...
After determining the goal, Xu Chuan did not waste any more time and started the experiment directly.
Rather than leaving the job to others at the institute, he took matters into his own hands.
The test method is very simple. Since it is suspected that there is a problem with lithium difluoroxalate borate, just change the electrolyte lithium salt directly.
There are many products that can replace it, whether it is lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate and other materials in conventional inorganic electrolyte lithium salts; or lithium bisoxaloborate, bisdifluoride in organic electrolyte lithium salts.
Materials such as lithium sulfonylimide can be substituted.
Making some crude laboratory batteries won't take long.
In less than six hours, Xu Chuan completed the overall experiment, not only replacing the electrolyte lithium salt material, but also completing preliminary testing of the new battery.
However, the result made Xu Chuan frown.
After replacing the electrolyte lithium salt material, the problems of lithium precipitation and lithium deposition are still not solved.
"The problem is not the lithium salt?"
Looking at the preliminary test results, Xu Chuan was a little surprised.
According to his analysis, the probability of problems with lithium salts is as high as over 80%, but experimental results show that the problem does not occur with lithium salts.
If it's not lithium, what's wrong?
Organic solvent? Or additive?
It is very troublesome to check one by one. There are many additive materials in the electrolyte, and every change of material must consider its compatibility with other materials.
For a laboratory like Chuanhai Institute of Materials, which has almost no experience in battery research and development before, there is no previous experience data to refer to, and it can be said that it has to start from scratch.
After thinking about it, Xu Chuan rearranged the work at hand.
For subsequent testing of the electrolyte lithium salt, he handed it over to others in the laboratory.
After all, there are still some omissions in one or two experiments. Only by repeating the experiment many times can we determine whether there is any problem with the electrolyte lithium salt.
As for himself, he conducted research on ethylene carbonate, a commonly used additive.
Although no problem has been found in the electrolyte lithium salt, Xu Chuan still believes that the key to the problem of lithium precipitation and lithium deposition lies in the electrolyte. And it must be in the three main materials.
For the research on ethylene carbonate, just like the electrolyte lithium salt, he neatly chose to directly replace the material.
It is a simple detection problem to determine whether there is any problem with the corresponding material, without considering the adaptability. This is the fastest and most effective way.
Although material research and development is a matter of luck, experience and mathematical analysis can help researchers make relatively correct choices and greatly reduce research and development time and costs.
After replacing ethylene carbonate with another 'odorized carbonate' with similar effects, Xu Chuan re-tested the battery.
The test result, which he didn't have much hope for, surprised him greatly.
After replacing ethylene carbonate, the lithium evolution and lithium deposition rate of lithium-ion batteries have been greatly improved.
When using ethylene carbonate as an additive to improve battery performance, the highest Coulombic efficiency of the new battery is only about 99.93%.
This chapter is not over yet, please click on the next page to continue reading! After replacing it with odorant carbonate, the Coulombic efficiency of the new battery increased to about 99.98%.
An increase of 0.05 percentage points is enough to increase the number of charge and discharge cycles by 300 to 400 times.
But there are also disadvantages. After replacing ethylene carbonate, the performance of the lithium battery dropped a lot.
For example, the charging speed has been reduced by nearly 18%, and the activation performance of the electrolyte has also been reduced a lot.
However, compared with the problem of lithium precipitation, these are acceptable.
.......
"The problem is ethylene carbonate? It's unbelievable."
Looking at the test results, Xu Chuan was surprised again.
If he remembered correctly, the additive ethylene carbonate will be used in future lithium-ion batteries, lithium metal batteries, and even lithium-sulfur batteries.
Because compared to other additives, ethylene carbonate can improve the performance of lithium batteries very much, and other additives are simply incomparable.
This is also the reason why he didn't think much about the problem that would arise here.
But now, the experimental results clearly told him that the culprit causing lithium precipitation and lithium deposition is ethylene carbonate.
"It's really hard to believe."
Staring at the test results, Xu Chuan fell into deep thought again.
Solving the lithium precipitation problem should have been a very happy thing, but he had doubts about it.
When the American research institute solves the problem of lithium dendrites in the future, they will definitely encounter this problem, but they still choose ethylene carbonate as an additive.
why is that?
As an additive, ethylene carbonate can indeed improve the performance of lithium batteries, but if it is the culprit causing the lithium dendrite problem, then it should be replaced at all costs.
Why didn't that institute do this?
Xu Chuan was a little confused about this issue.
Chapter completed!