Separators

The separator decides whether a cell merely runs or actually survives abuse — it sets thermal-shutdown temperature, dendrite tolerance, and electrolyte uptake all at once. This collection covers the full membrane stack we stock for lithium-ion, solid-state, lithium-sulfur, aqueous, and supercapacitor builds, organised by the three families researchers actually shop by: polyolefin baselines, ceramic/polymer-coated composites, and high-temperature or aqueous specialty membranes.

Polyolefin baselines (PE, PP, PP/PE). Microporous polyethylene and polypropylene films remain the workhorses for non-aqueous lithium-ion R&D. PE provides the ~135 °C thermal-shutdown fuse; PP layers add mechanical strength and a higher meltdown ceiling. Use these as drop-in references when benchmarking a new coating or electrolyte.

Coated composite separators. A ceramic or polymer skin on a polyolefin substrate decouples the shutdown function from dimensional and chemical stability:

• Alumina (Al2O3) coatings — non-conductive heat shields that resist thermal shrinkage well above the PE melt point and improve electrolyte wetting.
• Alumina + PVDF coatings — pair the ceramic shield with a fluoropolymer binder that also gels with carbonate electrolytes for better electrode adhesion.
• Garnet-type LLZTO-coated PE — a tantalum-doped Li-La-Zr-O garnet skin that adds an active Li-ion conduction pathway and suppresses dendrites via its high shear modulus, bridging conventional and quasi-solid-state cells.
• NASICON-type LATP-coated PE (with or without PMMA) — a Li-Al-Ti phosphate solid electrolyte coating for semi-solid-state work; PMMA versions add a polar binder that improves liquid-electrolyte uptake.
• Graphene-coated PE — a thermally conductive, polysulfide-blocking layer aimed at lithium-sulfur cells.

High-temperature and aqueous specialty membranes. Polyimide rolls and PI-coated PE handle environments where polyolefins distort — PI keeps structural integrity above 200 °C and is the default for high-rate or abuse-tolerant designs. For aqueous chemistries (Ni-Zn, Ni-Cd, Zn-air, lead-acid, alkaline supercapacitors), surfactant-coated and sulfonated polyolefin separators give instantaneous KOH / H2SO4 wetting and low impedance; sulfonated PP/PET adds fixed -SO3H ion-exchange sites that suppress soluble-metal shuttle.

If you are building conventional Li-ion, start with the alumina or alumina+PVDF coated PE rolls. For solid-state and Li-S work, see the LLZTO, LATP, and graphene-coated families. For aqueous batteries and supercapacitors, see the hydrophilic PP and sulfonated PP/PE / PP/PET options. Related stacks live in Battery Consumables, Electrolytes, and Electrodes.