ESS Inc. entered into a letter of intent to acquire ACON S2 Acquisition Corp. (NasdaqCM:STWO) from ACON S2 Sponsor, L.L.C., ACON Investments, L.L.C. and others in a reverse merger transaction on March 1, 2021. ESS Inc. entered into a definitive agreement to acquire ACON S2 Acquisition Corp. from ACON S2 Sponsor, L.L.C., ACON Investments, L.L.C. and others in a reverse merger transaction for approximately $980 million on May 6, 2021. The business combination values the combined company at a $1.072 billion pro forma enterprise value. The transaction will provide approximately $465 million of pro forma net cash to the combined company, assuming no redemptions by ACON S2 shareholders. The transaction will result in ESS becoming a publicly listed company. Assuming no public shareholders of ACON S2 exercise their redemption rights, ESS' existing shareholders, including its founders, will own approximately 64% of the combined company. As part of the transaction, ACON S2 raised a $250 million fully committed PIPE from institutional investors including Fidelity Management & Research Company LLC, SB Energy Global Holdings Ltd, a wholly owned subsidiary of SoftBank Group Corp., Breakthrough Energy Ventures and BASF Venture Capital. In total, investors in the PIPE will own approximately 16% of the issued and outstanding shares of common stock of the combined company at closing. Founder share will own 4% and ACON S2 public shareholders will own 16% of the combined company. ESS' shareholders will roll their 100% equity. Upon closing, the combined company expects to list its common shares and warrants on the New York Stock Exchange (the “NYSE”) under the ticker symbols “GWH” and “GWH.W,” respectively. Trading is currently expected to begin on the NYSE on or about October 11, 2021 following the consummation of the Business Combination.

Board of directors of combined company will consist of nine directors from which seven directors will be designated by ESS and two directors will be designated by certain current shareholders of ESS. Additionally, the current ESS management team will move to combined company in their current roles and titles. The transaction is subject to certain closing conditions, including, but not limited to, (i) the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, (ii) the approval of ACON S2's shareholders, (iii) the approval of ESS's shareholders (iv) the Registration Statement becoming effective, (v) The ACON S2 common stock to be issued in connection with the transactions shall have been approved for listing on NYSE. (vi) the closing ACON S2 cash shall equal or exceed two hundred million dollars $200 million. The Boards of Directors of ESS and ACON S2 have unanimously approved the transaction and recommended the shareholders to vote. As of September 14, 2021, the Registration Statement of ACON S2 declared effective. Shareholders of ACON S2 will hold a meeting on October 5, 2021 to approve the transaction. The transaction is expected to close in the third quarter of 2021. As of September 14, 2021, if the transaction is approved by shareholders of ACON S2, will close shortly thereafter, subject to the satisfaction or waiver (as applicable) of all other closing conditions. As of October 5, 2021, ACON S2 Acquisition shareholders approved the business combination proposal. As of September 22, 2021, the transaction is expected to close in early October 2021. As of September 28, 2021, the transaction is expected to close on October 8, 2021. The net proceeds from this transaction will be used to increase manufacturing capacity globally and invest in extending ESS' technology advantage.

Deutsche Bank Securities Inc. is serving as capital markets advisor and placement agent to ACON S2. Douglas Bacon, Anthony Speier, R.J. Malenfant, Matthew R. Pacey and Shawn O'Hargan of Kirkland & Ellis LLP are serving as legal counsels to ACON S2. Nomura Greentech is serving as financial advisor and Mark Baudler and Andrew Hoffman of Wilson Sonsini Goodrich & Rosati, P.C. are serving as legal counsels to ESS. Fried, Frank, Harris, Shriver & Jacobson LLP is serving as placement agent's counsel on the PIPE transaction. Deutsche Bank Securities Inc., Cowen and Company and Stifel, Nicolaus & Company served as joint book running managers for the ACON S2 initial public offering. Bicrom Das of Walkers acted as legal advisor for ACON S2. The Depository Trust Company acted as depository and Continental Stock Transfer & Trust Company acted as transfer agent to ACON S2 as part of the transaction. Okapi Partners LLC is acting as proxy solicitor of ACON S2. ACON S2 will pay a fee of $25,000 to Okapi. Robert W. Baird & Co. Incorporated served as a capital markets advisor to ESS Tech, Inc.

ESS Inc. completed the acquisition of ACON S2 Acquisition Corp. (NasdaqCM:STWO) from ACON S2 Sponsor, L.L.C., ACON Investments, L.L.C. and others in a reverse merger transaction on October 8, 2021. The combined company will retain the ESS Inc. name and its shares and warrants will commence trading on October 11, 2021 on the NYSE under the new ticker symbols “GWH” and “GWH.W”, respectively. The ESS executive management team will continue to be led by Eric Dresselhuys, Chief Executive Officer; Craig Evans, President and Co-founder; Julia Song, Chief Technology Officer and Co-founder; and Amir Moftakhar, Chief Financial Officer. The ESS Board of Directors will comprise eight members, including Chairman Michael R. Niggli, Eric Dresselhuys, Craig Evans, Raffi Garabedian, Rich Hossfeld, Shirley Speakman, Kyle Teamey, and Daryl Wilson.