Nasdaq- and TSX-listed Perpetua Resources has announced an antimony supply deal with US energy storage company Ambri, which counts Indian oil conglomerate Reliance Industries, billionaire Bill Gates and investment management firm Paulson & Co among its investors.

The Stibnite gold project, in central Idaho, will supply Ambri, which has developed an antimony-based liquid metal battery for the stationary, long-duration, daily cycling energy storage market.

"This agreement is a meaningful step in support of the current administration's goal of achieving 100% clean electricity in the US, while prioritising the domestic manufacturing of battery technology," said Perpetua CEO Laurel Sayer.

The signing of the supply agreement coincides with Ambri's announcement that it secured $144-million in new financing led by Reliance New Energy Solar, a subsidiary of Reliance Industries, Paulson & Co., Gates, Fortistar and Goehring & Rozencwajg Associates.

Further, Reliance has been chosen as Ambri's joint venture partner for battery development in India as part of its broader plans to invest $10-billion to develop the Dhirubhai Ambani Green Energy Giga Complex. 

The capital raise will be used to accelerate the commercialisation of Ambri's leading liquid metal battery and build a domestic manufacturing facility to fundamentally change the way power grids operate.

Ambri executive chairperson Dan Leff commented in a statement that the company recognised the strategic importance of antimony as a metal in the green energy transformation.

“[We] support the responsible production of critical metals, especially within the United States,” he said.

The Stibnite agreement contains certain standard commercial terms which contain options for treatment, refining, transport, and tolling charges. The minimum commitment of Perpetua's antimony production for Ambri's battery manufacturing is expected to power over 13 GWh of battery capacity, which is equivalent to more than eight times the total additions to the entire US energy storage market in 2020.

The agreement contains a provision for fixed pricing and higher volumes that can be mutually agreed to by both parties. Perpetua and Ambri will also collaborate to identify opportunities to lower carbon emissions in their respective operations with the use of renewable energy combined with battery storage.

"Today's agreement directly links the redevelopment of the Stibnite gold project – and the restoration of the site - to a new battery manufacturing partner that is poised to play a critical role in reducing carbon emissions," said Sayer.

"Our partnership with Ambri significantly increases the strategic and long-term value of our project and breathes further life into our guiding ESG principles."

John Paulson-backed Perpetua is focused on the exploration, site restoration and redevelopment of gold/antimony/silver deposits in the Stibnite-Yellow Pine district of central Idaho that are encompassed by the Stibnite gold project. 

The company expects to reach a mining decision at Stibnite in early 2023. The project is under scrutiny from the US Environmental Protection Agency over fears it would pollute Native American fishing grounds.