The top student must be diligent.

Chapter 195 Solid Electrolytes and Nanoporous Materials
Science Island Laboratory, in the sample preparation room.

"Well...for now, we have prepared four typical solid electrolytes."

"There are oxide-based solid electrolytes such as LLZO, sulfide-based solid electrolytes such as Li3PS4 and Li6PS5Cl, and polymer-based PEO-based electrolytes."

"The battery positive electrode material should be sulfur positive electrode, specifically S/C composite material."

“The negative electrode is lithium metal.”

"Then……"

Xiao Yi carefully took out all the materials needed.

Then he took the 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 of energy materials such as batteries and capacitors.
Then, Xiao Yi began to prepare to assemble the battery.

Assemble the battery in a glove box to ensure an anhydrous and oxygen-free environment, and then use a CR2032-type button cell housing. The assembly order is lithium metal anode-solid electrolyte-sulfur cathode.

Then the electrochemical test was started first, mainly constant current charge and discharge test and electrochemical impedance spectroscopy test.

At present, solid-state lithium batteries can already be realized in the laboratory, but there is still a long way to go before they can move from the laboratory to commercial applications.

Of course, Xiao Yi's current experiment is mainly to obtain the corresponding experimental data, and then activate his own [Material Mastery] to choose the target direction of his next research.

For example, whether to choose oxides, sulfides, or polymers.

"Well, for the constant current charge and discharge test, let's test it 50 times first."

After each battery is built, the circuits are turned on and the cycle results are awaited.

Of course, in addition to this, there is also nanoindentation testing.

The hardness and elastic modulus of the solid electrolyte film are measured using a nanoindenter. In this way, the inhibitory effect of various solid electrolytes on lithium dendrites can be measured.

Xiao Yi naturally also prepared more sets of materials and started testing directly.

The nanoindentation test produced results very quickly.

"Hmm...LLZO has the highest hardness and elastic modulus. The mechanical strength of other electrolyte materials is significantly lower than that of LLZO, especially PEO-based electrolytes. This type of polymer electrolyte has the worst mechanical properties."

"From this perspective, LLZO is relatively 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 lithium dendrites in these solid electrolytes, Xiao Yi also increased the charging and discharging speed to about 2C, so it is estimated that it will take 50 hours.

That is just 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 contact those who have received admission notices to ask when they can start work.
The vast majority of recent graduates said they would be able to start work soon.

After all, these fresh graduates have relatively ample time and do not have any positions, so they can reach the laboratory quickly.

Only those who already have positions as full or associate researchers, or professors or lecturers, need to deal with their work matters before coming here.

What is a little special is that some people were already postdoctoral fellows, and then chose to quit and come back to Science Island Laboratory to study for a postdoctoral degree.

There are problems with the mechanism in this regard for domestic postdoctoral fellows. Postdoctoral fellows are no longer students but workers. If they want to leave their original doctoral site, they still need the signature of their supervisor.

However, among the postdoctoral fellows recruited this time, only Liu Xiaodong is a postdoctoral fellow.

Liu Xiaodong also sent a message saying that it would take some time to deal with the matter.

So Xiao Yi didn't ask any more questions.

In this way, more than two days passed.

Xiao Yi once again came to the electrochemical testing room and took a look at the experimental situation. All 50 cycles had been completed and various results had been counted.

“LLZO和Li6PS5Cl表现出较高的初始放电容量，表明这两者都有较高的离子电导率，嗯……分别是1.0×10^-3S/cm和5.0×10^-4S/cm。”

"In terms of cycle stability, LLZO has the best cycle stability, which shows that it has a good inhibitory effect on polysulfide shuttle effect and lithium dendrites."

"The last one is the coulombic efficiency, which is also the highest for LLZO, and the electrochemical reaction is relatively stable."

From this perspective, LLZO, lithium lanthanum zirconium oxide, does have great potential.

"However... the preparation cost of LLZO is relatively high."

Xiao Yi pondered.

Although LLZO is a hot topic in current solid electrolyte research, its preparation process requires sintering at a high temperature of more than 1000 degrees Celsius, which has relatively high requirements for energy consumption and equipment. It also has strict requirements on the environment during the preparation process. Coupled with the high purity requirement, the difficulty is further increased.

From a commercialization perspective, LLZO still has many problems to overcome.

