Document:

EX-10.1

 Exhibit 10.1 

Execution Version 

STOCKHOLDER SUPPORT AGREEMENT 

This Stockholder Support Agreement (this “Agreement”) is made and entered into as of June 15, 2021, by and among
Solid Power, Inc., a Colorado corporation (the “Company”), Decarbonization Plus Acquisition Corporation III, a Delaware corporation (“DCRC”) and the undersigned stockholders (each, a
“Written Consent Party” and, collectively, the “Written Consent Parties”) of the Company. Capitalized terms used but not otherwise defined herein shall have the respective meanings ascribed to such
terms in the Business Combination Agreement (as defined below). 
 RECITALS 

WHEREAS, on June 15, 2021, DCRC, DCRC Merger Sub Inc., a Delaware corporation (the “Merger Sub”), and the
Company, entered into a Business Combination Agreement and Plan of Reorganization (the “Business Combination Agreement”), pursuant to which, among other things, Merger Sub will merge with and into the Company, with the
Company surviving the merger as a wholly owned subsidiary of DCRC (the “Merger”); 
 WHEREAS, each Written Consent
Party agrees to enter into this Agreement with respect to all Company Securities (as defined below) that such Written Consent Party now or hereafter owns, beneficially (as defined in Rule 13d-3 under the
Exchange Act) or of record; 
 WHEREAS, each Written Consent Party is the beneficial and/or record owner of, and has the sole right to vote
or direct the voting of, such number of shares of Company Common Stock and Company Preferred Stock (collectively, “Company Stock”) as are set forth on Schedule A attached hereto opposite the name of
such Written Consent Party; 
 WHEREAS, each of DCRC and each Written Consent Party has determined that it is in its best interests to enter
into this Agreement; 
 WHEREAS, each Written Consent Party understands and acknowledges that DCRC is entering into the Business Combination
Agreement in reliance upon such Written Consent Party’s execution and delivery of this Agreement; and 
 WHEREAS, following the date
hereof, DCRC intends to file with the SEC a registration statement on Form S-4 in connection with the matters set forth in Section 7.02(a) of the Business Combination Agreement (the
“Registration Statement”). 
 NOW, THEREFORE, in consideration of the foregoing and the respective representations,
warranties, covenants and agreements set forth below and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto, intending to be legally bound, do hereby agree as follows: 

1. Definitions. When used in this Agreement, the following terms in all of their tenses, cases and correlative forms shall have the meanings assigned to
them in this Section 1 or elsewhere in this Agreement. Capitalized but undefined terms used herein shall have the meaning ascribed to such terms in the Business Combination Agreement. 

 “Affiliate” of a specified person means a Person who,
directly or indirectly through one or more intermediaries, controls, is controlled by, or is under common control with, such specified Person (provided that if a Written Consent Party is a venture capital, private equity, growth equity, angel fund
or similar funding vehicle, no portfolio company of such Written Consent Party will be deemed an Affiliate of such Written Consent Party, and the Company shall not be deemed to be an Affiliate of any Written Consent Party for purposes of this
Agreement). 
 “Company Securities” means, collectively, any Company Common Stock, Company Preferred Stock,
Company Options, Company Restricted Stock, Company Warrants, any securities convertible into or exchangeable for any of the foregoing, and any interest in or right to acquire any of the foregoing. 

“Expiration Time” shall mean the earlier to occur of (a) the Effective Time, (b) such date as the
Business Combination Agreement shall be validly terminated in accordance with Article IX thereof, (c) with respect to each Written Consent Party and DCRC, the effective date of a written agreement between DCRC and such Written Consent Party
terminating this Agreement, and (d) with respect to each Written Consent Party and DCRC, the effective date of an amendment or modification of the Business Combination Agreement without such Written Consent Party’s written consent to
(i) decrease the consideration payable under the Business Combination Agreement, or impose any additional material burdens, limitations, obligations or restrictions on the Written Consent Party, (ii) extend the timing of payment of any
consideration after Closing (other than pursuant to an extension of the Outside Date upon agreement by the Company and DCRC), (iii) change the form of merger consideration in a manner adverse to such Written Consent Party or (iv) make any other
change which is materially adverse to such Written Consent Party. 
 “Person” means an individual,
corporation, partnership, limited partnership, limited liability company, syndicate, person (including a “person” as defined in Section 13(d)(3) of the Exchange Act), trust, association or entity or government, political subdivision,
agency or instrumentality of a government. 
 “Transfer” shall mean the (a) sale of, offer to sell,
contract or agreement to sell, hypothecate, pledge, grant of any option to purchase or otherwise dispose of or agreement to dispose of, directly or indirectly, or establishment or increase of a put equivalent position or liquidation with respect to
or decrease of a call equivalent position within the meaning of Section 16 of the Exchange Act, and the rules and regulations of the SEC promulgated thereunder with respect to, any security, (b) entry into any swap or other arrangement
that transfers to another, in whole or in part, any of the economic consequences of ownership of any security, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or (c) public announcement of any
intention to effect any transaction specified in clause (a) or (b), excluding entry into this Agreement and the Business Combination Agreement and the consummation of the transactions contemplated hereby and thereby. 

  
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 2. Agreement to Retain the Company Securities. 

2.1 No Transfer of Company Securities. Until the Expiration Time, each Written Consent Party agrees not to, other than as expressly
required by the Business Combination Agreement, (a) Transfer any Company Securities or (b) deposit any Company Securities into a voting trust or enter into a voting agreement or any similar agreement, arrangement or understanding with
respect to Company Securities or grant any proxy (except as otherwise provided herein), consent or power of attorney with respect thereto (other than pursuant to this Agreement); provided, (1) that any Written Consent Party may Transfer
any such Company Securities (i) to any officer, director, stockholder, member, partner or any other Affiliate of such Written Consent Party, (ii) to any employee of such Written Consent Party or such Affiliates, (iii) by virtue of
such Written Consent Party’s organizational documents upon liquidation or dissolution of the Written Consent Party, (iv) to another stockholder of the Company that is a party to this Agreement and bound by the terms and obligations hereof,
or (v) if such Written Consent Party is a natural person, (A) to immediate family or a trust for the benefit of immediate family for estate planning purposes, (B) to an Affiliate of such person or to a charitable organization,
(C) by virtue of laws of descent and distribution upon death of the individual, or (D) pursuant to qualified domestic relations order, in the case of clauses (i) – (v), if, and only if, the transferee of such Company Securities signs
a joinder hereto confirming such transferee’s agreement to be bound by and subject to the terms and provisions hereof to the same effect as such Written Consent Party and (2) any Written Consent Party may grant a proxy to its own employees
or to employees of its Affiliates for purposes of voting on behalf of such Written Consent Party in the manner required by the Agreement. 

