Nickel is a silvery-white, magnetic transition metal that sits at atomic number 28 on the periodic table and turns up in an astonishing range of places, from the molten core of the Earth to the cathode of an electric-vehicle battery. It is the fifth most abundant element on the planet by mass, though most of it is locked thousands of kilometers below your feet. What makes nickel fascinating is the sheer variety of roles it plays: it strengthens steel, powers stars at the end of their lives, feeds ancient microbes, triggers a uniquely human allergic reaction, and is now central to the global push for cleaner energy.
Forged in Dying Stars
Every atom of nickel on Earth was created inside a star. Nickel-56, a radioactive isotope, is one of the most important products of thermonuclear supernovae. When a white dwarf in a binary star system explodes as a Type Ia supernova, the blast typically produces around half a solar mass of radioactive nickel-56. That isotope decays first to cobalt-56 and then to stable iron-56, and the energy released during that chain of decay is what makes supernovae shine for weeks after the initial explosion. Observations of the nearby supernova SN2014J detected gamma-ray lines from nickel-56 decay only about 20 days after the explosion, far earlier than models predicted, suggesting that some of the freshly made nickel was near the outer edge of the expanding debris cloud rather than buried deep inside it.1PubMed. Early ⁵⁶Ni decay gamma rays from SN2014J suggest an unusual explosion That finding shook up assumptions about how these explosions unfold and hinted that asymmetry or a belt of accreted helium from a companion star might be involved.
Because so much nickel-56 is produced in supernovae and eventually decays to iron, the cosmic abundances of iron and nickel are tightly linked. This is why nickel is the second most common metal in iron meteorites. Early geochemical work on meteorites proposed that the metallic cores of their parent bodies started as a homogeneous iron melt containing roughly 11 percent nickel, and that the variation in nickel content among different iron meteorites reflects the gradual crystallization and separation of that melt over time.2Geochimica et Cosmochimica Acta. Differentiation in the iron-nickel core of a parent meteorite body More recent isotopic studies have refined this picture, showing that differences in nickel isotope signatures between classes of meteorites are better explained by mineral-scale fractionation processes during cooling than by any patchiness in the original solar nebula.3Geochimica et Cosmochimica Acta. Thermal equilibration of iron meteorite and pallasite parent bodies recorded at the mineral scale by Fe and Ni isotope systematics
The Metal That Lives Beneath Us
Earth’s core, like those ancient meteorite parent bodies, is dominated by an iron-nickel alloy. The inner core alone contains more nickel than exists in the entire crust many times over. During Earth’s formation roughly 4.5 billion years ago, dense iron and nickel sank toward the center while lighter silicate minerals floated upward, a process geologists call planetary differentiation. The result is that the crust has relatively little nickel. Most of the nickel we mine today comes from two types of ore deposits: magmatic sulfide deposits, where nickel concentrated in sulfide minerals as magma cooled, and laterite deposits, where tropical weathering of nickel-bearing rocks left behind enriched soils. Laterites account for the majority of known nickel reserves, particularly in Indonesia, the Philippines, and New Caledonia.
Why Stainless Steel Stays Stainless
The single largest industrial use of nickel is in stainless steel, which typically contains between 8 and 12 percent nickel alongside chromium and iron. Chromium gets most of the credit for stainless steel’s corrosion resistance because it forms a thin, self-healing oxide layer on the surface. But nickel does something chromium alone cannot: it stabilizes the crystal structure of the steel in a form called austenite, which is tougher, more ductile, and easier to weld. Without nickel, high-chromium steels tend to be brittle.
Recent electrochemical research has quantified just how important nickel is for resisting pitting, the localized corrosion that eats tiny holes through metal surfaces. In iron-chromium alloys with more than 12 percent chromium, adding as little as 3 percent nickel significantly improved pitting resistance. The effect was even more dramatic in lower-chromium alloys: an iron alloy with 10 percent chromium showed no passivation at all, but adding 20 percent nickel enabled spontaneous passivation.4ECS Meeting Abstracts. Unravelling the Role of Nickel in Enhancing the Corrosion Resistance of Fe-Cr Alloys Passivation is what happens when a metal spontaneously forms a protective oxide film that shields it from further attack. Nickel essentially makes that protective film more stable and harder to break through.
