Five major bottlenecks are tackled to bridge the "chasm" in all-solid-state battery manufacturing

"There is a manufacturing gap between liquid and solid," said Dr. Du Yixian, director of the Lyrics Research Institute, at the 2025 Gaogong Solid-State Battery Technology and Application Summit.

In the industrialization process of all-solid-state batteries, "interface problems" are recognized as the biggest process difficulty. Du Yixian divides it into two categories: one is that the interface density between the same materials is insufficient, and the internal porosity of the electrode or electrolyte is high, resulting in obstructed ion transmission; the second is the poor bonding between different material layers, such as the poor adhesion between the electrode and the electrolyte membrane, which is easy to peel off during the cycle.

There are not only interface problems of film formation and composite materials in the front stage. In the middle stage, the lamination link triggers new structural risks. All-solid-state batteries eliminate diaphragms, and materials are prone to deformation at the edges under high pressure, resulting in short circuits. In the later stage, the pressure demand for all-solid-state battery capacity has increased sharply, and a pressure of 10-30MPa needs to be applied, while liquid batteries only need 0.1-1MPa.

Based on the research on all-solid-state battery technology, Lyric Robot has identified four key process nodes: high-voltage densification, composite of electrolyte and electrode sheet, electrode sheet packaging and insulation, and high-voltage formation and capacity division.

In addition to the preparation of battery cells, the toxicity and flammability of hydrogen sulfide produced by the combination of sulfide and water bring new challenges to personnel safety, and excessive concentrations may even endanger life.

The solution to the above five problems constitutes a new manufacturing chain, and the "opening up" of each link requires a subversive paradigm innovation of the traditional battery production line.

High-voltage densification

- Solve the problem of insufficient density of material interface

"Isostatic pressing still faces challenges in the mass production of solid-state batteries." Du Yixian pointed out that although isostatic pressing can effectively reduce the porosity of solid-state batteries and optimize interface contact, its batch production mode (battery cells need to be pressed batch by batch in a pressure autoclave) is in conflict with the high speed, continuity and high consistency requirements required for large-scale production.

"The success of liquid battery industrialization is due to the efficiency advantage of roll-to-roll continuous production. If all-solid-state batteries are to achieve true commercialization, they must solve the dependence on the existing batch isostatic pressing process." Therefore, Liyuanheng believes that it is necessary to innovate the process of high-pressure densification of materials, introduce roller pressing or dry process routes that are more suitable for continuous production lines, and promote the real industrialization of all-solid-state batteries. In terms of alternative ideas, Liyuanheng's solution is a combination of "multi-stage roller pressing + dry electrode". The company has developed a laboratory-level four-roller pressing system, which ensures pressure by using large rollers and small rollers. The multi-stage roller pressing process can reduce the porosity to 20-30%. At the same time, the equipment is equipped with a quantitative feeding system to improve the uniformity and consistency of the film layer, fundamentally improving the interface densification level. Interface composite -- "roller hot composite double rolling machine" explores the optimal solution In the composite process of electrolyte and electrode pole piece, Liyuanheng systematically studied three mainstream paths, and conducted comparative analysis around interface density, bonding strength, process maturity and controllability. Electrolyte membrane pressing and transfer: After the electrolyte is made into a separate film, it is transferred to the electrode sheet by hot pressing. Its advantages are dry process, no solvent interference, strong material adaptability, and good interface chemical stability; and the film making and electrode preparation are separated, which is conducive to segmented quality control. However, because its interface is in physical contact, the bonding force is weak, which may cause stratification; "secondary contact" defects are prone to occur at the transfer edge.

Direct coating of electrolyte: The slurry containing electrolyte is directly coated on the electrode and dried and solidified. The process is relatively simple and the equipment is highly mature. However, there are problems such as solvent residue and chemical stability incompatibility with sulfide electrolytes; at the same time, it is difficult to control the coating uniformity and thickness, and the interface quality depends on the slurry formula.

Electrolyte and electrode co-roll synchronous filming: The electrolyte and electrode materials are simultaneously pressed by co-rolling to form an integrated composite layer. This is a completely dry method without solvent introduction; under the action of stress, a "fiber network" is formed, with the best interface density and bonding strength and the lowest porosity. However, this process requires extremely high precision in temperature and pressure control.

Du Yixian said that the most suitable solution at this stage is to form the electrode and electrolyte membrane independently first, and then complete the bonding through hot composite rolling. After weighing the interface quality, equipment maturity and mass production controllability, Liyuanheng recommends the "roller hot composite double rolling machine" solution. Liyuanheng's "roller hot composite double rolling machine" can achieve independent control of electrode and membrane quality; segmented control of hot pressing parameters; film formation and composite integration, improving the integration and stability of the production line.

This roller hot composite double rolling machine solution is more suitable for the current staged demand from pilot to mass production. It can not only ensure quality, but also gradually evolve towards automation and continuity, leaving room for subsequent process upgrades.

