Wikipedia Deep Dive

Lithium-ion battery

15 min read

In 2019, three scientists shared a Nobel Prize for helping create something you probably have within arm's reach right now. Not a cure for disease. Not a breakthrough in physics. A battery.

That might sound underwhelming until you consider what that battery made possible: the smartphone in your pocket, the laptop on your desk, the electric car that might be parked in your driveway. The lithium-ion battery didn't just improve existing technology—it created entirely new categories of devices that couldn't have existed without it.

By late 2024, the world was consuming more than one terawatt-hour of lithium-ion batteries every year. To put that in perspective, that's enough energy storage to power every home in a city of ten million people for about a month. And production capacity? More than double that demand. We're manufacturing these things at a scale that would have seemed like science fiction just a few decades ago.

The Rocking Chair That Powers Your Life

Engineers sometimes call lithium-ion batteries "rocking-chair batteries." It's a charmingly domestic name for something so technologically sophisticated, but it perfectly captures how they work.

Imagine a rocking chair moving back and forth, back and forth. Now imagine that instead of a chair, it's lithium ions—electrically charged atoms of the lightest metal on Earth—shuttling between two electrodes. When the battery discharges (powering your phone), lithium ions rock from the negative electrode to the positive one. When you plug in your charger, they rock back the other way.

This back-and-forth motion is what makes lithium-ion batteries rechargeable. Unlike disposable batteries, which undergo irreversible chemical reactions, lithium-ion batteries use a process called intercalation. That's a technical term that simply means the lithium ions slip in and out of the electrode materials like cards sliding into and out of a deck. The structure of the electrodes stays intact, which is why you can charge your phone thousands of times before the battery degrades significantly.

The negative electrode is typically made of graphite—yes, the same material in pencil lead. Graphite has a layered structure, like a stack of paper, and lithium ions can slide between those layers. The positive electrode is usually some kind of metal oxide or phosphate. And between them sits an electrolyte, a liquid that allows lithium ions to flow but doesn't conduct electricity itself. This separation is crucial: electrons have to take the long way around, through your phone's circuits, to reach the other electrode. That flow of electrons is the electricity that powers your device.

A Battery Born From Failure

The path to the modern lithium-ion battery was paved with explosions, fires, and abandoned prototypes.

In the 1970s, a British chemist named M. Stanley Whittingham was working at Exxon—yes, the oil company—when he created the first rechargeable lithium battery. His design used titanium disulfide for one electrode and lithium metal for the other. It worked, technically. But it had a tendency to spontaneously catch fire.

The problem was the lithium metal itself. During charging, lithium would plate onto the electrode in an uneven, branching pattern, forming structures called dendrites. These metallic whiskers could grow across the battery and pierce the separator, causing a short circuit. When that happened with a flammable electrolyte inside, the results were predictably catastrophic. Exxon abandoned the project.

But other scientists kept working on the problem. In 1980, John Goodenough—a physicist with perhaps the most aptly named surname in the history of science—made a crucial improvement. Working at Oxford University, he replaced Whittingham's titanium disulfide with lithium cobalt oxide. This new material could hold more energy and was more stable. It would eventually become the cathode material in the first commercial lithium-ion batteries.

The breakthrough that made everything safe came from Akira Yoshino at Japan's Asahi Kasei Corporation in 1985. Yoshino realized that instead of using lithium metal as the negative electrode—which caused all those fires—he could use a carbon-based material that would absorb and release lithium ions without the dangerous dendrite formation. He chose petroleum coke, a byproduct of oil refining.

The result was a battery that could be assembled in a discharged state, making it safer and cheaper to manufacture. There was no metallic lithium anywhere in the battery—just lithium ions moving through the system.

Sony's Gamble

In 1991, Sony took Yoshino's design and bet the company's reputation on it. They began mass-producing lithium-ion batteries for their new line of camcorders.

