How does a lithium-ion battery store energy?

A lithium-ion battery stores energy by keeping lithium ions parked in one electrode and letting them move to the other. It is a rechargeable battery that uses the reversible intercalation of lithium ions into electronically conducting solids to store energy. Intercalation just means the ions slip into the structure of a solid, like books slid into the gaps of a shelf.

Here is how it runs. When the battery discharges, the negative electrode is the anode and the positive electrode the cathode. Electrons flow from the anode to the cathode through the external circuit, which is the part of the current that powers your phone. Meanwhile the lithium ions move through the electrolyte, a medium inside the cell, and electrons recombine with the cathode material.

Charging reverses everything. Electrons move from the positive electrode to the negative electrode through the external circuit, and the external circuit has to provide electrical energy. That energy is stored as chemical energy in the cell. Because the lithium ions rock back and forth between the two electrodes, these batteries are also called rocking-chair batteries.

The cost of the technology tells the story of its success. Li-ion batteries have enabled portable consumer electronics, laptop computers, cellular phones and electric cars. Between 1991 and 2024, prices for all types of lithium-ion cells fell approximately 99%. The three scientists behind the idea shared the 2019 Nobel Prize in Chemistry.