ESS Tech, Inc.

ESS Tech, Inc. became a publicly traded company through its business combination with ACON S2 Acquisition Corp, which listed under the ticker STWO and was sponsored by ACON Investments. ACON S2 Acquisition Corp completed its initial public offering in 2020, targeting the clean energy and sustainability sector. The merger with ESS Tech closed in October 2021, bringing the iron flow battery developer — focused on long-duration, grid-scale energy storage — to public markets. ESS Tech filed an 8-K with the SEC on July 11, 2025, disclosing current material business developments. Sign up at SpacDesk for full filings, deal data, and real-time analytics on ESS Tech and the broader de-SPAC universe.