The key to solving the problem of lithium dendrites lies in a common additive in the electrolyte.

This answer is somewhat unexpected.

After all, the industry and battery industry have always focused on solving the problem of lithium dendrites on artificial SEI films or lithium salts in electrolytes.

In the opinion of most experts or researchers, these two materials are the key.

If Xu Chuan had not come back with twenty years of vision and experience, Xu Chuan would not have directly set his sights on the electrolyte.

As the saying goes, the more easily neglected a place is, the more likely it is that the most deadly things will breed.

Ethylene carbonate, a material added to almost all lithium-ion batteries, has greatly improved lithium batteries.

However, it may also be the culprit of the lithium dendrite problem.

...

After replacing the additives in the electrolyte, Xu Chuan conducted a variety of tests on the new batteries in his hands, and also manufactured several new batteries at the same time, using different additive materials to verify his previous judgments.

The final experimental and testing results show that different types of additives will indeed affect the working performance of the new artificial sei film.

Among them, materials such as ethylene carbonate and alkyl phosphates are particularly serious.

While organophosphorus and organofluoride additives are relatively light, the best-performing fluoroalkyl phosphate can even achieve a Coulombic efficiency of 99.98%.

This data is enough to increase the number of charge and discharge cycles of lithium batteries to four digits and thousands of times.

This is more than double the current standard lithium battery charge and discharge times of 500 times.

But at the same time, after replacing ethylene carbonate, the performance of the lithium battery, from battery capacity, to charging and discharging speed, to the activation performance of the electrolyte, has been significantly reduced.

Among them, the fluoroalkyl phosphate with the best Coulombic efficiency directly reduces the charge and discharge efficiency by about 25%.

And the lower the external temperature, the greater the interference with charging and discharging efficiency, but when the temperature is too high, the instability of the electrolyte will increase.

If the temperature is too high, the battery will bulge, expand, etc.

Although there have been no problems such as spontaneous combustion or explosion in the current tests, Xu Chuan knows that as time and the number of tests increase, if fluoroalkyl phosphate is used instead of ethylene carbonate, these problems will appear.

He didn't want the battery he developed to be comparable to a certain star company.

A battery that can explode and spontaneously ignite at any time is of no use no matter how high its capacity is, and its safety performance simply cannot pass the test.

.......

Finding an additive that can replace ethyl carbonate has become the current focus of the Sichuan and Hai Materials Research Institute.

Yu Zhen and Ye Zan's research and development of artificial SEI films and electrolytes have temporarily stopped and entered into this work.

In the laboratory, including those with doctoral and master's degrees who were able to conduct battery experiments alone, Xu Chuan also arranged experiments in pairs.

Compared with formal researchers, the abilities of these people are still lacking a lot.

But if you can get to the doctoral level, it's basically not too bad.

These people can be trained as the team of Chuanhai Materials Research Institute, and Xu Chuan will not be stingy with his own resources and money.

And for these doctoral and master's students, there is nothing more gratifying than this.

After all, only with experiments can we have data, achieve results, graduate, and have qualifications...

...

"Boss, these are the experimental results of various groups of people these days."

In the laboratory, Fan Pengyue handed the information in his hand to Xu Chuan, and at the same time made some simple statements: "According to your request, seven groups of laboratory personnel conducted experiments on a total of fourteen different ethylene carbonate substitutes.

"

"In the experimental results, the two best materials are fluoroethylene carbonate and trimethylsilyl sulfite."

"These two materials can match the current artificial SEI film to a large extent. The calculated Coulomb efficiencies after replacement are 99.645% and 99.721% respectively."

"But correspondingly, these two materials also have their own shortcomings after being replaced."

"For example, after the replacement of fluoroethylene carbonate, there were problems such as reduced charge and discharge efficiency..."

"The amount of experimental data is relatively small and can only be used as a preliminary reference. After all, we do not have enough time to conduct complete experiments and tests."

"In addition, some safety tests have not been done..."

In the laboratory, Xu Chuan took over the experimental data from Fan Pengyue over the past few days, and while listening to his brief description, he looked through the information in his hand.

Since it was discovered in early November that ethylene carbonate is the main cause of lithium dendrites and lithium precipitation problems, the Sichuan-Hai Materials Research Institute has been conducting experiments on it.

Although the time was short, only about twenty days, it was enough for them to experiment with many new materials as long as they had a goal and sufficient manpower and equipment.

Of course, the experiments and testing these days are not perfect and not very formal.

