Dr. Andy Robinson reports

STANDARD LITHIUM'S EAST TEXAS DRILLING PROGRAM DELIVERS NEW HIGHEST CONFIRMED GRADE LITHIUM BRINE IN NORTH AMERICA

Standard Lithium Ltd. has drilled and sampled, to the best of its knowledge, a new highest confirmed lithium grade brine in North America, with a grade of 663 milligrams per litre lithium. The results reflect lithium sample analyses from a newly drilled well from the company's significant expansion work in the east Texas Smackover region.

Dr. Andy Robinson, president and chief operating officer of Standard Lithium, commented: "We continue to be very excited by the quality and scale of the lithium brine assets we're adding in east Texas. The lithium sample analysis from a newly drilled well delivered, to the best of our knowledge, a new highest-grade lithium brine concentration in North America and confirmed that we are securing the highest-grade lithium brine resource outside of Chile and Argentina.

"We continue to expand our footprint in the east Texas Smackover and derisk the opportunity with additional drilling, sampling and definition work.

"East Texas is a significant addition to our two more advanced projects in Arkansas, the phase 1A and South West Arkansas projects," added Dr. Robinson. "We expect our east Texas landholdings to form a substantially larger and higher-grade lithium brine project for future production. Standard Lithium will continue to progress its portfolio of projects to help meet U.S. demand for lithium over the next decade."

Strategic importance

The Smackover formation represents North America's premier lithium brine asset, with grades comparable to certain resources in South America. As detailed in the company's definitive feasibility study, results for the phase 1A project in El Dorado, Ark., target production of 5,400 tonnes per annum of battery-quality lithium carbonate over a 25-year operating life, with an average lithium grade of 217 milligrams per litre. The preliminary feasibility study for the company's South West Arkansas project outlines plans for at least 30,000 tonnes per annum of battery-quality lithium hydroxide over a 20-year operating life, with an average reported lithium grade of 437 milligrams per litre.

Lithium grades in the company's projects indicate an increasing trend moving westward from phase 1A to the South West Arkansas project and finally into east Texas. In Standard Lithium's experience, higher lithium grades in brine are directly correlated with lower capital and operating expenses per tonne of lithium produced, thereby enhancing the economic viability of potential projects.

Analysis and testing details

The Standard Lithium team, comprising technically diverse Smackover specialists and a robust team of land professionals, has been working in the Smackover formation in east Texas for over 3.5 years. The company shared initial sample analysis from expansion work completed in the latter half of 2022 and early 2023 (see news release dated March 28, 2023).

The data provided in this news release are from a newly drilled well completed in the east Texas Smackover (ETX new well No. 2). Brine samples collected from ETX new well No. 2 are provided in the attached table. These samples were analyzed, performed and reported by Western Environmental Testing Laboratories of Sparks, Nev., a third party, accredited testing facility. Additional representative lithium brine analyses from other lithium brine projects in North America are provided for context.

Quality assurance

Steve Ross, PGeol, a qualified person as defined by National Instrument 43-101, has reviewed and approved the relevant scientific and technical information that forms the basis for this news release. Mr. Ross is a consultant to the company.

About Standard Lithium Ltd.

Standard Lithium is a leading near-commercial lithium development company focused on the sustainable development of a portfolio of lithium-brine-bearing properties in the United States. The company prioritizes brine projects characterized by the highest-grade resources, robust infrastructure, skilled labour and streamlined permitting. The company aims to achieve sustainable, commercial-scale lithium production through the application of a scalable and fully integrated direct lithium extraction and purification process. The company's flagship projects, the phase 1A project and the South West Arkansas project, are located on the Smackover formation in southern Arkansas near the Louisiana state line, a region with a long-standing and established brine processing industry. The company has also identified a number of highly prospective lithium brine project areas in the Smackover formation in east Texas and began an extensive brine leasing program in the key project areas. In addition, the company has an interest in certain mineral leases located in the Mojave desert in San Bernardino county, California.

Standard Lithium trades on both the TSX Venture Exchange and the NYSE American under the symbol SLI and on the Frankfurt Stock Exchange under the symbol S5L.

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