2.2 Additional Company Securities. Until the Expiration Time, each Written Consent Party agrees that any Company Securities that such
Written Consent Party purchases or otherwise hereinafter acquires or with respect to which such Written Consent Party otherwise acquires sole or shared voting power after the execution of this Agreement and prior to the Expiration Time shall be
subject to the terms and conditions of this Agreement to the same extent as if they were owned by such Written Consent Party as of the date hereof. 

2.3 Unpermitted Transfers. Any Transfer or attempted Transfer of any Company Securities in violation of this
Section 2 shall, to the fullest extent permitted by applicable Law, be null and void ab initio. 
 3. Agreement to
Consent and Approve. 
 3.1 Hereafter until the Expiration Time, each Written Consent Party agrees that, within five Business Days of the
Registration Statement being declared effective by the SEC (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 time during such period) and except as
otherwise agreed in writing with DCRC, such Written Consent Party, in its, his or her capacity as a stockholder of the Company, shall execute and deliver a written consent substantially in the form attached as Exhibit F to the Business Combination
Agreement, with such modifications as may be agreed by the Company and DCRC that are not materially adverse to such Written Consent Party (the “Stockholder Written Consent”), which consent shall, among other things, approve
(i) the Business Combination Agreement, the Merger and the other Transactions and (ii) the termination of certain agreements set forth in a schedule to the Stockholder Written Consent. Following such execution and delivery, each Written
Consent Party hereby agrees that it will not revoke, withdraw or repudiate the Stockholder Written Consent. The Stockholder Written Consent shall be coupled with an interest and, prior to the Expiration Time, shall be irrevocable. 

  
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 Hereafter until the Expiration Time, and subject to Section 2 hereof, no Written
Consent Party shall enter into any tender or voting agreement, or any similar agreement, arrangement or understanding, or grant a proxy or power of attorney, with respect to the Company Securities that is inconsistent with this Agreement or
otherwise take any other action with respect to the Company Securities that would prevent, materially restrict, materially limit or materially interfere with the performance of such Written Consent Party’s obligations hereunder or the
consummation of the transactions contemplated hereby. 
 3.2 Hereafter until the Expiration Time, at any meeting of the stockholders of the
Company, or at any postponement or adjournment thereof, called to seek the affirmative vote of the holders of the outstanding shares of Company Stock to adopt the Business Combination Agreement, or approve the Merger and the other Transactions, or
in any other circumstances upon which a vote, consent or other approval (including the Stockholder Written Consent) with respect to the Business Combination Agreement, the Merger or the other Transactions is sought, each Written Consent Party shall
vote (or cause to be voted) all shares of Company Stock currently or hereinafter owned by such Written Consent Party in favor of the foregoing. 

3.3 Hereafter until the Expiration Time, at any meeting of the stockholders of the Company or at any postponement or adjournment thereof or in
any other circumstances upon which a Written Consent Party’s vote, consent or other approval (including by written consent) is sought, such Written Consent Party shall vote (or cause to be voted) all Company Securities (to the extent such
Company Securities are then entitled to vote thereon), currently or hereinafter owned by such Written Consent Party against and withhold consent with respect to any Alternative Transaction (as defined below). No Written Consent Party shall commit or
agree to take any action inconsistent with the foregoing that would be effective prior to the Expiration Time. 
 4. Additional Agreements. 

4.1 Litigation. Each Written Consent Party agrees not to commence, join in, facilitate, assist or encourage, and agrees to take all
actions necessary to opt out of any class in any class action with respect to, any claim, derivative or otherwise, against DCRC, Merger Sub, the Company or any of their respective successors, directors or officers (a) challenging the validity
of, or seeking to enjoin the operation of, any provision of this Agreement or the Business Combination Agreement or (b) alleging a breach of any fiduciary duty of any Person in connection with the evaluation, negotiation or entry into this
Agreement or the Business Combination Agreement. 
 4.2 Waiver of Certain Rights. Each Written Consent Party hereby waives any
requirement for notice with respect to the Transactions under any agreements with the Company. 
 4.3 Confidentiality. Until the
Expiration Time, each Written Consent Party shall be bound by and subject to Section 7.05(b) and (c) (Confidentiality) of the Business Combination Agreement to the same extent as such provisions (including the provisions of the Confidentiality
Agreement) apply to the Company, in each case, mutatis mutandis, as if the Written Consent Party is directly party thereto. 

  
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 4.4 Registration Rights Agreement. Upon, and subject to, the consummation of the
transactions contemplated by the Business Combination Agreement, each of DCRC and the Written Consent Parties that will be Affiliates of DCRC after Closing shall deliver duly executed counterparts to the Registration Rights Agreement in the form
appended to the Business Combination Agreement to be effective as of the Closing. 
 4.5
Lock-up. Each Written Consent Party acknowledges and agrees that it shall be bound by and subject to the terms of the Amended and Restated Bylaws of DCRC, a form of which is attached as Exhibit H (the
“Bylaws”) to the Business Combination Agreement and which will be adopted and effective as of the Effective Time, including, for avoidance of doubt, the lock-up provisions contained in
Section 6.8 of the Bylaws; provided, however, that in the event that the board of directors of DCRC grants a discretionary waiver or termination of such obligations contained in Section 6.8 of the Bylaws with respect to DCRC Class A
Common Stock held by any of BMW Holding B.V., Ford Motor Company, Volta Energy Storage Fund I, LP, Volta SPV SPW, LLC, Volta SPW Co-Investment, LP or any of their respective Affiliates or their respective
successors or permitted assigns (collectively, the “Covered Stockholders”), the board of directors of DCRC shall be deemed to have waived or terminated such obligations with respect to the same percentage of the other Covered
Stockholders’ DCRC Class A Common Stock as the relative percentage of aggregate shares held by such Covered Stockholder receiving the waiver that are subject to the waiver. 

4.6 The Company hereby represents, warrants, covenants and agrees that each Key Company Stockholder (as defined in the Business Combination
Agreement) has, or simultaneous with the execution of the Business Combination Agreement will have, executed and delivered this Agreement. DCRC hereby represents and warrants that it has not entered into any side letter or similar agreement with any
Key Company Stockholder in connection with this Agreement, the Merger or the related transactions. It is further acknowledged and agreed by the parties hereto that each Written Consent Party’s agreement to the covenants and agreements set forth
in Section 4.5 hereof is conditioned upon and subject to the representations and warranties and covenants and agreements of DCRC set forth herein being accurate and complete in all respects. 

