Battery separators formed from aramid nanofiber.

Nanostructured para-aramid — one ten-thousandth the width of typical aramid fibers — assembles to form a separator thinner, stiffer and more heat-resistant than leading commercial polyolefin separators.

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Scanning electron micrograph, in cross-section, of an ARACHNE aramid nanofiber separator deposited directly on a sulfur–carbon cathode — **Fig. 1** ARACHNE separator (top) deposited directly on a sulfur–carbon cathode, cross-section. SEM, 120 000×, FEI Helios 650.

ARACHNE differs structurally from polyolefin separators.

Both surfaces imaged on the same microscope at 35 000×. Stretched polypropylene opens slit-shaped pores; ARACHNE is a continuous mesh of aramid nanofibers.

Scanning electron micrograph of a Celgard 2400 polypropylene separator surface showing elongated slit-shaped pores — **Fig. 2a** Celgard 2400 (dry-stretched PP), surface. SEM, 35 000×, FEI Helios 650.

Scanning electron micrograph of an ARACHNE separator surface showing a dense, interconnected aramid nanofiber mesh — **Fig. 2b** ARACHNE, surface. SEM, 35 000×, FEI Helios 650.

ARACHNE 25, quantified.

Valerion's 2.5 µm free-standing para-aramid nanofiber separator benchmarked against two commercially available separators. Vendor-reported values vs. ARACHNE in-house data.

Technical data sheet · rev. Oct 2026

Property	Celgard 2500	Gellec UltraThin	ARACHNE 25
Material	PP, dry-stretch	Wet PE + ceramic coat	Para-aramid nanofiber
Thickness	25 µm	9 µm PE + 3 µm ceramic	2.5 µm
Melting point	≈165 °C	≈135 °C	None; carbon decomposition at 574 °C
Heat shrinkage	1.1 % MD, 105 °C	1.4 % MD, 90 °C	0.1 % at 250 °C
Tensile strength (weakest axis)	12.7 MPa	Not available	177 MPa, isotropic
Young's modulus	≈0.5 GPa	Not available	8.8 GPa
Puncture strength	3.2 N	3–10 N	5.4 N
Porosity · Gurley	55 % · 200 s	40 % · 80–400 s	27 % · 430 s
Areal resistance	≈2.3 Ω·cm²	Not available	≈0.7 Ω·cm²
Maturity	Commercial	Commercial, GWh scale	Low throughput pilot line, scale PoC

ARACHNE 25: Valerion in-house measurements on engineering samples; preliminary, indicative values.

Gellec: published table for its 9 µm PE base film; puncture and Gurley are product ranges.

Celgard 2500: datasheet (rev. 10/21).

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ARACHNE application advantages.

ARACHNE 25's characteristics translate to improved battery performance in critical areas.

High-energy EV: Reclaim separator volume; highest 0.1C capacity in our NMC811 tests.
Safety-critical packs: No melting point, 0.1% change at 250°C, self-extinguishing [4].
Fast charge: ≈30% lower impedance than Celgard 2500; 9° electrolyte contact angle.
Li-metal · Li–S · Na-ion: Dendrite suppression; 3,500+ Li–S cycles demonstrated [2,3].
Solid-state & polymer: ANF scaffold reinforces thin polymer and gel electrolytes [5]. Enables aSEI formation.
Structural battery designs: Load-bearing membranes for drones, eVTOL, wearables [5].

Investors

Backed by domain experts and regional investors.

Team

Aramid nanofiber pioneers from the University of Michigan, paired with experience in venture capital and technology translation.

Nicholas Kotov, PhD

Founder and Inventor

Director of the NSF Center for Complex Particles and Particle Systems. Irving Langmuir Professor, University of Michigan. National Academy of Engineering.