UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE

SECURITIES EXCHANGE ACT OF 1934

For the month of December, 2025

NOVONIX LIMITED

(Translation of registrant’s name into English)

Level 38

71 Eagle Street

Brisbane, QLD 4000 Australia

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20‑F or Form 40‑F.

Form 20-F ☒ Form 40-F ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

EXHIBIT INDEX

Exhibit No. Description

Exhibit 99.21 Appendix 3X (Initial Director's Interest Notice) filed December 15, 2025

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: December 16, 2025

EX-99.1

Appendix 3X

Initial Director’s Interest Notice

EXHIBIT 99.1

Rule 3.19A.1

Appendix 3X

Initial Director’s Interest Notice

Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public.

Introduced 30/9/2001.

We (the entity) give ASX the following information under listing rule 3.19A.1 and as agent for the director for the purposes of section 205G of the Corporations Act.

Part 1 - Director’s relevant interests in securities of which the director is the registered holder

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part.

• See chapter 19 for defined terms.

11/3/2002 Appendix 3X Page 1

Appendix 3X

Initial Director’s Interest Notice

Part 2 – Director’s relevant interests in securities of which the director is not the registered holder

In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust

Part 3 – Director’s interests in contracts

Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part.

• See chapter 19 for defined terms.

Appendix 3X Page 2 11/3/2002