Pole piece packaging and insulation

-Prevent short circuit risk

In the manufacture of all-solid-state batteries, the cancellation of the diaphragm causes the pole piece to be prone to edge deformation under high-voltage conditions, causing the risk of direct contact between the positive and negative electrodes and short circuits. To address this problem, there are four mainstream packaging solutions on the market.

Steel screen printing process: Use a high-precision steel screen to print an insulating glue frame on the edge of the negative electrode of the electrode to form a circular structure to isolate the positive and negative electrodes. It has the advantages of high dimensional control accuracy, fast production cycle (single-chip printing time <2s), strong equipment compatibility, and can adapt to different sizes of electrodes.

Prefabricated glue frame transfer process: Prepare the insulating glue frame in advance and transfer it to the surface of the electrode by hot pressing or adhesive. The thickness uniformity of the glue frame prepared in this way is excellent, but the transfer yield is affected by the flatness of the glue frame and the electrode.

Glue dispensing process: Use a high-precision glue dispensing valve to spray insulating glue on the edge of the electrode. Although the investment cost of glue dispensing equipment is low, the dimensional accuracy is poor, and the production efficiency is low due to the long curing time of the glue.

UV printing process: Use ultraviolet light to cure glue to directly print the insulating layer on the surface of the electrode. This is an emerging non-contact processing, but it is limited by the current process level. The UV printing speed is slow, the process stability needs to be verified, and the equipment cost is high.

Based on the above comparison, Liyuanheng recommends the steel screen printing integrated solution, which realizes high-speed and uniform coating of the resin glue frame through a high-throughput printing system. The width accuracy of the glue frame can be controlled to 0.1mm, and the thickness uniformity is 10μm; then it is integrated into a glue frame-stacking integrated equipment, integrating the glue frame printing and the stacking process.

High-voltage formation

-How to design the formation of all-solid-state batteries

The solid electrolyte and electrode particles of all-solid-state batteries are in point contact, and the ion transmission impedance is much higher than that of liquid batteries. In the formation and capacity stage, high pressure (10-30MPa) is required to force the solid electrolyte and electrode particles to undergo plastic deformation, fill the pores, form surface contact, and thus construct a low-impedance ion transmission channel.

Specifically in the formation design of all-solid-state batteries, Du Yixian pointed out that the formation of all-solid-state batteries requires 60-80 tons of restraint force (corresponding to a single cell pressure ≥10MPa), which is much higher than the 3-10 tons required for conventional liquid batteries. The fixture body needs to be made of high-strength alloy steel to avoid deformation under high pressure.

Liyuanheng adopts a horizontal fixture structure, and the flatness between the layers is controlled within 0.1mm to ensure that the pressure is evenly transmitted to the surface of the battery cell. In contrast, the deformation of the layers of the traditional vertical fixture can reach 0.5mm under the same pressure, resulting in pressure attenuation at the edge of the battery cell.

Sulfide anti-toxic and explosion-proof

——Introducing ideas from the semiconductor industry

Sulfide is one of the mainstream routes for all-solid-state batteries. Sulfide combines with water to produce hydrogen sulfide. The toxic properties of this substance bring higher manufacturing safety risks. Du Yixian emphasized, "The terrible thing about hydrogen sulfide is that it is 'dangerous only when you can't smell it', so we must assume the worst and design the most strictly."

It is worth mentioning that Liyuanheng has rich experience in many fields of new energy, and the demand for toxic environment prevention and control of all-solid-state batteries is similar to that of the semiconductor industry (more toxic chemicals and toxic gases are involved in the complex manufacturing process of semiconductors).

Lyrics borrowed the ideas of the semiconductor industry for environmental control of all-solid-state batteries, and used semiconductor clean room standards to carry out hierarchical control of production areas:

Green Zone/Blue Zone (Safe Zone): The core production area of the production line, the equipment body and the pipeline system are completely enclosed, and personnel only operate through the monitoring terminal;

Yellow Zone (Restricted Zone): 1 meter outside the equipment, you need to wear a positive pressure respirator to enter;

Orange Zone/Red Zone/Black Zone (Restricted Zone): Accident emergency area, personnel are prohibited from entering.

In addition, Lyrics formulates anti-toxic and explosion-proof design specifications, combines intelligent monitoring systems, and builds a personnel safety management system based on the production characteristics of all-solid-state batteries, forming a safety closed loop from man-machine-material-method-environment-testing.

Crossing the "manufacturing gap" between liquid and solid is not only an iteration of material formula, but also a battle for the entire industry chain involving breakthroughs in physical limits, reconstruction of process paradigms, and upgrades in safety assurance.

The solutions for the five core process nodes displayed by Lyrics are a pragmatic roadmap for the mass production of all-solid-state batteries. It not only concerns the innovation of battery form, but also heralds a systematic upgrade of the precision, intelligence and safety standards of high-end manufacturing.

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