Puresci: Breakthrough in Hydrogen Sulfide Treatment Technology Takes Another Step Forward to Mass Production of All-Solid-State Batteries

Currently, the industrialization path for all-solid-state batteries has been largely clarified, with several companies planning to achieve small-batch vehicle installations in 2027, marking the official start of large-scale application for this technology.

Industry analysts believe that 2025-2026 will be a period of rapid growth in demand for pilot production line equipment, a crucial stage for process verification, equipment debugging, and egineering finalization; from 2027 to 2030, the construction of GWh-level solid-state battery production capacity will gradually commence, propelling the industry into a new cycle of large-scale production.

From a technological perspective, the sulfide route is widely recognized as the technology with the greatest performance potential in solid-state batteries. Toyota has been deeply involved in this field, accumulating over 1,300 patents. In China, CATL, BYD, and FAW are all focusing on overcoming the technological hurdles of sulfide technology.

All-solid-state batteries have extremely high requirements for the production environment. For example, the sulfide route is extremely sensitive to humidity and oxygen, releasing toxic hydrogen sulfide (H₂S) upon contact with moisture, and it is also prone to explosion. This places extremely high demands on the production line environment, and how to safely, environmentally, and efficiently handle hydrogen sulfide gas has become a challenge for the entire industry.

High and low concentrations of hydrogen sulfide

Currently, hydrogen sulfide (H₂S) gas generated during the production of all-solid-state sulfide battery systems is mainly classified into two categories: high-concentration hydrogen sulfide and low-concentration hydrogen sulfide. High-concentration hydrogen sulfide originates from numerous process units and has a relatively high concentration, approximately 10 ppm or even higher; low-concentration hydrogen sulfide originates from spatial diffusion and has a concentration of approximately 1-5 ppm (hydrogen sulfide concentration data is based on feedback from existing processes and will be updated synchronously after production process optimization).

Traditional approach: Suppress at the source

Currently, the industry (in laboratories or small-scale pilot lines) generally adopts inert gas protection systems, coupled with valves, pipes, and seals with ultra-low dew points and ultra-high sealing performance. Its core mechanism is based on "suppressing generation." This method is applicable in experimental, glove box, and small-scale testing stages, and the operating costs and initial investment are acceptable. However, the cost of large-scale production is too high, making it difficult to promote and apply on a large scale, and thus failing to meet the requirements for large-scale industrial verification of all-solid-state batteries.

New approach: Process purification

After H₂S gas is generated, the H₂S problem is solved through process purification.

1. Purification in conjunction with a dust removal system

In pilot production lines, areas with high H₂S concentrations and dust generation typically have H₂S concentrations above 10 ppm.

① First, the H₂S is treated by dust removal equipment, then activated carbon and metal oxides are used to adsorb the H₂S.

②For pilot production lines with H₂S concentrations above 10ppm and after pretreatment by dust removal equipment, rotary adsorption can achieve deep purification of sulfides, and the final outlet H₂S concentration can be reduced to a level close to 0.

2. Purification in conjunction with a dehumidification system

Low-concentration H₂S gas in the production workshop is drawn into the dehumidifier by the negative pressure return air of the dehumidification system. This dehumidifier is equipped with an activated carbon filter/desulfurization impeller, which first adsorbs hydrogen sulfide before dehumidification.

① Adding activated carbon filter to the dehumidification system

Advantages of activated carbon adsorption:

• Simple equipment

• No renewable energy required

• Suitable for treating low concentrations

Disadvantages of activated carbon adsorption:

• Initial investment is relatively high.

• Regular replacement is required, approximately every 1-3 months, resulting in high maintenance costs.

• Higher concentrations require larger quantities, making it unsuitable for confined spaces.

• It generates hazardous solid waste.

• Suitable for lower wind speeds, generally below 0.5 m/s.

• Replacement requires shutdown.

  
  

a. With an air velocity of 2 m/s and a residence time of 5 seconds, the activated carbon filter section needs to be 10 m long.

b. With an air velocity of 0.5 m/s and a residence time of 5 seconds, the activated carbon filter section needs to be 2.5 m long, but its cross-sectional area will be much larger than that of a dehumidifier.

