Modification of sulfide and halide solid electrolyte by spray drying and embedding

Undoubtedly, solid electrolytes are an extremely critical component of solid-state batteries.

Looking at the current research on solid-state electrolytes, ceramic solid-state electrolyte systems such as oxides involve complexity and poor mechanical processing performance, making it difficult to solve physical contact problems; The thermodynamic stability, compatibility with positive and negative electrodes, and ability to inhibit dendrite growth of borohydrides are insufficient; Polymer solid electrolytes require high temperature operation and have weak ion conductivity.

Therefore, the focus of industry research and development has shifted to sulfides and halides, among which sulfides have high ionic conductivity but are sensitive to moisture and oxygen; Halide electrolytes have the characteristic of easy deliquescence, which can easily form crystalline water and cause a sharp decrease in ion conductivity. The drying and dehydration temperature of halide electrolytes is higher than 200 ℃, which conflicts with the temperature tolerance of the binder in the electrode sheet and limits the commercial use of the material. Therefore, numerous research institutions and enterprises have conducted in-depth studies on the modification of sulfides and oxides.

Coating modification is a common method. Traditional coating modification uses impact to coat small wall materials on the surface of electrolytes through mechanical energy, resulting in a certain degree of balling effect. Common equipment includes high mixing machines and fusion machines. Based on the characteristics of sulfides and halides, the R&D department needs to place the equipment in isolation or special environments to complete the coating operation, which poses significant challenges for commercial production.

Through the spray drying process, oxides and sulfides can be embedded. Yes, it is embedding, not coating. Specifically, a suspension is formed by adding oil or organic solvents to solid electrolytes and polymer materials. After being atomized by a spray gun, it is dried using an extremely dry and anhydrous inert gas that has been heated to achieve embedding effect. Unlike fusion, due to the transition of the wall material from solution to solid, a continuous membrane structure is formed on the surface of the solid electrolyte, which has a better embedding effect compared to encapsulation.

Requirements for equipment: The equipment is designed with a closed loop to avoid solvent emissions into the environment. The solvent evaporated from the circulating gas is condensed and collected, and the dehumidified gas is heated and endowed with drying ability again. From a safety perspective, the system design requires high airtightness, explosion-proof, etc. If the solvent is acidic, the tower material needs to be replaced with Hastelloy alloy.

For the particle size of the product, it can be adjusted through the atomization parameters of the spray gun to achieve products that meet the particle size requirements. Generally, the particle size D50 of polymer coated electrolytes is 0.1-10 μ m.