5. Representations and Warranties of the Written Consent Parties. Each Written Consent Party hereby represents and warrants, severally and not jointly,
to DCRC as follows: 
 5.1 Due Authority. Such Written Consent Party has the full power and authority to execute and deliver this
Agreement and perform its obligations hereunder. If such Written Consent Party is an individual, the signature to this agreement is genuine and such Written Consent Party has legal competence and capacity to execute the same. This Agreement has been
duly and validly executed and delivered by such Written Consent Party and, assuming due execution and delivery by the other parties hereto, constitutes a legal, valid and binding obligation of such Written Consent Party, enforceable against such
Written Consent Party in accordance with its terms, except as limited by applicable Remedies Exceptions. 
 5.2 Ownership of the Company
Securities. As of the date hereof, such Written Consent Party is the owner of the Company Securities set forth opposite such Written Consent Party’s name on Schedule A, free and clear of any and all Liens, options,
rights of first refusal and limitations on such Written Consent Party’s voting rights, other than transfer restrictions under the Right of 

  
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First Refusal and Co-Sale Agreement, applicable securities laws or the certificate of incorporation or bylaws or any equivalent organizational documents of
the Company, as applicable. Such Written Consent Party has sole voting power (including the right to control such vote as contemplated herein), power of disposition and power to issue instructions with respect to all Company Securities currently
owned by such Written Consent Party, and the power to agree to all of the matters applicable to such Written Consent Party set forth in this Agreement. As of the date hereof, such Written Consent Party does not own any Company Securities other than
the Company Securities set forth opposite such Written Consent Party’s name on Schedule A. As of the date hereof, such Written Consent Party does not own any rights to purchase or acquire any Company Securities, except
for the Company Warrants and Company Options set forth opposite such Written Consent Party’s name on Schedule A. 

5.3 No Conflict; Consents. 

(a) The execution and delivery of this Agreement by such Written Consent Party does not, and the performance by such Written
Consent Party of the obligations under this Agreement and the compliance by such Written Consent Party with any provisions hereof do not and will not: (i) conflict with or violate any Law applicable to such Written Consent Party, (ii) if
such Written Consent Party is an entity, conflict with or violate the certificate of incorporation or bylaws or any equivalent organizational documents of the Company or such Written Consent Party, or (iii) result in any breach of, or
constitute a default (or an event, which with notice or lapse of time or both, would become a material default) under, or give to others any rights of termination, amendment, acceleration or cancellation of, or result in the creation of a Lien on
any of the Company Securities owned by such Written Consent Party pursuant to any note, bond, mortgage, indenture, contract, agreement, lease, license, permit, franchise or other instrument or obligation to which such Written Consent Party is a
party or by which such Written Consent Party is bound, except, in the case of clauses (i) and (iii), as would not reasonably be expected, individually or in the aggregate, to materially impair the ability of such Written Consent
Party to perform its obligations hereunder or to consummate the transactions contemplated hereby. 
 (b) The execution and
delivery of this Agreement by such Written Consent Party does not, and the performance of this Agreement by such Written Consent Party will not, require any consent, approval, authorization or permit of, or filing or notification to, or expiration
of any waiting period by any Governmental Authority or any other Person with respect to such Written Consent Party, other than those set forth as conditions to Closing in the Business Combination Agreement and other than those pursuant to, in
compliance with or required to be made under the Exchange Act. 
 5.4 Absence of Litigation. As of the date hereof, there is no Action
pending against, or, to the knowledge of such Written Consent Party after reasonable inquiry, threatened against such Written Consent Party that would reasonably be expected to materially impair the ability of such Written Consent Party to perform
its obligations hereunder or to consummate the transactions contemplated hereby. 

  
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 5.5 Absence of Other Voting Agreement. Other than the Company Voting Agreement, such
Written Consent Party has not: (i) entered into any voting agreement, voting trust or any similar agreement, arrangement or understanding, with respect to any Company Securities owned by such Written Consent Party(other than as contemplated by
this Agreement), (ii) granted any proxy, consent or power of attorney with respect to any Company Securities owned by such Written Consent Party (other than as contemplated by this Agreement) or (iii) entered into any agreement,
arrangement or understanding that would prohibit or prevent it from satisfying or would materially interfere with, or is otherwise materially inconsistent with, its obligations pursuant to this Agreement. 

6. Fiduciary Duties. The covenants and agreements set forth herein shall not prevent any designee of any Written Consent Party from serving on the board
of directors of the Company or from taking any action, subject to the provisions of the Business Combination Agreement, while acting in such designee’s capacity as a director or officer of the Company. Each Written Consent Party is entering
into this Agreement solely in its capacity as the owner of such Written Consent Party’s Company Securities. Notwithstanding anything in this Agreement to the contrary, (x) the Written Consent Party shall not be responsible for the actions
of the Company or the board of directors of the Company (or any committee thereof), any subsidiary of the Company, or any officers (in their capacity as such), directors (in their capacity as such), employees (in their capacity as such) and
professional advisors of any of the foregoing (collectively, the “Company Related Parties”) or any other owner of equity securities of the Company (or Affiliate of such owner), (y) the Written Consent Party 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 Business Combination Agreement shall not be considered a breach of this Agreement (it being understood that, for the avoidance of doubt, such Written
Consent Party or his, her or its representatives other than any such representative that is a Company Related Party) shall remain responsible for any breach by such Written Consent Party or his, her or its representatives of this Agreement). 

7. Termination. This Agreement shall terminate and be of no further force or effect at the Expiration Time. Notwithstanding the foregoing sentence,
Section 4.5, this Section 7 and Section 9 shall survive any termination of this Agreement and continue in full force and effect in accordance with their respective terms.
Upon termination of this Agreement, except as provided for in Section 4.5, none of the parties hereto shall have any further obligations or liabilities under this Agreement; provided, that nothing in this
Section 7 shall relieve any party hereto of liability for any fraud or willful breach of this Agreement prior to its termination committed by such party. 

8. No Ownership Interest. Nothing contained in this Agreement shall be deemed to vest in DCRC any direct or indirect ownership or incidence of ownership
of or with respect to any Written Consent Party’s Company Securities. All rights, ownership and economic benefits of and relating to each Written Consent Party’s Company Securities shall remain fully vested in and belong to such Written
Consent Party, and DCRC shall have no authority to direct any Written Consent Party in the voting or disposition of any of Company Securities except as otherwise provided herein. 

  
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 9. Miscellaneous. 

9.1 Severability. If any term or other provision of this Agreement is invalid, illegal or incapable of being enforced by any rule of
law, or public policy, all other conditions and provisions of this Agreement shall nevertheless remain in full force and effect so long as the economic or legal substance of the Agreement is not affected in any manner materially adverse to any
party. Upon such determination that any term or other provision is invalid, illegal or incapable of being enforced, the parties hereto shall negotiate in good faith to modify this Agreement so as to effect the original intent of the parties as
closely as possible in a mutually acceptable manner in order that the transactions be consummated as originally contemplated to the fullest extent possible. 

9.2 Non-survival of Representations and Warranties. None of the representations, warranties,
covenants or agreements in this Agreement or in any schedule, instrument or other document delivered pursuant to this Agreement shall survive the Expiration Time. Notwithstanding the foregoing, this Section 9.2 shall not
limit any covenant or agreement contained in this Agreement (including Section 4.5 hereof) that by its terms is to be performed in whole or in part after the Expiration Time. 