It was a risky move. No one had ever manufactured these batteries at scale before. The chemistry was new, the production processes were untested, and the memory of Exxon's exploding prototypes lingered in the industry's collective consciousness.

But Sony's gamble paid off spectacularly. The new batteries lasted longer, weighed less, and recharged faster than anything else on the market. Within a few years, lithium-ion became the standard for portable electronics. The following year, a joint venture between Toshiba and Asahi Kasei released their own lithium-ion battery, and the technology race was on.

The improvements came fast. In the 1990s, researchers replaced Yoshino's petroleum coke with graphite, which could store more lithium. Jeff Dahn at Dalhousie University in Canada figured out the right combination of solvents to make graphite electrodes work reliably. Energy density increased. Costs dropped. By 2010, global production capacity had reached 20 gigawatt-hours. By 2020, it was 767 gigawatt-hours—a nearly forty-fold increase in just ten years.

Why Lithium?

You might wonder why lithium, of all elements, became the foundation for this technology. The answer lies in the periodic table.

Lithium is the third-lightest element, after hydrogen and helium, and the lightest metal. It's so light that it floats on water—though you'd never want to try this, because it reacts violently with water, releasing hydrogen gas and enough heat to ignite it.

This reactivity, dangerous as it sounds, is exactly what makes lithium so useful in batteries. Atoms "want" to reach a stable electron configuration, and lithium atoms readily give up their single outer electron. This eagerness to participate in chemical reactions translates into high voltage and high energy density. Pound for pound, a lithium-based battery can store more energy than almost any other battery chemistry.

Each gram of lithium can theoretically provide about 11.6 kilowatt-hours per kilogram—slightly more energy than burning the same weight of gasoline. Of course, practical batteries don't achieve this theoretical maximum because of the weight of other components, but the comparison illustrates why lithium has become so valuable for energy storage.

The Chemistry of Everyday Magic

When you use your phone, here's what's happening inside the battery at a molecular level.

The graphite negative electrode starts fully loaded with lithium. As you use your phone, lithium ions leave the graphite and travel through the electrolyte to the positive electrode—let's say it's lithium cobalt oxide. As each lithium ion arrives at the cobalt oxide, it brings with it a cobalt atom that changes from its +4 oxidation state to +3, accepting an electron that has traveled through your phone's circuits.

This flow of electrons is the electricity. The chemical potential difference between the two electrodes—essentially, how much the lithium "wants" to move from one side to the other—determines the voltage. For a lithium cobalt oxide battery, this is about 3.7 volts per cell.

When you plug in your charger, you're reversing this process. The charger pushes electrons back to the negative electrode, and the lithium ions follow through the electrolyte. The energy from your wall outlet gets stored as chemical potential energy, ready to be released again when you unplug.

There's a limit to how far you can push these reactions. Overdischarge a lithium-ion battery—drain it completely—and you can damage the cobalt oxide structure irreversibly. Overcharge it, and you risk creating unstable compounds or, in extreme cases, thermal runaway: a self-accelerating reaction that can cause the battery to catch fire or explode. This is why every lithium-ion battery includes electronic circuits that monitor voltage and temperature, cutting off charging or discharging before dangerous conditions develop.

A Dozen Different Batteries

When people say "lithium-ion battery," they might actually be talking about any of at least twelve different chemical formulations. The term is a bit like saying "car"—it covers everything from a compact sedan to a heavy-duty truck.

The most common chemistry for smartphones and laptops uses lithium cobalt oxide for the positive electrode. It offers excellent energy density, meaning you can pack a lot of storage into a small space. But cobalt is expensive, somewhat toxic, and often mined under questionable conditions. It's also prone to thermal runaway if damaged or improperly charged.

Electric vehicles often use lithium nickel manganese cobalt oxide, which battery engineers shorten to "NMC." By replacing some of the cobalt with nickel and manganese, manufacturers get a battery that's cheaper, safer, and can deliver power more quickly—important when you need to accelerate a two-ton vehicle onto a highway.

