Document:

EX-10.1

 Exhibit 10.1 

SUBSCRIPTION AGREEMENT 
 ACON S2
Acquisition Corp. 
 133 Connecticut Avenue NW, Ste. 700 

Washington, DC 20036 
 Ladies and Gentlemen: 

This Subscription Agreement (this “Subscription Agreement”) is being entered into as of the date set forth on the signature
page hereto, by and between ACON S2 Acquisition Corp., a Cayman Islands exempted company (“ACON”), which shall be domesticated as a Delaware corporation prior to the closing of the Transaction (as defined herein), and the
undersigned subscriber (the “Investor”), in connection with the Agreement and Plan of Merger, dated as of the date hereof (as may be amended, supplemented or otherwise modified from time to time, the “Merger
Agreement”), by and among ACON, ESS Tech, Inc., a Delaware corporation (the “Company”), and SCharge Merger Sub, Inc. a Delaware corporation (“Merger Sub”), pursuant to which, among other things, Merger Sub
will merge with and into the Company, with the Company as the surviving company in the merger and, after giving effect to such merger, becoming a subsidiary of ACON, on the terms and subject to the conditions therein (such merger, the
“Transaction”). In furtherance of the Transaction, certain existing shareholders in the Company will sign transaction support agreements (the “Existing Shareholder Support Arrangements”) pursuant to which they
will, among other things, agree to consent to the consummation of the Transaction. In connection with the Transaction, ACON is seeking commitments from interested investors to purchase, following the Domestication (as defined below) and prior to the
closing of the Transaction, shares of ACON’s common stock, par value $0.0001 per share (the “Shares”), in a private placement for a purchase price of $10.00 per share (the “Per Share Purchase Price”). On or
about the date of this Subscription Agreement, ACON is entering into (a) separate subscription agreements (the “Insider Subscription Agreements”) with certain existing securityholders of the Company (“Insider PIPE
Investors”, and such investment, the “Insider PIPE Investment”) and (b) separate subscription agreements (the “Other PIPE Agreements,” and together with the Insider Subscription Agreements, the
“Other Subscription Agreements”) with certain other investors other than the Insider PIPE Investors (the “Other Investors” and, together with Insider PIPE Investors and the Investor, the
“Investors”), pursuant to which the Investors, severally and not jointly, have agreed to purchase on the closing date of the Transaction, inclusive of the Shares subscribed for by the Investor, an aggregate amount of up to [•]
Shares, at the Per Share Purchase Price. 
 Prior to the closing of the Transaction (and as more fully described in, and on the terms and
subject to the conditions set forth in, the Merger Agreement), ACON will domesticate as a Delaware corporation in accordance with Section 388 of the General Corporation Law of the State of Delaware and Part XII of the Cayman Islands
Companies Law (2020 Revision) (the “Domestication”). The aggregate purchase price to be paid by the Investor for the subscribed Shares (as set forth on the signature page hereto) is referred to herein as the “Subscription
Amount.” 
 In connection therewith, and in consideration of the foregoing and the mutual representations, warranties and
covenants, and subject to the conditions, set forth herein, and intending to be legally bound hereby, each of the Investor and ACON acknowledges and agrees as follows: 

1. Subscription. The Investor hereby subscribes for and agrees to purchase from ACON, and ACON agrees to issue and sell to the Investor,
the number of Shares set forth on the signature page of this Subscription Agreement on the terms and subject to the conditions provided for herein. The Investor acknowledges and agrees that, as a result of the Domestication, the Shares that
will be purchased by the Investor and issued by ACON pursuant to the terms and subject to the conditions hereto shall be shares of common stock in a Delaware corporation (and not, for the avoidance of doubt, ordinary shares in a Cayman Islands
exempted company). 
 2. Closing. The closing of the sale, purchase and issuance of the Shares contemplated hereby (the
“Closing”) is contingent upon the substantially concurrent consummation of the Transaction. The Closing shall occur on the date of, and substantially concurrently with and conditioned upon the effectiveness of, the Transaction. Upon
(a) satisfaction or waiver of the conditions set forth in Section 3 below and (b) delivery of written notice from (or on behalf of) ACON to the Investor (the “Closing Notice”) that ACON reasonably expects all
conditions to the closing of the Transaction to be satisfied or waived on a date that is not less than five (5) business days from the date on which the Closing Notice is delivered to the Investor, the Investor shall deliver to ACON, three
(3) business days prior to the 
  

 closing date specified in the Closing Notice (the “Closing Date”), (i) the Subscription
Amount by wire transfer of United States dollars in immediately available funds to the account(s) specified by ACON in the Closing Notice and (ii) any other information that is reasonably requested in the Closing Notice in order for ACON to
issue the Investor’s Shares, including, without limitation, the legal name of the person in whose name such Shares are to be issued and a duly executed Internal Revenue Service Form W-9 or W-8, as applicable. On the Closing Date, ACON shall issue a number of Shares to the Investor set forth on the signature page to this Subscription Agreement and subsequently cause such Shares to be registered in book
entry form in the name of the Investor on ACON’s share register; provided, however, that ACON’s obligation to issue the Shares to the Investor is contingent upon ACON having received the Subscription Amount in full accordance
with this Section 2. In the event that (i) ACON does not accept the subscription or (ii) the consummation of the Transaction does not occur within ten (10) business days after the anticipated Closing Date specified in the Closing
Notice, unless otherwise agreed to in writing by ACON and the Investor, ACON shall promptly (but in no event later than fifteen (15) business days after the anticipated Closing Date specified in the Closing Notice) return the Subscription
Amount so delivered by the Investor to ACON by wire transfer in immediately available funds to the account specified by the Investor, and any book entries shall be deemed cancelled. Notwithstanding such return or cancellation, unless and until this
Subscription Agreement is terminated in accordance with Section 8 herein, the Investor shall remain obligated (A) to redeliver funds to ACON in escrow following ACON’s delivery to the Investor of a new Closing Notice and (B) to
consummate the Closing immediately prior to or substantially concurrently with the consummation of the Transaction. For purposes of this Subscription Agreement, “business day” shall mean a day other than a Saturday or Sunday or
other day on which commercial banks in New York, New York are authorized or required by law to close. 
 In lieu of the foregoing
paragraph for Fidelity and Van Eck investors: [The closing of the sale, purchase and issuance of the Shares contemplated hereby (the “Closing”) is contingent upon the substantially concurrent consummation of the Transaction. The
Closing shall occur on the date of, and substantially concurrently with and conditioned upon the effectiveness of, the Transaction. Upon (a) satisfaction or waiver of the conditions set forth in this Section 2 and Section 3 below and
(b) delivery of written notice from (or on behalf of) ACON to the Investor (the “Closing Notice”), that ACON reasonably expects all conditions to the closing of the Transaction to be satisfied or waived on a date that is not
less than five (5) business days from the date on which the Closing Notice is delivered to the Investor (the “Closing Date”), the Investor shall deliver to ACON at least three (3) business days prior to the Closing Date
such information that is reasonably requested in the Closing Notice in order for ACON to issue the Shares, including, without limitation, the legal name of the person in whose name such Shares are to be issued and a duly executed Internal Revenue
Service Form W-9 or W-8, as applicable. On the Closing Date, (1) the Investor shall deliver to ACON the Subscription Amount by wire transfer of United States
dollars in immediately available funds to the account(s) specified by ACON in the Closing Notice (which account(s) shall not be escrow account(s)) against delivery of the Shares as set forth in the following clause (2), and (2) ACON shall
issue the number of Shares to the Investor set forth on the signature page to this Subscription Agreement in book-entry form in the name of the Investor (or its nominee) or as otherwise directed by the Investor, free and clear of any liens or other
restrictions (other than those arising under applicable securities laws), on ACON’s share register. If the closing of the Transaction does not occur within one (1) business day after the Closing, ACON shall promptly (but not later than one
(1) business day thereafter) return the Subscription Amount to the Investor, and any book entries shall be deemed cancelled. Notwithstanding such return or cancellation, unless and until this Subscription Agreement is terminated in accordance
with Section 8 herein, the Investor shall remain obligated (A) to redeliver funds to ACON following ACON’s delivery to the Investor of a new Closing Notice and (B) to consummate the Closing immediately prior to or substantially
concurrently with the consummation of the Transaction. For purposes of this Subscription Agreement, “business day” shall mean a day, other than a Saturday or Sunday or other day on which commercial banks in New York, New York are
authorized or required by law to close.] 
 3. Closing Conditions. 

a. The obligation of the parties hereto to consummate the sale, purchase and issuance of the Shares pursuant to this Subscription Agreement is
subject to the following conditions: 
 (i) no applicable governmental authority shall have enacted, issued, promulgated,
enforced or entered any judgment, order, law, rule or regulation (whether temporary, preliminary or permanent) which is then in effect and has the effect of making consummation of the transactions contemplated hereby illegal or otherwise restraining
or prohibiting consummation of the transactions contemplated hereby, and no such governmental authority shall have instituted or threatened in writing a proceeding seeking to impose any such restraint or prohibition; and 

  
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 (ii) all conditions precedent to the closing of the Transaction under the
Merger Agreement shall have been satisfied (as determined by the parties to the Merger Agreement and other than those conditions under the Merger Agreement which, by their nature, are to be satisfied at the closing of the Transaction, including to
the extent that any such condition is dependent upon the consummation of the sale, purchase and issuance of the Shares pursuant to this Subscription Agreement or the Other Subscription Agreements) or waived by the parties to the Merger Agreement.

 b. The obligation of ACON to consummate the sale and issuance of the Shares pursuant to this Subscription Agreement shall be subject to
the following conditions (which may be waived in writing by ACON; provided, that ACON provides prior written notice to the Placement Agent (as defined below) of any such waiver): 

(i) all representations and warranties of the Investor contained in this Subscription Agreement are true and correct in all
material respects (other than representations and warranties that are qualified as to materiality, which representations and warranties shall be true in all respects) at and as of the Closing Date, and consummation of the Closing shall constitute a
reaffirmation by the Investor of each of the representations and warranties of the Investor contained in this Subscription Agreement as of the Closing Date; and 

(ii) the Investor shall have performed or complied in all material respects with all agreements and covenants required by this
Subscription Agreement. 
 c. The obligation of the Investor to consummate the purchase of the Shares pursuant to this Subscription
Agreement shall be subject to the following conditions (which may be waived in writing by the Investor): 
 (i) all
representations and warranties of ACON contained in this Subscription Agreement shall be true and correct in all material respects (other than representations and warranties that are qualified as to materiality, which representations and warranties
shall be true in all respects) at and as of the Closing Date, and consummation of the Closing shall constitute a reaffirmation by ACON of each of the representations and warranties of ACON contained in this Subscription Agreement in all material
respects as of the Closing Date; 
 (ii) ACON shall have performed or complied in all material respects with all agreements
and covenants required by this Subscription Agreement to be satisfied or complied with by it at or prior to the Closing; 

(iii) no amendment or modification of, or waiver under, the Merger Agreement shall have occurred that would reasonably be
expected to materially and adversely affect the economic benefits that the Investor would reasonably expect to receive under this Subscription Agreement; 

(iv) no suspension of the qualification of the Shares for offering or sale or trading by The Nasdaq Capital Market
(“Nasdaq”) or the United States Securities and Exchange Commission (the “SEC”) shall be in effect, and the Shares acquired hereunder shall have been approved for listing on Nasdaq or the New York Stock Exchange, as
applicable, subject to official notice of issuance; and 
 (v) there shall have been no amendment, waiver or modification to
the Other Subscription Agreements (including via a side letter or other agreement) that materially benefits the Other Investors thereunder unless the Investor has been offered the same benefits, provided that, for the avoidance of
doubt, this Section 3(c)(v) shall not apply to (i) any document entered into in connection with the Insider PIPE Investment, provided, however, that such Insider PIPE Investment shall be with respect to the same class of
Shares being acquired by the Investor hereunder and at the same Per Share Purchase Price, or (ii) any document entered into for the purchase of the Company’s equity securities (or warrants to purchase such securities) between the Company
and certain of the existing securityholders of the Company, as described in the Merger Agreement (including any schedules thereto). 

  
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 4. Further Assurances. At the Closing, the parties hereto shall execute and deliver
such additional documents and take such additional actions as the parties reasonably may deem to be practical and necessary in order to consummate the subscription as contemplated by this Subscription Agreement. 

