Study on Compatibility Between Dry-Process Electrodes and Solid-State Electrolytes: Accelerating the Commercialization of Next-Generation Energy Storage Technology

Solid-state batteries are regarded as the core direction of next-generation energy storage technology. With their characteristics of no leakage, high safety, and long lifespan, they are expected to completely address the pain points of traditional liquid lithium-ion batteries. However, the industrialization of solid-state batteries has long been limited by the "electrode-electrolyte" interface compatibility challenge: ion conduction in solid-state electrolytes relies on tight solid-solid contact. Traditional wet-process electrodes, due to solvent residues and loose structures, struggle to form stable interfaces with solid-state electrolytes, resulting in high battery internal resistance and poor cycling performance. In contrast, dry-process electrodes, with their inherent advantages of "no solvent residues, controllable structure, and clean interfaces," have become the key to breaking the compatibility bottleneck of solid-state electrolytes. The in-depth integration of the two is accelerating the transition of solid-state batteries from laboratory research to industrial application.

I. Interface Contact: Dry-Process Electrodes Solving the "Ion Transport Dead Zone" of Solid-State Electrolytes

The quality of interface contact between solid-state electrolytes and electrodes directly determines the ion transport efficiency of solid-state batteries. During the preparation of traditional wet-process electrodes, solvent evaporation leads to the collapse of electrode surface micropores and residual impurities. When in contact with solid-state electrolytes, "contact gaps" are easily formed, creating "ion transport dead zones." The interface impedance is usually as high as 1000 Ω·cm² or more, severely restricting battery performance.

Dry-process electrodes fundamentally optimize the interface contact state through a "dry calendering + dense structure" design. On one hand, the dry process requires no solvents, significantly improving the cleanliness of the electrode surface with residual impurities below 0.01%, thus avoiding interface side reactions caused by solvent residues in wet-process electrodes. On the other hand, by precisely controlling calendering pressure and temperature, dry-process electrodes can form a dense structure with uniform density. When in contact with solid-state electrolytes, the contact area is increased by more than 35% compared to wet-process electrodes, effectively eliminating microscale contact gaps. Taking sulfide solid-state electrolytes as an example, when paired with dry-process electrodes, the interface impedance can be reduced to below 180 Ω·cm², far lower than the 800 Ω·cm² of wet-process electrodes, and the room-temperature ionic conductivity is increased by 2-3 orders of magnitude.

In practical applications, a research team assembled batteries using dry-process electrodes and Li₇La₃Zr₂O₁₂ (LLZO) oxide solid-state electrolytes. Through a "hot-pressing assisted bonding" process, atomic-level tight contact was achieved between the electrode and electrolyte interface. After 1000 cycles, the battery retained 90% of its capacity, while the control group using wet-process electrodes only retained 65%. This result proves that dry-process electrodes, by improving interface contact, build an efficient channel for ion transport in solid-state electrolytes and serve as a core means to enhance the cycling stability of solid-state batteries.

II. Material Compatibility: Dry-Process Electrodes Adapting to Diverse Solid-State Electrolyte Systems

The solid-state electrolyte system shows a diversified development trend of "sulfides, oxides, and polymers." The significant differences in physicochemical properties of different systems impose strict requirements on the compatibility of electrode materials. Traditional wet-process electrodes, due to the tendency of binders (e.g., PVDF) to undergo interface reactions with solid-state electrolytes and the potential dissolution of some solid-state electrolyte components by solvents, struggle to adapt to diverse systems. In contrast, dry-process electrodes, through material selection and process optimization, achieve broad compatibility with different solid-state electrolytes.

To address the "hydrolysis susceptibility and active cathode side reactions" of sulfide solid-state electrolytes, dry-process electrodes adopt a "inorganic binder + surface coating" strategy: inorganic binders such as Li₄SiO₄, which are compatible with sulfides, are used to avoid side reactions caused by organic binders; meanwhile, a LiPO₃ coating layer is introduced on the surface of positive active materials through dry mixing to inhibit the diffusion of transition metal ions and reduce the decomposition of sulfide electrolytes. Experimental data shows that batteries assembled with dry-process positive electrodes using this scheme and sulfide electrolytes have 75% fewer interface side reaction products than those with wet-process electrodes, and the battery rate performance is doubled.