Then there's lithium iron phosphate, or "LFP." This chemistry gives up some energy density compared to cobalt-based batteries, but it's significantly safer, cheaper, and longer-lasting. Iron and phosphate are abundant and inexpensive. Tesla uses LFP batteries in some of its vehicles, and in April 2025, the Chinese manufacturer CATL unveiled an LFP battery claiming over 1,000 kilometers of range on a single charge—with ultra-fast charging that can add 600 kilometers of range in just ten minutes.

Each chemistry represents a different trade-off between energy density, power delivery, safety, cost, and lifespan. The "best" battery depends entirely on what you're trying to do with it.

The Hidden Components

Beyond the electrodes and electrolyte, lithium-ion batteries contain several components that are easy to overlook but absolutely essential.

The separator is a thin sheet of porous material, usually a polymer, that sits between the two electrodes. Its job is to prevent the electrodes from touching each other—which would cause a short circuit—while still allowing lithium ions to pass through. If the separator fails, the battery fails, often dramatically.

Current collectors are thin metal foils that connect the electrode materials to the outside world. The negative electrode typically uses copper; the positive electrode uses aluminum. These metals are chosen for their electrical conductivity and their stability in the electrochemical environment of each electrode. The aluminum, in particular, develops a thin passive layer of lithium hexafluorophosphate that protects it from corroding.

The electrolyte itself is more complex than it might appear. It's typically a lithium salt—usually lithium hexafluorophosphate—dissolved in a mixture of organic carbonates. These solvents must remain liquid across a wide temperature range, conduct lithium ions efficiently, and not react with the electrodes. Ethylene carbonate is crucial for forming a protective layer on the graphite electrode, but since it's solid at room temperature, it's mixed with other carbonates like propylene carbonate or diethyl carbonate.

Lithium reacts violently with water, so the entire battery must be sealed against moisture. Even tiny amounts of water contamination can cause degradation and gas formation. This is why lithium-ion batteries are manufactured in dry rooms with humidity levels lower than the Atacama Desert.

The Fire Problem

Lithium-ion batteries have an uncomfortable relationship with fire.

The organic carbonates in the electrolyte are flammable. The electrodes contain materials that can release oxygen when overheated. And the high energy density that makes these batteries so useful also means there's a lot of stored energy that can be released violently if something goes wrong.

When a lithium-ion battery experiences "thermal runaway," the temperature rises rapidly in a self-reinforcing cycle. Heat causes reactions that release more heat, which causes more reactions. Temperatures can exceed 1,000 degrees Celsius. The battery can ignite, explode, or both.

These incidents are rare—you don't think twice about carrying a lithium-ion battery in your pocket all day—but they do happen. Phone batteries occasionally catch fire. Electric vehicles have burned. Cargo planes carrying lithium batteries have crashed.

The industry has responded with multiple layers of protection. Battery management systems monitor temperature and voltage constantly, shutting down cells that show signs of trouble. Separators are designed to melt and close their pores if the temperature rises too high, stopping the flow of ions and halting the reaction. New electrolyte formulations are less flammable. Solid-state batteries, which replace the liquid electrolyte with a solid material, promise to eliminate the fire risk entirely—though they're not yet ready for mass production.

The Hidden Costs

The lithium-ion battery's success story has a shadow side.

Lithium mining often occurs in arid regions where water is already scarce. The process uses enormous quantities of water to extract lithium from underground brine deposits, potentially depleting aquifers that communities depend on. In Chile's Atacama region, lithium operations have been blamed for lowering water tables and affecting flamingo populations that nest in the salt flats.

Cobalt presents even thornier problems. More than two-thirds of the world's cobalt comes from the Democratic Republic of Congo, where mining operations have been linked to child labor, unsafe working conditions, and armed conflict. This has pushed manufacturers toward chemistries that use less cobalt or none at all—hence the growing popularity of LFP batteries.

