Is Graphite an Anode Or Cathode For Li-Ion Batteries?
An electrode is a conductor of electricity used to make contact with a nonmetallic part of an electro-chemical cell. Anodes are the positively charged electrodes and cathodes are the negatively charged ones.
Graphite is a metastable allotrope of carbon with the structure of a hexagonal crystal lattice, with a unique property that allows it to be used in negative electrodes in lithium-ion batteries. This is because the lattice’s spaces can host lithium ions, a process called intercalation. This is essential to enabling the battery to store energy by reversibly charging and discharging lithium-ions.
As a material, graphite has several advantages over other potential anode materials for EV Li-ion batteries: it’s chemically inert, it’s an excellent electrical conductor, and it’s relatively inexpensive. It’s also highly porous and able to absorb a lot of lithium-ions.
However, the problem with this is that it leads to a high volume expansion, which degrades the energy storage performance of the anode. This is why the industry has been looking for alternative materials.
The main alternative to graphite is silicon, which has been shown to be a good anode in theory because of its ability to reversibly place lithium-ions within its layers. However, the challenge is that silicon is unable to tolerate large volumes of lithium ions during charging, so it experiences a very rapid degradation in energy storage performance.
Nevertheless, even with this issue, the vast majority of research and development work to date has focused on graphite for EV anodes. And, despite some disappointing results, the industry still believes that it can achieve an optimum balance of mass loading and initial CE for practical KIBs.
