Lithium Americas made a $400-million stock-and-cash offer for Argentina-focused lithium developer Millennial Lithium on Monday, seeking to outbid China's Contemporary Amperex Technology Co Limited (CATL) for a promising source of the ultra-light battery metal.

The bidding war comes amidst surging demand for lithium ion batteries used to power electric vehicles (EVs), with many global automakers planning to have fully electric fleets by 2035. There are not enough global lithium projects under development, though, to meet that target.

Millennial's Pastos Grandes lithium project in Argentina is "an asset that we see a lot of value in, and we feel we can unlock that value," Jon Evans, the Lithium Americas CE, told Reuters.

The company's experience building the Cauchari lithium project with Ganfeng Lithium Co near Pastos Grandes should be appealing to Millennial's shareholders, Evans said. CATL, the world's largest EV battery manufacturer, does not produce lithium.

Lithium Americas is also developing the Thacker Pass lithium mine in Nevada. That and Cauchari will remain the company's focus, with Millennial a "potential future development," Evans said.

Each Millennial shareholder would receive C$4.70 ($3.80) per share, payable in Lithium Americas common shares, and C$0.001 in cash. Millennial shareholders will own about 9.9% of Lithium Americas, based on the company's closing price on Friday.

Shares of Millennial rose 27% in Monday morning trading, while shares of Lithium Americas fell about 2%.

A buyout of Millennial would give Lithium Americas an additional 24 000 t/y of battery-quality lithium carbonate for 40 years.

The Lithium Americas offer trumped a C$3.85 per share bid that CATL made in September, the largest Lithium Americas shareholder.

Evans said he did not see the Lithium Americas offer as reflective of any broader fight between two Chinese companies for Argentina lithium assets.

"There's no geopolitical angle at all. We purely look at this as an exciting future," he said.

Millennial has given CATL until November 16 to revise the offer to match the proposal from Lithium Americas.