At the end of a battery's life, recycling presents challenges. Lithium-ion batteries contain toxic metals and flammable materials. Damaged batteries can catch fire in recycling facilities, and the complex chemistry makes material recovery difficult and expensive. Currently, only a small fraction of lithium-ion batteries are recycled. Most end up in landfills.

These environmental and ethical concerns have spurred interest in alternative technologies. Sodium-ion batteries use abundant, cheap sodium instead of lithium. Iron-air batteries use iron and oxygen from the air, making them potentially very inexpensive for grid-scale storage. Neither technology matches lithium-ion's energy density, but for applications where weight matters less than cost, they could prove transformative.

Thirty Years of Progress

Since Sony's first commercial lithium-ion battery in 1991, the technology has improved at a remarkable pace.

Volumetric energy density—how much energy you can pack into a given volume—has tripled. This is why a modern smartphone can run all day on a battery you barely notice, while early cellular phones needed battery packs the size of bricks.

Costs have dropped by a factor of ten. In the early 1990s, lithium-ion batteries cost over $1,000 per kilowatt-hour of storage capacity. Today, prices are approaching $100 per kilowatt-hour. This plummeting cost is what has made electric vehicles economically viable.

Cycle life has improved dramatically. Early lithium-ion batteries might last for a few hundred charge cycles before degrading significantly. Modern batteries can last for thousands of cycles. Some manufacturers now warranty electric vehicle batteries for eight years or 100,000 miles—whichever comes first.

Manufacturing scale has exploded. In 2010, the world could produce 20 gigawatt-hours of lithium-ion batteries per year. By 2020, production capacity had grown to 767 gigawatt-hours—and it continues to expand rapidly, with new battery factories opening around the world.

The Ongoing Quest

Despite three decades of refinement, researchers continue pushing the boundaries of lithium-ion technology.

Silicon anodes could dramatically increase energy density. Silicon can absorb far more lithium than graphite—in theory, about ten times more. The problem is that silicon swells enormously as it absorbs lithium, then shrinks as it releases it. This repeated expansion and contraction pulverizes the silicon. Engineers are experimenting with nanostructured silicon, silicon-carbon composites, and other approaches to solve this problem. Many modern batteries already incorporate small amounts of silicon into their graphite anodes for a modest capacity boost.

Solid-state batteries replace the flammable liquid electrolyte with a solid material, potentially improving safety while also enabling the use of lithium metal anodes for higher energy density. Several companies have announced solid-state battery prototypes, though manufacturing at scale remains challenging.

New cathode materials continue to emerge. Lithium-rich layered oxides, for example, can store more lithium than conventional materials, boosting capacity. But they tend to lose voltage over time, and their long-term stability remains an open question.

The ultimate goal is a battery that's cheaper, safer, more energy-dense, faster-charging, and longer-lasting than today's best lithium-ion cells. No single breakthrough is likely to deliver all of these improvements simultaneously, but incremental progress on each front continues to push the technology forward.

The Quiet Revolution

When Whittingham, Goodenough, and Yoshino accepted their Nobel Prizes in 2019, the Swedish Academy noted that lithium-ion batteries had "laid the foundation of a wireless, fossil fuel-free society."

That might sound like hyperbole, but consider what these batteries have enabled. Without lithium-ion technology, there would be no smartphones, no tablets, no laptops that last more than an hour on battery power. There would be no viable electric cars—the lead-acid and nickel-metal hydride batteries that preceded lithium-ion simply couldn't store enough energy. There would be no practical way to store electricity from solar panels and wind turbines for use when the sun isn't shining and the wind isn't blowing.

The three scientists solved a problem that had vexed researchers for decades: how to safely and efficiently store electrical energy in a compact, rechargeable form. Their solution, refined over years of patient experimentation, has quietly transformed modern life.

The rocking chair keeps rocking, lithium ions shuttle back and forth, and the devices we've come to depend on continue to work. It's so reliable now that we barely think about it—which is perhaps the truest sign of a successful technology.