Dry Electrode - Battery Design

Eliminating the solvents in the processing and coating of the electrodes has a number of benefits [1]:

environmental friendliness
lower cost
reduced production footprint and capex
enhanced battery performance

Samsung SDI show the benefit in this simple graphical comparison [3]

However, this is a significant technical step and has some disadvantages. Some of these issues are due to the lower maturity and breadth of development.

The Structural Role of Carbon Black in Dry Electrode Processing – the conventional framing of carbon black in lithium-ion battery electrodes is electrochemical – it is an electronic conducting agent that enables the formation of the electrical wiring within an electrode. It has typically been specified by loading, surface area and subsequent powder or electrode resistivity. For wet slurry coating, this framing is broadly adequate. The solvent carries components into intimate contact and the carbon performs its conductivity function without much fanfare, or much else being asked of it. Dry electrode processing breaks this assumption. The evidence is accumulating that in the absence of a solvent carrier; carbon black does something considerably more structural, particularly during processing.

PTFE Fibrillation Mechanics

Most dry electrode processes replace the PVDF/NMP or SBR/CMC binder systems used in wet coating with PTFE, and the reason is a mechanical property almost no other polymer shares: under shear stress alone, with no solvent and no melting, PTFE particles unravel into long, sub-micron fibrils that entangle the active material and conductive carbon into a self-supporting film. This is why dry electrode lines can mix, calender, and laminate a working electrode without ever running a drying oven.

The fibrillation itself comes from PTFE’s crystal structure rather than from anything special in its chemistry. PTFE forms an unusually regular, highly crystalline, ribbon-like lamellar structure, and the lamellae are connected to each other only by comparatively weak, sparse tie chains. When the powder is subjected to shear during mixing and calendering, those tie points let the lamellae slide and peel apart locally before the chain itself breaks, drawing the material out into fibrils rather than fracturing into shorter particles. Melt-processable fluoropolymers such as PFA or FEP are built from the same backbone chemistry but with comonomer units inserted into the chain; those units disrupt the crystal regularity, cut crystallinity roughly in half, and lower the molecular weight enough that the polymer can flow as a melt. That same disruption is what stops them fibrillating under shear the way PTFE does — fibrillation and melt-processability are, in effect, opposite ends of the same structural trade-off [4][5].

The degree of fibrillation is a process variable, not a fixed property of the material: mixing time, shear rate, and calendering pressure all change how developed the fibril network is, and this is one of the main levers dry electrode manufacturers use to tune electrode cohesion and flexibility. Under-fibrillated PTFE leaves a weak, dusting film that struggles to survive calendering and slitting; over-fibrillated PTFE can over-bind the electrode, raising tortuosity and impeding electrolyte wetting and ion transport once the cell is assembled. Recent process studies have modelled this shear-versus-fibrillation relationship directly to find a working window that gives adequate mechanical integrity without over-binding the film [6][7]. PTFE is itself a fluoropolymer and sits inside the same regulatory PFAS scrutiny discussed above for cathode binders, which is part of what is now motivating early research into fluorine-free fibrillating binder systems for dry processing [8] — though as of September 2026 none of these has displaced PTFE at production scale.