Science Island Laboratory, in the sample preparation room.
"Well... we have prepared four typical solid electrolytes for the time being."
"The oxide-based solid electrolyte LLZO, the sulfide-based solid electrolytes Li3PS4 and Li6PS5Cl, and the polymer-based PEO-based electrolyte."
"The battery cathode material should be sulfur cathode, specifically S/C composite material."
"The negative electrode is lithium metal."
"Then..."
Xiao Yi carefully took out various required materials.
Then he took this pile of materials to the electrochemical testing room next door.
The electrochemical testing room is a functional room specially prepared for electrochemical experiments. It is used to test the electrochemical properties of materials, especially the research on energy materials such as batteries and capacitors.
Subsequently, Xiao Yi began to prepare to assemble the battery.
Assemble the battery in the glove box to ensure a water-free and oxygen-free environment, and then use a CR2032 button battery casing. The assembly sequence is lithium metal negative electrode - solid electrolyte - sulfur positive electrode.
Then the electrochemical tests were started first, mainly galvanostatic charge and discharge tests and electrochemical impedance spectroscopy tests.
At present, solid-state lithium batteries can be realized in the laboratory, but there is still a long way to go from the laboratory to commercial applications.
Of course, Xiao Yi's current experiment is mainly to obtain corresponding experimental data, and then launch his own [Material Mastery] to choose the target direction of his next research.
For example, whether to choose oxides, sulfides, or polymers.
"Well, for constant current charge and discharge testing, just test 50 cycles first."
Complete the construction of each battery, then turn on the circuit uniformly and wait for the cycle results.
Of course, in addition to this, there is also nanoindentation testing.
A nanoindentation instrument is used to measure the hardness and elastic modulus of solid electrolyte films. In this way, the inhibitory effect of various solid electrolytes on lithium dendrites can be measured.
Xiao Yi naturally prepared more sets of materials for direct testing.
The results of the nanoindentation test came out quickly.
"Well... LLZO has the highest hardness and elastic modulus. The mechanical strength of other electrolyte materials is significantly lower than LLZO, especially PEO-based electrolytes. This kind of polymer electrolyte has the worst mechanical properties."
"Looking at it this way, LLZO is more ideal."
"Let's wait for the electrochemical test results over there."
The time required for 50 cycles is not short. Of course, in order to better test the problems of these solid electrolytes in lithium dendrites, Xiao Yi also speeds up the charge and discharge speed, which is about 2C, so it is expected to take 50 hours.
That is two days.
Xiao Yi began to wait.
Of course, he has not been idle these two days. He continues to collect various relevant information, and by the way, he contacts those who have received the admission notice and asks them when they will be available to work.
The vast majority of fresh graduates say they will be able to find their jobs soon.
After all, these fresh graduates have plenty of time and don't have any positions, so they can get to the laboratory quickly.
In other words, those who were originally employed as Associate Researcher or professors and lecturers still needed to deal with their work matters before they could come over.
What is a little bit special is that I was a postdoc, and then I chose to quit and come back to Science Island Laboratory to study as a postdoc.
There are problems with the domestic postdoctoral mechanism in this regard. Postdoctoral fellows are no longer students, but are considered wage earners. If they want to leave the original doctoral site, they still need the signature of their supervisor.
However, among the postdocs recruited this time, only Liu Xiaodong is a postdoc.
Liu Xiaodong also sent a message, saying that it will probably take some time to process the matter.
So Xiao Yi didn't ask any more questions.
In this way, more than two days passed.
Xiao Yi came to the electrochemical testing room again and took a look at the experimental situation. 50 cycles have been completed and various results have been calculated.
"LLZO and Li6PS5Cl exhibit higher initial discharge capacities, indicating that both have higher ionic conductivities, well... 1.0×10^-3S/cm and 5.0×10^-4S/cm, respectively."
"In terms of cycle stability, LLZO has the best cycle stability, indicating that it has a better inhibitory effect on polysulfide shuttle effects and lithium dendrites."
"The last one is Coulombic efficiency, which is also the highest Coulombic efficiency of LLZO, and the electrochemical reaction is relatively stable."
Looking at it this way, LLZO, lithium lanthanum zirconium oxygen, has indeed high potential.
"However... the preparation cost of LLZO is relatively high."
Xiao Yi groaned.
Although LLZO is currently a hot topic in solid electrolyte research, its preparation process requires sintering at a high temperature of more than 1,000 degrees Celsius, which requires relatively high energy consumption and equipment. It also has strict environmental requirements during the preparation process, coupled with high purity requirements, which further increases the difficulty.
From a commercialization perspective, LLZO still has many problems that need to be overcome.
As for why it has become a hot topic in research, we all know it. From an experimental point of view, this kind of thing with relatively excellent performance is easier to produce results. Anyway, we don't care about the high cost in the laboratory.