5. ACON Representations and Warranties. Except with respect to ACON’s ongoing review of the implications of the SEC’s
issuance of the Statement on Accounting and Reporting Considerations for Warrants Issued by Special Purpose Acquisition Companies, made on April 12, 2021 on the accounting treatment of the Warrants (as defined below), and any actions taken by
ACON in connection with such review or statement, including, for the avoidance of doubt, any restatement of ACON’s historical financial statements, ACON represents and warrants to the Investor and the Placement Agent that: 

a. ACON is an exempted company duly incorporated, validly existing and in good standing under the laws of the Cayman Islands (to the extent
such concept exists in such jurisdiction). ACON has all power (corporate or otherwise) and authority to own, lease and operate its properties and conduct its business as presently conducted and to enter into, deliver and perform its obligations
under this Subscription Agreement. As of the Closing Date, following the Domestication, ACON will be duly incorporated, validly existing as a corporation and in good standing under the laws of the State of Delaware with all power (corporate or
otherwise) and authority to own, lease and operate its properties and conduct its business as currently contemplated to be conducted and to perform its obligations under this Subscription Agreement. 

b. As of the Closing Date, the Shares will be duly authorized and, when issued and delivered to the Investor against full payment therefor in
accordance with the terms of this Subscription Agreement, the Shares will be validly issued, fully paid and non-assessable, free and clear of any liens or other restrictions, and will not have been issued in
violation of or subject to any preemptive or similar rights created under ACON’s certificate of incorporation or bylaws (each as amended to the Closing Date) or under the General Corporation Law of the State of Delaware. 

c. This Subscription Agreement has been duly authorized, executed and delivered by ACON and, assuming that this Subscription Agreement
constitutes the valid and binding agreement of the Investor, this Subscription Agreement constitutes the legal, valid and binding agreement of ACON, enforceable against ACON in accordance with its terms, except as may be limited or otherwise
affected by (i) bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium or other laws relating to or affecting the rights of creditors generally, and (ii) principles of equity, whether considered at law or equity. 

d. The execution and delivery of this Subscription Agreement, the sale and issuance of the Shares and the compliance by ACON with all of the
provisions of this Subscription Agreement and the consummation of the transactions contemplated herein will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, or result in the
creation or imposition of any lien, charge or encumbrance upon any of the property or assets of ACON or any of its subsidiaries pursuant to the terms of (i) any indenture, mortgage, deed of trust, loan agreement, lease, license or other
agreement or instrument to which ACON or any of its subsidiaries is a party or by which ACON or any of its subsidiaries is bound or to which any of the property or assets of ACON is subject that would reasonably be expected to have a material
adverse effect on the business, financial condition, stockholders’ equity or results of operations of ACON and its subsidiaries, taken as a whole (a “Material Adverse Effect”) or materially affect the validity of the Shares or
the legal authority of ACON to comply in all material respects with the terms of this Subscription Agreement; (ii) result in any violation of the provisions of the organizational documents of ACON; or (iii) result in any violation of any
statute or any judgment, order, rule or regulation of any court or governmental agency or body, domestic or foreign, having jurisdiction over ACON or any of their properties that would reasonably be expected to have a Material Adverse Effect or
materially affect the validity of the Shares or the legal authority of ACON to comply in all material respects with this Subscription Agreement. 

  
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 e. As of their respective dates, all reports (the “SEC Reports”) required
to be filed by ACON with the SEC complied in all material respects with the applicable requirements of the Securities Act of 1933, as amended, (the “Securities Act”) and the Securities Exchange Act of 1934, as amended (the
“Exchange Act”), and the rules and regulations of the SEC promulgated thereunder, and none of the SEC Reports, when filed, contained any untrue statement of a material fact or omitted to state a material fact required to be stated
therein or necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The financial statements of ACON included in the SEC Reports comply in all material respects with applicable
accounting requirements and the rules and regulations of the SEC with respect thereto as in effect at the time of filing and fairly present in all material respects the financial position of ACON as of and for the dates thereof and the results of
operations and cash flows for the periods then ended, subject, in the case of unaudited statements, to normal, year-end audit adjustments. A copy of each SEC Report is available to the Investor via the
SEC’s EDGAR system. There are no outstanding or unresolved comments in comment letters received by ACON from the staff of the Division of Corporation Finance of the SEC with respect to any of the SEC Reports. 

f. ACON is not required to obtain any consent, waiver, authorization or order of, give any notice to, or make any filing or registration with,
any court or other federal, state, local or other governmental authority, self-regulatory organization or other person in connection with the execution, delivery and performance by ACON of this Subscription Agreement (including, without limitation,
the issuance of the Shares), other than (i) filings with the SEC, (ii) filings required by applicable state securities laws, (iii) filings required by Nasdaq or such other applicable stock exchange on which ACON’s common equity
is then listed, and (iv) the failure of which to obtain would not be reasonably likely to have, individually or in the aggregate, a Material Adverse Effect. 

g. Except for such matters as have not had and would not be reasonably likely to have, individually or in the aggregate, a Material Adverse
Effect, there is no (i) action, suit, claim or other proceeding, in each case by or before any governmental authority pending, or, to the knowledge of ACON, threatened against ACON or (ii) judgment, decree, injunction, ruling or order of
any governmental entity or arbitrator outstanding against ACON. 
 h. As of the date hereof, the authorized capital stock of ACON consists
of 500,000,000 Class A ordinary shares, par value $0.0001 (“Class A Shares”), 50,000,000 Class B ordinary shares, par value $0.0001 (the “Class B Shares”), and
5,000,000 preference shares, par value $0.0001 per share. As of the date of hereof, 25,000,000 Class A Shares are issued and outstanding and 6,250,000 Class B Shares are issued and outstanding, and 13,000,000 warrants to acquire
Class A Shares issued and outstanding (the “Warrants”). All issued and outstanding Class A Shares and Class B Shares have been duly authorized and validly issued, are fully paid and are
non-assessable. Except as set forth above and pursuant to the Other Subscription Agreements, the Merger Agreement and the other agreements and arrangements referred to therein, as of the date hereof, there are
no outstanding options, warrants or other rights to subscribe for, purchase or acquire from ACON any Class A Shares, Class B Shares or other equity interests in ACON, or securities convertible into or exchangeable or exercisable for such
equity interests. As of the date hereof, ACON has no subsidiaries, other than Merger Sub, and does not own, directly or indirectly, interests or investments (whether equity or debt) in any person, whether incorporated or unincorporated. There are no
stockholder agreements, voting trusts or other agreements or understandings to which ACON is a party or by which it is bound relating to the voting of any securities of ACON, other than (1) as set forth in the SEC Reports and (2) as
contemplated by the Merger Agreement. Other than Class B Shares, which have the anti-dilution rights described in ACON’s amended and restated memorandum and articles of association that will be waived in connection with the Transaction, or
as set forth in the Merger Agreement (including any schedules thereto), there are no securities or instruments issued by or to which ACON is a party containing anti-dilution or similar provisions that will be triggered by the issuance of the Shares
hereunder or to be issued pursuant to any Other Subscription Agreement. Following the Domestication, and immediately prior to the Closing (assuming that no elections to redeem any Class A Shares in connection with the consummation of the
Transaction have been validly made), the authorized share capital of ACON will consist of (i) no shares of preferred stock, with a par value of $0.0001 per share (“Preferred Shares”), and (ii) 500,000,000 shares of common stock,
with a par value of $0.0001 per share (the “Common Shares”). Following the Domestication, and immediately prior to the Closing (assuming that no elections to redeem any Class A Shares in connection with the consummation of the
Transaction have been validly made): 25,000,000 Common Shares and no Preferred Shares will be issued and outstanding, 13,000,000 warrants to purchase Common Shares will be issued and outstanding, and [no] Common Shares will be subject to issuance
upon exercise of outstanding options. 

  
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 i. As of the date hereof, the issued and outstanding Class A Shares are registered
pursuant to Section 12(b) of the Exchange Act and are listed for trading on Nasdaq under the symbol “STWO” (it being understood that the trading symbol will be changed in connection with the Transaction). There is no suit, action,
proceeding or investigation pending or, to the knowledge of ACON, threatened against ACON by Nasdaq or the SEC, respectively, to prohibit or terminate the listing of the Class A Shares or, when issued, the Common Shares, on Nasdaq or the New
York Stock Exchange, as applicable, or to deregister the Class A Shares or, when registered and issued in connection with the Domestication, the Common Shares, under the Exchange Act. ACON has taken no action that is designed to terminate the
registration of the Class A Shares under the Exchange Act, other than in connection with the Domestication and subsequent registration under the Exchange Act of the Common Shares. 

j. Other than the Placement Agent (as defined below), ACON has not engaged any broker, finder, commission agent, placement agent or arranger
in connection with the sale of the Shares, and ACON is not under any obligation to pay any broker’s fee or commission in connection with the sale of the Shares other than to the Placement Agent. 

k. Assuming the accuracy of the Investor’s representations and warranties set forth in Section 6 of this Subscription Agreement, no
registration under the Securities Act is required for the offer and sale of the Shares by ACON to the Investor under this Subscription Agreement. The Shares (i) were not offered by any form of general solicitation or general advertising and
(ii) are not being offered in a manner involving a public offering under, or in a distribution in violation of, the Securities Act, or any state securities laws. 

l. ACON is in compliance with all applicable laws, except where such non-compliance would not
reasonably be expected to have a Material Adverse Effect. ACON has not received any written communication from a governmental authority that alleges that ACON is not in compliance with or is in default or violation of any applicable law, except
where such non-compliance, default or violation would not reasonably be expected to have, individually or in the aggregate, a Material Adverse Effect. 

m. Other than the Other Subscription Agreements, the Merger Agreement and other agreements expressly contemplated by the Merger Agreement, the
Existing Shareholder Support Arrangements or as described in the SEC Reports, ACON has not entered into any side letter or similar agreement with any Other Investor or other investor in connection with such Other Investor’s or other
investor’s direct or indirect investment in ACON. No Other Subscription Agreement includes terms and conditions that are more favorable to the Other Investor thereunder than the Investor hereunder, other than terms particular to the regulatory
requirements of such Other Investor or its affiliates or related funds that are mutual funds or are otherwise subject to regulations related to the timing of funding and the issuance of the related Shares. For the avoidance of doubt, this
Section 5(m) shall not apply to (i) any document entered into in connection with the Insider PIPE Investment, provided, however, that such Insider PIPE Investment shall be with respect to the same class of Shares being
acquired by the Investor hereunder and at the same Per Share Purchase Price, or (ii) any document entered into for the purchase of the Company’s equity securities (or warrants to purchase such securities) between the Company and certain of
the existing securityholders of the Company, as described in the Merger Agreement (including any schedules thereto). 
 6. Investor
Representations and Warranties. The Investor represents and warrants to ACON and the Placement Agent that: 
 a. The Investor (i) is
a “qualified institutional buyer” (as defined in Rule 144A under the Securities Act) or an institutional “accredited investor” (within the meaning of Rule 501(a) under the Securities Act), in each case, satisfying the applicable
requirements set forth on Schedule A, (ii) is acquiring the Shares only for his, her or its own account and not for the account of others, or if the Investor is subscribing for the Shares as a fiduciary or agent for one or more investor
accounts, each owner of each such account is a qualified institutional buyer, the Investor has full investment discretion with respect to each such account, and the full power and authority to make the acknowledgements, representations and
agreements herein on behalf of each owner of each such account, and (iii) is not acquiring the Shares with a view to, or for offer or sale in connection with, any distribution thereof in violation of the Securities Act or the securities laws of
any other jurisdiction (and shall provide the requested information set forth on Schedule A). The Investor is not an entity formed for the specific purpose of acquiring the Shares. 

  
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 b. The Investor acknowledges and agrees that the Shares are being offered in a transaction
not involving any public offering within the meaning of the Securities Act and that the offer and sale of the Shares have not been registered under the Securities Act. The Investor acknowledges and agrees that the Shares may not be offered, resold,
transferred, pledged or otherwise disposed of by the Investor absent an effective registration statement under the Securities Act except (i) to ACON or a subsidiary thereof, (ii) to non-U.S. persons
pursuant to offers and sales that occur outside the United States within the meaning of Regulation S under the Securities Act or (iii) pursuant to another applicable exemption from the registration requirements of the Securities Act, and in
each of clauses (i) and (iii) in accordance with any applicable securities laws of the states and other jurisdictions of the United States, and that any certificates representing the Shares shall contain a restrictive legend to such effect. The
Investor acknowledges and agrees that the Shares will be subject to the foregoing transfer restrictions and, as a result of these transfer restrictions, the Investor may not be able to readily offer, resell, transfer, pledge or otherwise dispose of
the Shares and may be required to bear the financial risk of an investment in the Shares for an indefinite period of time. The Investor acknowledges and agrees that the Shares will not be eligible for offer, resale, transfer, pledge or disposition
pursuant to Rule 144 promulgated under the Securities Act until at least one year from the date that ACON files a Current Report on Form 8-K following the Closing Date that includes the “Form 10”
information required under the applicable SEC rules and regulations. The Investor acknowledges and agrees that it has been advised to consult legal counsel prior to making any offer, resale, transfer, pledge or disposition of any of the Shares. The
Investor acknowledges and agrees that the Investor is purchasing the Shares from ACON. The Investor further acknowledges that there have been no representations, warranties, covenants and agreements made to the Investor by or on behalf of ACON, the
Company, any of their respective affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing or any other person or entity, expressly or by implication, other than those
representations, warranties, covenants and agreements of ACON expressly set forth in Section 5 of this Subscription Agreement. 
 c.
Either (1) the Investor’s acquisition and holding of the Shares will not constitute or result in a non-exempt prohibited transaction under Section 406 of the Employee Retirement Income Security
Act of 1974, as amended (“ERISA”), Section 4975 of the Internal Revenue Code of 1986, as amended, or any applicable similar law or (2) the Investor is not a Benefit Plan Investor as contemplated by ERISA. 

d. The Investor acknowledges and agrees that the Investor has received and has had an opportunity to review such information as the Investor
deems necessary in order to make an investment decision with respect to the Shares, including, without limitation, with respect to ACON, the Transaction and the business of the Company and its subsidiaries. Without limiting the generality of the
foregoing, the Investor acknowledges that he, she or it has had an opportunity to review the SEC Reports. The Investor acknowledges and agrees that the Investor and the Investor’s professional advisor(s), if any, have received and reviewed the
offering materials made available to the Investor and had an opportunity to ask such questions, receive such answers and obtain such information as the Investor and such Investor’s professional advisor(s), if any, have deemed necessary to make
an investment decision with respect to the Shares. The Investor further acknowledges that the information provided to the Investor may change after the date hereof and ACON is under no obligation to inform the Investor regarding any such changes,
except to the extent such changes would reasonably be expected to cause the failure of ACON to satisfy a condition to the Investor’s obligations at the Closing set forth in Section 3(c). 

