ESS Tech, Inc., which trades under the ticker STWO, is a clean energy company focused on long-duration iron flow battery storage systems for utility and commercial applications. The company came to the public markets through a SPAC transaction with ACON S2 Acquisition Corp, a blank-check vehicle sponsored by ACON Investments that completed its IPO in 2020. The November 2020 10-Q filing reflects an early reporting period during the SPAC's pre-merger phase, when the vehicle was targeting opportunities in the energy transition and industrial technology sectors. ESS Tech subsequently completed its business combination, continuing to operate in the grid-scale energy storage industry. Sign up for full data, filings history, and deal analytics on SpacDesk.