Issues such as the compatibility between materials and battery safety performance testing are not considered.

However, compared to these problems, it is more important to find an additive that can replace ethylene carbonate. As for other things, they can be slowly improved later.

Xu Chuan wants to resolve this issue before going to Sweden to receive the award on December 10th.

After finishing it, I went to receive a Nobel Prize. After returning from Europe, the testing of the two protective materials in the nuclear beta radiation energy concentration and conversion into electrical energy project was almost completed.

In this way, he can devote his main energy to nuclear energy projects after the Nobel Prize.

But judging from the current progress, this wish may be difficult to realize.

Among the dozens of additives tested, none of them are very suitable so far, and basically all have problems of one kind or another.

If we put aside the problems of lithium dendrites and lithium precipitation, ethylene carbonate is really the best performing additive among all additives.

"Perhaps you can try diluting the concentration of ethylene carbonate? Or find a material to neutralize it?"

Looking at the test report in his hand, another way to solve the problem came to Xu Chuan's mind.

Ethylene carbonate will still be active in future lithium batteries in the future, and it will definitely have its role.

"If we can find a way to solve the problem of lithium evolution caused by ethylene carbonate, maybe ethylene carbonate has another role."

Suddenly, another term appeared in Xu Chuan's mind.

"Planned scrapping!"

The so-called planned obsolescence refers to a strategy in industry.

That is, the product supplier intentionally designs a limited service life for the product so that the product will be scrapped after a certain period of time.

First appeared on light bulbs.

During the Christmas period of 1924, companies such as Osram, Philips, General Electric and others gathered in Geneva to form a monopoly group called "phoebus" with the purpose of controlling the life of light bulbs to about 1,000 hours (at that time, the life of light bulbs could reach 1,000 hours).

2500 hours)

In 1942, the U.S. government took the "Phoebus" group to court, accusing the other party of its behavior. In the end, although the agreement was nominally terminated, these companies did not pay any compensation.

More importantly, this alliance proposed life control for ordinary light bulbs, which has continued. To date, the lifespan of most light bulbs is only 1,000 hours.

This was the plan to scrap it at that time.

Then, as time went by, this agreement gradually spread to other products.

For example, batteries and chips in mobile phones and computers; ink cartridges in printers; key buttons of various electrical equipment, etc.

This thing now has the ability to be planned for scrap, even if it is used for a period of time, it will be damaged due to various reasons.

For manufacturers of these things, if a product can be used in the hands of users for a long time, then fewer people will buy the new product after it is launched.

Therefore, in order to introduce new products and expand their own interests, manufacturers will inevitably choose to eliminate old products on the market, because new products face competition from old products to a certain extent.

In lithium-ion batteries, the presence of ethylene carbonate can, on the one hand, improve the performance of the lithium battery. On the other hand, as the number of charge and discharge cycles increases, the lithium precipitation in the negative electrode will become more serious, which will naturally lead to battery damage.

As long as the impact of ethylene carbonate on lithium-ion batteries needs to be well controlled, it can be said that the natural plan is scrapped.

This may be the reason why ethylene carbonate will cause lithium precipitation problems, but it will still exist in future lithium batteries, right?

Xu Chuan has probably figured out where to start to solve the problem of lithium precipitation.

If his guess just now is correct, then the solution to this problem is nothing more than controlling the content of ethylene carbonate or using another additive.

...

After confirming his suspicion, Xu Chuan immediately started to conduct the experiment again.

To simply verify the method in mind, the method used is very simple, just directly reduce the content of ethylene carbonate in the electrolyte.

In the first experiment, he reduced the ethylene carbonate content in the electrolyte by 20%, made a new lithium-ion battery, and retested it.

One-fifth of the amount is enough to ensure that if the content of ethylene carbonate really affects the lithium evolution of the negative electrode, it will definitely be reflected in the data, and it will be in a larger arc.

The test results were as he had guessed. After reducing the ethylene carbonate content in the electrolyte by 20%, the problem of lithium precipitation in the negative electrode of lithium batteries was greatly improved. The Coulombic efficiency of the battery increased from about 99.91% before.

Improved to 99.95%.

The Coulombic efficiency of 99.95% is enough to ensure that a battery can still maintain more than 80% of its capacity after completing 500 charge and discharge cycles.

This has reached the standard of lithium-ion batteries used on the market today.

"The hearts of capitalists are indeed black."

Looking at the preliminary test results, Xu Chuan shook his head.
To be continued...