② Add a hydrogen sulfide removal impeller to the dehumidification system

a. Single impeller

The dew point system has a simple structure, is easy to install and maintain, is small in size, and low in cost, making it suitable for spaces with limited space. It achieves low and ultra-low dew point environments and is widely used by Japanese and Korean companies.

b. Dual-rotor dehumidifier

Suitable for solid-state battery factories requiring high airflow and relatively energy efficiency. The regeneration temperature is lower than that of a single-rotor dehumidifier (120-140℃), and the regeneration airflow is smaller (1/10 of the processing airflow). Operating energy consumption is also lower than that of a single-rotor dehumidifier. However, the dehumidifier is larger than a single-rotor dehumidifier, and its application range is relatively limited.

c. Multi-stage dehumidifier

Suitable for solid-state battery factories with high air volume and super energy efficiency, this system uses a multi-stage dehumidifier rotor, with a low regeneration temperature of 70-90℃, and is compatible with low-grade heat sources, making it a super energy-efficient system.

Process integration: System coupling of dust removal, dehumidification and desulfurization

As can be seen, the production workshops for liquid batteries cannot meet the stringent environmental standards required for sulfide-based production. In liquid battery production, dust removal and dehumidification are not inherently related. However, in all-solid-state batteries, especially sulfide-based solid-state batteries, dust removal and dehumidification are closely linked due to H₂S. "Currently, due to H₂S issues, desulfurization functions need to be added to the downstream of dust removal equipment, and desulfurization functions also need to be added to the upstream or midstream of dehumidification equipment," an industry insider pointed out. If the desulfurization effect at the downstream of dust removal is good, the pressure on dehumidification and desulfurization will be reduced. "This is a key point that must be considered in the overall design."

In large-scale solid-state battery production lines, in addition to conventional activated carbon, Provac's independently developed H₂S adsorption rotor has attracted the attention of many battery companies' solid-state battery pilot lines. This technology does not require periodic shutdowns to replace filters like activated carbon, and it does not generate hazardous waste.

Dew point balance: The lower the dew point, the less H₂S is generated, corresponding to a larger air volume and higher energy consumption. When the generated H₂S can be treated, such a low dew point is not required, the air volume can be reduced, and energy consumption can be lowered. There is a balance between dew point treatment and H₂S treatment.

Technical Challenges: Limitations of Activated Carbon Adsorption in Wind Speed Matching

Modified activated carbon requires a certain amount of time to adsorb H₂S, and the airflow velocity should not be too high. However, the internal airflow velocity of dehumidifiers is typically 2–4 m/s, which is extremely detrimental to the adsorption of H₂S by activated carbon. Excessive airflow velocity severely affects the adsorption effect.

The solution is to significantly increase the thickness of the activated carbon, but this leads to an increase in the length of the dehumidifier, making the system more complex and longer. This problem is particularly prominent in large-scale production, while it is less noticeable in pilot or pilot-scale stages.

In solid-state battery dust and sulfur removal, activated carbon also faces airflow velocity limitations, generally requiring a velocity below 0.5 m/s. Since the airflow volume for dust and sulfur removal is not large, activated carbon can be applied by increasing its height. The industry also uses metal oxides to assist activated carbon to solve the problems of insufficient adsorption capacity and decreased accuracy caused by excessive airflow velocity, but both the activated carbon and metal oxides still need to be replaced periodically.

Mainstream desulfurization technology routes

In large-scale production, the desulfurization solutions for dust removal and dehumidification systems mainly fall into two categories:

1: Activated carbon + metal oxides

2: H₂S adsorption rotor

Dust removal and desulfurization, as well as dehumidification and desulfurization, will be applied in combination using the above two methods.

Economic Comparison Analysis

(The above assessment requires experimental and engineering applications to obtain accurate data and is only a trend assessment.)

(Note: The copyright of the solutions and text mentioned in this article belongs to Puresci, and the solutions have been patented.)