Beyond stainless steel, nickel is the backbone of a family of materials called superalloys, engineered for extreme environments where ordinary metals would soften or corrode. Single-crystal nickel-based superalloys are the material of choice for high-pressure turbine blades in jet engines, where temperatures routinely exceed 1,000 °C. These alloys achieve their remarkable heat resistance through careful control of their internal crystal structure and the chemistry of strengthening phases within the metal.5Comptes Rendus. Physique. High temperature materials for aerospace applications: Ni-based superalloys and γ-TiAl alloys Every commercial flight you take relies on nickel superalloys spinning at tens of thousands of revolutions per minute inside the engines.
Nickel in Batteries and the Clean-Energy Push
If stainless steel is nickel’s legacy industry, lithium-ion batteries are its growth industry. The cathodes in many modern electric-vehicle batteries are so-called “high-nickel” formulations, where nickel makes up a large fraction of the cathode’s metal content. The reason is straightforward: increasing the nickel share raises both the energy stored per unit of weight and per unit of volume, which translates directly into longer driving range.6Journal of Energy Storage. High‑nickel cathodes for lithium-ion batteries: From synthesis to electricity Battery chemistries have steadily evolved toward higher nickel content over the past decade, moving from formulations with roughly equal parts nickel, manganese, and cobalt toward cathodes where nickel accounts for 80 percent or more of the transition-metal content.
This shift has geopolitical consequences. Indonesia is the world’s largest nickel producer by a wide margin, and the country has used export restrictions on raw nickel ore to attract smelting and battery-material investment. As electric vehicles scale up globally, securing a reliable nickel supply chain has become a strategic concern for automakers and governments alike. Recycling is increasingly seen as part of the answer: recovering nickel from end-of-life batteries can reduce the environmental footprint of mining and help stabilize supply for the industry.7Geosystems and Geoenvironment. The future of recycling for critical metals: The example of EV batteries
An Unsung Catalyst
Long before batteries, nickel earned its industrial keep as a catalyst. Raney nickel, a finely divided form of the metal created by dissolving aluminum out of a nickel-aluminum alloy, has been a workhorse of organic chemistry since the 1920s. It is widely used for hydrogenation reactions, where hydrogen gas is added across double bonds. In the food industry, Raney nickel catalyzes the hydrogenation of vegetable oils. In pharmaceutical manufacturing, it converts sugars into sugar alcohols. A study of glucose hydrogenation using Raney nickel, for example, achieved roughly 95 percent conversion of the starting sugar under mild conditions.8Journal of Engineering. HYDROGENATION OF D-GLUCOSE TO D-MANNITOL USING RANEY NICKEL CATALYST Sorbitol, the main product of that reaction, is found in everything from toothpaste to sugar-free candy.
Nickel in Living Things
Nickel is not just an industrial metal. It is also a biologically essential trace element, though its importance varies dramatically across the tree of life. In bacteria, archaea, and plants, nickel sits at the active site of at least nine known classes of enzymes. These include urease, which breaks down urea and is critical for nitrogen metabolism in soil bacteria and some plants; hydrogenase, which processes hydrogen gas; and methyl-coenzyme M reductase, the enzyme that produces methane in methanogenic archaea.9PubMed Central. Structure, function, and biosynthesis of nickel-dependent enzymes In the nonredox nickel enzymes like urease and glyoxylase-I, the nickel stays in its +2 oxidation state throughout catalysis, acting more as a structural anchor and Lewis acid than as an electron shuttle.10Encyclopedia of Inorganic and Bioinorganic Chemistry. Nickel Enzymes & Cofactors
Humans, by contrast, have no known nickel-dependent enzymes. We do absorb trace amounts of nickel from food (a few hundred micrograms a day from a typical diet), but whether our bodies actually need it remains an open question. Some animal studies suggest nickel deprivation causes subtle problems in reproduction and iron metabolism, but no human deficiency state has been clearly documented. For most of us, nickel’s biological relevance is more about what happens when we get too much of it than too little.