As for why it has become a hot topic in research, everyone knows it. From an experimental point of view, something with excellent performance in all aspects is easier to produce results. Anyway, in the laboratory, we don't care about the high cost.
"On the contrary, lithium phosphorus sulfur chlorine Li6PS5Cl is more suitable."

"It can be synthesized at a temperature below 500 degrees Celsius, which is considered a relatively low temperature. The requirements for the atmosphere are not as strict as those for LLZO, including the purity. In addition, if the mechanical strength of the material is too much pursued, it will affect the final processability. The flexibility of lithium phosphorus sulfur chlorine is more suitable for processing."

"There are also raw materials. In LLZO, both lanthanum and zirconium are very expensive, and lithium, phosphorus, sulfur and chlorine..."

Needless to say, ordinary people may know the four elements of lithium, phosphorus, sulfur and chlorine, but few people have heard of lanthanum and zirconium.

If there hadn't been so many children in the Zhu family, they probably wouldn't have known how to name this element.

After comprehensive consideration, Xiao Yi is more inclined to solid electrolyte materials such as lithium phosphorus sulfur chlorine.

After all, his goal is to achieve commercial production and make it a consumer product that can enter thousands of households, rather than a laboratory product that can only be used to produce results.

Afterwards, he said no more, took out another lithium phosphorus sulfur chlorine sample, added various experimental data of this sample, and then started to master the materials.

As his vision once again entered the microscopic world, Xiao Yi's expression once again revealed an expression of enjoyment.

The completely different world of solid electrolytes and previous superconductors allowed him to experience a different microscopic world.

"The main problems of lithium phosphorus sulfur chlorine are, first, chemical stability. When it combines with water and oxygen in the air, it will produce harmful byproducts such as hydrogen sulfide. Secondly, there is a chemical compatibility problem between it and the metal lithium electrode, which will lead to some chemical reactions and eventually form a more unstable interface..."

"Then there is... still the interface problem. The interface impedance between lithium phosphorus sulfur chlorine and the electrode material is high, which affects the ion conduction efficiency."

"Interface problem... Interface problem..."

Xiao Yi narrowed his eyes.
In the field of electrochemistry, interface problem is a widely studied issue, which mainly studies the interaction and reaction process between electrode surface and electrolyte.

At present, the biggest problem for solid electrolytes is also the various uncontrollable situations that may exist on the interface.

There are issues like interfacial impedance and chemical compatibility with electrodes like metallic lithium.

"Can not control?"

Xiao Yi thought for a moment, and then with his ability to control the material, he simulated an ultra-thin silicon dioxide protective layer on the surface of lithium phosphorus sulfur chlorine, 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 chlorine, a chemical reaction can occur, affecting the performance of lithium phosphorus sulfur chlorine.

But now, with this ultra-thin protective layer of silicon dioxide, this problem no longer exists.

"However, silicon dioxide will affect the conductivity of lithium phosphorus sulfur chlorine, which is like picking up sesame seeds and losing watermelons, which is not appropriate."

"Hmm...how about a nanoporous middle layer?"

As Xiao Yi's mind moved, the ultra-thin layer of silicon dioxide changed into a nanoporous structure. "Hmm... it can be optimized a little bit, so let's add some interface adhesive."

Then, in the microscopic world, a layer of Li3N is tightly bonded to the surface of the nanoporous silica layer.

This interfacial adhesive can not only enhance the bonding strength of the interface, but also enhance the ionic conductivity.

"In this way, it should be considered a relatively good solid electrolyte."

Xiao Yi thought for a moment, and then simulated the growth of lithium dendrites again.

This time, nanoporous silica was able to physically block the growth of lithium dendrites with its strong enough mechanical strength and hardness. The uniform nanoporous structure ensured uniform distribution of force, thereby preventing local stress concentration and reducing the possibility of dendrite penetration.

In addition, nanoporous silica, due to its porous structure, helps to evenly distribute the flow of lithium ions, which naturally reduces the possibility of concentrated growth of lithium dendrites.

"From this perspective, nanoporous silica is a good material."

However, Xiao Yi soon shook his head.

It does look good at the moment, but there is still a problem: the volume of various materials in the battery will change.

In the microscopic world, as the charging and discharging process progresses, the brittleness of silicon dioxide itself causes cracks to form during the process of volume expansion and contraction.

"So it would be best if..."

Xiao Yi fell into deep thought, and suddenly, his eyes lit up.

“What if it’s carbon?”

There are quite a lot of carbon-related nanomaterials, and research in this area is very mature.

