Solid-state battery production process analysis

Since the 1990s, lithium-ion batteries have developed into the most mature and widely used battery technology. As people's demand for battery energy density, safety and economy is getting higher and higher, the traditional lithium-ion battery has gradually failed to meet the demand. Using solid electrodes and solid electrolyte, with high energy density and safety of the "solid state battery" was developed.

Solid batteries have many advantages, such as the structure and density of the solid electrolyte can gather more charged ions, conduct more current, lithium metal and other materials can be used as the anode,best lithium ion battery machine company to improve the capacity of the battery and the endurance of the unit volume; the sealing of the solid electrolyte is relatively simple, which can save costs, reduce the size of the battery, and make it more portable; the solid electrolyte has a stable chemical structure, which reduces the chemical reaction and explosion risk of the battery at high temperature, and the battery performance can be improved. The chemical structure of solid electrolyte is stable, which can reduce the risk of chemical reaction and explosion of the battery at high temperature, and the performance of the battery is more stable.

The traditional lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte and a diaphragm. Solid-state batteries replace the electrolyte with a solid-state electrolyte.equipment for lithium battery assembly The key difference between solid-state batteries and conventional lithium-ion batteries is that the electrolyte is changed from a liquid to a solid state in consideration of safety and high energy density.

For solid-state batteries, the production process requires breakthroughs in electrodes, electrolyte, interface engineering and encapsulation technologies, and the optimization and improvement of the production process is an important part of realizing the engineering and commercial application of solid-state batteries. Compared with traditional liquid lithium-ion batteries, the first stage process of solid-state batteries is basically the same as that of liquid lithium-ion batteries, while in the mid- and late-stage processes, solid-state batteries need to be pressurized or sintered, and will not be liquefied.

Solid-state batteries can be categorized into polymer solid-state batteries, sulfide solid-state batteries, oxide solid-state batteries, and thin-film solid-state batteries. The electrolyte film forming process is the key process in the whole solid state battery production process. Fast Ion Conductors The thickness and ionic conductivity of fast ion conductors are affected by different processes. Excessively thick films reduce the mass and volumetric energy density of all-solid-state batteries while increasing the internal resistance of the batteries. On the other hand, the poor mechanical properties of fast ion conductor films may lead to short circuits. After decades of research, different types of solid electrolytes (polymers, oxides, sulfides, etc.) have been successfully synthesized for material development.

The electrolyte film formation process, as the core process of solid-state batteries, can be categorized into two main types: dry process and wet process. In addition to the dry and wet processes, solid electrolyte membranes can also be prepared by the vapor phase methods of chemical vapor deposition, physical vapor deposition, electrochemical vapor deposition, and vacuum sputtering. However, the preparation cost of the vapor phase method is higher and is only applicable to thin film solid state batteries.

1. Polymer Solid State Battery

For the preparation of polymer solid state batteries, all use the coating method to prepare a composite polymer solid electrolyte anode layer and polymer solid electrolyte intermediate layer, laminated to polymer solid state batteries. The electrode sheet is prepared in a similar way to existing liquid batteries and is compatible with existing production lines.

In the case of the polymer solid-state battery preparation process at RWTH Aachen University's research institute PEM, for example, the cathode and solid-state battery electrolyte materials are prepared in parallel, and the cathode and electrolyte slurries are formed through a process of high-temperature melting and re-mixing and extrusion. The two slurries are stacked on the anode collector material by extruding them together. Afterwards, lithium metal is pressed into a slurry and then coated on the surface of the electrolyte material, forming a hybrid multilayer core of collector-cathode material-solid electrolyte-lithium negative electrode. Finally, the multilayer core is compacted by the roller pressing method.

The prepared cores are cut into fixed sizes and stacked in series-parallel connection according to different needs. After that, the stacked cells are compacted and encapsulated, and the production is completed after the formation and aging process. The battery is then tested and rated.

In the manufacture of polymer solid-state batteries, it is characterized by the fact that both dry and wet methods can prepare composite solid-state positive electrodes and polymer electrolyte layers. Both the dry and wet methods are very well established and both readily prepare large cells as well as bipolar internal series cells. However, there are some problems in the preparation of solid polymer batteries, such as the difficulty of controlling the uniformity of the film formation, the difficulty of compatibility with high-voltage cathode materials, which leads to low energy density, and the limitations of ether polymer electrolyte materials, and the batteries are often operated at high temperatures.

2.Sulfide solid state battery

For sulfide solid state battery dry process, its technical advantages include saving de-solventing process preparation costs and saving preparation cycle; no other substances (solvents) on the electrolyte; dry battery performance is more stable. However, sulfide solid state battery dry process also exists technical disadvantages, such as the preparation of large-capacity battery difficulties; electrolyte layer thickness is thicker, higher impedance; powder compaction requires a high level of compression pressure (10t/cm2), and so on.

3. Oxide solid-state battery

For oxide solid-state battery preparation, take the German RWTH PEM preparation process as an example. Battery cathode and solid-state battery electrolyte material preparation by ball milling way respectively; using high-frequency sputtering method, the solid-state battery sputtering to the surface of the cathode material; will be a good composite of the cathode-electrolyte material for high-temperature sintering; through the electron-beam evaporation method will be the distribution of the negative electrode to the electrolyte material.

4. Thin Film Solid State Battery

Japan ULVAC's LIPON thin-film all-solid-state battery, for example, its LIPON amorphous oxide solid-state electrolyte, prepared by the U.S. Oak Ridge Laboratory in 1992 by radio frequency magnetron sputtering Li3PO4 target. Positive electrode collector, positive electrode, LIPON, negative electrode collector, lithium metal negative electrode, and outer protective layer are prepared by vacuum coating technology.

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