A French minerals company is buying a British startup in a tie-up that could produce enough lithium carbonate to power 500,000 electric vehicles a year.

Imerys, a Paris-based industrial supplier, announced Thursday it had acquired 80% of British Lithium, a small private company that's found a way to extract lithium from the ground in Cornwall, in the southwest of England.

The companies will form a joint venture to develop a mine that they estimate will ultimately churn out enough lithium to produce 20,000 tons of lithium carbonate a year, which could be used in batteries for half a million electric cars, Imerys said in a statement.

That rate of production is expected to be reached "by the end of the decade, meeting roughly two-thirds of Britain's estimated battery demand by 2030," the firm said.

That year is important as Britain is set to ban the sale of new petrol and diesel vehicles in 2030, forcing manufacturers to switch to electric vehicles. A ban on hybrids is slated to start from 2035.

The combination of the new facility and an existing one in France "would make Imerys the largest integrated lithium producer in Europe, representing more than 20% of the announced European lithium output by 2030," the company said.

Terms of the deal were not disclosed. But the project is expected to cost more than 660 million euros ($720.5 million) in investment, according to a person familiar with the matter.

The move is timely for another reason: Next year, tougher "rules of origin" requirements for businesses will take effect under a post-Brexit trade deal.

They will require that 45% of the value of electric vehicles traded between Britain and the European Union are sourced from one of the two regions in order to avoid costly tariffs.

Last month, Stellantis, which owns brands such as Peugeot and Fiat, warned that UK car factories — and thousands of jobs — were at risk if the government did not renegotiate terms of the Brexit trade agreement.

The new mine could also help alleviate fears about the future of auto manufacturing in Britain, exacerbated by the collapse of homegrown battery startup Britishvolt. Industry experts have said there is an urgent need to attract more battery manufacturers to the country.

Once the new facility is up and running, it will likely also provide a big economic boost to Cornwall, the coastal English county that was a global mining center until the late 19th century.

In recent years, local officials have pushed to revive old mining sites that shuttered in the face of global competition. The area remains rich in natural resources, including tin, which is crucial for the making of electronics.

The deposit of lithium being developed there is set to be the largest in the country, according to Imerys.