New Perspectives on Lithium-Ion Battery Processes: In-Depth Analysis of Wet and Dry Electrodes

In the field of lithium-ion battery manufacturing, electrode preparation processes serve as the foundation, underpinning the performance of batteries. Wet electrode processes have long dominated as a traditional and mature method, while dry electrode processes—an emerging force—are gaining prominence with unique advantages. These two approaches differ significantly in principles, workflows, and performance, collectively shaping a new landscape for lithium-ion battery process development.

I. Process Principles: The Divide Between Liquid and Solid Phases

Wet Electrodes: Molecular Integration via Solution Media

The core of wet electrode preparation lies in using a solution as a medium to achieve uniform mixing of active materials, conductive agents, and binders. Take the preparation of a common lithium-ion battery cathode using lithium iron phosphate (LiFePO₄) as an example: first, LiFePO₄ powder, conductive carbon black, and a binder (e.g., polyvinylidene fluoride, PVDF) are dissolved in organic solvents like N-methyl-2-pyrrolidone (NMP) to form a slurry with good fluidity. In this process, solvent molecules act as "carriers," facilitating full contact and dispersion of components at the molecular level. The slurry is then uniformly coated onto current collectors such as aluminum foil via coating equipment; leveraging the solvent’s fluidity, components form a uniform, continuous thin layer on the current collector surface. Finally, a drying step removes the solvent, binding components tightly to form an electrode film with sufficient mechanical strength and electrochemical performance.

Dry Electrodes: Structural Construction via Solid-Phase Mixing

Dry electrode processes abandon solvents entirely, directly mixing powders of active materials, conductive agents, and binders in a dry state. For instance, in preparing a dry electrode for high-nickel ternary (e.g., NCM811) cathodes, NCM811 active material powder, conductive agents (e.g., carbon nanotubes), and specialized binders (e.g., polytetrafluoroethylene, PTFE) are added to high-speed mixing equipment in specific proportions. Under intense mechanical stirring and shear forces, PTFE binders are stretched from granular to fibrous form, acting like "bridges" to tightly connect active material particles and conductive agents, forming a stable three-dimensional conductive network. The uniformly mixed powder is then processed via rolling into self-supporting electrode films of defined thickness and strength, or composite with current collectors to form complete electrodes.

II. Preparation Workflows: Complex vs. Streamlined Paths

Wet Electrodes: Multi-Step Precision Operations

Wet electrode preparation involves a relatively complex workflow with several critical stages. Slurry preparation is the starting point, requiring precise control of component ratios, slurry viscosity, and solid content to ensure uniformity and stability—similar to a chef carefully balancing ingredients. Coating demands high-precision equipment to maintain uniform thickness, with deviations typically controlled at the micrometer level to avoid compromising battery consistency. Drying is equally crucial: it must fully evaporate solvents while preventing material degradation from excessive heat, requiring precise temperature control and uniform airflow in drying equipment. Subsequent steps like rolling further increase electrode compaction density to optimize performance. The entire process involves coordinated operation of multiple devices and strict control of environmental conditions (e.g., temperature, humidity) to prevent rapid solvent evaporation or slurry contamination from moisture.

Dry Electrodes: Innovative Simplicity and Efficiency

Dry electrode workflows are far more streamlined, with core steps including dry mixing and forming. Dry mixing achieves uniform dispersion of powder components via high-speed equipment, avoiding solvent-related variables and enabling more direct operation compared to wet slurry preparation. Forming—whether via rolling to produce self-supporting films or spraying mixed powders onto current collectors followed by hot pressing—eliminates the cumbersome coating and drying steps of wet processes. For example, rolling involves pressing dry-mixed powder between counter-rotating rollers to gradually form electrode films of specified thickness and density, requiring only control of pressure and speed. Equipment is simpler, space-efficient, and avoids environmental or safety issues from solvent evaporation.

III. Performance: Divergent Strengths in Battery Support

Wet Electrodes: Stable Performance from Mature Technology

Wet electrodes, refined through long-term development, exhibit excellent performance stability. The slurry’s fluidity during coating ensures uniform coverage of current collectors, forming dense, evenly thick electrode films. This results in uniform current distribution during charge-discharge cycles, supporting long battery life. In conventional applications—such as 3C products (mobile phones, laptops) and early electric vehicle batteries—wet electrodes meet most performance requirements. However, they have inherent limitations: complete solvent removal is challenging, and trace residues may react with electrolytes over time, reducing capacity retention and safety.

Dry Electrodes: Performance Breakthroughs from Emerging Technology

Dry electrodes offer significant advantages in energy density. By eliminating solvents, they achieve higher compaction density, accommodating more active material in limited space and boosting energy density by 10%-20% compared to wet electrodes. This is highly attractive for electric vehicles (pursuing longer range) and aerospace (where space and weight are critical). Additionally, dry electrodes excel with high-nickel cathodes and silicon-based anodes: high-nickel materials, sensitive to moisture, degrade in wet processes but remain stable in dry ones; silicon anodes, prone to volume expansion, are better buffered by the dry binder’s 3D network, enhancing cycle stability. However, challenges remain in industrialization, including improving consistency, yield, and scaling production efficiency.

IV. Application Scenarios: Process Selection Aligned with Needs

Wet Electrodes: Broad Coverage in Conventional Applications

Leveraging mature technology and stable performance, wet electrodes dominate current markets. In 3C products—where size, weight, cost, cycle life, and charge-discharge performance are critical—wet electrodes meet requirements effectively, making them the mainstream for 3C batteries. In energy storage (grid storage, household distributed systems), their maturity and lower cost ensure prominence in large-scale applications. They also find wide use in low-speed electric vehicles and power tools, where extreme performance is not required.

Dry Electrodes: Pioneering Emerging High-End Fields

Dry electrodes, with unique strengths, are advancing in high-end sectors. In electric vehicles, as range demands grow, their energy density gains are pivotal—Tesla’s adoption in 4680 cylindrical batteries drives innovation. In aerospace, their ability to reduce weight while boosting energy density supports lighter spacecraft and longer missions. They also hold promise in specialized fields like deep-sea exploration and medical implants, where solvent-free production reduces safety risks.

As lithium-ion technology evolves, wet and dry electrodes continue to deepen their advantages while exploring hybrid approaches—combining strengths to further battery performance. Together, they will play an increasingly vital role in future energy storage.