Dry Electrode Process: The Key to Mass Production of High-Performance Solid-State Battery

In all-solid-state batteries, the liquid electrolyte is replaced by a solid-state electrolyte membrane. Consequently, the front-end production process requires the preparation of this solid electrolyte film in addition to the traditional positive and negative electrode sheets. This process is a critical link in the battery manufacturing workflow, directly determining the performance and quality of the final cell. While the wet process currently dominates solid-state battery production lines, the dry process is increasingly becoming the mainstream direction for next-generation solid-state battery front-end technology, thanks to its combined advantages in cost, process efficiency, and material compatibility.

01. Key Upgrades in Solid-State Battery Pre-Forming Production

The manufacturing process for solid-state batteries fundamentally differs from that of traditional liquid batteries. The front-end film preparation segment is the critical, transitional phase in the battery manufacturing process. This stage directly dictates the finished cell's energy density, rate performance, and cycle life. In all-solid-state batteries, the solid-state electrolyte membrane replaces the liquid electrolyte. Therefore, front-end preparation must include not only the conventional positive and negative electrode sheets but also the solid-state electrolyte film. This fundamental change introduces new challenges and simultaneously presents opportunities for process upgrading.

02. Technological Transformation: The Leap from Wet to Dry Process

Current solid-state battery front-end preparation processes are mainly categorized into two technical routes: wet and dry. The wet process still relies on the solvent system of traditional liquid batteries, where electrode or electrolyte materials are mixed with a binder to form a slurry, coated, and then dried to complete film formation.

While this process is relatively mature, it has inherent drawbacks: it requires the use of large amounts of toxic organic solvents (such as NMP), necessitates high-energy-consumption steps for drying and solvent recovery, and restricts the application of certain cutting-edge materials sensitive to solvents.

In contrast, the dry process innovates electrode manufacturing by eliminating the use of solvents and the subsequent drying step. The dry process relies more heavily on high-shear dry mixing and fibrillation equipment to achieve uniform material dispersion and pre-forming, by multi-roll pressing to complete the film formation directly.

The core advantages of dry film formation technology are evident across three dimensions:

• Cost Efficiency: By omitting the coating, drying, and solvent recovery stages, equipment investment is lower, energy consumption is reduced, and overall cell manufacturing costs can be reduced by approximately 18%.

• Performance Enhancement: The dry process effectively increases the active material's compaction density, leading to an energy density increase of about 20%. SAIC Group's semi-solid-state battery, integrated into its MG4 model, has achieved a system energy density of 400Wh/kg, supporting a 12-minute fast charge for 400 km.

• Environmental and Material Compatibility: The dry process eliminates the need for toxic solvents, solving the environmental pollution issues of the traditional wet process. Concurrently, it enables the application of more cost-effective materials (such as manganese-based cathodes).

03. Technology Matrix: Diversified Paths for Dry Film Formation

Dry film formation is not a single process but a matrix encompassing various technical routes. Currently, the more representative dry electrode preparation technologies primarily include six types:

• Fibrillation Method: Uses high shear force to fibrillate the binder, enabling it to tightly encapsulate active materials and conductive agents, forming a self-supporting electrode film. This process demands extremely high shear force and temperature control capabilities from the equipment.

• Dry Spray Deposition: Utilizes charged powder, which is uniformly deposited onto the current collector under an electric field, by hot pressing to melt and fix the binder, forming a self-supporting film.

• Other Methods: Vapor deposition, hot-melt extrusion, direct pressing, and 3D printing are applied based on different material characteristics and application scenarios.

These different paths vary in technical principles, applicable materials, film-forming capability, and equipment complexity, and are suited for different applications such as large-scale, flexible electrodes, small-sized devices, and thick electrode sheets.

Comparison of Major Dry Film Formation Technical Routes

The industry generally considers the Binder Fibrillation Method to exhibit superior performance stability and processability, positioning it as the emerging mainstream route.

04. Industrialization Challenges: Bridging the Gap from Laboratory to Mass Production

Despite the clear advantages of dry film formation, scaling from the laboratory to mass production faces numerous hurdles. Capacity and efficiency are paramount concerns. Dry coating capacity and speed still lag behind traditional wet processes, and uniformity and adhesion performance during wide-format spraying require significant improvement.

Coating uniformity and quality control present another major challenge. Non-uniform dry electrode coatings can create "hot spots" within the electrode, leading to accelerated battery performance degradation and potential safety risks.

Binder and material compatibility also need further optimization. Achieving uniform distribution of PTFE fibrils within the mixture while preventing damage to active material particles is essential. Furthermore, PTFE is unstable at low potentials and reacts irreversibly with lithium, which limits its application in negative electrodes.

Challenges on the equipment side are equally severe. The dry process imposes higher demands on core roller-pressing machinery. The performance and production efficiency of the calendaring machine as the core equipment are central to determining the dry process's viability for mass production.

TOB NEW ENERGY is actively working to address these challenges, aiming to control the binder content in the negative electrode to 0.7% and the positive electrode below 1.5% to achieve more efficient, low-cost film-forming performance.

05. Equipment Innovation: The Critical Force Driving Dry Process Implementation

Equipment typically spearheads the industrialization of solid-state batteries. In the realm of dry film formation, equipment innovation is the key driver for technological implementation.

• Front-End Process Equipment: Accounts for approximately 32% of the entire production line's value, including core equipment for high-efficiency mixing, material dispersion, coating, and high-shear treatment.

• Mid-End Process Equipment: Accounts for approximately 45% of the line's value, centered around high-efficiency stacking machine (25% of the line's value) and horizontal isostatic presses (13% of the line's value), covering the entire process from shaping to densification.

• Back-End Process Equipment: Accounts for approximately 23% of the line's value, including dry powder comprehensive testers and horizontal high-temperature fixture solutions for solid-state battery integrated cabinets, achieving high-voltage formation and capacity grading and assembly.

06. TOB NEW ENERGY: Providing Comprehensive Solutions from Laboratory to Mass Production

Addressing the industrialization opportunities and challenges of dry film formation technology, TOB NEW ENERGY leverages years of technical accumulation in battery manufacturing to offer customers a complete solution spanning from the laboratory to mass production.

Solutions for Laboratory-Scale Dry Electrode Lines

We provide a full suite of customized equipment and services for dry electrode experimental lines. Our developed Laboratory Jet Mill integrates miniaturization, intelligence, and high precision, suitable for experimental-grade powder preparation needed for the fibrillation of lithium battery dry electrode materials. The Lab Dry Electrode Film Forming Machine is a laboratory dry electrode research equipment that can be used for the powder to film forming process.

Solutions for Pilot-Scale Production

We offer Dry Electrode Film Forming Machines that support various production line requirements, including equipment for GWh-level mass production capacity. Through precise tension control and thickness adjustment, we can achieve the preparation of dry electrode sheets as thin as 27μm or even thinner.

Solutions for Industrial Mass Production

For industrial mass production needs, we provide complete dry electrode production line solutions. Our system covers all processes, including controllable feeding, film formation, thinning, current collector compounding, and quality inspection. Product width can reach 1000mm, with a thickness range of 40-300μm, and is compatible with 2 to 6 dry electrode sheets operating in parallel for high-efficiency production.

Our technical team deeply understands every aspect of the dry film formation process and can provide customized process optimization solutions based on the client’s specific material systems (such as graphite/silicon-carbon negative electrodes, ternary/LFP positive electrodes, and various all-solid-state electrode materials) and equipment needs. On the materials front, we support our clients with cutting-edge battery materials, including specialized binders and modified conductive agents suitable for the dry process, ensuring optimal compatibility between materials and process.