How Nickel Helped Reshape Earth’s Atmosphere
One of the most striking stories in Earth science links nickel availability in the ancient oceans to the rise of oxygen in the atmosphere. About 2.7 billion years ago, the ratio of nickel to iron in banded iron formations, layered rocks deposited on ancient seafloors, began to decline. Researchers have attributed this to cooling of Earth’s upper mantle, which meant fewer eruptions of nickel-rich ultramafic lavas and therefore less nickel washing into the oceans.11PubMed. Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event
This matters because methane-producing archaea (methanogens) depend on nickel for several of their key enzymes, including methyl-coenzyme M reductase. As dissolved nickel in the oceans dropped, methanogens would have struggled. Less biological methane production would have weakened the methane greenhouse effect that had been keeping early Earth warm and oxygen-free. The proposal is that this “methanogen famine” helped set the stage for the Great Oxidation Event around 2.4 billion years ago, when oxygen first accumulated to significant levels in the atmosphere. In this view, the cooling of Earth’s interior indirectly triggered one of the most consequential chemical changes the planet has ever undergone, and nickel was the link between mantle geology and atmospheric chemistry.
Nickel in the Modern Ocean
Nickel still cycles through the oceans today, and its distribution follows a pattern oceanographers call “nutrient-like.” Surface concentrations are lower because phytoplankton take up dissolved nickel, and deep-water concentrations are higher because sinking organic matter releases nickel as it decomposes. In the North Atlantic, surface nickel concentrations can dip below 2 nanomoles per liter while deep-water values climb above 5 nanomoles per liter, though the contrast between surface and deep water varies with latitude and ocean circulation.12Earth and Planetary Science Letters. The essential bioactive role of nickel in the oceans: Evidence from nickel isotopes
Nickel isotope measurements have added a new dimension to this picture. Phytoplankton preferentially take up the lighter isotopes of nickel, leaving the surface ocean enriched in heavier isotopes. This fractionation is especially pronounced in the tropical Pacific. Interestingly, despite the steady accumulation of biologically recycled nickel in deep Pacific waters, nickel isotope values in the deep North Pacific are similar to those in the deep Atlantic, suggesting that other processes, including hydrothermal input from ocean-floor vents, help balance the budget.13Geophysical Research Letters. Distribution and Cycling of Nickel and Nickel Isotopes in the Pacific Ocean Hydrothermal vents can push deep-ocean nickel isotopes in either direction depending on the vent’s chemistry and distance, making the global nickel cycle more complicated than a simple surface-uptake, deep-release loop.
Why Nickel Makes Humans Itch
Nickel allergy is the most common cause of allergic contact dermatitis worldwide. Somewhere between 10 and 20 percent of the general population is sensitized, with rates higher among women, largely because of historical exposure to nickel-containing jewelry. The rash itself, itchy, red, sometimes blistered, appears where nickel-releasing metal touches the skin: earlobes, wrists, belt lines, the backs of jean buttons.
What is remarkable about nickel allergy is its mechanism, which turns out to be unique to humans. The immune receptor TLR4, best known for detecting bacterial endotoxin, can be directly activated by nickel ions in humans. This happens because the human version of TLR4 has a cluster of histidine residues on its outer domain that are positioned to coordinate nickel ions. Most other species lack this histidine cluster, which is why nickel allergy is essentially a human-specific phenomenon.14PubMed Central. MD-2 determinants of nickel and cobalt-mediated activation of human TLR4 Peptide-level studies have confirmed that these non-conserved histidines cooperate in binding nickel and that the binding enables the downstream immune signaling cascade that produces inflammation.15Journal of Trace Elements in Medicine and Biology. Ni(II) interaction with a peptide model of the human TLR4 ectodomain
In practical terms, this means that nickel allergy is not a learned response to a foreign protein the way a pollen allergy is. The nickel ion itself acts as the trigger, directly bridging and activating innate immune receptors. Once someone is sensitized, even trace amounts of nickel leaching from jewelry, watch backs, belt buckles, or phone cases can provoke a flare. European regulations now limit the rate at which nickel can leach from items intended for prolonged skin contact, and this has measurably reduced sensitization rates in countries that adopted the rules early.
