Smackover Lithium Files Definitive Feasibility Study for Its South West Arkansas Project, North America’s Highest-Grade Reported Lithium Brine Reserve

Smackover Lithium, a 55:45 owned Joint Venture (“JV”) between Standard Lithium Ltd. (“Standard Lithium” or the “Company”) (TSXV: SLI) (NYSE.A: SLI) and Equinor (“Equinor”), announced that the Definitive Feasibility Study (“DFS” or the “Report”) for its South West Arkansas (“SWA”) project (the “Project” or “SWA Project”) has been filed.

All figures are in US dollars unless otherwise stated. All terms not otherwise defined have the meaning given to them under the CIM Definition Standards for mineral resources and mineral reserves.

The DFS contemplates production capacity of 22,500 tonnes per annum of battery-quality lithium carbonate over a 20-year modeled operating life, producing 447,000 tonnes (Proven Reserves) of lithium carbonate equivalent (“LCE”), or 38% of the in-situ Measured and Indicated Resources of 1,177,000 tonnes LCE. The Project will begin production at an average lithium concentration of 549 mg/L, and will process 0.50 km3 of brine over its modelled 20-year life at an average lithium concentration of 442 mg/L.

The Report is highlighted by a 20.2% unlevered pre-tax internal rate of return (“IRR”), with competitive average cash operating costs of $4,516/t and all-in costs of $5,924/t over the operating life, and an all-in Class III capex estimate of $1.45 billion, which includes a 12.3% Monte Carlo risked contingency.

The Project maintains strong support from the local community, the state of Arkansas and the U.S. government. The Project would mark the first commercial Direct Lithium Extraction (“DLE”) operation in the United States and the first lithium production in the Smackover Formation. It is intended as the first of several projects to be developed by the JV throughout the Smackover Formation, and it is envisaged that the major design decisions and learnings from this first greenfield facility will form the basis for future expansion phases or projects, including in East Texas.

The development schedule for the Project is estimated at 34 months from start of construction to the commercial operation date.   The principal recommendation from the DFS is that the Project is ready to progress to a final investment decision (“FID”). Construction is expected to commence in 2026 shortly after FID, with first production targeted in 2028.

The Report is available for review under the Company’s profile on SEDAR+ at www.sedarplus.ca and on the Company’s website at www.standardlithium.com/projects/arkansas-smackover.   For highlights of this Report, please refer to the Company’s press release dated 3 September 2025.

Qualified Person

All scientific and technical disclosure in this news release was reviewed and approved by Mr. Stephen Ross, P.Geo., British Columbia, Vice President of Resource Development for Standard Lithium and a Qualified Person for purposes of, and as that term is defined in, National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI 43-101”). Mr. Ross is not independent of the Company.

Smackover Lithium | www.standardlithium.com/projects/arkansas-smackover