9.3 Assignment. No party hereto may assign, directly or indirectly, including by operation of Law, either this Agreement or any of its
rights, interests or obligations hereunder without the prior written approval of the other parties hereto, except with respect to a Transfer completed in accordance with Section 2.1. Subject to the first sentence of this
Section 9.3, this Agreement shall be binding upon and shall inure to the benefit of the parties hereto and their respective successors and permitted assigns. Any assignment in violation of this
Section 9.3 shall be void. 
 9.4 Amendments and Modifications. This Agreement may be amended by the parties
hereto at any time by execution of an instrument in writing signed on behalf of each of the parties hereto. 
 9.5 Specific
Performance. The parties hereto agree that irreparable damage would occur if any provision of this Agreement were not performed in accordance with the terms hereof, and, accordingly, that the parties shall be entitled to an injunction or
injunctions to prevent breaches of this Agreement or to enforce specifically the performance of the terms and provisions hereof in the Court of Chancery of the State of Delaware, County of Newcastle, or, if that court does not have jurisdiction, any
court of the United States located in the State of Delaware without proof of actual damages or otherwise, in addition to any other remedy to which they are entitled at Law or in equity as expressly permitted in this Agreement. Each of the parties
hereby further waives (1) any defense in any action for specific performance that a remedy at Law would be adequate and (2) any requirement under any Law to post security or a bond as a prerequisite to obtaining equitable relief. 

9.6 Notices. All notices, requests, claims, demands and other communications hereunder shall be in writing and shall be given (and shall
be deemed to have been duly given upon receipt) by delivery in person, by email or by registered or certified mail (postage prepaid, return receipt requested) to the respective parties at the following addresses (or at such other address for a party
as shall be specified in a notice given in accordance with this Section 9.6): 

  
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 (i) if to DCRC, to: 

Decarbonization Plus Acquisition Corporation III 

2744 Sand Hill Road, Suite 100 

Menlo Park, CA 94025 
 Attention:
Erik Anderson, Peter Haskopoulos and Robert Tichio 
 Email: erik@wrg.vcl; phaskopoulos@riverstonellc.com; 

rtichio@riverstonellc.com 

with a copy (which shall not constitute notice) to: 

Vinson & Elkins L.L.P. 

1114 Avenue of the Americas 
 32nd Floor 
 New York, NY 10036 

Attention: Dan Komarek; Ramey Layne 

Email: dkomarek@velaw.com; rlayne@velaw.com 

(ii) if to a Written Consent Party, to the address for notice set forth opposite such Written Consent Party’s name on
Schedule A hereto, 
 with a copy (which shall not constitute notice) to: 

Solid Power, Inc. 
 486 S. Pierce
Ave. Suite E 
 Louisville, CO 80027 

Email: legal@solidpowerbattery.com 

with a copy to: 
 Wilson Sonsini
Goodrich & Rosati LLP 
 One Market Plaza 

Spear Tower, Suite 3300 
 San
Francisco, CA 94105 
 Attention: Robert O’Connor 

Email: roconnor@wsgr.com 

9.7 Governing Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware applicable
to contracts executed in and to be performed in that State. All legal actions and proceedings arising out of or relating to this Agreement shall be heard and determined exclusively in any Delaware Chancery Court; provided, that if jurisdiction is
not then available in the Delaware Chancery Court, then any such legal Action may be brought in any federal court located in the State of Delaware or any other Delaware state court. The parties hereto hereby (a) irrevocably submit to the
exclusive jurisdiction of the aforesaid courts for themselves and with respect to their respective properties for the purpose of any Action arising out 

  
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of or relating to this Agreement brought by any party hereto, and (b) agree not to commence any Action relating thereto except in the courts described above in Delaware, other than Actions
in any court of competent jurisdiction to enforce any judgment, decree or award rendered by any such court in Delaware as described herein. Each of the parties further agrees that notice as provided herein shall constitute sufficient service of
process and the parties further waive any argument that such service is insufficient. Each of the parties hereby irrevocably and unconditionally waives, and agrees not to assert, by way of motion or as a defense, counterclaim or otherwise, in any
Action arising out of or relating to this Agreement or the transactions contemplated hereby, (a) any claim that it is not personally subject to the jurisdiction of the courts in Delaware as described herein for any reason, (b) that it or
its property is exempt or immune from jurisdiction of any such court or from any legal process commenced in such courts (whether through service of notice, attachment prior to judgment, attachment in aid of execution of judgment, execution of
judgment or otherwise) and (c) that (i) the Action in any such court is brought in an inconvenient forum, (ii) the venue of such Action is improper or (iii) this Agreement, or the subject matter hereof, may not be enforced in or by
such courts. 
 9.8 WAIVER OF JURY TRIAL. EACH OF THE PARTIES HERETO HEREBY WAIVES TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW
ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY WITH RESPECT TO ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF, UNDER OR IN CONNECTION WITH THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY. EACH OF THE PARTIES HERETO (A) CERTIFIES THAT 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 THAT FOREGOING WAIVER AND (B) ACKNOWLEDGES THAT IT AND THE OTHER PARTIES
HERETO HAVE BEEN INDUCED TO ENTER INTO THIS AGREEMENT AND THE TRANSACTIONS CONTEMPLATED HEREBY, AS APPLICABLE, BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION 9.8. 

9.9 Entire Agreement; Third-Party Beneficiaries. This Agreement constitutes the entire agreement among the parties hereto with respect
to the subject matter hereof and supersedes all prior agreements and understandings, both written and oral, among the parties hereto with respect to the subject matter hereof, and is not intended to confer upon any other Person other than the
parties hereto any rights or remedies; provided, however, that the Company is an express third party beneficiary of this Agreement. 

9.10 Counterparts. This Agreement may be executed and delivered (including by facsimile or portable document format (pdf) transmission
or other electronic transmission) in one or more counterparts, and by the different parties hereto in separate counterparts, each of which when executed shall be deemed to be an original but all of which taken together shall constitute one and the
same agreement. 
 9.11 Headings. The descriptive headings contained in this Agreement are included for convenience of reference only
and shall not affect in any way the meaning or interpretation of this Agreement. 

  
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 9.12 Legal Representation. Each of the parties hereto agrees that it has been
represented by independent counsel of its choice during the negotiation and execution of this Agreement and each party hereto and its counsel cooperated in the drafting and preparation of this Agreement and the documents referred to herein and,
therefore, waive the application of any Law, regulation, holding or rule of construction providing that ambiguities in an agreement or other document will be construed against the party hereto drafting such agreement or document. Each Written
Consent Party acknowledges that Wilson Sonsini Goodrich & Rosati LLP is acting as counsel to the Company in connection with the Business Combination Agreement and the Transactions, and is not acting as counsel to any Written Consent Party.