e. The Investor acknowledges and agrees that the Investor has determined based on its own independent review and such professional advice as
it has deemed appropriate, that the purchase of the Shares and participation in the Transaction are consistent with the Investor’s financial needs, objectives and condition and comply and are consistent with all material investment policies,
guidelines and other restrictions applicable to the Investor. 
 f. The Investor became aware of this offering of the Shares solely by means
of direct contact between the Investor and ACON, the Company or a representative of ACON or the Company (including the Placement Agent, as defined below), and the Shares were offered to the Investor solely by direct contact between the Investor and
ACON, the Company or a representative of ACON or the Company. The Investor did not become aware of this offering of the Shares, nor were the Shares offered to the Investor, by any other means. The Investor acknowledges that the Shares (i) were
not offered to it by any form of general solicitation or general advertising and (ii) to its knowledge, are not being offered to it in a manner involving a public offering under, or in a distribution in violation of, the Securities Act, or any
state securities laws. The Investor acknowledges that it is not relying upon, and has not relied upon, any statement, representation or warranty made by any person, firm or corporation (including, without

  
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limitation, ACON, the Company, the Placement Agent, any of their respective affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the
foregoing), other than the representations and warranties of ACON contained in Section 5 of this Subscription Agreement, in making its investment or decision to invest in ACON, and except for the foregoing, the Investor is relying exclusively
on its own sources of information, investment analysis and due diligence (including professional advice it deems appropriate) with respect to the Transaction, the Shares and the business, condition (financial and otherwise), management, operations,
properties and prospects of ACON, including but not limited to all business, legal, regulatory, accounting, credit and tax matters. The Investor acknowledges that none of ACON, the Placement Agent, or their respective representatives has acted as an
investment adviser, broker or dealer to the Investor. 
 g. The Investor acknowledges that it is aware that there are substantial risks
incident to the purchase and ownership of the Shares, including, without limitation, those set forth in ACON’s filings with the SEC. The Investor has such knowledge and experience in financial and business matters as to be capable of evaluating
the merits and risks of an investment in the Shares, and the Investor has sought such accounting, legal and tax advice as the Investor has considered necessary to make an informed investment decision. 

h. Alone, or together with any professional advisor(s), the Investor has adequately analyzed and considered the risks of an investment in the
Shares and determined that the Shares are a suitable investment for the Investor and that the Investor is able at this time and in the foreseeable future to bear the economic risk of a total loss of the Investor’s investment in ACON. The
Investor acknowledges specifically that a possibility of total loss exists. 
 i. In making its decision to purchase the Shares, the
Investor has relied solely upon independent investigation made by the Investor. Without limiting the generality of the foregoing, the Investor has not relied on any statements or other information provided by or on behalf of the Placement Agent or
any of its affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing concerning ACON, the Company, the Transaction, the Merger Agreement, this Subscription Agreement or the
transactions contemplated hereby or thereby, the Shares or the offer and sale of the Shares. 
 j. The Investor acknowledges that no federal
or state agency has passed upon or endorsed the merits of the offering of the Shares or made any findings or determination as to the fairness of this investment. 

k. The Investor, if not an individual, has been duly formed or incorporated and is validly existing and is in good standing under the laws of
its jurisdiction of formation or incorporation, with power and authority to enter into, deliver and perform its obligations under this Subscription Agreement. 

l. The execution, delivery and performance by the Investor of this Subscription Agreement are within the powers of the Investor, have been
duly authorized and will not constitute or result in a breach or default under or conflict with any order, ruling or regulation of any court or other tribunal or of any governmental commission or agency, or any agreement or other undertaking, to
which the Investor is a party or by which the Investor is bound, and, if the Investor is not an individual, will not conflict with or violate any provisions of the Investor’s organizational documents, including, without limitation, its
incorporation or formation papers, bylaws, indenture of trust or partnership or operating agreement, as may be applicable. The signature on this Subscription Agreement is genuine, and the signatory, if the Investor is an individual, has legal
competence and capacity to execute the same or, if the Investor is not an individual, the signatory has been duly authorized to execute the same, and this Subscription Agreement has been duly executed and delivered by the Investor and, assuming that
this Subscription Agreement constitutes the valid and binding agreement of ACON, constitutes a legal, valid and binding obligation of the Investor, enforceable against the Investor in accordance with its terms, except as may be limited or otherwise
affected by (i) bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium or other laws relating to or affecting the rights of creditors generally, and (ii) principles of equity, whether considered at law or equity. 

m. The Investor is not (i) a person or entity named on the List of Specially Designated Nationals and Blocked Persons administered by the
U.S. Treasury Department’s Office of Foreign Assets Control (“OFAC”) or in any Executive Order issued by the President of the United States and administered by OFAC (“OFAC List”), or a person or entity
prohibited by any OFAC sanctions program, (ii) a Designated National as defined in the Cuban Assets Control Regulations, 31 C.F.R. Part 515, or (iii) a non-U.S. shell bank or providing banking
services 

  
 8 

 
indirectly to a non-U.S. shell bank. The Investor agrees to provide law enforcement agencies, if requested thereby, such records as required by applicable
law, provided that the Investor is permitted to do so under applicable law. If the Investor is a financial institution subject to the Bank Secrecy Act (31 U.S.C. Section 5311 et seq.) (the “BSA”), as amended by the USA
PATRIOT Act of 2001 (the “PATRIOT Act”), and its implementing regulations (collectively, the “BSA/PATRIOT Act”), the Investor maintains policies and procedures reasonably designed to comply with applicable
obligations under the BSA/PATRIOT Act. To the extent required, it maintains policies and procedures reasonably designed for the screening of its investors against the OFAC sanctions programs, including the OFAC List. To the extent required by
applicable law, the Investor maintains policies and procedures reasonably designed to ensure that the funds held by the Investor and used to purchase the Shares were legally derived. 

n. The Investor acknowledges that no disclosure or offering document has been prepared by Deutsche Bank Securities Inc. or any of its
affiliates (the “Placement Agent”) in connection with the offer and sale of the Shares. 
 o. The Investor acknowledges
that neither the Placement Agent, nor any of its affiliates nor any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing have made any independent investigation with respect to ACON, the
Company or its subsidiaries or any of their respective businesses, or the Shares, or the accuracy, completeness or adequacy of any information supplied to the Investor by ACON. 

p. The Investor acknowledges that in connection with the issue and purchase of the Shares, the Placement Agent has acted solely as placement
agent in connection with the Transaction and has not acted as underwriter and in any other capacity and shall not be construed as a financial advisor or fiduciary to the Investor in connection with the Transaction. 

q. The Investor acknowledges that Deutsche Bank Securities Inc. acted as an underwriter in connection with the initial public offering of ACON
and, upon the closing of the Transaction, Deutsche Bank Securities Inc. shall be entitled to receive its portion of the deferred underwriting commissions described in the Prospectus (as defined below), pursuant to the underwriting agreement by and
among ACON, Deutsche Bank Securities Inc., Cowen and Company, LLC and Stifel, Nicolaus & Company, Incorporated, dated September 16, 2020. 

r. The Investor, when required to deliver payment to ACON pursuant to Section 2 above, will have, sufficient funds to pay the
Subscription Amount and consummate the sale, purchase and issuance of the Shares pursuant to this Subscription Agreement. 
 s. The Investor
acknowledges that the purchase and sale of Shares hereunder meets the exemptions from filing under FINRA Rule 5123(b)(1). 
 t. The Investor
acknowledges that the Placement Agent may have acquired, or during the term of the Shares may acquire, non-public information with respect to ACON, which the Investor agrees need not be provided to it. 

u. The Investor is not a “foreign person” or a “foreign entity,” as defined in Section 721 of the Defense Production
Act of 1950, as amended, including, without limitation, all implementing regulations thereof (the “DPA”). The Investor is not controlled by a “foreign person,” as defined in the DPA. The Investor does not permit any
foreign person affiliated with the Investor, whether affiliated as a limited partner or otherwise, to obtain through the Investor any of the following with respect to ACON or the Company: (i) access to any “material nonpublic technical
information” (as defined in the DPA) in the possession of ACON or the Company; (ii) membership or observer rights on the board of directors or equivalent governing body of ACON or the Company or the right to nominate an individual to a
position on the board of directors or equivalent governing body of ACON or the Company; (iii) any involvement, other than through the voting of shares, in the substantive decision-making of ACON or the Company regarding (x) the use,
development, acquisition, or release of any “critical technology” (as defined in the DPA), (y) the use, development, acquisition, safekeeping, or release of “sensitive personal data” (as defined in the DPA) of U.S. citizens
maintained or collected by ACON or the Company, or (z) the management, operation, manufacture, or supply of “covered investment critical infrastructure” (as defined in the DPA); or (iv) “control” (as defined in the DPA) of
ACON or the Company. 

  
 9 

 v. The Investor acknowledges the SEC’s issuance of the Statement on Accounting and
Reporting Considerations for Warrants Issued by Special Purpose Acquisition Companies, made on April 12, 2021, and ACON’s ongoing review of the implications of such statement on the accounting treatment of the Warrants, and the Investor
agrees that any actions taken by ACON in connection with such review or in response to such statement, including, for the avoidance of doubt, any restatement of ACON’s historical financial statements, shall not be deemed to constitute a breach
of any of the representations, warranties or covenants in this Subscription Agreement. 
 7. Registration Rights. 

a. In the event that the Shares are not registered in connection with the consummation of the Transaction, ACON agrees that, within thirty
(30) calendar days after the consummation of the Transaction (the “Filing Date”), it will file with the SEC (at its sole cost and expense) a registration statement registering the offering of the resale of the Shares (the
“Registration Statement”), and it shall use its commercially reasonable efforts to have the Registration Statement declared effective as soon as practicable after the filing thereof but no later than the earlier of (i) sixty
calendar days (or ninety (90) calendar days if the SEC notifies ACON that it will review the Registration Statement) following the Closing and (ii) five (5) business days after ACON is notified (orally or in writing, whichever is earlier)
by the SEC that the Registration Statement will not be reviewed or will not be subject to further review (such date, the “Effectiveness Date”). ACON agrees to cause such Registration Statement, or another shelf registration
statement that includes the Shares to be sold pursuant to this Subscription Agreement, to remain effective until the earliest of (i) the third anniversary of the Closing, (ii) the date on which the Investor ceases to hold any Shares issued
pursuant to this Subscription Agreement, or (iii) on the date on which the Investor is able to sell all of its Shares issued pursuant to this Subscription Agreement (or shares received in exchange therefor) under Rule 144 of the Securities Act
within ninety (90) days without limitation as to the amount of such securities that may be sold and without the requirement for ACON to be in compliance with the current public information requirement under Rule 144(c) (or Rule 144(i)(2), if
applicable). The Investor agrees to disclose its ownership and any other information reasonably requested to ACON upon request to assist it in making the determination described above. ACON’s obligations to include the Shares issued pursuant to
this Subscription Agreement (or shares issued in exchange therefor) for resale in the Registration Statement are contingent upon the Investor furnishing in writing to ACON such information regarding the Investor, the securities of ACON held by the
Investor and the intended method of disposition of such Shares, which shall be limited to non-underwritten public offerings, as shall be reasonably requested by ACON to effect the registration of such Shares,
and shall execute such documents in connection with such registration as ACON may reasonably request that are customary of a selling stockholder in similar situations. Notwithstanding the foregoing, if the SEC prevents ACON from including any or all
of the Shares proposed to be registered under the Registration Statement due to limitations on the use of Rule 415 of the Securities Act for the resale of the Shares by the applicable shareholders or otherwise, such Registration Statement shall
register for resale such number of Shares which is equal to the maximum number of Shares as is permitted by the SEC. In such event, the number of Shares to be registered for each selling shareholder named in the Registration Statement shall be
reduced pro rata among all such selling shareholders and as promptly as practicable after being permitted to register additional Shares under Rule 415 under the Securities Act, ACON shall file a new Registration Statement to register such Shares not
included in the initial Registration Statement and cause such Registration Statement to become effective as promptly as practicable consistent with the terms of this Section 7. For purposes of clarification, any failure by ACON to file the
Registration Statement by the Filing Date or to effect such Registration Statement by the Effectiveness Date shall not otherwise relieve ACON of its obligations to file or effect the Registration Statement set forth in this Section 7. For
purposes of this Section 7, “Shares” shall mean, as of any date of determination, the Shares acquired by the Investor pursuant to this Subscription Agreement and any other equity security issued or issuable with respect to such Shares
by way of stock split, dividend, distribution, recapitalization, merger, exchange, replacement or similar event, and “Investor” shall include any affiliate of the undersigned Investor to which the rights under this Section 7 have been
duly assigned. 
 a. ACON shall advise the Investor within three (3) business days (at ACON’s expense): (i) when a Registration
Statement or any post-effective amendment thereto has become effective; (ii) of the issuance by the SEC of any stop order suspending the effectiveness of any Registration Statement or the initiation of any proceedings for such purpose;
(iii) of the receipt by ACON of any notification with respect to the suspension of the qualification of the Shares included therein for sale in any jurisdiction or the initiation or threatening of any proceeding for such purpose; and
(iv) subject to the provisions in this Subscription Agreement, of the occurrence of any event that requires the making of any changes in any Registration Statement or prospectus so that, as of such date, the statements therein are not
misleading and do not omit to state a material fact required to be stated therein or necessary 

