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.
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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.