 9.13 Expenses. Except as otherwise set forth in this Agreement, all fees and expenses incurred in connection with this Agreement
and the transactions contemplated hereby shall be paid by the party hereto incurring such expenses. 
 9.14 Further Assurances. At the
request of DCRC or the Company, in the case of any Written Consent Party, or at the request of any Written Consent Party, in the case of DCRC, and without further consideration, each party shall execute and deliver or cause to be executed and
delivered such additional documents and instruments and take such further action as may be reasonably necessary to consummate the transactions contemplated by this Agreement. 

9.15 Waiver. No failure or delay on the part of either party to exercise any power, right, privilege or remedy under this Agreement
shall operate as a waiver of such power, right, privilege or remedy; and no single or partial exercise of any such power, right, privilege or remedy shall preclude any other or further exercise thereof or of any other power, right, privilege or
remedy. Neither party shall be deemed to have waived any claim available to such party arising out of this Agreement, or any power, right, privilege or remedy under this Agreement, unless the waiver of such claim, power, right, privilege or remedy
is expressly set forth in a written instrument duly executed and delivered on behalf of such waiving party; and any such waiver shall not be applicable or have any effect except in the specific instance in which it is given. 

9.16 Several Liability. The liability of any Written Consent Party hereunder is several (and not joint). Notwithstanding any other
provision of this Agreement, in no event will any Written Consent Party be liable for any other Written Consent Party’s breach of such other Written Consent Party’s representations, warranties, covenants, or agreements contained in this
Agreement. 
 9.17 No Recourse. Notwithstanding anything to the contrary contained herein or otherwise, but without limiting any
provision in the Business Combination Agreement, this Agreement may only be enforced against, and any claims or causes of action that may be based upon, arise out of or relate to this Agreement, or the negotiation, execution or performance of this
Agreement or the transactions contemplated hereby, may only be made against the entities and Persons that are expressly identified as parties to this Agreement in their capacities as such and no former, current or future stockholders, equity
holders, controlling persons, directors, officers, employees, general or limited partners, members, managers, agents or Affiliates of any party hereto, or any former, current or future direct or indirect stockholder, equity holder, controlling
person, director, officer, employee, general or limited partner, member, manager, agent or Affiliate of any 

  
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of the foregoing (each, a “Non-Recourse Party”) shall have any liability for any obligations or liabilities of the parties to this
Agreement or for any claim (whether in tort, contract or otherwise) based on, in respect of, or by reason of, the transactions contemplated hereby or in respect of any oral representations made or alleged to be made in connection herewith. Without
limiting the rights of any party against the other parties hereto, in no event shall any party or any of its Affiliates seek to enforce this Agreement against, make any claims for breach of this Agreement against, or seek to recover monetary damages
from, any Non-Recourse Party. Notwithstanding the foregoing, nothing herein shall limit the liability of any party for fraud or willful breach committed by such party. 

[Signature pages follow.] 

  
 12 

 In witness whereof, the parties hereto have caused this Agreement to be executed as of the
date first set forth above. 
  

			
	DECARBONIZATION PLUS ACQUISITION CORPORATION III
		
	By:	 	 /s/ Peter Haskopoulos

	Name:	 	Peter Haskopoulos
	Title:	 	Chief Financial Officer, Chief Accounting Officer and Secretary
	
	SOLID POWER, INC.
		
	By:	 	 /s/ Dave Jansen

	Name:	 	Dave Jansen
	Title:	 	President

 SIGNATURE PAGE TO 

STOCKHOLDER SUPPORT AGREEMENT 

 In witness whereof, the parties hereto have caused this Agreement to be executed as of the
date first set forth above. 
  

			
	Umicore Holding Belgium
		
	By:	 	 /s/ Thomas Jansseune

	Name:	 	Thomas Jansseune
	Title:	 	Director
		
	By:	 	 /s/ Tom Vandebosch

	Name:	 	Tom Vandebosch
	Title:	 	Director
	
	 /s/ Conrad Stoldt

	Conrad Stoldt
	
	 /s/ Sehee Lee

	Sehee Lee
	
	BMW Holding B.V.
		
	By:	 	 /s/ Walter Unopp

	Name:	 	Walter Unopp
	Title:	 	Chief Executive Officer
		
	By:	 	 /s/ Glenn Ramcharan

	Name:	 	Glenn Ramcharan
	Title:	 	Authorized Representative
	
	BMW I Ventures SCS, SICAV RAIF
	
	DULY REPRESENTED BY BMW I VENTURES, INC. ITSELF
	
	DULY REPRESENTED BY MARCUS BEHRENDT
		
	By:	 	 /s/ Marcus Behrendt

	Name:	 	Marcus Behrendt
	Title:	 	Chief Executive Officer

 SIGNATURE PAGE TO 

STOCKHOLDER SUPPORT AGREEMENT 

 
			
	By:	 	 /s/ Baris Guzel

	Name:	 	Baris Guzel
	Title:	 	Principal
	
	Solvay Holdings Inc.
		
	By:	 	 /s/ Mark Dahlinger

	Name:	 	Mark Dahlinger
	Title:	 	Treasurer
	
	VOLTA SPV SPW, LLC
	By: Volta Energy Technology, LLC
	Its: Managing Member
		
	By:	 	 /s/ Jeffrey P. Chamberlain

	Name:	 	Jeffrey P. Chamberlain
	Title:	 	Manager
	
	Volta SPW CO-INVESTMENT, LP
	By: Volta Energy Storage Fund I GP, LLC
	By: General Partner
	
	By: Volta Energy Technologies, LLC
	Its: Manager
		
	By:	 	 /s/ Jeffrey P. Chamberlain

	Name:	 	Jeffrey P. Chamberlain
	Title:	 	Manager
	
	Volta ENERGY STORAGE FUND I, LLC
	By: Volta Energy Storage Fund I GP, LLC
	By: General Partner
	
	By: Volta Energy Technologies, LLC
	Its: Manager
		
	By:	 	 /s/ Jeffrey P. Chamberlain

	Name:	 	Jeffrey P. Chamberlain
	Title:	 	Manager
	
	 /s/ Douglas Campbell

	Douglas Campbell
	
	FORD MOTOR COMPANY
		
	By:	 	 /s/ Corey MacGilivray

	Name:	 	Corey MacGilivray
	Title:	 	Assistant Secretary

 SIGNATURE PAGE TO 

STOCKHOLDER SUPPORT AGREEMENT 

 Schedule A 

 

															
	 Holder
	  	Number of Shares of
Common Stock
Outstanding	 	  	Number of Shares of Series
A-1 Preferred Stock
Outstanding	 	  	Number of Shares of Series
B Preferred Stock
Outstanding	 	  	 Notice Address

	 BMW Holding B.V.
	  	 	549,370	 	  				  	 	2,746,853	 	  	 Attention: Board of Directors

