How Lithium-Ion Batteries Work

Lithium-ion batteries are the fastest-growing secondary batteries after nickel-cadmium and nickel-hydrogen batteries. The positive and negative active materials of lithium-ion batteries are compounds that can reversibly intercalate and extract lithium. At least one electrode material is in a lithium intercalation state before assembly, such as transition metal oxides LiCoO2, LiNiO2 and LiMn2O4 as the positive electrode. Various carbon materials, metal oxides or alloys, etc. are used as negative electrode materials.

The working principle of a lithium-ion battery is shown in Figure 1, with graphite as the negative electrode and LiCoO2 as the positive electrode. During charging, lithium ions are extracted from the positive electrode material, and migrated to the negative electrode through the electrolyte under the driving of the electrochemical potential gradient. The charge balance requires that the same amount of electrons flow from the positive electrode to the negative electrode under the external circuit, and the lithium ions that obtain electrons are regenerated after reaching the negative electrode. It is embedded into the lattice of the negative electrode material; during discharge, the reverse process is performed, that is, the lithium ions leave the negative electrode lattice and are embedded in the positive electrode to form LiCoO2 again.