Inside a high-security chemical plant, a mysterious project named “Lionheart” is helping prepare Germany for what could be its biggest crisis since the invasion of Ukraine.

Under heavy snowfall, workers bring crates of brinewater from the Rhineland into the factory in Frankfurt and convert it into battery-grade lithium, labelled “V-Lion”.

If it sounds like something out of a Cold War-era thriller, you would not be wildly far off the mark.

Lithium, also known as white gold, is a crucial ingredient in mobile phone and electric car batteries. Half of Germany’s lithium batteries are sourced from China, even though Beijing poses a growing security threat to Europe.

Project Lionheart’s goal is to help Germany scale back its heavy reliance on Chinese batteries.

It comes as European tensions rise with Beijing over its apparent desire to invade Taiwan and its tacit support for Vladimir Putin’s war on Ukraine.