  
 10 

 
to make the statements therein (in the case of a prospectus, in the light of the circumstances under which they were made) not misleading (provided that any such notice pursuant to this
Section 7(b)(iv) shall solely provide that the use of the Registration Statement or prospectus has been suspended without setting forth the reason for such suspension). ACON shall use its commercially reasonable efforts to obtain the withdrawal
of any order suspending the effectiveness of any Registration Statement as soon as reasonably practicable. Upon receipt of any written notice from ACON of the happening any event contemplated in clauses (ii) through (iv) above during the period
that the Registration Statement is effective or if as a result of the occurrence of such event the Registration Statement or related prospectus contains any untrue statement of a material fact or omits to state any material fact required to be
stated therein or necessary to make the statements therein, in light of the circumstances under which they were made (in the case of the prospectus) not misleading, the undersigned agrees that (1) it will immediately discontinue offers and
sales of the Shares under the Registration Statement (excluding, for the avoidance of doubt, sales conducted pursuant to Rule 144) until the undersigned receives copies of a supplemental or amended prospectus (which ACON agrees to promptly prepare)
that corrects the misstatement(s) or omission(s) referred to above and receives notice that any post-effective amendment has become effective or unless otherwise notified by ACON that it may resume such offers and sales, and (2) it will
maintain the confidentiality of any information included in such written notice delivered by ACON except (A) for disclosure to the Investor’s employees, agents and professional advisers who need to know such information and are obligated
to keep it confidential, (B) for disclosures to the extent required in order to comply with reporting obligations to its limited partners who have agreed to keep such information confidential and (C) as required by law or subpoena. Upon
the occurrence of any event contemplated in clauses (i) through (iv) above, except for such times as ACON is permitted hereunder to suspend, and has suspended, the use of a prospectus forming part of a registration statement, ACON shall use its
commercially reasonable efforts to as soon as reasonably practicable prepare a post-effective amendment to such registration statement or a supplement to the related prospectus, or file any other required document so that, as thereafter delivered to
purchasers of the Shares included therein, such prospectus will not include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein, in the light of the circumstances under which they were
made, not misleading. The Investor acknowledges and agrees that ACON may suspend the use of any such Registration Statement if it determines in good faith, upon advice of legal counsel that, in order for such registration statement not to contain a
material misstatement or omission, an amendment thereto would be needed to include information that would at that time not otherwise be required in a current, quarterly or annual report under the Exchange Act, provided, that (i) ACON
shall not so delay filing or so suspend the use of the Registration Statement on more than two (2) occasions, or for a period of more than sixty (60) consecutive days or more than a total of one hundred twenty (120) calendar days, in
each case in any three hundred sixty (360) day period, and (ii) ACON shall use commercially reasonable efforts to make such registration statement available for the sale by the Investor of such securities as soon as practicable thereafter.

 b. For as long as the Investor holds Shares, ACON will use commercially reasonable efforts to file all reports necessary to enable the
undersigned to resell the Shares pursuant to the Registration Statement. For as long as the Investor holds Shares, ACON will use commercially reasonable efforts to file all reports necessary to enable the undersigned to resell the Shares pursuant to
Rule 144 of the Securities Act (when Rule 144 of the Securities Act becomes available to the Investor). In addition, in connection with any sale, assignment, transfer or other disposition of the Shares by the Investor pursuant to Rule 144 or
pursuant to any other exemption under the Securities Act such that the Shares held by the Investor become freely tradable and upon compliance by the Investor with the requirements of this Section 7(c), if requested by the Investor, ACON shall
cause the transfer agent for the Shares (the “Transfer Agent”) to remove any restrictive legends related to the book entry account holding such Shares and make a new, unlegended entry for such book entry Shares sold or disposed of
without restrictive legends within three (3) trading days of any such request therefor from the Investor, provided that ACON and the Transfer Agent have timely received from the Investor customary representations and other documentation
reasonably acceptable to ACON and the Transfer Agent in connection therewith. Subject to receipt from the Investor by ACON and the Transfer Agent of customary representations and other documentation reasonably acceptable to ACON and the Transfer
Agent in connection therewith, the Investor may request that ACON remove any legend from the book entry position evidencing its Shares and ACON will, if required by the Transfer Agent, cause an opinion of ACON’s counsel be provided, in a form
reasonably acceptable to the Transfer Agent, to the effect that the removal of such restrictive legends in such circumstances may be effected under the Securities Act, following the earliest of such time as such Shares (i) (x) are subject to or
(y) have been or are about to be sold or transferred pursuant to an effective registration statement, (ii) have been or are about to be sold pursuant to Rule 144, or (iii) are eligible for resale under Rule 144(b)(1) or any successor
provision without the requirement for ACON to be in compliance with the current public information requirement under Rule 144 and without volume or manner-of-sale
restrictions applicable to the sale or transfer of 

  
 11 

 
such Shares. If restrictive legends are no longer required for such Shares pursuant to the foregoing, ACON shall, in accordance with the provisions of this section and within three
(3) trading days of any request therefor from the Investor accompanied by such customary and reasonably acceptable representations and other documentation referred to above establishing that restrictive legends are no longer required, deliver
to the Transfer Agent irrevocable instructions that the Transfer Agent shall make a new, unlegended entry for such book entry Shares. ACON shall be responsible for the fees of its Transfer Agent, its legal counsel and all DTC fees associated with
such issuance. 
 c. Indemnification. 

(i) ACON agrees to indemnify and hold harmless, to the extent permitted by law, the Investor, its directors, officers,
employees and agents, and each person who controls the Investor (within the meaning of the Securities Act or the Exchange Act) and each affiliate of the Investor (within the meaning of Rule 405 under the Securities Act) from and against any and all
losses, claims, damages, liabilities and expenses (including, without limitation, any reasonable attorneys’ fees and expenses incurred in connection with defending or investigating any such action or claim) caused by any untrue or alleged
untrue statement of material fact contained in any Registration Statement, prospectus included in any Registration Statement or preliminary prospectus or any amendment thereof or supplement thereto or any omission or alleged omission of a material
fact required to be stated therein or necessary to make the statements therein not misleading, except insofar as the same are caused by or contained in any information furnished in writing to ACON by or on behalf of the Investor expressly for use
therein. 
 (ii) The Investor agrees, severally and not jointly with any person that is a party to the Other Subscription
Agreements or any other selling shareholder under the Registration Statement, to indemnify and hold harmless ACON, its directors and officers and agents and each person who controls ACON (within the meaning of the Securities Act) against any losses,
claims, damages, liabilities and expenses (including, without limitation, reasonable attorneys’ fees) resulting from any untrue statement of material fact contained in the Registration Statement, prospectus or preliminary prospectus or any
amendment thereof or supplement thereto or any omission of a material fact required to be stated therein or necessary to make the statements therein not misleading, but only to the extent that such untrue statement or omission is contained in any
information or affidavit so furnished in writing by the Investor expressly for use therein. In no event shall the liability of the Investor be greater in amount than the dollar amount of the net proceeds received by the Investor upon the sale of the
Shares purchased pursuant to this Subscription Agreement giving rise to such indemnification obligation. 
 (iii) Any person
entitled to indemnification herein shall (1) give prompt written notice to the indemnifying party of any claim with respect to which it seeks indemnification (provided that the failure to give prompt notice shall not impair any person’s
right to indemnification hereunder to the extent such failure has not prejudiced the indemnifying party) and (2) permit such indemnifying party to assume the defense of such claim with counsel reasonably satisfactory to the indemnified party.
If such defense is assumed, the indemnifying party shall not be subject to any liability for any settlement made by the indemnified party without its consent. An indemnifying party who elects not to assume the defense of a claim shall not be
obligated to pay the fees and expenses of more than one counsel for all parties indemnified by such indemnifying party with respect to such claim, unless in the reasonable judgment of legal counsel to any indemnified party a conflict of interest
exists between such indemnified party and any other of such indemnified parties with respect to such claim. No indemnifying party shall, without the consent of the indemnified party, consent to the entry of any judgment or enter into any settlement
which cannot be settled in all respects by the payment of money (and such money is so paid by the indemnifying party pursuant to the terms of such settlement) or which settlement does not include as an unconditional term thereof the giving by the
claimant or plaintiff to such indemnified party of a release from all liability in respect to such claim or litigation. 

  
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 (iv) The indemnification provided for under this Subscription Agreement
shall remain in full force and effect regardless of any investigation made by or on behalf of the indemnified party or any officer, director, employee, agent, affiliate or controlling person of such indemnified party and shall survive the transfer
of the Shares purchased pursuant to this Subscription Agreement. 
 (v) If the indemnification provided under this
Section 7(d) from the indemnifying party is unavailable or insufficient to hold harmless an indemnified party in respect of any losses, claims, damages, liabilities and expenses referred to herein, then the indemnifying party, in lieu of
indemnifying the indemnified party, shall contribute to the amount paid or payable by the indemnified party as a result of such losses, claims, damages, liabilities and expenses in such proportion as is appropriate to reflect the relative fault of
the indemnifying party and the indemnified party, as well as any other relevant equitable considerations. The relative fault of the indemnifying party and indemnified party shall be determined by reference to, among other things, whether any action
in question, including any untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact, was made by, or relates to information supplied by, such indemnifying party or indemnified party, and the
indemnifying party’s and indemnified party’s relative intent, knowledge, access to information and opportunity to correct or prevent such action. The amount paid or payable by a party as a result of the losses or other liabilities referred
to above shall be deemed to include, subject to the limitations set forth above, any legal or other fees, charges or expenses reasonably incurred by such party in connection with any investigation or proceeding. No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution pursuant to this Section 7(d) from any person who was not guilty of such fraudulent misrepresentation. In no event shall the
liability of the Investor be greater in amount than the dollar amount of the net proceeds received by the Investor upon the sale of the Shares purchased pursuant to this Subscription Agreement giving rise to such contribution obligation. 

8. Termination. This Subscription Agreement shall terminate and be void and of no further force and effect, and all rights and
obligations of the parties hereunder shall terminate without any further liability on the part of any party in respect thereof, upon the earliest to occur of (a) such date and time as the Merger Agreement is terminated in accordance with its
terms, (b) upon the mutual written agreement of each of the parties hereto, or (c) the Termination Date (as defined in the Merger Agreement as in effect on the date hereof) or the Extended Termination Date (as defined in the Merger
Agreement as in effect as of the date hereof), as applicable, if the Closing has not occurred by such date (the termination events described in clauses (a)–(d) above, collectively, the “Termination Events”); provided that
nothing herein will relieve any party from liability for any willful breach hereof prior to the time of termination, and each party will be entitled to any remedies at law or in equity to recover losses, liabilities or damages arising from any such
willful breach. ACON shall notify the Investor of the termination of the Merger Agreement as promptly as practicable after the termination of such agreement. Upon the occurrence of any Termination Event, this Subscription Agreement shall be void and
of no further effect and any monies paid by the Investor to ACON in connection herewith shall promptly (and in any event within one (1) business day) following the Termination Event be returned to the Investor. 

9. Trust Account Waiver. The Investor acknowledges that ACON is a blank check company with the powers and privileges to effect a
merger, asset acquisition, reorganization or similar business combination involving ACON and one or more businesses or assets. The Investor further acknowledges that, as described in ACON’s prospectus relating to its initial public offering
dated September 16, 2020 (the “Prospectus”) available at www.sec.gov, substantially all of ACON’s assets consist of the cash proceeds of ACON’s initial public offering and private placement of its securities, and
substantially all of those proceeds have been deposited in a trust account (the “Trust Account”) for the benefit of ACON, its public shareholders and the underwriters of ACON’s initial public offering. Except with respect to
interest earned on the funds held in the Trust Account that may be released to ACON to pay its tax obligations, if any, the cash in the Trust Account may be disbursed only for the purposes set forth in the Prospectus. For and in consideration of
ACON entering into this Subscription Agreement, the receipt and sufficiency of which are hereby acknowledged, the Investor hereby irrevocably waives any and all right, title and interest, or any claim of any kind it has or may have in the future, in
or to any monies held in the Trust Account, and agrees not to seek recourse against the Trust Account, as a result of or arising out of this Subscription Agreement or the transactions contemplated hereby, regardless of whether such claim arises
based on contract, tort, equity or any other theory of legal liability; provided, however, that nothing in this Section 9 shall be deemed to limit the Investor’s right, title, interest or claim to any monies held in the Trust
Account by virtue of its record or beneficial ownership of Class A Shares acquired by means other than pursuant to this Subscription Agreement, including pursuant to an exercised redemption right with respect to any such Class A Shares,
except to the extent that the Investor has otherwise agreed in writing with ACON, the Company or any of their respective affiliates to not exercise such redemption right. 
  

  
 13 

 10. No Short Sales. The Investor hereby agrees that, from the date of this
Subscription Agreement until the Closing, none of the Investor, its controlled affiliates, or any person or entity acting on behalf of the Investor or any of its controlled affiliates or pursuant to any understanding with the Investor or any of its
controlled affiliates will engage in any Short Sales with respect to securities of ACON. For purposes of this Section 10, “Short Sales” shall include, without limitation, all “short sales” as defined in Rule 200
promulgated under Regulation SHO under the Exchange Act, and all types of direct and indirect stock pledges (other than pledges in the ordinary course of business as part of prime brokerage arrangements), forward sale contracts, options, puts,
calls, swaps and similar arrangements (including, without limitation, on a total return basis), and sales and other transactions through non-U.S. broker dealers or foreign regulated brokers. 

