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High-voltage catholyte additive tris(trimethylsilyl) phosphite (TTSPi) and bis(2,2,2-trifluoroethyl) carbonate (DTFEC) combination

But the combination of these two additives (TTSPi and DTFEC CAS:1513-87-7) is particularly effective for protecting the interphase

High-voltage catholyte additive tris(trimethylsilyl) phosphite (TTSPi) and bis(2,2,2-trifluoroethyl) carbonate (DTFEC) combination

bis(2,2,2-trifluoroethyl) carbonate(DTFEC) CAS:<a href=/e/p/1513-87-7.html>1513-87-7</a>

bis(2,2,2-trifluoroethyl) carbonate(DTFEC) CAS:1513-87-7

 

There is no doubt that most cars will be battery powered within ten years. We need to study sustainable materials. This is why we started to study high-pressure nickel manganese oxide spinel.
PA: Can you describe the impact of LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode coating on battery performance? Especially NiPOx coating, which is the subject of your paper in "Materials Today" in 2020.

SP: This is the result of the work of the binder. A few years ago, the prevailing view in this field was that you cannot use water-based adhesives with nickel cobalt manganese oxides because they degrade. We optimized the formula and added a little phosphoric acid to the slurry at that time. We noticed that the cathode material is no longer degrading, so we investigated this to understand why. We realized that once the transition metal oxides are dissolved in the water phase, the phosphate anions will react with them and precipitate out in the form of nickel cobalt manganese phosphate. This is the reason for protecting the material. We had a patent in the process, and then a friend of mine, Dr. Ilias Belharouak, obtained a follow-up patent. He also made some other changes.

We tell ourselves whether the formation of phosphate can be protected in a nasty environment (because the water of these oxides is a nasty environment), why don't we try to put the paint directly on the particles before exposing the paint to the water-based environment? We are still working on these two methods. One is to form phosphate in situ during the slurry preparation process, and then coat the electrode. Another method is to first coat the particles in a separate environment. It seems to work very well. Some phosphates are better than others. This is one of the reasons why we want to operate in a separate environment so that we can decide which phosphate we have-nickel phosphate, cobalt phosphate or manganese phosphate. Because when we process in the slurry, we have no choice. Anything that comes out of the particles will precipitate out in the form of phosphate, and we cannot control the chemical reaction. We see that nickel phosphate is very good.

PA: One of the main challenges of high-voltage cathodes is the electrolyte. You are trying to solve the problems of various electrolyte additives, such as those in the 2021 paper published in the "Power Journal".

SP: At a certain point, we synthesized a lithium-rich nickel manganese cobalt oxide compound with no matching characteristics. However, there is a problem of reaction with the electrolyte, so we started to study electrolyte additives. The two additives used in tris(trimethylsilyl) phosphite (TTSPi) and bis(2,2,2-trifluoroethyl) carbonate (TFEC) are not new, but these two additives The combination of (TTSPi and TFEC) is particularly effective for protecting phases. We do not have this patent yet because the synergy used to enhance the performance is not yet clear.

PA: What type of electrolyte are you exploring for solid-state battery research?

SP: Since 1986, I have been engaged in polymer electrolyte research. Just after Michel Armand proposed polyethylene oxide (PEO), Scrosati got involved in this field, and I was the officer. A few years ago, I started working with Samsung (Japan branch). They hope that we will explore new solid-state battery cathode materials using sulfurized electrolytes. We have quite a wealth of knowledge in this field, and now we are very active. Pure solids can be very difficult. We published a paper on Small by 2020, which will use an ionic liquid intermediate layer to reduce interface resistance. We have proved that placing several layers of ionic liquid on the interface of lanthanum lanthanum zirconate and lithium metal and the cathode side will greatly reduce the interface resistance. In the first paper, we just reported better performance.

We co-authored a follow-up paper on this topic with Professor Jurgen Janek, and we collaborated on one of the German-funded projects. In cooperation, we are explaining why we need better performance. When you have a solid-solid interface, the behavior of the two solids may be different, and then there will be a problem of matching their interface. The solid electrolyte has its own interface and stays there. The electrode expands and contracts during cycling. Ionic liquids can fill these gaps formed during operation and reduce the interface resistance by one to two orders of magnitude. The paper we published in 2020 inspired us to continue this project. We will submit a manuscript developed in this direction. We use a high Ni cathode (NMC811) on the positive side and Li metal on the negative side. We have also developed this hybrid solid electrolyte, which is flexible. We can even demonstrate batteries that cycle between 8 and 13 volts.

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