PPO

Polypore International Inc

A maker of microporous membranes that act as separators inside batteries, Polypore International supplies the porous films that keep lithium-ion and lead-acid batteries safe by letting ions pass while blocking shorts. Its Celgard and Daramic brands appear in electric cars, buses, and energy storage. Formed in 2004, it was bought by Japan's Asahi Kasei in 2015. The name comes from "polypore" fungi—Greek for "many passages"—fitting for a company that makes sheets of microscopic pores.