Common Stock, par value $0.0001 per share

ESS Tech, Inc.

26440 SW PARKWAY AVE., WILSONVILLE, OR, 97070

This Schedule 13D is being filed on behalf of SoftBank Group Corp., a Japanese kabushiki kaisha ("SoftBank"), SoftBank's wholly owned subsidiary SoftBank Group Capital Ltd, a private limited company incorporated in England and Wales ("SBGC"), SBGC's wholly owned subsidiary SB Energy Global Holdings Limited, a private limited company incorporated in England and Wales ("Holdings Limited") and Holdings Limited's wholly owned subsidiary SB Energy Global Holdings One Ltd., a private limited company incorporated in England and Wales ("Holdings One" and together with SoftBank, SBGC and Holdings Limited, the "Reporting Persons").

The principal business address of SoftBank is 1-7-1, Kaigan, Minato-ku, Tokyo 105-7537 Japan. The principal business address of SBGC, Holdings Limited and Holdings One is 69 Grosvenor Street, London, England, United Kingdom W1K 3JP.

SoftBank is a Japanese publicly traded holding company that manages its holdings and conducts its operations through various subsidiaries. SBGC, Holdings Limited and Holdings One are holding companies for various SoftBank investments.

See Item 2(d) above.

See Item 2(a) above.

The information contained in lines 7 to 11 and 13 of the cover pages of this Schedule 13D and the information set forth in Item 6 is incorporated herein by reference. The percentage ownership reflected in line 13 of the cover pages is based on 11,882,871 shares of Common Stock outstanding as of November 8, 2024. As Holdings One is a wholly owned subsidiary of Holdings Limited, which is a wholly owned subsidiary of SBGC, which is a wholly owned subsidiary of SoftBank, each of Holdings Limited, SBGC and SoftBank may be deemed to indirectly beneficially own the shares of Common Stock directly beneficially owned by Holdings One. Each of Holdings Limited, SBGC and SoftBank disclaim beneficial ownership of all such shares of Common Stock, except to the extent of their respective pecuniary interest.

See Item 5(a) above.

Neither the Reporting Persons nor, to the Reporting Persons' knowledge, any of the persons set forth on Appendices A-1, A-2, A-3 and A-4, has effected any transaction in shares of Common Stock during the past sixty (60) days.