Einsteinlaan 5
 2289 CC Rijswijk

The Netherlands
 Email: Walter.Knopp@bmw.nl with a copy to:

Stefan.Hienzsch@bmwgroup.com

	 BMW i Ventures SCS SICAV RAIF
	  	 	59,941	 	  				  	 	299,707	 	  	 2606 Bayshore Pkwy.
 Mountain View, CA
94043
 Email: baris@bmwiventures.com;

marcus@bmwiventures.com

	 Ford Motor Company
	  	 	332,575	 	  	 	1,660,417	 	  	 	1,662,879	 	  	 American Road
 Dearborn, MI 48121

Email: wpatton9@ford.com
 tmille22@ford.com

	 Solvay Holding Inc.
	  	 	17,774	 	  	 	1,660,417	 	  	 	88,870	 	  	 Attention: Matthew Jones
 504 Carnegie
Center
 Princeton, NJ 08540
 Email:
matthew.jones@solvay.com

	 Volta Energy Storage Fund I, LP
	  	 	128,420	 	  				  	 	642,104	 	  	 28365 Davis Pkwy STE 202
 Warrenville,
IL 60555
 Email:

jeff.chamberlain@voltaenergytechnologies.com

	 Volta SPV SPW, LLC
	  	 	181,625	 	  	 	2,767,361	 	  	 	908,130	 	  	 28365 Davis Pkwy STE 202

Warrenville, IL 60555

Email:

jeff.chamberlain@voltaenergytechnologies.com

  
 Schedule A 

															
	 Volta SPW Co-Investment, LP
	  	 	166,287	 	  				  	 	831,439	 	  	 28365 Davis Pkwy STE 202
 Warrenville,
IL 60555
 Email:

jeff.chamberlain@voltaenergytechnologies.com

	 Umicore Holding Belgium
	  				  	 	1,660,417	 	  	 	422,621	 	  	 Attention: Thomas Jansseune
 Rue du
Marais 31 Broekstraat
 B-1000 Brussels, Belgium

RPR/RMP Brussels 0401 574 852
 Email:
Thomas.Jansseune@eu.umicore.com

	 Conrad Stoldt
	  	 	2,100,000	 	  				  				  	 Attention: Conrad Stoldt
 Solid Power,
Inc.
 486 S. Pierce Ave. Suite E
 Louisville, CO 80027

Email: stoldt111@gmail.com

	 Sehee Lee
	  	 	2,100,000	 	  				  				  	 Attention: Sehee Lee
 Solid Power,
Inc.
 486 S. Pierce Ave. Suite E
 Louisville, CO 80027

Email: sehee00@gmail.com

	 Douglas Campbell
	  	 	2,100,000	 	  				  				  	 Attention: Douglas Campbell
 Solid
Power, Inc.
 486 S. Pierce Ave. Suite E
 Louisville, CO
80027
 Email: doug.campbell@solidpowerbattery.com

  
 Schedule AEX-10.2

 Exhibit 10.2 

Execution Version 

Decarbonization Plus Acquisition Sponsor III LLC 

c/o Riverstone Holdings LLC 
 712
Fifth Avenue, 36th Floor 
 June 15, 2021 

Decarbonization Plus Acquisition Corporation III 
 2744 Sand Hill
Road 
 Menlo Park, CA 
 Re: Sponsor
Letter 
 Ladies and Gentlemen: 
 This letter (this
“Sponsor Letter”) is being delivered to you in accordance with that Business Combination Agreement, dated as of the date hereof (as it may be amended, restated, or otherwise modified from time to time in accordance with its
terms), by and among Decarbonization Plus Acquisition Corporation III, a Delaware corporation (“SPAC”), DCRC Merger Sub Inc., a Delaware corporation, and Solid Power, Inc., a Colorado corporation (the
“Company”) (the “Business Combination Agreement”) and the transactions contemplated therein (the “Business Combination”). Certain capitalized terms used herein are
defined in paragraph 4 hereof. Capitalized terms used but not otherwise defined herein shall have the respective meanings ascribed to such terms in the Business Combination Agreement. 

Decarbonization Plus Acquisition Sponsor III LLC, a Delaware limited liability company (“Sponsor”), currently is the record owner of
8,390,000 shares of DCRC Founders Stock and 6,367,263 outstanding DCRC Warrants, which were acquired in a private placement that occurred simultaneously with the consummation of the SPAC’s initial public offering (the “Private
Placement Warrants” and, collectively, the “Sponsor Equity”), and certain individuals, each of whom is a member of SPAC’s board of directors (the “Insiders”) currently are the record
owners of 360,000 shares of DCRC Founders Stock and 299,404 Private Placement Warrants (collectively, the “Insider Equity”). 
 In
order to induce the Company and SPAC to enter into the Business Combination Agreement and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Sponsor and each Insider agree as follows: 

 

	1)	 Each of the Sponsor and the Insiders unconditionally and irrevocably agrees that it shall:

  

	 	a)	 vote any DCRC Class A Common Stock and DCRC Founders Stock owned by it (all such common stock, the
“Covered Shares”) in favor of the Business Combination and each other proposal related to the Business Combination included on the agenda for any meeting of stockholders, however called, (including any adjournment or
postponement thereof), and in any action by written resolution of the stockholders of SPAC, relating to the Business Combination and any transactions contemplated by the Business Combination Agreement; 

 

	 	b)	 when such meeting of stockholders is held, appear at such meeting or otherwise cause the Covered Shares to be
counted as present thereat for the purpose of establishing a quorum; 

  

	 	c)	 vote (or execute and return an action by written consent), or cause to be voted at such meeting, or validly
execute and return and cause such consent to be granted with respect to, all of such Covered Shares against any DCRC Alternative Transaction and any other action that would reasonably be expected to impede, interfere with, delay, postpone or
adversely affect the Merger or any of the other transactions contemplated by the Business Combination Agreement or result in a breach of any covenant, representation or warranty or other obligation or agreement of SPAC under the Business Combination
Agreement or result in any of the conditions set forth in Article IX of the Business Combination Agreement not being fulfilled, result in a breach of any covenant, representation or warranty or other obligation or agreement of the Sponsor
contained in this Sponsor Letter or change in any manner the dividend policy or capitalization of, including the voting rights of, any class of capital stock of SPAC (other than as contemplated by the Business Combination Agreement);

  

	 	d)	 vote (or execute and return an action by written consent), or cause to be voted at such meeting, or validly
execute and return and cause such consent to be granted with respect to, all of such Covered Shares against any change in business, management or Board of Directors of SPAC (other than in connection with the Business Combination and the other
proposals related to the Business Combination); and 

  

	 	e)	 not redeem any shares of DCRC Class A Common Stock owned by it in connection with such stockholder
approval. 

