Celgard (Sumitomo Electric)

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Intelligence

What's known

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• Did you know2023

  Celgard's microporous polypropylene membrane technology serves two life-critical applications from the same polymer science: (1) Battery separator — the thin film inside every lithium-ion battery (EV, smartphone, laptop) that prevents short circuits and enables safe energy storage; Celgard supplies ~15% of global Li-Ion battery separator demand primarily to LG Energy Solution and Samsung SDI; (2) Hemodialysis membranes — the same microporous polymer membrane technology, in hollow fiber form, is the basis for hemodialysis: the membrane that filters uremic toxins from blood when kidneys fail. Celgard's parent company heritage (Polypore International, originally Hoechst Celanese) maintained both medical membrane and battery separator businesses because they share the same fundamental manufacturing process: dry-stretching polypropylene to create controlled microporous structure. A Japanese company (Sumitomo Electric) now owns both the EV battery safety component and the kidney failure treatment component from the same US manufacturing heritage. The same Charlotte NC polymer technology is keeping EV batteries from catching fire AND keeping kidney failure patients alive.

  Celgard, LLC ↗

• Concentration2023

  The microporous battery separator was invented in 1975 by scientists at Celanese Corporation (then a major US chemicals and fiber company) in Charlotte, North Carolina — through a process called 'stretch-induced crystallinity' where a polypropylene or polyethylene film is stretched biaxially at precise temperatures, creating a microporous structure with pores in the range of 20-100 nanometers. This 1975 innovation — patented under the Celgard brand — is the foundation of the entire Li-ion battery industry's separator technology 50 years later. The Celgard process (dry process, no solvent) was later complemented by the competing wet process (using paraffin oil as pore former, then extracting it) developed by Japanese companies (Asahi Kasei, Tonen). Celanese sold its separator business to Polypore International in 2000; Sumitomo Electric Industries acquired Celgard/Polypore in 2014 for $1.03B. A 1975 polymer film stretching invention from a Charlotte NC chemical company is the physical barrier preventing thermal runaway in every Tesla, GM, and BYD battery on the road today.

  Celgard LLC ↗

• Origin2023

  Celgard was developed as a technology inside Hoechst Celanese Corporation (the US subsidiary of the German Hoechst chemical company) in the 1970s — originally to make microporous polypropylene membranes for kidney dialysis (hemodialysis) machines. The same thin microporous polymer film that allows dialysis by permitting small molecule diffusion while blocking blood cells was adapted to battery use: in a battery, the separator film allows lithium ions to pass through microscopic pores while preventing anode-cathode contact that would cause a short circuit. The battery application was a secondary discovery from the dialysis membrane technology. Polypore International (Charlotte NC) was created to commercialize both the dialysis and battery separator businesses. Sumitomo Electric (Japan) acquired Polypore in 2015, valuing the combined medical and energy applications of a single polymer membrane technology. The history of the separator inside every LG Energy Solution EV battery traces to a 1970s German chemical company's research into artificial kidneys.

  Celgard, LLC ↗