11. Miscellaneous. 
 a.
Neither this Subscription Agreement nor any rights that may accrue to the Investor hereunder (other than the Shares acquired hereunder, if any) may be transferred or assigned. Notwithstanding the foregoing, the Investor may assign its rights and
obligations under this Subscription Agreement to one or more funds or accounts managed by the investment manager or investment advisor that manages the Investor (or an affiliate that controls, is controlled by or is under common control with such
investment manager or investment advisor), to a wholly-owned subsidiary of the Investor or, with ACON’s prior written consent, to another person, provided, in each case, that any assignee agrees in writing to be bound by the terms hereof as if
it were an original party hereto and that no such assignment shall relieve the Investor of its obligations hereunder if any such assignee fails to perform such obligations. 

b. ACON may request from the Investor such additional information as ACON may deem necessary to register the resale of the Shares and evaluate
the eligibility of the Investor to acquire the Shares, and the Investor shall provide such information as may reasonably be requested, to the extent readily available and to the extent consistent with the Investor’s internal policies and
procedures; provided that ACON agrees to keep any such information provided by the Investor confidential except (i) as required by the federal securities law or pursuant to other routine proceedings of regulatory authorities or
(ii) to the extent such disclosure is required by law, at the request of the staff of the SEC or regulatory agency or under the regulations of any national securities exchange on which ACON’s securities are listed for trading. The Investor
acknowledges that ACON may file a copy of this Subscription Agreement with the SEC as an exhibit to a periodic report or a registration statement of ACON. 

c. The Investor acknowledges that (i) ACON will rely on the acknowledgments, understandings, agreements, representations and warranties
of the Investor contained in this Subscription Agreement and (ii) the Placement Agent will rely on the acknowledgments, understandings, agreements, representations and warranties contained in Section 6, Section 12 and Section 13
of this Subscription Agreement. Prior to the Closing, the Investor agrees to promptly notify ACON if any of the acknowledgments, understandings, agreements, representations and warranties set forth in Section 6 are no longer accurate. 

d. ACON, the Company and the Placement Agent are each entitled to rely upon the acknowledgments, understandings, agreements, representations
and warranties contained in this Subscription Agreement and each is irrevocably authorized to produce this Subscription Agreement or a copy hereof to any interested party in any administrative or legal proceeding or official inquiry with respect to
the matters covered hereby; provided, however, nothing in this Section 11(d) shall give the Company or the Placements Agent any rights other than those expressly set forth in this Section 11(d). 

e. All of the agreements, representations and warranties made by each party hereto in this Subscription Agreement shall survive the Closing.

  
 14 

 f. This Subscription Agreement may not be terminated other than pursuant to the terms of
Section 8. The provisions of this Subscription Agreement may not be modified, amended or waived except by an instrument in writing signed by each of the parties hereto, provided, however, that Section 6, Section 11(d), this
Section 11(f), Section 11(g), and Section 12 of this Subscription Agreement may not be amended, terminated or waived in a manner that is material and adverse to the Placement Agent without the prior written consent of the Placement
Agent. No failure or delay of either party in exercising any right or remedy hereunder shall operate as a waiver thereof, nor shall any single or partial exercise of any such right or power, or any abandonment or discontinuance of steps to enforce
such right or power, or any course of conduct, preclude any other or further exercise thereof or the exercise of any other right or power. The rights and remedies of the parties hereunder are cumulative and are not exclusive of any rights or
remedies that they would otherwise have hereunder. 
 g. This Subscription Agreement (including the schedule hereto) constitutes the entire
agreement, and supersedes all other prior agreements, understandings, representations and warranties, both written and oral, among the parties, with respect to the subject matter hereof. Except as set forth in Section 7(d), Section 11(c),
Section 11(d), Section 11(f) this Section 11(g) and Section 12 with respect to the persons specifically referenced therein, this Subscription Agreement shall not confer any rights or remedies upon any person other than the
parties hereto, and their respective successor and assigns, and the parties hereto acknowledge that such persons so referenced are third party beneficiaries of the acknowledgments, understandings, agreements, representations and warranties contained
in this Subscription Agreement for the purposes of, and to the extent of, the rights granted to them, if any, pursuant to such provisions. 

h. Except as otherwise provided herein, this Subscription Agreement shall be binding upon, and inure to the benefit of the parties hereto and
their heirs, executors, administrators, successors, legal representatives, and permitted assigns, and the agreements, representations, warranties, covenants and acknowledgments contained herein shall be deemed to be made by, and be binding upon,
such heirs, executors, administrators, successors, legal representatives and permitted assigns. 
 i. If any provision of this Subscription
Agreement shall be adjudicated by a court of competent jurisdiction to be invalid, illegal or unenforceable, the validity, legality or enforceability of the remaining provisions of this Subscription Agreement shall not in any way be affected or
impaired thereby and shall continue in full force and effect. 
 j. This Subscription Agreement may be executed in one or more counterparts
(including by facsimile or electronic mail or in .pdf) and by different parties in separate counterparts, with the same effect as if all parties hereto had signed the same document. All counterparts so executed and delivered shall be construed
together and shall constitute one and the same agreement. 
 k. The Investor hereby consents to (i) the publication and disclosure in
any Form 8-K or Form 6-K filed by ACON with the SEC in connection with the execution and delivery of this Subscription Agreement, the Merger Agreement and the
transactions contemplated hereby and thereby and the Proxy Statement (as defined in the Merger Agreement) and (ii) as and to the extent otherwise required by the federal securities laws, exchange rules, the SEC or any other securities
authorities or any rules and regulations promulgated thereby, any other documents or communications provided by the Company or ACON to any governmental entity or to any securityholders of the Company, of the Investor’s identity and beneficial
ownership of the subscribed Shares and the nature of the Investor’s commitments, arrangements and understandings under and relating to this Subscription Agreement and, if deemed appropriate by the Company or ACON, a copy of this Subscription
Agreement, all solely to the extent required by applicable law or any regulation or stock exchange listing requirement. The Investor will promptly provide any information reasonably requested by ACON for any regulatory application or filing made or
approval sought in connection with the Transaction (including filings with the SEC). Notwithstanding the foregoing, ACON shall provide to the Investor a copy of any proposed disclosure relating to the Investor in accordance with the provisions of
this Section 11(k) in advance of any publication thereof and shall include such revisions to such proposed disclosure as the Investor shall reasonably request. Notwithstanding anything to the contrary in this Subscription Agreement, ACON shall
not, and shall cause to the Placement Agent and the Company not to, publicly disclose the name of the Investor, its investment advisor or any of their respective affiliates or advisers, or include the name of the Investor, its investment advisor or
any of their respective affiliates or advisers in any press release, without the prior written consent of the Investor. 

  
 15 

 l. The parties hereto acknowledge and agree that irreparable damage would occur in the event
that any of the provisions of this Subscription Agreement were not performed in accordance with their specific terms or were otherwise breached. It is accordingly agreed that the parties shall be entitled to an injunction or injunctions to prevent
breaches of this Subscription Agreement, without posting a bond or undertaking and without proof of damages, to enforce specifically the terms and provisions of this Subscription Agreement, this being in addition to any other remedy to which such
party is entitled at law, in equity, in contract, in tort or otherwise. 
 m. THIS SUBSCRIPTION AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK (REGARDLESS OF THE LAWS THAT MIGHT OTHERWISE GOVERN UNDER APPLICABLE PRINCIPLES OF CONFLICTS OF LAWS THEREOF) AS TO ALL MATTERS (INCLUDING ANY ACTION, SUIT, LITIGATION, ARBITRATION, MEDIATION,
CLAIM, CHARGE, COMPLAINT, INQUIRY, PROCEEDING, HEARING, AUDIT, INVESTIGATION OR REVIEWS BY OR BEFORE ANY GOVERNMENTAL ENTITY RELATED HERETO), INCLUDING MATTERS OF VALIDITY, CONSTRUCTION, EFFECT, PERFORMANCE AND REMEDIES. 

n. THE PARTIES HERETO IRREVOCABLY SUBMIT TO THE EXCLUSIVE JURISDICTION OF THE UNITED STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW
YORK AND THE SUPREME COURT OF THE STATE OF NEW YORK SOLELY IN RESPECT OF THE INTERPRETATION AND ENFORCEMENT OF THE PROVISIONS OF THIS SUBSCRIPTION AGREEMENT AND THE DOCUMENTS REFERRED TO IN THIS SUBSCRIPTION AGREEMENT AND IN RESPECT OF THE
TRANSACTIONS CONTEMPLATED HEREBY, AND HEREBY WAIVE, AND AGREE NOT TO ASSERT, AS A DEFENSE IN ANY ACTION, SUIT OR PROCEEDING FOR INTERPRETATION OR ENFORCEMENT HEREOF OR ANY SUCH DOCUMENT THAT IS NOT SUBJECT THERETO OR THAT SUCH ACTION, SUIT OR
PROCEEDING MAY NOT BE BROUGHT OR IS NOT MAINTAINABLE IN SAID COURTS OR THAT VENUE THEREOF MAY NOT BE APPROPRIATE OR THAT THIS SUBSCRIPTION AGREEMENT OR ANY SUCH DOCUMENT MAY NOT BE ENFORCED IN OR BY SUCH COURTS, AND THE PARTIES HERETO IRREVOCABLY
AGREE THAT ALL CLAIMS WITH RESPECT TO SUCH ACTION, SUIT OR PROCEEDING SHALL BE HEARD AND DETERMINED BY SUCH A NEW YORK STATE OR FEDERAL COURT. THE PARTIES HEREBY CONSENT TO AND GRANT ANY SUCH COURT JURISDICTION OVER THE PERSON OF SUCH PARTIES AND
OVER THE SUBJECT MATTER OF SUCH DISPUTE AND AGREE THAT MAILING OF PROCESS OR OTHER PAPERS IN CONNECTION WITH SUCH ACTION, SUIT OR PROCEEDING IN THE MANNER PROVIDED IN SECTION 11(o) OF THIS SUBSCRIPTION AGREEMENT OR IN SUCH OTHER MANNER AS MAY BE
PERMITTED BY LAW SHALL BE VALID AND SUFFICIENT SERVICE THEREOF. 
 EACH PARTY ACKNOWLEDGES AND AGREES THAT ANY CONTROVERSY WHICH MAY ARISE UNDER THIS
SUBSCRIPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY IS LIKELY TO INVOLVE COMPLICATED AND DIFFICULT ISSUES, AND THEREFORE EACH SUCH PARTY HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT SUCH PARTY MAY HAVE TO A TRIAL BY JURY IN
RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS SUBSCRIPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED BY THIS SUBSCRIPTION AGREEMENT. EACH PARTY CERTIFIES AND ACKNOWLEDGES THAT (I) NO REPRESENTATIVE, AGENT
OR ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER; (II) SUCH PARTY UNDERSTANDS AND HAS CONSIDERED THE IMPLICATIONS OF THE
FOREGOING WAIVER; (III) SUCH PARTY MAKES THE FOREGOING WAIVER VOLUNTARILY AND (IV) SUCH PARTY HAS BEEN INDUCED TO ENTER INTO THIS SUBSCRIPTION AGREEMENT BY, AMONG OTHER THINGS, THE MUTUAL WAIVER AND CERTIFICATIONS IN THIS SECTION 11(n).

 o. All notices, requests, demands, claims, and other communications hereunder shall be in writing. Any notice, request, demand, claim, or
other communication hereunder shall be deemed duly given, delivered and received (i) when delivered personally to the recipient, (ii) when sent by electronic mail, on the date of transmission to such recipient, with no mail undeliverable
or other rejection notice, (iii) one (1) business day after being sent to the recipient by reputable overnight courier service (charges prepaid), with confirmation of receipt, or (iv) four (4) business days after being mailed to the
recipient by certified or registered mail, return receipt requested and postage prepaid, and, in each case, addressed to the intended recipient at its address specified on the signature page hereof or to such electronic mail address or address as
subsequently modified by written notice given in accordance with this Section 11(o). 

  
 16 

 12. Non-Reliance and Exculpation. The
Investor acknowledges that it is not relying upon, and has not relied upon, any statement, representation or warranty made by any person, firm or corporation (including, without limitation, the Placement Agent, the Company or any of their
respective affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing), other than the statements, representations and warranties of ACON expressly contained in Section 5 of
this Subscription Agreement, in making its investment or decision to invest in ACON. The Investor acknowledges and agrees that none of (i) any Other Investor pursuant to any Other Subscription Agreement (including such investor’s
affiliates or any control persons, officers, directors, employees, partners, agents or representatives of such investor), (ii) the Placement Agent, its affiliates or any control persons, officers, directors, employees, partners, agents or
representatives of any of the foregoing, or (iii) the Company or any of its affiliates, shall have any liability to the Investor, or any other investor, pursuant to, arising out of or relating to this Subscription Agreement or any other
subscription agreement related to the private placement of the Shares, the negotiation hereof or thereof or its subject matter, or the transactions contemplated hereby or thereby, including, without limitation, with respect to any action heretofore
or hereafter taken or omitted to be taken by any of them in connection with the purchase of the Shares or with respect to any claim (whether in tort, contract or otherwise) for breach of this Subscription Agreement or in respect of any written or
oral representations made or alleged to be made in connection herewith, as expressly provided herein, or for any actual or alleged inaccuracies, misstatements or omissions with respect to any information or materials of any kind furnished by ACON,
the Company, the Placement Agent or any Non-Party Affiliate concerning ACON, the Company, the Placement Agent, any of their controlled affiliates, this Subscription Agreement or the transactions contemplated
hereby. For purposes of this Subscription Agreement, “Non-Party Affiliates” means each former, current or future officer, director, employee, partner, member, manager, direct or indirect
equityholder or affiliate of ACON, the Company, the Placement Agent or any of ACON’s, the Company’s or the Placement Agent’s controlled affiliates or any family member of the foregoing. 

