Lithium-ion batteries generally contain three important components: anode, cathode, and electrolyte.
Anode: During discharge, electrons are transferred away through the external circuit, and the electrode material is oxidized. Most commercial batteries use carbon/graphite-based electrode materials; however, metals or alloys can also be used as anode materials.
Cathode: During the discharge process, it receives electrons through an external circuit; transition metal oxides or phosphides are usually used as cathode materials.
Electrolytes: Electrolytes are ionic conductors but poor conductors of electrons. They act as a barrier between the anode and cathode of a battery, while simultaneously providing a medium for electron transfer. Electrolytes are typically non-aqueous organic solvents containing dissolved Li+ salts. For example, LiPF6 is dissolved in propylene carbonate.
Note: Description of the diaphragm and outer shell is omitted here.
The charging and discharging process of lithium-ion batteries
A. Charging process
Electrons typically assemble during the discharge state. During charging, the cathode material (e.g., LiCoO2) is oxidized, and lithium ions are extracted from the layered intercalation material, pass through the electrolyte, and then intercalate into the graphite layer.
B. Discharge process
During discharge, oxidation occurs at the negative electrode, causing lithium ions to be released from the anode and reintercalate into the cathode through the electrolyte. Correspondingly, a corresponding number of electrons pass through the external circuit to balance the charge. Simultaneously, the positive electrode material receives electrons from the external circuit and Li+ ions from the solution, resulting in a reduction reaction. An exchange of electron and ion currents occurs at the electrode-electrolyte interface.