 Prior to any valid termination of the Business Combination Agreement, the Sponsor shall take, or cause to be
taken, all actions and to do, or cause to be done, all things reasonably necessary under applicable Laws to consummate the transactions contemplated by this Sponsor Letter. 

The obligations of the Sponsor specified in this paragraph 1 shall apply whether or not the Merger or any action described above is recommended
by the DCRC Board. 
  

	2)	 The Sponsor and the Insiders hereby agree and acknowledge that the terms set forth in the Letter Agreement,
including the lock-up provisions described in Section 7 of the Letter Agreement, shall continue to be in effect and are binding against such parties, and none of the Sponsor, the Insiders or SPAC shall
amend, modify, limit or terminate such obligations without the prior written consent of the Company (which may be given in its sole discretion). The Sponsor and the Insiders hereby agree and acknowledge that the terms set forth in the Letter
Agreement shall continue to be in effect and are binding against such parties, and none of the Sponsor, the Insiders or SPAC shall amend, modify, limit or terminate such obligations without the prior written consent of the Company (which may be
given in its sole discretion). 

  

	3)	 Each of the Sponsor and the Insiders agrees that, after the date hereof, and until the Effective Time, it shall
not directly or indirectly, without the prior written consent of the Company, (a) sell, assign, transfer (including by operation of law), place a lien on, pledge, dispose of or otherwise encumber any of its DCRC Founders Stock or otherwise
agree to do any of the foregoing, (b) deposit any of its DCRC Founders Stock into a voting trust or enter into a voting agreement or arrangement or grant any proxy or power of attorney with respect any of its DCRC Founders Stock that conflicts
with any of the covenants or agreements set forth in this Sponsor Letter, (c) enter into any contract, option or other arrangement or undertaking with respect to the direct or indirect acquisition or sale, assignment, transfer (including by
operation of law) or other disposition of any of its DCRC Founders Stock, (d) engage in any hedging or other transaction which is designed to, or which would (either alone or in connection with one or more events, developments or events
(including the satisfaction or waiver of any conditions precedent)), lead to or result in a sale or disposition of its DCRC Founders Stock even if such DCRC Founders Stock would be disposed of by a person other than such person or (e) take any
action that would have the effect of preventing or materially delaying the performance of its obligations hereunder. 

  
 2 

	4)	 The Sponsor hereby agrees that, during the period commencing on the date hereof and ending at the Closing, the
Sponsor shall not modify or amend any contract between or among Sponsor, anyone related by blood, marriage or adoption to the Sponsor or any affiliate of the Sponsor (other than SPAC and its Subsidiaries), on the one hand, and SPAC or any of
SPAC’s subsidiaries, on the other hand. 

  

	5)	 As used herein, (i) “Beneficially Own” has the meaning ascribed to it in
Section 13(d) of the Exchange Act. 

  

	6)	 This Sponsor Letter, the Letter Agreement, the Business Combination Agreement and the other agreements
referenced herein and therein constitute the entire agreement and understanding of the parties hereto in respect of the subject matter hereof and supersede all prior understandings, agreements, or representations by or among the parties hereto,
written or oral, to the extent they relate in any way to the subject matter hereof or the transactions contemplated hereby. This Sponsor Letter may not be changed, amended, modified or waived (other than to correct a typographical error) as to any
particular provision, except by a written instrument executed by all parties hereto. 

  

	7)	 Subject to, and conditioned upon, the occurrence of the Closing, to the fullest extent permitted by Law and the
certificate of incorporation and bylaws of SPAC, each of the Sponsor and Insiders hereby irrevocably and unconditionally waives and agrees not to assert or perfect any rights to adjustment or other anti-dilution protection with respect to the rate
that the DCRC Founders Stock held by it convert into DCRC Class A Common Stock pursuant to Section 4.3 of the amended and restated certificate of incorporation of SPAC or any other adjustment or anti-dilution protections that arise in
connection with the transactions contemplated by the Business Combination Agreement. Sponsor and each Insider further agree that they will each cause each share of DCRC Founders Stock held by it to convert into one share of DCRC Class A Common
Stock effective prior to the Effective Time in accordance with the terms and provisions set forth in the Business Combination Agreement. 

  

	8)	 No party hereto may, except as set forth herein, assign either this Sponsor Letter or any of its rights,
interests, or obligations hereunder without the prior written consent of the other parties. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or title to
the purported assignee. This Sponsor Letter shall be binding on the Sponsor, SPAC and the Company and their respective successors, heirs, personal representatives and assigns and permitted transferees. 

 

	9)	 Nothing in this Sponsor Letter shall be construed to confer upon, or give to, any person or corporation other
than the parties hereto any right, remedy or claim under or by reason of this Sponsor Letter or of any covenant, condition, stipulation, promise or agreement hereof. All covenants, conditions, stipulations, promises and agreements contained in this
Sponsor Letter shall be for the sole and exclusive benefit of the parties hereto and their successors, heirs, personal representatives and assigns and permitted transferees. 

 

	10)	 This Sponsor Letter may be executed in any number of original, electronic or facsimile counterparts and each of
such counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. 

  

	11)	 This Sponsor Letter shall be deemed severable, and the invalidity or unenforceability of any term or provision
hereof shall not affect the validity or enforceability of this Sponsor Letter or of any other term or provision hereof. Furthermore, in lieu of any such invalid or unenforceable term or provision, the parties hereto intend that there shall be added
as a part of this Sponsor Letter a provision as similar in terms to such invalid or unenforceable provision as may be possible and be valid and enforceable. 

  
 3 

	12)	 This Sponsor Letter, and all claims or causes of action based upon, arising out of, or related to this Sponsor
Letter or the transactions contemplated hereby, shall be governed by, and construed in accordance with, the Laws of the State of Delaware, without giving effect to principles or rules of conflict of laws to the extent such principles or rules would
require or permit the application of Laws of another jurisdiction. Any Action based upon, arising out of or related to this Sponsor Letter or the transactions contemplated hereby may be brought in federal and state courts located in Wilmington in
the State of Delaware, and each of the parties irrevocably submits to the exclusive jurisdiction of each such court in any such Action, waives any objection it may now or hereafter have to personal jurisdiction, venue or convenience of forum, agrees
that all claims in respect of the Action shall be heard and determined only in any such court, and agrees not to bring any Action arising out of or relating to this Sponsor Letter or the transactions contemplated hereby in any other court. Nothing
herein contained shall be deemed to affect the right of any party to serve process in any manner permitted by Law or to commence legal proceedings or otherwise proceed against any other party in any other jurisdiction, in each case, to enforce
judgments obtained in any Action brought pursuant to this paragraph. The prevailing party in any such Action (as determined by a court of competent jurisdiction) shall be entitled to be reimbursed by the
non-prevailing party for its reasonable expenses, including reasonable attorneys’ fees, incurred with respect to such Action. EACH OF THE PARTIES HERETO HEREBY IRREVOCABLY WAIVES ANY AND ALL RIGHT TO
TRIAL BY JURY IN ANY ACTION BASED UPON, ARISING OUT OF OR RELATED TO THIS SPONSOR LETTER OR THE TRANSACTIONS CONTEMPLATED HEREBY. 