13. Non-Recourse. This Subscription Agreement may only be enforced against, and any claim or
cause of action based upon, arising out of, or related to any breach of any term or condition of this Subscription Agreement may only be brought against, the entities that are expressly named as parties hereto and then only to the extent of the
specific obligations set forth herein with respect to such party. 
 14. Disclosure. ACON shall, by 9:00 a.m., New York City time, on
the first (1st) business day immediately following the date of this Subscription Agreement, issue one or more press releases or file with the SEC a Current Report on Form 8-K (collectively, the
“Disclosure Document”) disclosing all material terms of the transactions contemplated hereby and by the Other Subscription Agreements, the Merger Agreement, the Transaction and any other material, nonpublic information that ACON has
provided to the Investor at any time prior to the filing of the Disclosure Document. Upon the issuance of the Disclosure Document, the Investor shall not be in possession of any material, non-public
information received from ACON or any of its officers, directors, or employees or agents, and the Investor shall no longer be subject to any confidentiality or similar obligations under any current agreement, whether written or oral, with ACON, the
Placement Agent or any of their respective affiliates, relating to the transactions contemplated by this Subscription Agreement. 
 15.
Separate Obligations. For the avoidance of doubt, all obligations of the Investor hereunder are separate and several from the obligations of any Other Investor. The decision of Investor to purchase the Shares pursuant to this Subscription
Agreement has been made by Investor independently of any Other Investor or any other investor and independently of any information, materials, statements or opinions as to the business, financial condition or results of operations of ACON, the
Company, or any of their respective subsidiaries which may have been made or given by any Other Investor or by any agent or employee of any Other Investor, and neither Investor nor any of its agents or employees shall have any liability to any Other
Investor (or any other person) relating to or arising from any such information, materials, statements or opinions. Nothing contained herein or in any Other Subscription Agreement, and no action taken by Investor or Other Investors pursuant hereto
or thereto, shall be deemed to constitute Investor and Other Investor as a partnership, an association, a joint venture or any other kind of entity, or create a presumption that Investor and Other Investors are in any way acting in concert or as a
group with respect to such obligations or the transactions contemplated by this Subscription Agreement and the Other Subscription Agreements. The Investor acknowledges that no Other Investor has acted as agent for Investor in connection with making
its investment hereunder and no Other Investor will be acting as agent of Investor in connection with monitoring its investment in the Shares or enforcing its rights under this Subscription Agreement. The Investor shall be entitled to independently
protect and enforce its rights, including without limitation the rights arising out of this Subscription Agreement, and it shall not be necessary for any Other Investor to be joined as an additional party in any proceeding for such purpose. 

  
 17 

 16. Massachusetts Business Trust. If Investor is a Massachusetts Business Trust, a
copy of the Declaration of Trust of Investor or any affiliate thereof is on file with the Secretary of State of the Commonwealth of Massachusetts and notice is hereby given that the Subscription Agreement is executed on behalf of the trustees of
Investor or any affiliate thereof as trustees and not individually and that the obligations of the Subscription Agreement are not binding on any of the trustees, officers or stockholders of Investor or any affiliate thereof individually but are
binding only upon Investor or any affiliate thereof and its assets and property. 
 [SIGNATURE PAGES FOLLOW] 

  
 18 

 IN WITNESS WHEREOF, the Investor has executed or caused this Subscription Agreement
to be executed by its duly authorized representative as of the date set forth below. 
  

			
	Name of Investor:	  	State/Country of Formation or Domicile:
		
	By:                                     
                                         
              	  	
	Name:
                                         
                                         
    	  	
	Title:
                                         
                                         
      	  	
		
	Name in which Shares are to be registered (if different):	  	Date: ________, 2021
		
	Investor’s EIN:	  	
		
	Business Address-Street:	  	Mailing Address-Street (if different):
		
	City, State, Zip:	  	City, State, Zip:
		
	Attn:                                     
                                         
          	  	Attn:                                     
                                         
          
		
	Telephone No.:	  	Telephone No.:
	 Facsimile No.:
  

Email:
	  	Facsimile No.:
		
	Number of Shares subscribed for:	  	
		
	Aggregate Subscription Amount: $	  	Price Per Share: $10.00

 You must pay the Subscription Amount by wire transfer of United States dollars in immediately available funds
to the account specified by ACON in the Closing Notice. 

 IN WITNESS WHEREOF, ACON has accepted this Subscription Agreement as of the date set forth
below. 
  

			
	ACON S2 ACQUISITION CORP.

 
			
		
	By:	 	  

 
			
	Name: Adam Kriger
	Title: Managing Partner

 Date: May 6, 2021 

 SCHEDULE A 

ELIGIBILITY REPRESENTATIONS OF THE INVESTOR 
  

	A.	 QUALIFIED INSTITUTIONAL BUYER STATUS 

(Please check if applicable): 

☐ The Investor is a “qualified institutional buyer” (as defined in Rule 144A under the Securities Act (a
“QIB”)). 
 ** OR ** 
  

	B.	 INSTITUTIONAL ACCREDITED INVESTOR STATUS 

(Please check the applicable subparagraphs, to the extent applicable): 

 

	 	1.	 ☐ The Investor is an “accredited investor” (within the meaning of Rule 501(a) under the
Securities Act or an entity in which all of the equity holders are accredited investors within the meaning of Rule 501(a) under the Securities Act), and has marked and initialed the appropriate box below indicating the provision under which the
Investor qualifies as an “accredited investor.” 

  

	 	2.	 ☐ The Investor is not a natural person. 

Rule 501(a), in relevant part, states that an “accredited investor” shall mean any person who comes within any of the below listed categories, or
who the issuer reasonably believes comes within any of the below listed categories, at the time of the sale of the securities to that person. The Investor has indicated, by marking and initialing the appropriate box below, the provision(s) below
which apply to the Investor and under which the Investor accordingly qualifies as an “accredited investor.” 
 ☐ Any
bank, registered broker or dealer, insurance company, registered investment company, business development company, or small business investment company; 

☐ Any plan established and maintained by a state, its political subdivisions, or any agency or instrumentality of a state or its
political subdivisions for the benefit of its employees, if such plan has total assets in excess of $5,000,000; 
 ☐ Any employee
benefit plan, within the meaning of the Employee Retirement Income Security Act of 1974, if a bank, insurance company, or registered investment adviser makes the investment decisions, or if the plan has total assets in excess of $5,000,000; 

☐ Any organization described in Section 501(c)(3) of the Internal Revenue Code, corporation, Massachusetts or similar business
trust, or partnership, not formed for the specific purpose of acquiring the securities offered, with total assets in excess of $5,000,000; 

☐ Any trust with assets in excess of $5,000,000, not formed to acquire the securities offered, whose purchase is directed by a
sophisticated person; or 
 ☐ Any entity in which all of the equity owners are accredited investors meeting one or more of the
above tests. 
 This page should be completed by the Investor 

and constitutes a part of the Subscription Agreement.EX-10.2

 Exhibit 10.2 

FORM OF TRANSACTION SUPPORT AGREEMENT 

This TRANSACTION SUPPORT AGREEMENT (this “Agreement”) is entered into as of May 6, 2021, by and among ACON S2
Acquisition Corp., a Cayman Islands exempted company (“Acquiror”) and [•], a [•] (the “Stockholder”). Each of Acquiror and the Stockholder are sometimes referred to herein individually as a
“Party” and collectively as the “Parties”. Capitalized terms used but not otherwise defined herein shall have the meanings ascribed to them in the Merger Agreement (defined below). 

RECITALS 
 WHEREAS, on
May 6, 2021, Acquiror, SCharge Merger Sub, Inc., a Delaware corporation (“Merger Sub”) and ESS Tech, Inc., a Delaware corporation (the “Company”), entered into that certain Merger Agreement (as amended,
supplemented or otherwise modified from time to time in accordance with its terms, the “Merger Agreement”) pursuant to which, among other things, Merger Sub will merge with and into the Company, with the Company as the surviving
company in the merger and, after giving effect to such merger, becoming a wholly-owned Subsidiary of Acquiror, and each share of Company Common Stock (including shares of Company Common Stock issued upon the conversion of Company Preferred Stock in
connection with this transaction and including the Subject Company Stock (as defined below)) will be converted into the right to receive Acquiror Common Stock, in each case, on the terms and subject to the conditions set forth in the Merger
Agreement; 
 WHEREAS, the Stockholder is the record and beneficial owner of the number and type of equity securities of the Company set
forth on Schedule A hereto (together with any other equity securities of the Company that the Stockholder acquires record or beneficial ownership after the date hereof, collectively, the “Subject Company Stock”); 

WHEREAS, in consideration for the benefits to be received by the Stockholder under the terms of the Merger Agreement and as a material
inducement to Acquiror agreeing to enter into, and consummate the transactions contemplated by, the Merger Agreement, the Stockholder agrees to enter into this Agreement and to be bound by the agreements, covenants and obligations contained in this
Agreement; and 
 WHEREAS, the Parties acknowledge and agree that Acquiror and Merger Sub would not have entered into, and agreed to
consummate the transactions contemplated by, the Merger Agreement without the Stockholder entering into this Agreement and agreeing to be bound by the agreements, covenants and obligations contained in this Agreement. 

NOW, THEREFORE, in consideration of the premises and the mutual promises set forth herein and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Parties, each intending to be legally bound, hereby agree as follows: 

AGREEMENT 
 1. Company
Stockholder Consent and Related Matters. 
 (a) Subject to the earlier termination of this Agreement in accordance with its terms,
(i) as promptly as reasonably practicable (and in any event within five Business Days) following the time at which the Registration Statement becomes effective under the Securities Act (subject to the Registration Statement not being subject to
a stop order issued by the SEC or proceeding by the SEC seeking a stop order at any point during such period), the Stockholder, in its, his or her capacity as a stockholder of the Company, shall duly execute and deliver to the Company and Acquiror
the Company Stockholder Approvals under which it shall irrevocably and unconditionally consent to the matters, actions and proposals contemplated by Section 7.03(e) of the Merger Agreement (the “Approval”), including the 

 
Merger and any other transactions contemplated by the Merger Agreement to occur at or immediately prior to the Closing (collectively, the “Transactions”) and (ii) without
limiting the generality of the foregoing, prior to the Closing, to the extent that it is necessary or advisable, in each case, as reasonably determined by Acquiror and the Company, for any matters, actions or proposals to be approved by the
Stockholder in connection with, or otherwise in furtherance of, the transactions contemplated by the Merger Agreement, the Stockholder shall vote (or cause to be voted) the Subject Company Stock against and withhold consent with respect to
(A) any Company Acquisition Proposal or (B) any other matter, action or proposal that would reasonably be expected to result in any of the conditions to the Closing set forth in Sections 8.01 or 8.02 of the Merger Agreement not being
satisfied; provided, that in the case of either (i) or (ii), the Merger Agreement shall not have been amended or modified without such Stockholder’s consent (x) to decrease the consideration payable under the Merger Agreement or
(y) to change the form of merger consideration in a manner adverse to such Stockholder. 
 (b) Without limiting any other rights or
remedies of Acquiror, in the event that the Stockholder fails to perform or otherwise comply with the covenants, agreements or obligations set forth in Section 1(a), the Stockholder hereby irrevocably appoints Acquiror or
any individual designated by Acquiror as the Stockholder’s agent, attorney-in-fact and proxy (with full power of substitution and
re-substitution), for and in the name, place and stead of the Stockholder, to attend on behalf of the Stockholder any meeting of the Company Stockholders with respect to the matters described in
Section 1(a), to include the Subject Company Stock in any computation for purposes of establishing a quorum at any such meeting of the Company Stockholders, to vote (or cause to be voted) the Subject Company Stock or
consent (or withhold consent) with respect to any of the matters described in Section 1(a) in connection with any meeting of the Company Stockholders or any action by written consent by the Company Stockholders (including
the Company Stockholder Approvals). The proxy granted in this Section 1(b) shall expire upon the termination of this Agreement. 

(c) The proxy granted by the Stockholder pursuant to Section 1(b) is coupled with an interest sufficient in law to
support an irrevocable proxy and is granted in consideration of Acquiror entering into the Merger Agreement, and agreeing to consummate the transactions contemplated thereby. The proxy granted by the Stockholder pursuant to
Section 1(b) is a durable proxy and shall survive the bankruptcy, dissolution, death, incapacity or other inability to act by the Stockholder and shall revoke any and all prior proxies granted by the Stockholder with
respect to the Subject Company Stock. The vote or consent of the proxyholder in accordance with Section 1(b) with respect to the matters described in Section 1(a) shall control in the event of any
conflict between such vote or consent by the proxyholder of the Subject Company Stock and a vote or consent by the Stockholder of the Subject Company Stock (or any other Person with the power to vote or provide consent with respect to the Subject
Company Stock) with respect to the matters described in Section 1(a). The proxyholder may not exercise the proxy granted pursuant to Section 1(b) on any matter except for those matters described in
Section 1(a). 
 (d) The Stockholder shall not hereafter, unless and until this Agreement terminates or expires
pursuant to its terms, purport to designate any other proxy or power of attorney with respect to the Subject Company Stock or enter into any other agreement, arrangement, or understanding with any person, directly or indirectly, to vote, grant any
proxy or give instructions with respect to the voting of the Subject Company Stock, in each case, with respect to any of the matters set forth herein. 