"On the contrary, lithium phosphorus, sulfur chloride Li6PS5Cl is more suitable."
"Synthesis can be carried out at temperatures below 500 degrees Celsius, which is relatively low temperature. The requirements for the atmosphere are not as strict as LLZO, including purity. In addition, if the mechanical strength of the material is too pursued, it will affect the final processability. The flexibility of lithium phosphorus, sulfur and chlorine makes it more suitable for processing."
"There are also raw materials. In LLZO, whether it is lanthanum or zirconium, the cost is very high, and lithium phosphorus, sulfur chloride..."
Needless to say, ordinary people may know the four elements of lithium, phosphorus, sulfur and chlorine, but very few people have heard of lanthanum and zirconium.
If there hadn't been enough children in Lao Zhu's family, he probably wouldn't have known how to name this element.
After comprehensive consideration, Xiao Yi still prefers solid electrolyte materials such as lithium phosphorus sulfur chloride.
After all, his goal is to achieve commercial production and become a consumer product that can enter thousands of households, rather than being a laboratory product that can only be used to produce results.
Afterwards, he said no more, took out another lithium phosphorus, sulfur and chlorine sample, added various experimental data of this sample, and then started to activate Material Mastery.
As the field of vision once again entered the microscopic world, Xiao Yi's expression once again showed an expression of enjoyment.
The world of solid electrolytes is completely different from the previous superconductors, allowing him to experience a different microscopic world.
"The current main problems with lithium phosphorus, sulfur and chloride are firstly the chemical stability. When it combines with water and oxygen in the air, it will generate harmful by-products such as hydrogen sulfide. Secondly, there is a chemical compatibility problem with the metallic lithium electrode, which will lead to some chemical reactions and eventually form a more unstable interface..."
"Then... it's still an interface problem. The interface resistance between lithium phosphorus, sulfur, chlorine and electrode materials is high, which affects the ion conduction efficiency."
"Interface problem... Interface problem..."
Xiao Yi narrowed his eyes.
In the field of electrochemistry, the interface problem is a very widely studied issue. It mainly studies the interaction and reaction process between the electrode surface and the electrolyte.
At present, it seems that the biggest problem for solid electrolytes is also the various uncontrollable situations that may exist at the interface.
Just like the interface impedance problem, there is also the chemical compatibility problem with electrodes such as metallic lithium.
"Uncontrollable?"
Xiao Yi thought for a moment, and then used Material Mastery's ability to simulate an ultra-thin silicon dioxide protective layer on the surface of lithium phosphorus, sulfur chloride, and then simulated a layer of water molecules and oxygen molecules on the outside.
Originally, when water molecules and oxygen molecules combine with lithium phosphorus, sulfur chloride, a chemical reaction can occur, which affects the performance of lithium phosphorus, sulfur chloride.
But now, with this ultra-thin protective layer of silicon dioxide, this problem no longer exists.
"However, silica will affect the conductivity of lithium, phosphorus, sulfur and chloride. On the contrary, it is choosing sesame seeds and losing watermelon, which is inappropriate."
"Hmm... how about replacing it with a nanoporous middle layer?"
As Xiao Yi's heart moved, the ultra-thin layer of silicon dioxide changed into a nano-porous structure.
"Well... it can be optimized a little bit, then fill it with some interface adhesive."
Subsequently, in the microscopic world, the surface of the nanoporous silica layer was tightly combined with a layer of Li3N.
This kind of interface binder can not only enhance the bonding force of the interface, but also enhance the ionic conductivity.
"In this way, it should be considered a better solid electrolyte."
Xiao Yi thought for a moment, and then simulated the growth of lithium dendrites again.
But this time, nanoporous silica can rely on sufficient mechanical strength and hardness to directly block the growth of lithium dendrites at the physical level, and the uniform nanoporous structure ensures uniform distribution of force, thereby preventing local stress concentration and reducing the possibility of dendrite penetration.
In addition, due to its porous structure, nanoporous silica helps to evenly distribute the lithium ion flow, which naturally reduces the possibility of concentrated growth of lithium dendrites.
"Looking at it this way, nanoporous silica is a good material."
However, Xiao Yi soon shook his head.
It looks really good so far, but another problem is that the volumes of various materials in the battery will change.
In the microscopic world, with the process of charging and discharging, the brittleness of silicon dioxide itself causes cracks to appear in the process of volume expansion and shrinkage.
"So it would be best to..."
Xiao Yi fell into deep thought, and suddenly, his eyes lit up.
"What if it's carbon?"
There are quite a few nanomaterials related to carbon, and research in this area is also very mature.
Materials such as graphene, carbon nanotubes, etc.
Thinking of this, Xiao Yi immediately began to continue trying.
Time passed day by day.
