From"Key Adhesive"to"Challenged": The Evolution of PTFE's Role in the Solid-State Battery Race

In the battery manufacturing workshop, as the roller press emits a deep roar, layers of ultra-thin solid electrolyte membranes are precisely wound into rolls, providing electric vehicles with twice the energy density of traditional batteries.

In June of this year, at the pilot production line built by Samsung at its Cheonan factory in South Korea, engineers were validating a new battery manufacturing process based on polytetrafluoroethylene (PTFE) dry electrode technology.

This technology uses PTFE as a core binder to create electrode sheets that support the layered structure of the active material through a fibrosis process.

With the accelerated global deployment of solid-state battery industrialization, PTFE—a polymer commonly found in the industrial field—has now become a key material in the solid-state battery race, despite its previously little-known status.

01 Technological Innovation

In traditional wet-process battery manufacturing, slurry preparation requires a large amount of organic solvents, while the sulfide electrolyte in solid-state batteries happens to be highly reactive with these solvents.

The dry process is completely different; it does not use any solvents when manufacturing composite cathode and electrolyte films, making it a key solution to this problem.

PTFE is the preferred adhesive for dry processes due to its unique physical properties . When pressure and shear forces are applied, PTFE forms a fibrous structure. These fibers intertwine to form a layered network that supports the active material and conductive agent.

This "fibrillation" process allows the electrode material to be uniformly dispersed, forming a robust thin film structure. It is this characteristic that makes PTFE irreplaceable in the dry electrode manufacturing of solid-state batteries.

02 Shortcomings become apparent

The limitations of PTFE have become increasingly apparent with the development of solid-state battery technology . As an insulating polymer, it cannot actively participate in the lithium-ion conduction process, which is a significant drawback in the pursuit of higher performance solid-state batteries.

In addition, PTFE provides limited interfacial adhesion, which cannot ensure that the active materials, solid electrolyte and conductive carbon maintain good interfacial contact at all times, which will affect the long-term cycle stability of the battery.

For ultrathin electrolyte membranes with a thickness of only 25-35 micrometers, the mechanical properties of the material are crucial, and there is still room for improvement in the flexibility and stress dissipation of electrolyte composite membranes made of PTFE.

03 Improvement and Breakthrough

Faced with the limitations of PTFE, global research teams are exploring improvement and alternative solutions . Researchers at a university in South Korea have attempted to use a lithium-ion conductive polymer as a binder, namely lithium poly(tetrafluoroethylene-co-perfluoro(3-oxo-4-pentenesulfonic acid)) salt.

This material combines the technological advantages of PTFE with its lithium-ion conductivity, ensuring good interfacial contact between the components of the composite cathode while promoting lithium-ion transport.

The research team from the Chinese Academy of Sciences adopted a different innovative approach. They used melt bonding technology to mix low-viscosity thermoplastic polyamide (TPA) with sulfide electrolytes to construct a polymer-permeable network.

The thickness of the ultrathin sulfide solid electrolyte membrane prepared by this method can be controlled to below 25 micrometers, while possessing excellent flexibility and ionic conductivity (2.1 mS/cm).

04 Alternative Exploration

TPA exhibits multiple advantages over PTFE . By inducing TPA to permeate between sulfide particles through hot pressing, the research team constructed a complete polymer percolation network.

This structure not only enables ultra-thin film formation, but also effectively dissipates uneven internal stress generated during battery operation, reducing the risk of mechanical failure.

In practical applications, all-solid-state batteries based on TPA fused bonding technology exhibit excellent cycle performance. Full cells adapted with pure silicon anodes can cycle 2000 times, and after 9200 hours and 1400 cycles under high load conditions, the areal capacity still remains above 2.5 mAh·cm-2.

When the cathode material loading is increased to 53.1 mg·cm-2, the battery energy density exceeds 390 Wh/kg and 1020 Wh/L.

05 Industry Trends

Global battery companies have been actively developing the industrialization of solid-state batteries . Samsung has chosen PTFE dry electrode technology as a competitive strategy to reduce manufacturing costs and increase mass production speed.

The company believes this process has the potential for shorter production cycles, simplified equipment, and thicker films, and is continuously improving its mass production maturity. Industry giants such as Tesla, BYD, CATL, and LG New Energy are also actively adopting dry electrode technology.

Chinese equipment manufacturers have launched the third-generation all-solid-state process of dry stirring fiberization and dry film formation, and have successfully delivered solid electrode coating equipment to leading customers.

Industry forecasts indicate that the solid-state battery industry will enter a critical period of pilot line deployment from the second half of 2025 to the first half of 2026, and small-scale mass production and vehicle installation are expected to begin in 2027.

As Samsung continued to validate its PTFE-based dry process on its pilot production line, researchers at a German battery lab discovered that solid-state batteries using polyamide instead of PTFE only experienced a 3.2-degree Celsius increase in surface temperature after a nail penetration test .

According to industry data, at least seven major equipment manufacturers worldwide have launched dedicated equipment solutions for dry electrodes in solid-state batteries.

Solid-state batteries have achieved an energy density exceeding 600Wh/kg, which means that electric vehicles equipped with such batteries could easily achieve a range of over 1,000 kilometers.