2. Other Covenants and Agreements. 

(a) The Stockholder hereby agrees that, notwithstanding anything to the contrary in any such agreement and to the extent such Stockholder is a
party to any such agreement, effective as of the Closing, (i) each of the agreements set forth on Schedule B hereto shall be automatically terminated and of no further force and effect (including any provisions of any such agreement
that, by its terms, survive such termination) effective as of, and subject to and conditioned upon the occurrence of, the Closing and (ii) 

  
 2 

 
upon such termination neither the Company nor any of its Affiliates (including from and after the Effective Time, Acquiror and its Affiliates) shall have any further obligations or liabilities
under each such agreement. Without limiting the generality of the foregoing or Section 2(d), the Stockholder hereby agrees to promptly execute and deliver all additional agreements, documents and instruments and take, or
cause to be taken, all actions necessary or reasonably advisable in order to achieve the purpose of the preceding sentence. Without limiting the generality of the foregoing or Section 2(d), the Stockholder hereby agrees to
promptly execute and deliver all additional mutually agreed upon agreements, documents and instruments (such agreement not to be unreasonably withheld, conditioned or delayed; provided, that the Stockholder agrees that any document that
reflects the substance of the immediately preceding sentence (and not any other substantive provisions) and is solely for purposes of properly effectuating any such termination as provided in accordance with the terms of the immediately preceding
sentence shall be reasonable) and take, or cause to be taken, all actions necessary or reasonably advisable in order to achieve the purpose of the preceding sentence. 

(b) The Stockholder shall be bound by and subject to (i) Section 7.05 (Confidentiality; Publicity) of the Merger Agreement to the
same extent as such provisions apply to the parties to the Merger Agreement, and (ii) Section 5.04 (No Claim Against the Trust Account) of the Merger Agreement to the same extent as such provisions apply to the Company, in each
case, mutatis mutandis, as if the Stockholder is directly party thereto. Notwithstanding anything in this Agreement to the contrary, (x) the Stockholder shall not be responsible for the actions of the Company or the Company Board (or any
committee thereof) or any officers, directors (in their capacity as such), employees and professional advisors of any of the foregoing (the “Company Related Parties”) or any other owner of equity securities of the Company (or
Affiliate of such owner), including with respect to any of the matters contemplated by this Section 2(b), (y) the Stockholder is not making any representations or warranties with respect to the actions of any of the Company
Related Parties or any other owner of equity securities of the Company (or Affiliate of such owner) and (z) any breach by the Company or any other owner of equity securities of the Company (or Affiliate of such owner) of its respective
obligations under the Merger Agreement shall not be considered a breach of this Section 2(b) (it being understood for the avoidance of doubt that the Stockholder shall remain responsible for any breach by it of this
Section 2(b)). 
 (c) The Stockholder acknowledges and agrees that Acquiror and Merger Sub are entering into the
Merger Agreement in reliance upon the Stockholder entering into this Agreement and agreeing to be bound by, and perform, or otherwise comply with, as applicable, the agreements, covenants and obligations contained in this Agreement and but for the
Stockholder entering into this Agreement and agreeing to be bound by, and perform, or otherwise comply with, as applicable, the agreements, covenants and obligations contained in this Agreement Acquiror and Merger Sub would not have entered into, or
agreed to consummate the transactions contemplated by, the Merger Agreement. 
 (d) Upon, and subject to, the consummation of the
transactions contemplate by the Merger Agreement, each of the Acquiror and the Stockholder shall deliver duly executed counterparts to the Registration Rights Agreement in the form attached hereto as Exhibit A [and the Stockholder’s
Agreement in the form attached hereto as Exhibit B to be effective as of the Closing]. 

  
 3 

 (e) Upon the Closing, the Parties hereby acknowledge that certain Registration and
Shareholder Rights Agreement, dated as of September 16, 2020, by and among the Acquiror, the Sponsor and the other parties thereto, and all of the respective rights and obligations of the parties thereunder are hereby terminated in their
entirety and shall be of no further force or effect. 
 3. Consent to Entry into Merger Agreement. Stockholder hereby consents to the
Company entering into the Merger Agreement, to the extent such consent is required to satisfy any requirements contained in Section 6(b)(i) of Article V of the Company’s Certificate of Incorporation. For the avoidance of doubt, such
consent shall not be deemed a consent or approval of the Merger or the other Approvals, or any consent or agreement to receive shares of Acquiror Common Stock or other securities pursuant to the Merger or otherwise, which consent shall only be given
pursuant to the terms of, subject to the conditions set forth in and at the time described in this Agreement and the Merger Agreement. 
 4.
Stockholder Representations and Warranties. The Stockholder represents and warrants to Acquiror as follows: 
 (a) The
Stockholder is a corporation, limited liability company or other applicable business entity duly organized or formed, as applicable, validly existing and in good standing (or the equivalent thereof, if applicable, in each case, with respect to the
jurisdictions that recognize the concept of good standing or any equivalent thereof) under the Laws of its jurisdiction of formation or organization (as applicable). 

(b) The Stockholder has the requisite corporate, limited liability company or other similar power and authority to execute and deliver this
Agreement, to perform its covenants, agreements and obligations hereunder (including, for the avoidance of doubt, those covenants, agreements and obligations hereunder that relate to the provisions of the Merger Agreement), and to consummate the
transactions contemplated hereby. The execution and delivery of this Agreement has been duly authorized by all necessary corporate (or other similar) action on the part of the Stockholder. This Agreement has been duly and validly executed and
delivered by the Stockholder and constitutes a valid, legal and binding agreement of the Stockholder (assuming that this Agreement is duly authorized, executed and delivered by Acquiror), enforceable against the Stockholder in accordance with its
terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium or other Laws affecting generally the enforcement of creditors’ rights and subject to general principles of equity). 

(c) No consent, approval or authorization of, or designation, declaration or filing with, any Governmental Authority is required on the part of
the Stockholder with respect to the Stockholder’s execution, delivery or performance of its covenants, agreements or obligations under this Agreement (including, for the avoidance of doubt, those covenants, agreements and obligations under this
Agreement that relate to the provisions of the Merger Agreement) or the consummation of the transactions contemplated hereby, except for any consents, approvals, authorizations, designations, declarations, waivers or filings, the absence of which
would not adversely affect the ability of the Stockholder to perform, or otherwise comply with, any of its covenants, agreements or obligations hereunder in any material respect, or which have already been obtained in advance of the
Stockholder’s entry into this Agreement. 
 (d) None of the execution or delivery of this Agreement by the Stockholder, the performance
by the Stockholder of any of its covenants, agreements or obligations under this Agreement (including, for the avoidance of doubt, those covenants, agreements and obligations under this Agreement 

  
 4 

 
that relate to the provisions of the Merger Agreement) or the consummation of the transactions contemplated hereby will, directly or indirectly (with or without due notice or lapse of time or
both) (i) result in any breach of any provision of the Stockholder’s organizational and governing documents, (ii) result in a violation or breach of, or constitute a default or give rise to any right of termination, consent,
cancellation, amendment, modification, suspension, revocation or acceleration under, any of the terms, conditions or provisions of any Contract to which the Stockholder is a party, (iii) violate, or constitute a breach under, any Governmental
Order or applicable Law to which the Stockholder or any of its properties or assets are bound or (iv) other than the restrictions contemplated by this Agreement, result in the creation of any Lien upon the Subject Company Stock, except, in the
case of any of clauses (ii) and (iii) above, as would not adversely affect the ability of the Stockholder to perform, or otherwise comply with, any of its covenants, agreements or obligations hereunder in any material respect. 

(e) The Stockholder is the record and beneficial owner of the Subject Company Stock and has valid, good and marketable title to the Subject
Company Stock, free and clear of all Liens (other than transfer restrictions under applicable Securities Law or under the Company Organizational Documents). Except for the equity securities of the Company set forth on Schedule A hereto,
together with any other equity securities of the Company that the Stockholder acquires record or beneficial ownership of after the date hereof that is either permitted pursuant to, or acquired in accordance with, Section 5.01 of the Merger
Agreement [(it being understood that the acquisition by the Stockholder of any such equity securities acquired pursuant to and in accordance with Section 2.1(c) of that certain Series C-2 Preferred Stock
Purchase Agreement and Amendment to Series C Preferred Stock Purchase Agreement, dated as of March 1, 2021, as amended (the “Series C-2 Stock Purchase Agreement”), complies with
Section 5.01 of the Merger Agreement),] the Stockholder does not own, beneficially or of record, any equity securities of the Company. [Except as provided in the Series C-2 Stock Purchase Agreement or
rights under the Company Warrants, t//T]he Stockholder does not own any right to acquire any equity securities of the Company. The Stockholder has the sole right to vote (and provide consent in respect of, as applicable) the Subject Company Stock
and, except for this Agreement and the Merger Agreement, the Stockholder is not party to or bound by (i) any option, warrant, purchase right or other Contract that would (either alone or in connection with one or more events or developments
(including the satisfaction or waiver of any conditions precedent)) require the Stockholder to Transfer any of the Subject Company Stock or (ii) any voting trust, proxy or other Contract with respect to the voting or Transfer of any of the
Subject Company Stock, in each case, that could reasonably be expected to (A) impair the ability of such Stockholder to perform its obligations under this Agreement or (B) prevent, impede or delay the consummation of any of the
transactions contemplated by this Agreement. 
 (f) There is no Proceeding pending or, to the Stockholder’s knowledge, threatened
against the Stockholder that, if adversely decided or resolved, would reasonably be expected to adversely affect the ability of the Stockholder to perform, or otherwise comply with, any of its covenants, agreements or obligations under this
Agreement in any material respect. 
 (g) The Stockholder, on its own behalf and on behalf of its Representatives, acknowledges, represents,
warrants and agrees that (i) it has conducted its own independent review and analysis of, and, based thereon, has formed an independent judgment concerning, the business, assets, condition, operations and prospects of, Acquiror and (ii) it
has been furnished with or given access to such documents and information about Acquiror and its respective businesses and operations as it and its 

  
 5 

 
Representatives have deemed necessary to enable it to make an informed decision with respect to the execution, delivery and performance of this Agreement, the other Ancillary Agreements to which
it is or will be a party and the transactions contemplated hereby and thereby. 
 (h) In entering into this Agreement and the other Ancillary
Agreements to which it is or will be a party, the Stockholder has relied solely on its own investigation and analysis and the representations and warranties expressly set forth in the Ancillary Agreements to which it is or will be a party and no
other representations or warranties of Acquiror or Merger Sub (including, for the avoidance of doubt, none of the representations or warranties of Acquiror set forth in the Merger Agreement or any other Ancillary Agreement), any of their respective
Affiliates or any other Person, either express or implied, and the Stockholder, on its own behalf and on behalf of its Representatives, acknowledges, represents, warrants and agrees that, except for the representations and warranties expressly set
forth in the Ancillary Agreements to which it is or will be a party, none of Acquiror, Merger Sub, any of their respective Affiliates or any other Person makes or has made any representation or warranty, either express or implied, in connection with
or related to this Agreement, the Ancillary Agreements to which it is or will be a party or the transactions contemplated hereby or thereby. 

5. Transfer of Subject Securities. Except as expressly contemplated by the Merger Agreement or with the prior written consent of
Acquiror (such consent to be given or withheld in its sole discretion), from and after the date hereof, the Stockholder agrees not to (a) Transfer any of the Subject Company Stock, (b) enter into (i) any option, warrant,
purchase right or other Contract that would (either alone or in connection with one or more events or developments (including the satisfaction or waiver of any conditions precedent)) require the Stockholder to Transfer the Subject Company Stock
prior to the Closing or termination of the Merger Agreement or (ii) any voting trust, proxy or other Contract with respect to the voting or Transfer of the Subject Company Stock, or (c) take any actions in furtherance of any of the
matters described in the foregoing clauses (a) or (b). For purposes of this Agreement, “Transfer” means any, direct or indirect, sale, transfer, assignment, pledge, mortgage, exchange, hypothecation, grant of a security
interest in or disposition or encumbrance of an interest (whether with or without consideration, whether voluntarily or involuntarily or by operation of law or otherwise). Notwithstanding the foregoing, the Stockholder may transfer its Subject
Company Stock (A) to Stockholder’s officers or directors, any members or partners of the Stockholder or any Affiliates of the Stockholder; (B) in the case of an individual, by gift to a member of one of the
individual’s immediate family, to a trust, the beneficiary of which is a member of the individual’s immediate family, an affiliate of such person or to a charitable organization; (C) in the case of an individual, by virtue of
laws of descent and distribution upon death of the individual; (D) in the case of an individual, pursuant to a qualified domestic relations order; (E) by private sales or transfers made in connection with the transactions
contemplated by the Merger Agreement; (F) to other Company Stockholders; and (G) by virtue of the Stockholder’s organizational documents upon liquidation or dissolution of the Stockholder; in each case of clauses (A)
– (G), with the prior written consent of Acquiror (such consent to be withheld or given in its sole discretion) and subject to any such transferee signing a joinder hereto agreeing to be bound by all provisions hereof to the same extent as the
Stockholder. 
 6. Termination This Agreement (including the proxy granted pursuant to Section 1) shall
automatically terminate, without any notice or other action by any Party, and be void ab initio upon the earliest of (a) the Effective Time, (b) the termination of the Merger Agreement in accordance with its terms, (c) the
amendment or modification of the Merger Agreement without the Stockholder’s written consent (i) to decrease the consideration payable under the Merger Agreement, (ii) to extend the timing of payment of any consideration after Closing
or impose any additional burdens, limitations, obligations or restrictions on the Stockholder or (iii) to change the form of merger consideration in a manner adverse to such Stockholder and (d) the effective date of a written agreement of
the parties hereto mutually terminating this Agreement. Upon termination of this Agreement as provided in the immediately preceding sentence, none of the Parties shall have any further obligations or liabilities under, or with respect to, this
Agreement. Notwithstanding the foregoing or anything to the contrary in this Agreement, (w) the termination of this Agreement pursuant 