Xiao Yi spends almost every day in the laboratory, constantly conducting experiments and speculations.
After various screenings, he finally determined that nanoporous carbon is the most ideal nanoporous material from a variety of nanoporous materials such as silica, carbon, alumina, and polymers.
However, it is only the primary election now.
Even nanoporous carbon has many forms, and how to make it most suitable still requires continuous attempts.
The research on materials is like this. Through various different ideas and different guesses, we finally find the most suitable material.
Most research in natural sciences is like this, through constant experiments and constant searches.
The choice of direction is the most important.
Material simulation makes Xiao Yi extremely convenient in the direction selection, which not only saves time, but also saves the cost of experiments.
Just like that, a week passed.
"Director Xiao, 13 people are on duty now."
In the office, a man in his 30s said to Xiao Yi.
This person is an assistant hired by Xiao Yi from USTC, named Wang Hao.
Finding an assistant is a last resort.
Although for scientific research institutions, administrative personnel always seem to make those who actually do scientific research feel uncomfortable, but it has to be said that as an institution, it is necessary to have such administrative personnel.
Otherwise, it is obviously not possible to rely on one person alone to ensure the output of scientific research and the orderly management of the institution.
Therefore, in universities, there are often executive vice presidents who are dedicated to managing the daily affairs of the school. The president may focus more on scientific research, and at most make decisions on some major matters.
Naturally, Xiao Yi cannot be responsible for all the daily management of the laboratory by himself, so he hired an assistant.
Wang Hao himself is a lecturer at the USTC School of Physics. However, since he does not like scientific research, he mostly deals with administrative matters. Since he also knows something about scientific research, he is quite popular among the professors.
Then after he saw the recruitment here at Science Island Laboratory, he took the initiative to apply, and soon became the assistant of Xiao Yi.
Of course, due to the small scale of Science Island Laboratory, there are not many people there, so it is not as busy as the school.
"Thirteen people, that's pretty good."
Xiao Yi nodded.
"In addition, Professor Qian Wanli has also confirmed that he will leave before next week."
"Oh? So fast?"
Xiao Yi was a little surprised. After all, Qian Wanli is Outstanding Young Scholar. There should be a lot of things to deal with, but he didn't expect it to be over so quickly.
Wang Hao nodded. "Yes, it's because Professor Qian Wanli has been preparing to leave Shanghai Jiao Tong University for a long time. All his students have graduated successfully, and he has not recruited new students. All other matters have been taken care of."
Xiao Yi nodded and couldn't help but smile. It seemed that Professor Qian had already planned something.
"That's fine. Is there anything else?"
"Oh, there is one more thing. You reminded me of a postdoc named Liu Xiaodong."
"Liu Xiaodong seems to be in trouble now. He applied to withdraw from the site, but his instructor did not sign it."
Upon hearing this, Xiao Yi frowned.
Sure enough, this thing still happened?
Recalling the interview process of Liu Xiaodong, although Liu Xiaodong's performance was not very good, Xiao Yi saw clues from the achievements during his postdoctoral period. The last one Check, his mentor named Zhao Guoqing, in the past, his research direction was in polymer materials, and he had nothing to do with those papers in the field of nanomaterials. As a result, he suddenly published an article on nanomaterials in JMS&T.
JMS&T is a top journal in the field of materials with an impact factor of more than 10. The quality of that paper must be very high. No matter how hard you think, Zhao Guoqing will be able to publish it first.
After that, Xiao Yi specifically contacted Qian Wanli. As Outstanding Young Scholar of Shanghai Jiao Tong University School of Materials Science, Qian Wanli did know something. Sure enough, the tutor of Liu Xiaodong was indeed famous in their college for squeezing students. Although he had been warned by the college before, he was not allowed to restrain himself too much because Zhao Guoqing's father, the enemy that Qian Wanli mentioned, was about to be elected as an academician.
Qian Wanli even had an impression of Liu Xiaodong, a postdoc, because they had met in the laboratory, and he was full of praise for some of Liu Xiaodong's insights.
Xiao Yi narrowed his eyes.
He can handle this matter.
Of course he can handle it. He also knows a lot of scholars in Shanghai, or in other words, he knows a lot of scholars across the country.
Because of his many achievements in the past, whether in the field of mathematics, physics, or materials, many people want to communicate with him. Even Qian Wanli's opponent once communicated with him through email.
Xiao Yi often does not refuse these emails of communication intentions. Basically, he will answer any interesting questions.
Although it was all based on interest, it also accumulated a lot of relationships for him invisibly.
Of course, if nothing else works, he can call Director Liu Cong, and it will be easier to solve the problem.
However, after much thought, he still decided to let Liu Xiaodong decide whether to accept his help, so he took out his mobile phone and called Liu Xiaodong directly.