Dry vs. Wet Processes: The Upgrade Path of Energy Storage Technology Under the Iteration of Lithium-Ion Battery Electrode Preparation

As the core device of new energy storage, the performance breakthrough of lithium-ion batteries is always deeply tied to the iteration of electrode preparation processes. From the traditional wet process that relies on organic solvents in the early days to the current solvent-free dry process, the competition and evolution of these two technical routes have not only reshaped the microstructure and performance boundaries of electrodes but also driven energy storage technology toward the upgrade direction of "higher energy density, lower cost, and better environmental friendliness." The difference between dry and wet processes has long gone beyond a simple process choice; it has become a key variable that determines the applicable scenarios, industrialization costs, and sustainable development potential of energy storage systems.

I. Process Foundation: From "Solvent Dependence" to "Solvent-Free Breakthrough," the Fundamental Differences Between the Two Routes

As the traditional mainstream technology for lithium-ion battery electrode preparation, the core logic of the wet process is "solvent as carrier + high-temperature curing": active materials, conductive agents, and binders such as PVDF are mixed into a uniform slurry using organic solvents like NMP. After being coated on current collectors, the slurry is dried at high temperatures to remove solvents, and then shaped by calendering. This process has high maturity and is suitable for large-scale production, but its essence is "achieving material dispersion through solvents," which inevitably faces inherent limitations such as difficult solvent recovery, high energy consumption, and weak structural controllability. The energy consumption of the drying process accounts for more than 30% of the total energy consumption of electrode preparation, and solvent residues may also increase the electrode interface impedance, affecting the cycle life of batteries.

The dry process completely breaks "solvent dependence," with "dry mixing + precision calendering" as its core: active materials, conductive agents, and dry binders (such as PTFE fibers and CMC) are directly mixed into a powder composite through high-speed shearing, and then tightly compounded on current collectors via calendering without solvents. This process eliminates the entire process of solvent procurement, drying, and recovery, not only eliminating solvent-related environmental and cost issues from the source but also enabling the construction of a better electrode microstructure by precisely controlling calendering pressure and temperature. For example, it preserves the pores of active materials more completely, reduces micropore collapse caused by wet drying, and opens up smoother channels for ion transport.

From the perspective of process flow diagrams, the wet process is a "multi-step, high-energy-consumption" linear flow, which requires 5 core steps: "slurry preparation - coating - drying - solvent recovery - calendering." It has a long equipment chain and occupies a large area. The dry process, on the other hand, is simplified to 3 steps: "dry mixing - fiberization - calendering," shortening the process by 40%. Its equipment investment and workshop layout are more flexible, making it particularly suitable for large-scale production scenarios with high environmental requirements and limited space.

II. Performance Competition: A Multi-Dimensional Contest in Energy Density, Cost-Environmental Protection, and Scenario Adaptability

The differences between the two processes are ultimately directly reflected in the core performance, industrialization costs, and scenario adaptability of lithium-ion batteries, forming a distinct "advantage-disadvantage competition" and determining the application boundaries of energy storage technology at different stages.

Energy Density: The Dry Process Breaks the "High Load" Ceiling

In the wet process, due to the volume occupied by solvents, the loading rate of active materials in electrodes is usually less than 90%. Moreover, the volatilization of solvents during drying easily causes agglomeration of active material particles, damaging the electrode micropore structure and restricting ion migration efficiency. Taking high-nickel ternary cathodes as an example, the active material loading of wet-process electrodes is about 4.5 mg/cm², with a maximum compaction density of 3.8 g/cm³. Through dry tight mixing, the dry process can increase the active material loading rate to more than 95%. Combined with "low-temperature calendering" technology, the compaction density of high-nickel cathodes exceeds 4.0 g/cm³, and the corresponding energy density of lithium-ion batteries can be increased from 200 Wh/kg (wet process) to more than 230 Wh/kg, directly supporting the extension of new energy vehicle range from 500 km to 700 km.

The advantage of the dry process is even more significant in the application of silicon-based anodes. Silicon-based materials have a volume expansion rate of up to 400% during lithiation. Wet-process electrodes are prone to cracking during cycling due to uneven binder distribution. However, the dry process constructs a "flexible conductive framework" through dry composite of carbon nanotubes and silicon powder, which can control the volume expansion rate of silicon-based anodes within 15%. After 1000 cycles, the capacity retention rate reaches 85%, far higher than the 70% of wet-process electrodes.

