Solid state batteries and liquid state batteries have many similarities in manufacturing processes, such as the manufacturing process of electrode plates based on slurry mixing, coating, and stretching, followed by electrode ear welding and PACK (battery pack processing group) after cutting, but there are also some differences.

There are three core differences:

1) Composite of positive electrode materials for solid-state batteries, where a mixture of solid electrolyte and positive electrode active material is used as the composite positive electrode;

2) The electrolyte addition method is different. Liquid batteries inject electrolyte into the battery and package it after welding the electrode tabs, while solid electrolytes not only form a composite positive electrode with the positive electrode active material, but also need to be coated again on the composite positive electrode that has been compressed;

3) Liquid lithium-ion battery electrodes can be combined by winding or stacking, while solid-state batteries are usually packaged in a stacked form due to the poor toughness of their solid electrolytes such as oxides and sulfides.

The core process of solid-state electrolytes lies in film formation, which can be divided into dry, wet, and other processes.

The core process of manufacturing solid-state batteries lies in the solid-state electrolyte film formation process. The film formation process of the electrolyte will affect the thickness and related properties of the electrolyte. Thin thickness can lead to relatively poor mechanical properties, which are prone to damage and internal short circuits. Thick thickness can increase internal resistance and reduce the energy density of battery cells and systems due to the absence of active substances in the electrolyte itself.

Wet film-forming process

Mold support for film formation, suitable for polymers and composite electrolytes. Pour the solid electrolyte solution into the mold and obtain the solid electrolyte membrane after solvent evaporation;

Positive electrode support film formation, suitable for inorganic and composite electrolyte membranes, which involves pouring a solid electrolyte solution directly onto the surface of the positive electrode, evaporating the solvent, and forming a solid electrolyte membrane on the surface of the positive electrode;

Skeleton supported membrane formation is suitable for composite electrolyte membranes. The electrolyte solution is injected into the skeleton, and after solvent evaporation, a solid electrolyte membrane with skeleton support is formed, which can improve the mechanical strength of the electrolyte membrane.

The core of wet process technology is the selection of adhesives and solvents, which are easy to evaporate and have good solubility and chemical stability for electrolytes.

The disadvantage of wet method is that the solvent may be toxic, and the overall cost is relatively high. If the solvent evaporates incompletely, it may reduce the ionic conductivity of the electrolyte.

Dry film formation process: Mix electrolyte and adhesive, grind and disperse, and apply pressure (heating) to the dispersed mixture to prepare a solid electrolyte membrane. This method does not use solvents and has no solvent residue. The disadvantage of dry method is that the electrolyte membrane is relatively thick, and due to the absence of active substances inside, it will reduce the energy density of the solid battery.

Other film-forming processes include chemical, physical, electrochemical vapor deposition, and other methods. This type of process has a high cost and is suitable for thin-film all solid state batteries.

There are many methods for solid electrolyte film formation, and polymers, sulfides, and oxides can be matched with the most suitable film formation process based on their own characteristics.

1) Polymer solid electrolytes have the best processing performance and the strongest process compatibility. In addition to being unsuitable for deposition methods due to the inability to pelletize, dry stretching, dry spraying, extrusion, casting, and infiltration processes can all be used to achieve film formation of polymer solid electrolytes.

2) Sulfides are not suitable for extrusion and small-sized deposition under high temperature conditions due to their poor air stability. Other processes such as stretching and spraying can be used for the formation of sulfide solid electrolyte films.

3) Due to its ceramic properties and high brittleness, oxides need to be formed into films through a combination of particle deposition and sintering, or by casting under solution blending conditions.

Semi solid state batteries are compatible with traditional lithium battery production processes, and the production equipment is basically compatible with lithium batteries. Only a new production line dedicated to producing semi-solid separators needs to be added, and the production equipment is compatible with the equipment for liquid battery separators.

Semi solid state batteries require larger pore size and higher strength of the separator, and adopt a wet coating process.

Compared to traditional batteries, the separator of semi-solid state batteries does not have significant process changes, and the parameters can be adjusted. However, because semi-solid state batteries need to improve ion conductivity, they require larger pore size and higher strength of the separator, so a wet stretching+coating process is needed.

In addition, the demand for separators in semi-solid state batteries has not changed.