Document

This Amendment No. 3 to that certain Promissory Note (this “Amendment”) is effective as of February 27, 2026 by and between ESS Tech, Inc., a Delaware corporation (the “Company”) and YA II PN, LTD., a Cayman Islands exempt limited company, or its registered assigns (the “Holder”). Each such person is referred to herein as a “Party” and, collectively, such persons are referred to herein as the “Parties.”

A.Reference is made to that certain Promissory Note, dated as of October 14, 2025, by and between the Parties (as amended by Amendment No. 1 to Promissory Note, effective as of October 31, 2025 and Amendment No. 2 to Promissory Note, effective as of December 4, 2025, the “Note”). Capitalized terms used but not otherwise defined herein shall have the meanings ascribed thereto in the Note.

B.In accordance with Section 11 of the Note, the Parties desire to enter into this Amendment for purposes of amending the Note as set forth herein.

Now, therefore, in consideration of the premises and the mutual premises set forth in this Amendment, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties hereby agree as follows.

“Maturity Date. On the Maturity Date, the Company shall pay to the Holder an amount in cash representing all outstanding Principal, accrued and unpaid Interest, and any other amounts outstanding pursuant to the terms of this Note. The “Maturity Date” shall be February 27, 2027, as may be extended at the option of the Holder.”

b.Schedule I of the Note is hereby amended and restated to read as follows in the form set forth attached hereto as Exhibit A.

2.Limited Effect. Except as expressly provided hereby, all of the terms and provisions of the Note are and shall remain in full force and effect and are hereby ratified and confirmed by the Company. The amendment contained herein shall not be construed as a waiver or amendment of any other provision of the Note or for any purpose except as expressly set forth herein, or a consent to any further or future action on the part of the Company that would require the waiver or consent of the Holder.

3.Representations and Warranties. The Company hereby represents and warrants to the Holder (before and after giving effect to this Amendment) that:

(a)This Amendment has been duly executed and delivered on behalf of the Company. This Amendment together with the Note constitutes the legal, valid and binding obligations of the Company and are enforceable against the Company in accordance with their terms except as enforceability may be limited by applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting the enforcement of creditors' rights generally and by general equitable principles (whether enforcement is sought by proceedings in equity or at law);

(b)Each of the representations and warranties made by the Company herein and the Note is true and correct in all material respects on and as of the date hereof, as if made on and as of the date hereof (except that any representation or warranty which by its terms is made as of an earlier date shall be true and correct in all material respects as of such earlier date); and

4.Successors and Assigns. This Amendment shall inure to the benefit of and be binding upon the Company, the Holder, and each of their respective permitted successors and assigns.

5.Governing Law. This Amendment shall be governed by, and construed in accordance with, the laws of the State of New York.

6.Counterparts. This Amendment may be executed in any number of counterparts, all of which shall constitute one and the same agreement, and any party hereto may execute this Amendment by signing and delivering one or more counterparts. Delivery of an executed counterpart of this Amendment electronically or by facsimile shall be effective as delivery of an original executed counterpart of this Amendment.