The lithium-ion battery is an electrochemical wunderkind. We use it for everything, whether it’s mundane gadgetry like phones and laptops or more extreme applications like electric ships and helicopters on Mars. The Li-ion battery is so important to modern life that it earned the trio of chemists who invented it a Nobel Prize last year. But somewhere along the way, the battery industry developed a cobalt dependency.
Cobalt is a scarce, toxic, and lustrous mineral that is found in the negatively charged electrode—or cathode—of almost all lithium-ion batteries used today. It’s expensive, heavy, and linked to unethical mining practices, wild price swings, and a tenuous global supply chain. It’s no wonder so many battery manufacturers want to kick their cobalt habit. But the material plays a crucial role in stabilizing batteries and boosting their energy density. Although experimental cobalt-free cells exist, they’ve all had major performance issues like limited lifetimes and slower charge rates—until now.
In July, a team of three researchers from the University of Texas reported the results from tests using a new cathode chemistry that eliminates cobalt entirely. They used their nickel-rich cathode in a small experimental lithium-ion pouch cell about the size of a deck of cards. Although the battery had a slightly lower energy density than typical cobalt batteries, it was able to operate at higher voltages and at similar charge rates. Even after 1,000 full charge-discharge cycles—the typical lifetime for a commercial battery—the experimental cell performed as well as comparable cells with cobalt cathodes.
“A significant number of people say that cobalt is essential, and that if you remove it you won’t be able to get the same kind of performance,” says Arumugam Manthiram, the director of the Texas Materials Institute at the University of Texas, Austin, and the lead author of the paper. “We are the first to show that it’s possible to eliminate cobalt without compromising performance.”
Cobalt can account for a fifth of the material in a lithium-ion cathode, which typically comes in one of two flavors: NMC (nickel manganese cobalt oxide) or NCA (nickel cobalt aluminum oxide). The cobalt in these batteries has a stabilizing effect and prevents cathode corrosion that can lead to a battery fire. It can also boost a battery’s charge rates, but the raw material is pretty expensive and hard to come by. It has some social problems too. Nearly two-thirds of the world’s cobalt is mined in the Democratic Republic of Congo as a secondary product of large-scale nickel and copper mining. But the DRC also has a large contingent of independent or artisan miners that effectively operate without any oversight. This has led to a multitude of human rights abuses in Congolese cobalt mines, including the use of child labor.
The cathode developed by Manthiram and his colleagues sidesteps cobalt by increasing nickel content; it makes up 89 percent of the metal in the cathode by weight. Their cell combines the ingredients of NMC and NCA cathodes to create a cobalt-free NMA (nickel manganese aluminum oxide) cathode. Although the team is not the first to develop a cobalt-free or high-nickel cathode, Manthiram says it’s the first one that doesn’t also have major performance drawbacks like short battery life and low energy density.