Rechargeable and lightweight, Lithium-ion batteries have changed our lives on the way we communicate, move and work. Let’s see how they were born and how they work.
These batteries have revolutionized the way of storing energy since the early nineties.
The real protagonist is LITHIUM, this metal is the lightest solid element in nature. Pure lithium is unstable, but more common is a positively charged lithium ion, formed by the release of an electron. Thanks to the positive charge of this particle, this batteries can be recharged over and over without reducing efficiency.
To understand how battery works, first it is important to remember how this great invention was discovered
In the 1970s, as the world was affected by the oil crisis and was looking for alternative sources of energy, Stanley Whittingham was working in the energy field at Exxon and he was researching solutions to the problem of energy storage inside rechargeable batteries. The British researcher was immediately struck by the ability of lithium to easily donate electrons and his studies led him to use metal lithium as the anode of a battery, that is the negative electrode from which electrons move. Instead as the cathode Whittingham used a material made of titanium disulfide, a compound that can stored lithium ions inside.
Whittingham’s battery worked like this: the lithium ions and electrons moved from the anode to the cathode with titanium disulfide, then they were brought back when the battery was charged.
The only problem with this battery was the lithium metal used in the anode which caused explosions. Even if some changes were made, Whittingham’s work was discontinued due to the oil price fall.
During the 1980s, the American chemist John Goodenough, realized that by changing the cathode’s constitution it would be possible to increase the power of the batteries: by replacing the titanium disulfide with cobalt oxide and he discovered they generated 4-volts, twice the power of Whittingham’s batteries.
The need for lighter and more powerful batteries gave the necessary impulse to research.
Akira Yoshino, considered the third protagonist of the evolution of lithium batteries, thought of using petroleum coke for the construction of the anode material to house the lithium ions, in a similar way to what has been done by cobalt oxide in the cathode.
The result was a stable, lightweight and safe product, ready to become a commercial product, in fact these advances allowed Sony and Asahi Kasei to start selling these batteries since 1991.
As we have previously described, the main feature of a lithium ion battery is the composition of its anode and cathode. There are many types of lithium ion batteries, each with different characteristics and applications: for example, cobalt oxide lithium batteries are specific for smartphones and laptops, they are formed by a cobalt oxide cathode and a graphite anode.
In the automotive sector, on the other hand, for cars with electric engines there is a particular chemical composition for its batteries: lithium, nickel, manganese and cobalt. With this composition the battery charge is optimized and maximum energy is provided, furthermore thanks to the nickel the battery obtains a high specific energy, while the manganese microcrystals form a three-dimensional structure that favors the flow of electrons, reducing the electrical resistance and allowing a control of the current, this because electrons pass through microscopic channels; this structure looks like a grid of crystals.
This type of batteries can have different cathode combinations: 1-1-1 wherein a part of nickel, a part of manganese and a part of cobalt are present, or 5-3-2. In order to cut costs, battery manufacturers are trying to reduce cobalt in favor of nickel // Because of the high cost of cobalt, battery manufacturers are trying to replace it in favor of nickel.