So what role does the cobalt play? “When the lithium ion is taken out of the oxide (in the cathode), the lithium ion has a positive charge, so the cobalt changes its oxidation state, so that the oxide stays electrically neutral. During discharging, exactly the opposite happens,” explained Abraham.

“In a lithium ion battery, what we are trying to do during charging is to take the lithium ions out of the oxide and intercalate, or insert them into a graphite electrode. One of the simplest cathode materials is lithium-cobalt-oxide (Li-Co-O 2) and he chose it as an example.

To understand the specifics better, Design News asked Senior Scientist Daniel Abraham from Argonne National Laboratory to explain how cobalt comes into play. The cathode electrode stores the lithium ions through electrochemical intercalation-a process by which the lithium ions are inserted into or removed from lattice sites within the cathode material structure. Because the working voltage of a battery is determined by the difference in electrochemical potential between the cathode and the anode, the cathode must be another material than graphite, and the choice of this material controls most of the performance characteristics of the lithium ion battery. Carbon graphite is the most common anode electrode material as it has an ordered layered structure that can accommodate and store the small lithium ions between its layers. This is where the electrochemistry comes in. During discharging, the lithium ions travel back from the anode to the cathode, in the process giving up electrons to the anode which travel via an external circuit to power an electronic device before returning via the circuit to the cathode. When the battery is being charged, the lithium ions pass from the positive cathode electrode, through the polymer membrane, to the negative anode electrode. A rechargeable lithium ion battery consists of two electrodes that are immersed in an electrolyte solution and that are separated by a permeable polymer membrane. Understanding the role of cobalt in a lithium ion battery requires knowing what parts make up the battery cell, as well as understanding some electrochemistry. Most cobalt production comes as a byproduct of copper mining as from this open pit mine in the Democratic Republic of the Congo (Image source: Katanga Mining Limited) HIU indicated that lithium reserves would be “much less strained” if the current production levels could be dramatically up-scaled.

The situation for cobalt, a metal that is typically produced as a byproduct of copper and nickel mining, appears to be especially dire as “…the cobalt demand by batteries might be twice as high as the today’s identified reserves,” the HIU report stated. A new report by the Helmholtz Institute Ulm (HIU) in Germany suggests that worldwide supplies of lithium and cobalt, materials used in electric vehicle batteries, will become critical by 2050.

Cathode anode battery