Flame Retardant PC Mylar Sheet Die Cut Insulator for Square Cylindrical Battery Cell

A die-cut flame retardant polycarbonate Mylar sheet engineered as the interlayer part inside lithium battery modules. Two dedicated profiles are produced: a square profile for aluminum-shell prismatic cells and a circular and ring profile for cylindrical cells. In a square shell module the sheet sits between the cell body and the aluminum module frame, and between the cell top plate and the busbar carrier, blocking metal-to-cell contact. On cylindrical cells the ring and strip profile isolates the shoulder, the vent and the nickel strip welding zone. Every part is punched from UL94 V-0 polycarbonate, so it combines the mechanical toughness required during module stacking with a self-extinguishing, non-dripping fire behavior.

• Dual cell profile in one sheet specification — square shell profile for prismatic cells plus ring and strip profile for 18650, 21700, 26650, 32700 cylindrical cells.
• UL94 V-0 flame retardant polycarbonate — self-extinguishing, no dripping, raising the fire safety level of the whole module.
• High dielectric strength — above 30 kV/mm, blocking leakage across series-connected cells at pack level voltage.
• Tough and dimensionally stable — PC base film resists tearing and creep during stacking and compression, unlike thin commodity PET.
• Precision die cut, burr free — +/-0.1mm tolerance on cell footprint, ring inner diameter and welding window, so the part never blocks the weld nugget.
• Temperature range -40°C to 140°C — keeps insulation and shape through module baking, glue curing and long-term service.

The base material is a biaxially stretched PET polyester film produced from dimethyl terephthalate and ethylene glycol by ester exchange and vacuum polycondensation. The following typical property values apply to both the flame retardant series and the standard series.

Reference standards: ISO 1183, ASTM D1003, ASTM D570, ISO 527, ISO 178, ISO 306, ISO 11359, IEC 60250, IEC 60243, IEC 60093, UL 94 / UL Bulletin 94. The above figures are typical values obtained under standard test methods and are not a guarantee of performance under unstable application conditions. Test reports for each batch are available on request.

• Square aluminum-shell prismatic cell modules and cell-to-frame insulation
• Cylindrical cell packs: shoulder, vent and nickel strip welding zone isolation
• New energy vehicle battery packs and busbar insulation
• Energy storage modules, power tool packs and portable power stations
• Drive power supplies, inverters, transformers and controller insulation

• Cell profile engineering — send a cell drawing or a single cell and we design the square shell or ring die to your exact footprint.
• One workshop for both profiles — prismatic sheet and cylindrical ring produced under the same ISO 9001 process, so quality is consistent.
• Weld-window accuracy — we control the ring inner diameter and window position tightly, so spot welding yield is not affected by the insulator.
• Free samples in 3-5 working days — standard square sheet and cylindrical ring samples for a fit and insulation trial on your own cells.
• Export service — FOB / CIF / EXW, T/T, L/C and Western Union, flat carton packing to avoid transit warp.