Materials such as graphene, carbon nanotubes, etc.

Thinking of this, Xiao Yi immediately began to try again.

……

Time passed day by day.

Xiao Yi spends almost every day in the laboratory, conducting experiments and speculations non-stop.

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, polymers, etc.

However, now it is just the primary election.

Even nanoporous carbon has many forms, and how to make it the most suitable still requires continuous attempts.

This is what material research is all about, through various different assumptions and guesses, we finally find the most suitable material.

Most research in natural sciences is like this, through constant experimentation and continuous exploration.

The choice of direction is the most important.

Material simulation makes it extremely convenient for Xiao Yi to choose the direction, which not only saves time but also saves the cost of the experiment.

And just like that, a week passed.

……

"Director Xiao, 13 people have already arrived at their posts."

In the office, a man who was about 30 years old said to Xiao Yi.

This person is an assistant hired by Xiao Yi from the University of Science and Technology, named Wang Hao.

Finding an assistant is a last resort.

Although administrative personnel in scientific research institutions always seem to make those who actually do scientific research feel unhappy, it must be said that as an institution, it is necessary to have such administrative personnel.

Otherwise, it is obviously not possible to ensure both the output of scientific research and the orderly management of the institution by one person alone.

Therefore, in universities, there is often an executive vice-president who is responsible for the daily management of the school affairs. The president may still focus more on scientific research and at most make decisions on some major matters.
Naturally, it was impossible for Xiao Yi to be responsible for all the daily management of the laboratory by himself, so he hired an assistant.

Wang Hao is a lecturer at the School of Physics at HKUST. However, since he does not like scientific research, he usually deals with administrative matters. However, since he has some understanding of scientific research, he is well-received among the professors.

Then he saw the recruitment notice at Science Island Laboratory and took the initiative to apply. He soon became Xiao Yi's assistant.

Of course, since the Science Island laboratory is small and there are not many people, it is not as busy as the school.

"Thirteen people? That's 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 was an outstanding young scholar and should have a lot of things to deal with, but he didn't expect that it would be resolved so quickly.

Wang Hao nodded: "Yes, it's because Professor Qian Wanli had already prepared to leave Shanghai Jiao Tong University. His students have all graduated successfully, and he has not recruited new students. All other matters have been dealt with."

Xiao Yi nodded and couldn't help but smile. It seemed that Professor Qian had already made plans.

"That's fine, anything else?"

"Oh, there is one more thing. It's about a postdoctoral fellow you reminded me to pay attention to, named Liu Xiaodong."

"Liu Xiaodong seems to be in trouble now. He applied to withdraw from the station, but his mentor did not sign."

Upon hearing this, Xiao Yi frowned.

Sure enough, this thing still happened?

Recalling the interview process with Liu Xiaodong, although Liu Xiaodong's performance was not very good, Xiao Yi saw clues from his achievements during his postdoctoral period. After a final check, he found that his mentor, Zhao Guoqing, had been researching polymer materials in the past, which had nothing to do with those papers in the field of nanomaterials. However, he suddenly published a paper on nanomaterials in JMS&T.

JMS&T is a top journal in the field of materials with an impact factor of over 10. The quality of that paper must be very high. It is impossible for Zhao Guoqing to publish his first paper there.

Afterwards, Xiao Yi contacted Qian Wanli specifically. As an outstanding young scholar from the School of Materials Science and Engineering of Shanghai Jiao Tong University, Qian Wanli did know something. As expected, Liu Xiaodong's tutor was indeed well-known in their school for exploiting students. Although he had been warned by the school before, it did not make him restrain too much, because Zhao Guoqing's father, the enemy Qian Wanli mentioned, was about to be elected as an academician.
Qian Wanli even had an impression of Liu Xiaodong, a postdoctoral fellow, because they had met in the laboratory before, 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 past achievements, whether in mathematics, physics, or materials, there are many people who want to communicate with him. Even Qian Wanli's rival has communicated with him through emails.

Xiao Yi often does not refuse these emails expressing communication intentions. Basically, as long as the questions are interesting, he will answer them.

Although they all originated from interests, he also accumulated a lot of relationships for himself invisibly.

Of course, if worst comes to worst, he can call Director Liu Cong and it will be easier to solve the problem.

However, after thinking it over again and again, he decided to let Liu Xiaodong decide for himself whether to accept his help, so he took out his mobile phone and called Liu Xiaodong directly.

……

(End of this chapter)