https://www.nature.com/articles/s41561-024-01480-8
TLDR:
They have found evidence of elemental oxygen production in a polymetallic nodule-covered abyssal seafloor in the Pacific Ocean.
However, for now they have identified neither how the dioxygen is produced nor which is the source of energy for this.
Their hypothesis for how the dioxygen is produced is that there may be a redox reaction between some metals in the polymetallic nodules, which might cause an electric current that could electrolyze the water.
However this hypothesis has very little value until an energy source is identified for it.
The voltage in a battery is not produced between metals in any state, but only between an oxidized metal and a reduced metal. The simplest batteries, like the AA or AAA batteries with saline or alkaline electrolyte, produce voltage by the reaction between reduced zinc and oxidized manganese.
So for a natural battery to form in those polymetallic nodules, some of the metals must be in a reduced state, and for them to be reduced, somewhere there should have been an energy source to provide energy for their reduction.
That must be determined to understand what happens.