead of hurriedly sorting out the data, he went into the laboratory with Wang Wei.
I want to see the experimental process.
In the laboratory, there was the familiar "buzzing" sound of equipment running. Hong Yayu collected the data of sample No. 138 in front of the X-ray diffractometer (XRD).
Gong Yunfei stayed next door to clean and filter the data.
Wang Wei and Xu Qingzhou were wearing goggles and making sample No. 139.
Of course, Wang Wei was mainly responsible for the operation, while Xu Qingzhou was watching from the side.
“This time, we chose high-purity nano-silicon as the negative active material.” Wang Wei explained to Xu Qingzhou while operating.
The conductive agent acetylene black and the binder CMC are then mixed in a certain proportion.
Then use a coater to evenly coat the negative electrode slurry on the copper foil current collector to form a coating with a certain thickness.
Drying and compaction.
Assemble with positive electrode material.
Install a Celgard separator to inject ethylene carbonate electrolyte containing lithium hexafluorophosphate.
A mediocre battery appeared in front of Xu Qingzhou.
After reading the information, he actually had a general understanding of the experiment. Although Professor Zhao and their experiments had made considerable progress, there were still many problems to face.
For example, silicon nanoparticles can alleviate the volume expansion effect that occurs when the silicon material itself inserts and removes lithium to a certain extent, but the specific surface area and surface energy increase.
That is to say, electrochemical agglomeration is prone to occur during the charge and discharge process, and then the amount of contact with the electrolyte increases, consuming a large amount of lithium ions, thereby reducing cycle performance and capacity retention rate.
Xu Qingzhou squinted his eyes, thinking about how to solve it.
At this end, Wang Wei carefully connected the BTS-5V3A-S1 charge and discharge tester. Seeing that Xu Qingzhou had not spoken, he joked: "Don't worry, it won't explode."
Xu Qingzhou He smiled, not to mention that this small battery exploded, he had even seen big scenes where the entire laboratory exploded.
Wang Wei was paying attention to the data on the screen while chatting with Xu Qingzhou:
“At a charge and discharge rate of 0.2C, the capacity decays slowly. After 20 cycles, the capacity is still stable at 3500mA·h/g. The capacity The retention rate is maintained at about 75%. "
"Currently, we have produced sample No. 109, which uses chemical etching technology to prepare boron-doped porous silicon nano-silicon, which charges and discharges at 2A/g. Under current, it can still maintain a capacity of 2000mA·h/g after 250 cycles.”
“If we continue to test, we will definitely get the results we want.”
Wang Wei is very confident. Confidence, Xu Qingzhou nodded, feeling that there was nothing wrong, and the results were accumulated from little experiments.
(End of this chapter)