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The structure of a lithium-ion battery

The discovery of a permanent power source (more here) laid the foundation for further battery research. At the very beginning is the realization that electrons are willing charge carriers. When they move, they create a voltage that triggers the flow of electric current. This is how a battery works. It consists of a negative electrode (the anode), a positive electrode (the cathode), a separator, the electrolyte, and the cell casing. Each component performs a different function:

• The cathode is the positively charged electrode of a lithium battery. It usually consists of a composite structure containing lithium. These also usually contain nickel, manganese, cobalt or iron.
• The anode is the negatively charged electrode of a lithium battery. It is usually made of carbon-based materials, (mainly graphite).
• The separator prevents electrical contact between the cathode and the anode and also serves to provide spatial separation.
• The electrolyte provides the flow of ions. Charged Li-ions can migrate in it, i.e. from the cathode to the anode and vice ver
• The current arresters are made of copper and aluminum and conduct the electrons from the cell to the load (discharging) or from the power source to the cell (charging).
• The housing protects the inside of the cell from external influences and prevents the electrolyte from leaking. The housing is usually made of steel or aluminum.

When a battery is used, the following happens: Negatively charged particles called electrons are released at the anode. They migrate to the cathode - not through the battery, but around it. This migration generates electricity. Conventional batteries, such as those found in remote controls, need to be replaced when all the electrons have migrated from the anode to the cathode. In lithium-ion batteries, however, the electrons move back and forth.

The pioneers of the lithium battery

But it was a long way to the lithium-ion battery we use today in laptops, cell phones and electric cars. English-American chemist Stanley Whittingham was the first to build a pure lithium battery. He used titanium disulfide as the cathode material. The bronze-colored powder has an electrical conductivity comparable to that of semi-metals. It is layered, which is good for absorbing lithium ions without changing the crystal structure of the material. For the anode, he used metallic lithium. But it is very reactive. When the battery was discharged, the Li-ions migrated to the cathode; when it was recharged, they migrated back. But there was a problem: with each charge, dendrites formed on the anode. These resemble a needle-like structure. As soon as the dendrites penetrated the separator between the two electrodes and made contact with the cathode, a short circuit occurred. The batteries exploded.

The second founding father of the battery, John Goodenough, continued Whittingham's research and was able to double the voltage of the batteries from 2 to 4 volts by using lithium cobalt oxide. The advantages of lithium cobalt oxide are better electrical conductivity and higher energy density compared to titanium disulfide. Ultimately, however, it was Akira Yoshino of Japan who developed the first commercial lithium battery in 1985. Unlike Whittingham and Goodenough, he focused on the anode and relied on petroleum coke instead of reactive lithium. This carbon material, like crystallite cobalt oxide, can hold lithium ions in the cathode. He also incorporated a thin membrane to separate the cathode and anode materials. This prevents the battery from overheating before it can catch fire. This made his battery more stable than other rechargeable batteries being developed at the time. Today, it is hard to imagine a world without lithium-ion batteries. The demand is correspondingly high.