How Do Lithium-ion Batteries Work?

Three researchers who developed technology at the heart of the smartphone era and its resulting societal transformation won the 2019 Nobel Prize in Chemistry. 

The work of John B. Goodenough, M. Stanley Whittingham and Akira Yoshino made crucial advances in lithium-ion batteries, which store large amounts of power in small battery cells and are quick and easy to recharge.

First sold commercially in 1991 by Sony for its camcorders, these types of batteries are suitable for much more than portable consumer electronics. They’re at the center of two other technological revolutions with the power to transform society: the transition from internal combustion engines to electric vehicles, and the shift from an electric grid powered by fossil fuels to renewable energy generators that store surplus electricity in batteries for future use.

How do lithium-ion batteries work? 

Scientists and engineers have spent entire careers trying to build better batteries and there are still mysteries that we don’t fully understand. Improving batteries requires chemists and physicists to look at changes on the atomic level, as well as mechanical and electrical engineers who can design and assemble the battery packs that power devices. 

As a materials scientist at the University of Washington and Pacific Northwest National Lab, my work has helped explore new materials for lithium-air batteries, magnesium batteries – and of course lithium-ion batteries.

Lithium-ion batteries work by storing and releasing electrical energy. The battery is made up of two electrodes, the anode, and the cathode, which is separated by an electrolyte. 

When the battery is charged, lithium ions move from the anode to the cathode through the electrolyte. When the battery is discharged, the lithium ions move back to the anode.

To illustrate this point, let’s consider a day in the life of two electrons. We’ll name one of them Alex and he has a friend named George.

Battery anatomy

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Alex lives inside a standard alkaline AA battery, like in your flashlight or remote control. Inside a AA battery, there is a compartment filled with zinc and another filled with manganese oxide. 

At one end, the zinc only weakly hangs onto electrons like Alex. On the other end, the manganese oxide powerfully pulls electrons toward itself. In between, stopping the electrons from going directly from one side to another, is a piece of paper soaked in a solution of potassium and water, which coexist as positive potassium ions and negative hydroxide ions.

When the battery is put into a device and switched on, the device’s internal circuit is completed. Alex gets pulled out of the zinc, through the circuit, and into the manganese oxide. Along the way, his movement powers the device, a light bulb, or whatever is connected to the battery. 

When Alex leaves, he can’t come back: The zinc has lost electron bonds with the hydroxide to form zinc oxide. This compound is extremely stable and cannot easily be converted back into zinc.

On the other side of the battery, the manganese oxide gains an oxygen atom from the water and leaves hydroxide ions behind to balance out the hydroxide being consumed by the zinc. Once all of Alex’s neighbors have left the zinc and moved to the manganese oxide, the battery is exhausted and needs to be recycled.

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Lithium-ion advantages

The technological revolution of lithium-ion batteries has led to the development of smaller, more powerful, and more efficient devices. 

This technology allowed manufacturers to create laptops, cell phones, and other devices that are much lighter in weight and more portable than ever before. In addition, the use of lithium-ion batteries has helped to reduce the environmental impact of these devices, as they do not release harmful chemicals into the atmosphere when they are used.

Let’s compare this to George, who lives in a lithium-ion battery. Lithium-ion batteries have the same basic building blocks as alkaline AA cells, with a few differences that confer major advantages.

George lives in graphite, which is even weaker than zinc at holding onto electrons. And the other part of his battery is lithium cobalt oxide, which pulls electrons much more powerfully than manganese oxide – which gives his battery the ability to store much more energy in the same amount of space than an alkaline battery. 

The solution separating the graphite and lithium cobalt oxide contains positively charged lithium ions, which easily form and break chemical bonds as the battery is discharged and recharged.

Those chemical reactions are reversible, unlike the formation of zinc oxide, which is what lets the electrons and the lithium ions flow back and forth over many cycles of charging and discharging.

This process isn’t 100% efficient, though – all batteries eventually lose their ability to hold energy. Nevertheless, the family of Li-ion chemistries has been powerful enough to dominate battery technology today.

Why are these batteries so effective?

Lithium-ion batteries are very efficient and have a high energy density, meaning that they can store a lot of energy in a small space. They also have a low self-discharge rate, meaning that they lose very little energy when not in use. 

For these reasons, lithium-ion batteries are often used in devices that need to be portable or that need to have a long battery life, such as cell phones and laptops.

However,  lithium-ion batteries have some disadvantages. They are more expensive than other types of batteries, and they can be dangerous if not used properly. Lithium-ion batteries can overheat and catch fire if they are damaged or if they are charged too quickly. 

Consequently, it is important to follow the instructions that come with your device when charging or replacing a lithium-ion battery.

Lithium-ion batteries in real life

One of the most important applications of lithium-ion battery technology is in the area of electric vehicles. 

Lithium-ion batteries are a key component of electric cars, providing the power needed to run the motors and other electronic components. Electric cars have become increasingly popular in recent years, due in part to the fact that they are much more efficient than gas-powered cars. 

While lithium-ion batteries are more expensive than lead-acid batteries, they are becoming increasingly affordable as technology improves and production increases. Several companies are now developing electric aircraft powered by lithium-ion batteries, and it is likely that this technology will play a major role in the future of electric aviation.

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Editor’s note: This is an updated version of an article originally published July 15, 2019.