  
 6 

 
to Section 6(b) shall not affect any liability on the part of any Party for a Willful Breach of any covenant or agreement set forth in this Agreement prior to such
termination or Fraud committed by such Party; (x) Sections 2(b)(i) (solely to the extent that it relates to Section 7.05 (Confidentiality; Publicity) of the Merger Agreement) and the representations and warranties set forth in
Section 4(g) and Section 4(h) shall each survive any termination of this Agreement; (y) Section 13 shall each survive the termination of this Agreement pursuant to
Section 6(a); and (z) Section 2(b)(ii) (solely to the extent that it relates to Section 5.04 (No Claim Against the Trust Account) of the Merger Agreement) shall survive the termination of
this Agreement pursuant to Section 6(b). For purposes of this Section 6: 
 (a)
“Willful Breach” means a material breach of a covenant that is a consequence of an intentional act undertaken or an intentional failure to act by the breaching Party with the actual knowledge (as opposed to constructive, imputed or
implied knowledge) that the taking of such act or such failure to act would constitute or result in a breach of this Agreement; and 
 (b)
“Fraud” means an act or omission by a Party, and requires: (i) a false or incorrect representation or warranty expressly set forth in this Agreement, (ii) with actual knowledge (as opposed to constructive, imputed or
implied knowledge) by the Party making such representation or warranty that such representation or warranty expressly set forth in this Agreement is false or incorrect, (iii) an intention to deceive another Party, to induce it to enter into
this Agreement, (iv) another Party, in justifiable or reasonable reliance upon such false or incorrect representation or warranty expressly set forth in this Agreement, causing such Party to enter into this Agreement, and (v) causing such
Party to suffer damage by reason of such reliance. 
 6. Fiduciary Duties. Notwithstanding anything in this Agreement to the contrary,
(a) the Stockholder makes no agreement or understanding herein in any capacity other than in such Stockholder’s capacity as a record holder and beneficial owner of the Subject Company Stock[, and not in such Stockholder’s capacity as
a director, officer or employee of the Company or any of the Company’s Subsidiaries] and (b) nothing herein will be construed to limit or affect any action or inaction by [such Stockholder // any representative of such Stockholder serving]
in its capacity as a member of the board of directors of the Company or as an officer, employee or fiduciary of the Company, in each case, acting in such person’s capacity as a director, officer, employee or fiduciary of the Company. 

7. [Reserved]. 
 8. No
Recourse. Except for claims pursuant to the Merger Agreement or any other Ancillary Agreement by any party(ies) thereto against any other party(ies) thereto, each Party agrees that this Agreement may only be enforced against, and any action for
breach of this Agreement may only be made against, the Parties. Notwithstanding the foregoing, nothing herein shall limit the Liability of any Party for Fraud or Willful Breach committed by such Party. 

9. Notices. All notices and other communications among the Parties shall be in writing and shall be deemed to have been duly given
(a) when delivered in person, (b) when delivered after posting in the United States mail having been sent registered or certified mail return receipt requested, postage prepaid, (c) when delivered by FedEx or other nationally
recognized overnight delivery service or (d) when e-mailed during normal business hours (and otherwise as of the immediately following Business Day), addressed as follows: 

(a) If to Acquiror (including in its capacity as Designee) or Merger Sub, to: 

ACON S2 Acquisition Corp. 
 1133
Connecticut Avenue NW 
 Suite 700 

  
 7 

 Washington, DC 20036 

Attn: Adam Kriger 
 E-mail: akriger@aconinvestments.com 
 with a copy to: 

Kirkland & Ellis LLP 

609 Main Street 
 Houston, TX
77002 
 Attn: Douglas Bacon 

Shawn O’Hargan 
 E-mail: douglas.bacon@kirkland.com 
 shawn.ohargan@kirkland.com 

(b) If to Stockholder, to: 

[•] 
 [•] 

Attn: [•] 
 E-mail: [•] 
 or to such other address or addresses as the Parties may from time to time designate in writing. 

10. Entire Agreement. This Agreement, the Merger Agreement and documents referred to herein and therein constitute the entire agreement
of the Parties with respect to the subject matter of this Agreement, and supersede all prior agreements and undertakings, both written and oral, among the Parties with respect to the subject matter of this Agreement, except as otherwise expressly
provided in this Agreement. 
 11. Amendments and Waivers; Assignment. Any provision of this Agreement may be amended or waived if,
and only if, such amendment or waiver is in writing and signed by the Stockholder and Acquiror. Notwithstanding the foregoing, no failure or delay by any Party in exercising any right hereunder shall operate as a waiver thereof nor shall any single
or partial exercise thereof preclude any other or further exercise of any other right hereunder. This Agreement and the rights, interests or obligations hereunder, shall only be assignable by the Stockholder solely to the extent permitted by
Section 5 hereof. 
 12. Fees and Expenses. Except as otherwise expressly set forth in the Merger Agreement,
all fees and expenses incurred in connection with this Agreement and the transactions contemplated hereby, including the fees and disbursements of counsel, financial advisors and accountants, shall be paid by the Party incurring such fees or
expenses. 
 13. Remedies. Except as otherwise expressly provided herein, any and all remedies provided herein will be deemed
cumulative with and not exclusive of any other remedy conferred hereby, or by law or equity upon such Party, and the exercise by a Party of any one remedy will not preclude the exercise of any other remedy. The Parties agree that irreparable damage
for which monetary damages, even if available, would not be an adequate remedy, would occur in the event that either Party does not perform its respective obligations under the provisions of this Agreement in accordance with their specific terms or
otherwise breach such provisions. It is accordingly agreed that each Party shall be entitled to an injunction or injunctions, specific performance and other equitable relief to prevent breaches of this Agreement and to enforce specifically the terms
and provisions of this Agreement, in each case, without posting a bond or undertaking and without proof of damages and this being in addition to any other remedy to which they are entitled at law or in equity. Each Party agrees that it will not
oppose the granting of an injunction, specific performance and other equitable relief when expressly available pursuant to the terms of this Agreement on the basis that the other Parties have an adequate remedy at law or an award of specific
performance is not an appropriate remedy for any reason at law or equity. 

  
 8 

 14. No Third-Party Beneficiaries. This Agreement shall be for the sole benefit of the
Parties and their respective successors and permitted assigns and is not intended, nor shall be construed, to give any Person, other than the Parties and their respective successors and permitted assigns, any legal or equitable right, benefit or
remedy of any nature whatsoever by reason this Agreement. Nothing in this Agreement, expressed or implied, is intended to or shall constitute the Parties acting as partners or participants in a joint venture. For the avoidance of doubt the Company
shall be a third party beneficiary of Section 3 of this Agreement. 
 15. Miscellaneous. Sections 1.02 (Construction), 10.06
(Governing Law), 10.07 (Captions; Counterparts), 10.11 (Severability), 10.12 (Jurisdiction; Waiver of Trial by Jury) and 10.15 (Non-Survival of Representations, Warranties and Covenants) of the Merger
Agreement are incorporated herein by reference and shall apply to this Agreement, mutatis mutandis. 
 Remainder of page
intentionally left blank; signature pages follow. 

  
 9 

 IN WITNESS WHEREOF, the Parties have executed and delivered this Transaction Support
Agreement as of the date first above written. 
  

			
	ACON S2 ACQUISITION CORP.
		
	By:	 	  

	Name:	 	Adam Kriger
	Title:	 	Chief Executive Officer

  
  
  

 
  
  

[Signature Page to Transaction Support Agreement] 

 
			
	[STOCKHOLDER]
		
	By:	 	  

	Name:
	Title:

 [Signature Page to Transaction Support Agreement] 

 SCHEDULE A 

 

					
	 Class/Series Securities
	  	Number of Shares	 
	 [•]
	  	 	[	•] 
	 [•]
	  	 	[	•] 
	 [•]
	  	 	[	•] 
	 [•]
	  	 	[	•] 

 SCHEDULE B 

 

	 	•	 	 Second Amended and Restated Investors’ Rights Agreement, dated as of August 28, 2019 between the
Company, SB Energy Global Holdings One Ltd., Breakthrough Energy Ventures, LLC, Cycle Capital Fund III, L.P., Pangaea Ventures Fund III, LP, Sand Hill Angels XV, LLC, Seattle Angel Conference Investors, LLC, Fund VI 2014 Series only, Portland Seed
Fund II, LP, Oregon Nanoscience and Microtechnologies Institute, Brian Arbogast, John E. Chadwick, Kathy Washienko, Energethic, LLC, 3x4y Angels – ESS 2015 LLC, 3x4y Angels – ESS 2016 LLC, Eimar Boesjes , Douglas G. Swartz, Eric Robert
Berman and Luann Kay Suthers Berman Living Trust, dated July 18, 2012, Erick Petersen, Jabe Blumenthal, Ramez Naam, RNN Ventures ESS Series C Note LLC, Monoc Capital Ltd. EESS LLC, Obsidian Renewables, LLC, BASF Venture Capital GmbH, Presidio-IPM
j.s.a., Vicap LLC, Michael R. Niggli Family Trust, Linda Naviaux Niggli Trust , Agharta Capital Ltd. , Energy Ventures, Inc., GC Ventures America, Craig Evans , including Side Letter dated as of March 1, 2021 

 

	 	•	 	 Second Amended and Restated Right of First Refusal and Co-Sale Agreement, dated August 28, 2019, by and
among the Company, SB Energy Global Holdings One Ltd., Breakthrough Energy Ventures, LLC, Cycle Capital Fund III, L.P., Pangaea Ventures Fund III, LP, Sand Hill Angels XV, LLC, Seattle Angel Conference Investors, LLC, Fund VI 2014 Series only,
Portland Seed Fund II, LP, Oregon Nanoscience and Microtechnologies Institute, Oregon Built Environment and Sustainable Technologies Center, Inc. Brian Arbogast, John E. Chadwick, Kathy Washienko, Energethic, LLC, 3x4y Angels – ESS 2015
LLC, 3x4y Angels – ESS 2016 LLC, Eimar Boesjes , Douglas G. Swartz, Eric Robert Berman and Luann Kay Suthers Berman Living Trust, dated July 18, 2012, Erick Petersen, Jabe Blumenthal, Ramez Naam, RNN Ventures ESS Series C Note LLC, Monoc
Capital Ltd. EESS LLC, Obsidian Renewables, LLC, BASF Venture Capital GmbH, Presidio-IPM j.s.a., Vicap LLC, Michael R. Niggli Family Trust, Linda Naviaux Niggli Trust , Agharta Capital Ltd. , Energy Ventures, Inc., GC Ventures America, Craig Evans
and Yang Song. 

  

	 	•	 	 Second Amended and Restated Voting Agreement, dated August 28, 2019, by and among the Company, SB Energy Global
Holdings One Ltd., Breakthrough Energy Ventures, LLC, Cycle Capital Fund III, L.P., Pangaea Ventures Fund III, LP, Sand Hill Angels XV, LLC, Seattle Angel Conference Investors, LLC, Fund VI 2014 Series only, Portland Seed Fund II, LP, Oregon
Nanoscience and Microtechnologies Institute, Oregon Built Environment and Sustainable Technologies Center, Inc. Brian Arbogast, John E. Chadwick, Kathy Washienko, Energethic, LLC, 3x4y Angels – ESS 2015 LLC, 3x4y Angels – ESS 2016 LLC,
Eimar Boesjes , Douglas G. Swartz, Eric Robert Berman and Luann Kay Suthers Berman Living Trust, dated July 18, 2012, Erick Petersen, Jabe Blumenthal, Ramez Naam, RNN Ventures ESS Series C Note LLC, Monoc Capital Ltd. EESS LLC, Obsidian
Renewables, LLC, BASF Venture Capital GmbH, Presidio-IPM j.s.a., Vicap LLC, Michael R. Niggli Family Trust, Linda Naviaux Niggli Trust , Agharta Capital Ltd. , Energy Ventures, Inc., GC Ventures America, Craig Evans and Yang Song.

  

	 	•	 	 Omibus Amendment to the Financing Agreements dated March 1, 2021 by and among the Company, SB Energy Global
Holdings One Ltd., Breakthrough Energy Ventures, LLC, Cycle Capital Fund III, L.P., Pangaea Ventures Fund III, LP, Energy Ventures, Inc., GC Ventures America, Craig Evans and Yang Song. 

 

	 	•	 	 Side Letter dated as of August 28, 2019 between the Company and Breakthrough Energy Ventures, LLC.

  

	 	•	 	 Side Letter dated as of October 15, 2019 between the Company and GC Ventures America and Amended and Restated
side letter by and between the Company and GC Ventures America, dated as of March 1, 2021. 

  

	 	•	 	 Side Letter dated as of July 10, 2018 between the Company and Presidio-IPM j.s.a. 

 

	 	•	 	 Side Letter dated as of December 11, 2017 between the Company Presidio-IPM j.s.a., Cycle Capital Fund III, L.P.
and BASF Venture Capital GmbH. 

  

	 	•	 	 Side Letter dated as of March 3, 2015 signed by the Company for the benefit of each member of Element 8 Group.

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