Anode and Cathode Materials in Lithium-Ion Batteries
In every lithium-ion battery (the kind you use in your electric vehicle, smartphone, or portable generator) there is an anode, a cathode, and an electrolyte. Lithium ions move between the anode and the cathode during charging, which generates electricity. During discharge, the electrons from the anode travel to the cathode, which is then able to gain energy by reducing metal oxides. This is what allows the battery to work.
Graphite is the anode material in most EV batteries. Its structure is well suited for the reversible intercalation of lithium into the spaces between its crystal lattice during charge. This process releases and stores energy as a voltage, which is what makes lithium-ion batteries so valuable.
The cathode, which is the positive electrode, is usually a metal oxide such as lithium nickel cobalt oxide or lithium iron phosphate. The anode and cathode are separated by a plastic separator and a liquid electrolyte buffer. During charging, lithium ions flow from the anode to the cathode, and then back again during discharge.
The anode in a lithium-ion battery is composed of natural or synthetic graphite. In commercial batteries, the graphite used is usually lithium-cobalt-graphite or a carbon anode with a first row transition metal oxide spinel such as Li4Ti5O12. Silicon, which has much greater specific energy than graphite, may be added to graphite anodes to increase capacity, but this will require significant technological advances to make it viable.