  

	13)	 Any notice, consent or request to be given in connection with any of the terms or provisions of this Sponsor
Letter shall be in writing and shall be sent by express mail or similar private courier service, by certified mail (return receipt requested), by hand delivery or facsimile or e-mail transmission.

  

	14)	 This Sponsor Letter shall terminate upon the earlier of (i) the Effective Time and (ii) the
termination of the Business Combination Agreement in accordance with its terms prior to the Closing. 

  

	15)	 Each of the Sponsor and the Insiders hereby represents and warrants to SPAC and the Company as follows:
(i) to the extent such party is not a natural person, it is duly organized, validly existing and in good standing under the laws of the jurisdiction in which it is organized, and such party has all necessary power and authority to execute,
deliver and perform this Sponsor Letter and consummate the transactions contemplated hereby; (ii) this Sponsor Letter has been duly executed and delivered by such party and, assuming due authorization, execution and delivery by the other
parties to this Sponsor Letter, this Sponsor Letter constitutes a legally valid and binding obligation of such party, enforceable against such party in accordance with the terms hereof (except as enforceability may be limited by bankruptcy Laws,
other similar Laws affecting creditors’ rights and general principles of equity affecting the availability of specific performance and other equitable remedies); (iii) the execution and delivery of this Sponsor Letter by such party does not,
and the performance by such party of its obligations hereunder will not, (A) in the case of the Sponsor, conflict with or result in a violation of the organizational documents of the Sponsor, or (B) require any consent or approval that has
not been given or other action that has not been taken by any third party (including under any contract binding upon such party’s DCRC Founders Stock or Private Placement Warrants, as applicable), in each case, to the extent such consent,
approval or other action would prevent, enjoin or materially delay the performance by such party of its obligations under this Sponsor Letter; (iv) there are no Actions pending against such party or, to the knowledge of such party, threatened
against such party, before (or, in the case of threatened Actions, that would be before) any arbitrator or any Governmental Authority, which in any manner challenges or seeks to prevent, enjoin or materially delay the performance by such party

  
 4 

	 	
of its obligations under this Sponsor Letter; (v) except for fees described on Section 5.12 of the DCRC Disclosure Schedules, no financial advisor, investment banker, broker, finder or
other similar intermediary is entitled to any fee or commission from such party or its controlled affiliates in connection with the Business Combination Agreement or the transactions contemplated thereby based upon any arrangement or agreement made
by such party or its controlled affiliates for which SPAC or any of its controlled affiliates or, following the Closing, the Company or any of their controlled affiliates, would have any obligations or liabilities of any kind or nature;
(vi) such party has had the opportunity to read the Business Combination Agreement and this Sponsor Letter and has had the opportunity to consult with its tax and legal advisors; (vii) such party has not entered into, and shall not enter
into, any agreement that would restrict, limit or interfere with the performance of such party’s obligations hereunder; (viii) such party has good title to all of its DCRC Founders Stock and Private Placement Warrants, and there exist no
Liens or any other limitation or restriction (including, without limitation, any restriction on the right to, as applicable, vote, sell or otherwise dispose of such DCRC Founders Stock or Private Placement Warrants) affecting any such DCRC Founders
Stock or Private Placement Warrants, other than pursuant to (A) this Sponsor Letter, (B) the amended and restated certificate of incorporation of SPAC, (C) the Business Combination Agreement, (D) the Amended and Restated Limited
Liability Company Agreement of the Sponsor, (E) the Letter Agreement or (F) any applicable securities laws; and (x) the Sponsor Equity or Insider Equity owned by such party are the only SPAC Founder Shares, Private Placement Warrants
or other equity securities of SPAC Beneficially Owned by such party as of the date hereof. 

  

	16)	 Each of the Sponsor and Insiders hereby agrees and acknowledges that: (i) SPAC and, prior to any valid
termination of the Business Combination Agreement, the Company would be irreparably injured in the event of a breach by the Sponsor and Insiders of its obligations under paragraphs 1 and 2, as applicable, of this Sponsor Letter, (ii) monetary
damages may not be an adequate remedy for such breach and (iii) the non-breaching party shall be entitled to injunctive relief, in addition to any other remedy that such party may have in law or in
equity, in the event of such breach. 

  

	17)	 If, and as often as, (a) there is any stock split, stock dividend, combination or reclassification that
results in the Sponsor acquiring new DCRC Founders Stock, DCRC Class A Common Stock, Private Placement Warrants or other equity securities of SPAC, (b) the Sponsor purchases or otherwise acquires Beneficial Ownership of any DCRC Founders
Stock, Private Placement Warrants, DCRC Class A Common Stock or other equity securities of SPAC after the date of this Sponsor Letter, or (c) Sponsor acquires the right to vote or share in the voting of any DCRC Founders Stock, DCRC
Class A Common Stock or other equity securities of SPAC after the date of this Sponsor Letter, then, in each case, such DCRC Founders Stock, DCRC Class A Common Stock, Private Placement Warrants and other equity securities of SPAC acquired
or purchased by the Sponsor shall be subject to the terms of this Sponsor Letter. 

  

	18)	 Each of the parties hereto agrees to execute and deliver hereafter any further document, agreement or
instrument of assignment, transfer or conveyance as may be necessary or desirable to effectuate the purposes hereof and as may be reasonably requested in writing by another party hereto. 

[Signature page follows.] 

  
 5 

 
			
	Sincerely,
	
	DECARBONIZATION PLUS
	ACQUISITION SPONSOR III LLC
		
	By:	 	 /s/ Peter Haskopoulos

		 	Name: Peter Haskopoulos
		 	Title: Authorized Person
		
		 	 /s/ Jennifer Aaker

		 	Name: Jennifer Aaker
		
		 	 /s/ Jane Kearns

		 	Name: Jane Kearns
		
		 	 /s/ James AC McDermott

		 	Name: James AC McDermott
		
		 	 /s/ Jeffrey H. Tepper

		 	 Name: Jeffrey H. Tepper

  

			
	Acknowledged and Agreed:
	
	DECARBONIZATION PLUS ACQUISITION
	CORPORATION III
		
	By:	 	 /s/ Peter Haskopoulos

		 	Name: Peter Haskopoulos
		 	 Title: Chief Financial, Chief Accounting

		 	 Officer and Secretary

  

			
	Acknowledged and Agreed:
	
	SOLID POWER, INC.
		
	By:	 	 /s/ Douglas Campbell

		 	Name: Douglas Campbell
		 	Title: Chief Executive Officer

 [Signature Page to the Sponsor Letter Agreement] 

  
 6

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