"A billion batteries’ worth of rare metals lie on the bottom of the sea"

And we don't know what happens when we roil up the seabed.
E to the S to the G, it's complicated.
From MotorTrend, June 16:

Rolling in the Deep: Metals for Future EV Batteries Could Come From the Ocean Floor

In my April "Green Issue" column, I fearlessly predicted that the long-term carbon-neutral future of personal transportation would be electric vehicles powered by renewable energy. Projections by Deloitte and Bloomberg New Energy Finance Group peg global EV penetration at around 20 percent by 2030, rising to 57 percent by 2040. If accurate, we could have a billion electric vehicles on the road by 2050.

Great news for the environment, right? Not when it comes to sourcing metals for a billion battery packs. Using current state-of-the-art NMC811 battery chemistry (nickel-manganese-cobalt in an 8:1:1 ratio), each EV with a 75-kW-hr battery pack requires 124 pounds of nickel, 18 pounds of lithium, and about 15 pounds each of manganese and cobalt, plus some 187 pounds of copper for connectors and harnesses.

Boosting mining operations to cover a billion such EV batteries in the face of steadily declining ore grades will force establishment of new strip or tunnel mines and/or wider or deeper mining of additional rock, which will require more energy and chemicals, contaminate more water, generate more toxic waste, cause environmental damage, and/or displace additional wildlife and human populations. Many of these minerals also happen to be located in not-so-nice parts of the world—meaning making ethically challenging deals with political strongmen who care more for looting the till than for human rights.

What about mining the seabed? Massive, mineral-rich sulfide deposits form around hydrothermal vents lining volcanic ridges on the seafloor. But extracting them threatens the vibrant ecosystem these vents support, and mechanical mining of these sulfides or the cobalt crusts in the deep ocean is extremely expensive.

There is a cheaper, easier-to-obtain seabed metal source, though.

Vast areas of the abyssal (13,000 to 20,000 feet deep) seafloor, like the 1.8 million square-mile Clarion-Clipperton Zone between Hawaii and Baja California, are covered in potato-sized polymetallic nodules. These form over millennia as water-soluble manganese from sediment pore water on the seafloor causes insoluble manganese hydroxide to precipitate on pieces of fish bones or teeth. These hydroxide materials then scavenge soluble copper, cobalt, and nickel from these same mineral-rich waters.

Each nodule is a BEV starter kit composed of 29.2 percent manganese, 1.3 percent nickel, 1.1 percent copper, and 0.2 percent cobalt. The rest is ammonium sulphate (fertilizer). It's easier and cleaner to isolate the metals from nodules than from land-based ores....

....MUCH MORE

Radio New Zealand had a story the day before MotorTrend, June 15:

Seabed mining debate stirs again in the Pacific

A group of researchers says damages from seabed mining would be significantly less than land-based mining.

It's a key finding in a report touted by the government of Nauru and Canadian company DeepGreen Metals.

DeepGreen has a license to explore the seabed of international waters in the Clarion Clipperton Zone, and has three exploration contracts which are sponsored by Nauru, Kiribati and Tonga.
Johnny Blades reports.

Proponents of seabed mining have the Pacific firmly in their sights, yet the industry has yet to find its feet.
Holding it back is the great range of unknowns about the potential environmental impacts of mining for metals contained in nodules on the seafloor.

One of the report's authors, marine biologist Dr Steven Katona, says these metals are required to produce batteries for electric vehicles to help the world's transition to a zero-carbon economy.
"Make no mistake...there will be damage to the environment down there. It's absolutely clear, You cannot remove 85 percent of the nodules from an area that large (500 km sq) without having substantial damage."...MORE

While MongaBay says NO:
Deep-sea mining: An environmental solution or impending catastrophe?

We've been tracking the issues for a decade, when we saw this tidbit in 2012 Screw the Asteroids: "DeepGreen strikes deal with Glencore for undersea mining metals" the reaction was:

What...the...hell?
I'm a bit late getting to this but when you see "Glencore" and a privately held Vancouver company in the same headline it gets my attention....

And then there was "Maersk Begins Support Operation for Deep Sea Mining Company, DeepGreen" in 2018.

And last year: "Mining the Sea: DeepGreen Raising $150 million"

If interested see also:
"History’s Largest Mining Operation Is About to Begin"
"China Leads Countries Plumbing the Ocean Depths for Metallic Rocks"
Japan is pretty far advanced as well. ...
"We Are About to Start Mining Hydrothermal Vents on the Ocean Floor" (now with added alchemist's fallacy"