Nickel and Cancer Risk
The allergy story is about the immune system overreacting to nickel. The cancer story is about what happens with prolonged, high-level exposure, primarily in occupational settings. Certain insoluble nickel compounds, particularly nickel subsulfide and nickel oxide, are classified as Group 1 carcinogens (carcinogenic to humans) by the International Agency for Research on Cancer. The primary concern is respiratory cancer in workers who inhale nickel-containing dust or fumes over years.
The mechanisms behind nickel’s carcinogenic effects are complex and still being worked out, but they appear to involve a combination of oxidative stress, direct damage to DNA, and changes in how genes are turned on and off without altering the DNA sequence itself.16PubMed. Carcinogenic effect of nickel compounds Nickel ions can generate reactive oxygen species inside cells and activate signaling pathways that promote cell survival and proliferation. It is worth noting that the cancer risk applies to specific nickel compounds at industrial exposure levels, not to the metallic nickel in your kitchen sink or the trace amounts in food. A stainless steel pot does not meaningfully increase your cancer risk.
Plants That Eat Nickel
While most plants treat nickel as a minor micronutrient needed only in tiny amounts, a few hundred species worldwide have evolved to hyperaccumulate it, pulling nickel out of the soil and concentrating it in their tissues to levels that would poison ordinary plants. The tree Phyllanthus balgooyi, native to the nickel-rich ultramafic soils of Borneo, is one of the most extreme examples. Detailed mapping of nickel distribution within the tree showed that concentrations were very high in the phloem of stems and petioles, and the leaves were enriched in the major vascular bundles, suggesting that nickel is present in a metabolically active form rather than simply being dumped into dead tissue for storage.17PubMed. Extreme nickel hyperaccumulation in the vascular tracts of the tree Phyllanthus balgooyi from Borneo
Why these plants hyperaccumulate nickel remains debated. Leading hypotheses include defense against herbivores and pathogens (nickel-laden leaves are unpalatable to most insects), drought tolerance, and simply an evolutionary side effect of growing on metal-rich soils where excluding nickel would cost more energy than tolerating it. Regardless of the reason, hyperaccumulator plants have attracted interest for a practice called phytomining, where they are grown on low-grade nickel ores or contaminated soils, harvested, and burned to recover nickel from the ash. The approach is still experimental, but it offers an intriguing low-energy alternative to conventional smelting for certain deposits.
The Coin That Gave a Metal Its Name
Nickel’s common name comes from a bit of frustrated German mining history. In the 1700s, Saxon miners encountered a reddish ore they expected to yield copper. When it stubbornly refused to produce any, they named it Kupfernickel, loosely translated as “copper demon” or “Old Nick’s copper,” blaming mischievous sprites for the disappointing mineral. The Swedish chemist Axel Cronstedt isolated the actual metal from the ore in 1751 and kept the name, minus the copper part. The association with coinage came later: the United States five-cent coin has been called a “nickel” since 1866, when the metal was first used in the alloy for that denomination. Today, the U.S. nickel is 75 percent copper and only 25 percent nickel by weight, making its name something of a misnomer.
Nickel’s monetary legacy extends well beyond the five-cent piece. The euro’s one- and two-euro coins use a nickel-brass alloy, and many vending machines worldwide rely on nickel’s distinctive magnetic signature to authenticate coins and reject counterfeits. The shift toward cashless payment may eventually make this application a historical footnote, but for now, nickel still jingles in pockets around the world.