For the "high hardness and ion conduction relying on tight contact" characteristics of oxide solid-state electrolytes, dry-process electrodes are adapted through a "flexible conductive network" design: carbon nanotubes are dry-mixed with active materials to build a flexible conductive framework, which buffers the mechanical stress generated when oxide electrolytes are bonded to electrodes and prevents electrolyte cracking. At the same time, the dense structure formed by dry calendering ensures continuous tight contact between oxide electrolytes and electrodes, maintaining stable ion transport channels. An enterprise using dry-process electrodes with this technology, paired with LLZO oxide electrolytes, found that the battery retained 75% of its capacity at -20℃, compared to only 40% in the wet-process electrode control group, demonstrating excellent low-temperature compatibility.

In polymer solid-state electrolyte systems, the "solvent-free characteristic" of dry-process electrodes is particularly critical. Polymer electrolytes usually have a certain degree of solubility, and solvents in wet-process electrodes may cause them to swell and deform, affecting battery structural stability. Dry-process electrodes, however, involve no solvents throughout the process, enabling "interface-pollution-free" bonding with polymer electrolytes. Additionally, the porous structure of dry-process electrodes provides space for polymer electrolyte penetration, forming a continuous ion transport network. A brand assembled flexible pouch batteries using dry-process electrodes and polyethylene oxide (PEO)-based polymer solid-state electrolytes. The batteries exhibited excellent flexibility, with no significant capacity attenuation after 1000 bends, laying the foundation for flexible solid-state battery applications.

III. Process Synergy: Dry-Process Electrodes Reducing the Industrialization Threshold of Solid-State Batteries

The industrialization of solid-state batteries relies not only on breakthroughs in material performance but also on process compatibility and economy. The traditional wet-process electrode preparation process (slurry mixing - drying - solvent recovery) contradicts the "solvent-free" production concept of solid-state batteries. Moreover, investment in solvent recovery equipment accounts for more than 20% of the production line cost, increasing the industrialization threshold. In contrast, the dry-process electrode technology is highly synergistic with the solid-state battery production process, fundamentally reducing manufacturing difficulty and costs.

In terms of process flow, dry-process electrodes eliminate solvent-related steps, enabling seamless integration with the "solvent-free assembly" process of solid-state electrolytes. The production line length is shortened by 40%, and equipment investment is reduced by 30%. For example, a pilot solid-state battery production line using dry-process electrode technology achieved continuous production of "electrode preparation - electrolyte bonding - battery packaging." The production efficiency was 50% higher than that of the wet process, and the unit cost was reduced by 15%, paving the way for large-scale mass production.

In terms of quality control, dry-process electrodes achieve uniform dispersion of active materials, conductive agents, and binders through "dry mixing + precision calendering." The performance consistency deviation of electrodes is controlled within ±2%, far better than the ±5% of wet-process electrodes. This high consistency is particularly important for solid-state batteries: interface defects between solid-state electrolytes and electrodes have an "amplification effect," and local performance deviations may lead to overall battery failure. The high consistency of dry-process electrodes can significantly reduce the interface defect rate and improve the mass production yield of solid-state batteries.

Furthermore, the process flexibility of dry-process electrodes supports structural innovation in solid-state batteries. For instance, dry-process electrodes using "multi-layer simultaneous calendering" technology can produce "gradient-structured electrodes": the content of solid-state electrolytes and conductive agents is increased on the side close to the electrolyte to improve interface conduction efficiency, while the content of active materials is increased inside to ensure energy density. This structural design is highly compatible with the "concentrated interface impedance" characteristic of solid-state batteries, enabling further reduction of battery internal resistance without sacrificing energy density and promoting the development of solid-state batteries toward "high energy density and high power density."

From optimizing interface contact and breaking through material compatibility to achieving process synergy for cost reduction, research on the compatibility between dry-process electrodes and solid-state electrolytes is advancing from "technical feasibility" to "industrial application." With the continuous maturity of their compatibility technology, the energy density of solid-state batteries is expected to exceed 400 Wh/kg, the cycle life to surpass 3000 cycles, and the cost to gradually approach that of traditional liquid lithium-ion batteries. Eventually, solid-state batteries will achieve large-scale application in new energy vehicles, energy storage stations, consumer electronics, and other fields. It can be said that the in-depth integration of dry-process electrodes and solid-state electrolytes not only addresses the core bottleneck of next-generation energy storage technology but also reshapes the technical landscape of the energy storage industry, providing key support for the global energy transition.