Cost and Environmental Protection: The Dry Process Practices the Dual Goals of "Cost Reduction and Carbon Emission Reduction"

The "hidden costs" of the wet process have long been overlooked: to produce 1 GWh of lithium-ion battery electrodes, more than 500 tons of NMP solvent are consumed. The investment in solvent recovery equipment accounts for 15%-20% of the total cost of the production line, and the high-temperature heating (usually 120-150℃) in the drying process consumes a large amount of electricity. In addition, the VOCs (Volatile Organic Compounds) generated by solvent volatilization require additional investment in treatment costs, and improper handling may also lead to the risk of environmental penalties.

The dry process achieves "win-win" in cost and environmental protection from the source: by eliminating solvent procurement and recovery links, the production cost per GWh of electrodes is reduced by 15%-20%; the elimination of the drying process reduces the energy consumption of electrode preparation by 40%, which is equivalent to reducing carbon emissions by about 800 tons per year per 1 GWh production line. According to calculations by an energy storage enterprise, after adopting the dry process, the comprehensive manufacturing cost of lithium-ion batteries decreased by 12%, and at the same time, it obtained local environmental subsidies due to "zero VOCs emissions," further enhancing the market competitiveness of its products.

Scenario Adaptability: The Wet Process Maintains Its Position in "Mature Fields," While the Dry Process Expands into "Emerging Scenarios"

With decades of technical accumulation, the wet process still dominates "mature scenarios" such as consumer electronics and traditional power batteries. These scenarios have high cost sensitivity and large production scales, and the "large-scale production stability" of the wet process can meet the demand. For example, lithium-ion batteries for smartphones have small volumes and relatively moderate energy density requirements, and the mature process of wet-process electrodes can ensure the consistency of million-level production capacity.

The dry process, however, is rapidly breaking into "high-demand emerging scenarios": in low-temperature energy storage scenarios (such as outdoor energy storage stations in northern regions), dry-process electrodes have no solvent residues and maintain a capacity retention rate of 85% at -30℃, far higher than the 70% of wet-process electrodes; in the field of solid-state batteries, the "solid-solid contact" between dry-process electrodes and solid electrolytes is tighter, reducing the interface impedance by 60%, making it a key supporting technology for the industrialization of solid-state batteries; in portable energy storage equipment, the thin design of dry-process electrodes (with a thickness controllable within 0.1 mm) reduces the weight of energy storage equipment by 20%, making it more in line with portable needs.

III. Iteration Path: From "Alternative Competition" to "Collaborative Complementation," the Future Direction of Energy Storage Technology

The dry and wet processes are not in an "either-or" alternative relationship; instead, they gradually form a pattern of "collaborative complementation" in process iteration, jointly promoting the upgrade of energy storage technology.

In the short term, the wet process will still maintain its advantages in "large-scale, low-cost" scenarios, but it will be optimized toward "low solvent, low energy consumption"—for example, using water-soluble binders instead of NMP or developing low-temperature drying technology to reduce environmental and energy costs. At present, some enterprises have launched the "semi-dry process," which reduces solvent usage by 50% while retaining the production stability of the wet process, becoming an important choice in the transition stage.

In the medium and long term, the dry process will become the mainstream in "high energy density, high safety, high adaptability" scenarios and drive energy storage technology to achieve three major breakthroughs: first, energy density breakthrough—through in-depth adaptation of the dry process with high-nickel cathodes, silicon-based anodes, and composite electrolytes, the energy density of lithium-ion batteries is expected to exceed 300 Wh/kg by 2030; second, safety performance upgrade—solvent-free residues and dense structural design reduce the risk of thermal runaway of lithium-ion batteries by more than 50%, meeting the high safety requirements of energy storage stations; third, expansion of scenario boundaries—the flexible and thin design of dry-process electrodes will promote energy storage technology to extend to emerging fields such as wearable devices, drones, and space energy storage.

More importantly, the iteration of the two processes will drive the upgrade of the entire energy storage industry chain: the demand for dry binders and precision calendering equipment from the dry process will promote technological innovation in upstream material and equipment enterprises; the exploration of low-toxicity solvents and high-efficiency recovery technology from the wet process will also accelerate the development of the green chemical industry. Eventually, a positive cycle of "process iteration - material upgrade - scenario expansion" will be formed, providing a more efficient and sustainable energy storage solution for the global energy transition.

From the "maturity and stability" of the wet process to the "innovation and breakthrough" of the dry process, the iteration of lithium-ion battery electrode preparation processes is essentially the continuous response of energy storage technology to the three core demands of "performance, cost, and environmental protection." In the future, with the further integration and optimization of the two processes, energy storage systems will no longer prioritize "single performance" but achieve a comprehensive balance of "coexistence of high energy density and high safety, and balance of low cost and low emissions," truly becoming the core cornerstone supporting the high-quality development of the new energy industry.