Diversified mining company Rio Tinto Group is deepening its presence in the battery metals space, announcing on Monday an agreement with Chile’s State-owned Codelco to jointly develop a major lithium project in the Salar de Maricunga.

Under the deal, Rio Tinto will acquire a 49.99% stake in Salar de Maricunga – the company through which Codelco holds its licences and mining concessions – by funding project development and studies amounting to $900-million. 

The transaction expands Rio’s critical minerals footprint in the 'Lithium Triangle' of South America, which CEO Jakob Stausholm believes is the right address for lithium mining. "The brines in the Lithium Triangle in Latin America – are, in my view, the right place for the world to find its lithium and for the miners the right place to get to the bottom of the cost curve," he told a conference last week.

Rio Tinto will invest $350-million in Maricunga to advance studies and resource assessments to support a final investment decision, and a further $500-million once the partners decide to proceed with construction. A $50-million milestone payment is also on the table if the venture delivers first lithium by the end of 2030.

“We are honoured to be chosen as Codelco’s partner to deliver a world-class project using direct lithium extraction technology in the Salar de Maricunga, leveraging our expertise as a leading producer of lithium for the global market,” said Stausholm on Monday. 

“Codelco is a strategic partner for Rio Tinto in Chile, with this agreement building on our copper joint ventures. We aim to bring significant investment and long-term benefits to the Atacama region as we advance Maricunga and Nuevo Cobre together.”

The Salar de Maricunga, located in Chile’s Atacama region, hosts one of the highest-grade lithium brine resources globally, with strong potential for scalable, low-cost production. The joint venture plans to use DLE to maximise recovery and minimise environmental impact—especially water use, a sensitive issue in the arid region.

Codelco chairperson Máximo Pacheco said the partnership with Rio Tinto marked an important step in the company’s lithium diversification strategy. “This project continues our lithium diversification strategy, which is essential for the energy transition, with a world-class partner in Rio Tinto that represents the most attractive option for Codelco and the country,” Pacheco said.

The transaction is expected to close by the end of the first quarter of 2026, subject to regulatory approvals and customary closing conditions.

Analysts at CreditSights said the investment aligns with Rio Tinto’s strategy to expand into lithium, while reducing its reliance on iron-ore. “Although this investment does not significantly impact the company's credit metrics, capital expenditures are expected to rise if the joint venture partners proceed with the project,” they said.

“Rio Tinto is aggressively pursuing lithium projects despite current low prices, while other major miners focus on acquiring copper assets,” the analysts added. 

“Although lithium prices have fallen due to oversupply, Rio Tinto’s strategic acquisitions and partnerships aim to position the company favorably, with management betting on market tightening and increased demand toward the end of the decade.”