The top student must be diligent

Xiao Yi naturally prepared more sets of materials and tested them directly.

The nanoindentation test came out quickly.

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

"From this point of view, LLZO is relatively ideal."

"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 increased the charging and discharging speed to about 2C, so it is expected to take 50 hours.

That is two days.

Xiao Yi began to wait.

Of course, he was not idle these two days. He continued to collect various relevant information and contacted those who received admission notices to ask when they could start work.

The vast majority of fresh graduates said that they would be able to start work soon.

After all, for these fresh graduates, time is relatively abundant and they don’t have any positions, so they can go to the laboratory soon.

Only those who were originally full-time or associate researchers or professors and lecturers who already had positions needed to deal with their work before coming here.

The slightly special ones were those who were postdoctoral fellows and then chose to quit the station and come back to the Science Island Laboratory to study for a postdoctoral fellowship.

There are problems with the mechanism of domestic postdoctoral fellows in this regard. Postdoctoral fellows are no longer students, but workers. If they want to leave their original doctoral station, 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 more.

In this way, more than two days passed.

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

"LLZO and Li6PS5Cl show high initial discharge capacity, indicating that both have high ionic conductivity, um... 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 good inhibitory effect on polysulfide shuttle effect and lithium dendrites."

"Finally, the coulombic efficiency is the highest for LLZO, and the electrochemical reaction is relatively stable."

From this point of view, LLZO, lithium lanthanum zirconium oxide, has great potential.

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

Xiao Yi pondered.

Although LLZO is a hot topic in the current research of solid electrolytes, 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, and strict requirements for the environment during the preparation process. Coupled with the high purity requirement, it further increases the difficulty.

From a commercial perspective, there are still many problems that LLZO needs to overcome.

As for why it has become a hot topic in research, everyone knows it. From an experimental point of view, this kind of thing with excellent performance is easier to produce results. Anyway, in the laboratory, no one cares 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 relatively low temperature. The requirements for the atmosphere are not as strict as LLZO, including the purity. In addition, if the mechanical strength of the material is too much, 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, whether it is lanthanum or zirconium, the cost is very high, and lithium phosphorus sulfur chlorine..."

This is even more needless to say. Ordinary people may know the four elements of lithium phosphorus sulfur chlorine, but few people have heard of lanthanum and zirconium.

If there were not enough children in the old Zhu family, I guess they would not know 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 become a consumer product that enters thousands of households, rather than a laboratory product that can only be used to produce results.

Then, 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 material.

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 the previous superconductors made him appreciate a different microscopic world.

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

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

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

Xiao Yi narrowed his eyes.

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

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

Like the interface impedance problem, there is also the chemical compatibility problem between electrodes such as metallic lithium.

"Uncontrollable?"

Xiao Yi thought about it for a while, and then, under the ability of material control, 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, if water molecules and oxygen molecules combine with lithium phosphorus sulfur chlorine, chemical reactions can occur, affecting the performance of lithium phosphorus sulfur chlorine.

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

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

"Hmm... How about changing it to a nanoporous middle layer?"

With a thought in Xiao Yi's mind, the ultra-thin silicon dioxide layer changed and became a nanoporous structure.

"Hmm... It can be optimized a little bit, then, fill it with some interface binder."

Then, in the microscopic world, the surface of the nanoporous silicon dioxide layer was tightly bonded with a layer of Li3N.

This interface binder can not only enhance the bonding force of the interface, but also enhance the ionic conductivity.

"In this way, it should be a better solid electrolyte."

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

This time, nanoporous silicon dioxide can directly block the growth of lithium dendrites from a physical level with its strong enough mechanical strength and hardness, and the uniform nanoporous structure ensures the 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.

"In this way, nanoporous silica is a good material."

However, Xiao Yi soon shook his head.

It is indeed good from the current point of view, but there is another problem that the volume of various materials in the battery will change.

In the microscopic world, with the process of charging and discharging, the brittleness of silica itself causes cracks in the process of volume expansion and contraction.

"Therefore, it is best..."

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

"What if it is carbon?"

There are quite a lot of 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 was in the laboratory almost every day, constantly conducting experiments and speculations.

After multiple 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 a preliminary selection now.

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

This is how material research works. Through various assumptions and guesses, the most suitable material is finally found.

Most of the research in natural sciences is also like this, through continuous experiments and continuous searches.

The choice of direction is the most important.

And material simulation makes Xiao Yi very convenient in choosing the direction, which can not only save time, but also save the cost of experiments.

In this way, a week passed.

…

"Director Xiao, 13 people have arrived now."

In the office, a man in his 30s 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 also a last resort.

Although for scientific research institutions, administrative staff always seem to make those who actually do scientific research feel uncomfortable, it must be said that as an institution, there must be such administrative staff.

Otherwise, it is obviously not enough to rely on one person 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 responsible for the daily affairs of the school. The president may still focus more on scientific research and make decisions on some major matters at most.

And Xiao Yi naturally cannot be responsible for all the affairs of the daily management of the laboratory alone, so he hired an assistant.

Wang Hao himself is a lecturer in the School of Physics of the University of Science and Technology, but because he does not like scientific research, he often handles administrative matters. Because he has some understanding of scientific research, he is also well-received among those professors.