The Application of Parylene in lithium battery

Parylene is a new type of polymer coating material launched by United Carbon Corporation in the 1960s. It is the common name for paraxylene polymere. At present, according to the different molecular structures, Parylene materials can be divided into various types such as Parylene N, Parylene C, Parylene D, Parylene F, Parylene HT, etc. Parylene C is mainly used as a high-purity passivation layer and dielectric layer in microelectronics and semiconductors. It can also be used as passivation, protection, lubrication and other coatings in microelectronics; In addition, it can also be used as isolation, solidification, and reinforcement materials in biomedical anti-corrosion and cultural relic protection.
Application of Parylene
Lithium metal is considered the ultimate negative electrode of lithium secondary batteries due to its extremely high theoretical specific capacity and extremely low electrochemical potential. At present, commercial lithium batteries generally use liquid electrolytes, but the metal lithium negative electrode is prone to side reactions with the liquid electrolyte due to its active chemical properties, and lithium dendrites are prone to grow at the interface, causing safety issues such as short circuits and thermal runaway in the battery, which hinders the development process of high-energy density metal lithium batteries. The use of non combustible and high elastic modulus solid electrolyte (SE) instead of liquid electrolyte to produce all solid lithium batteries is expected to fundamentally solve this safety problem and inhibit the growth of lithium dendrites. Solid state electrolytes are the core of all solid state lithium batteries, and common solid electrolytes include polymer and inorganic types. Among them, inorganic solid electrolytes are widely studied due to their high ion conductivity and lithium ion migration number close to 1mS/cm. However, the non ideal behavior of lithium ions at the interface of inorganic electrolytes can still lead to the growth of lithium dendrites, and in severe cases, lithium dendrites may even pass through the inorganic solid electrolyte, causing problems such as battery short circuits.
In response to existing problems, the CN113809388B patent provides a composite solid electrolyte material and its preparation method. The specific preparation method is to coat the inorganic solid electrolyte body with insulating polymer, forming a fully coated inorganic solid electrolyte body with a thickness of less than or equal to 20nm on the outer surface, to obtain a composite solid electrolyte material. Among them, the insulating polymer is at least one of Parylene N, Parylene C, Parylene D, Parylene F, and Parylene HT.
The material of the coating layer is polydimethylbenzene or its derivatives, which can be adhered to the inorganic solid electrolyte body through coating, chemical vapor deposition, vapor deposition, or sputtering. The formed coating layer has a uniform thickness, good continuity, and is dense without pinholes.

References
CN113809388B Composite solid electrolyte materials and their preparation methods, lithium secondary batteries and terminals.