Graphite As Anode in Li-Ion Batteries
In lithium-ion battery technology, graphite has historically been used as the anode. It has a high theoretical capacity, excellent conductivity and stability under cycling conditions. Currently, it accounts for 96% of all anodes in lithium-ion batteries. Graphite is produced from a carbonaceous material composed of petroleum or coal-tar-derived coke as aggregate and carbon-yielding binders such as needle coke or coal pitch. These materials are molded into rods and baked to carbonize the binder. The anode is then placed in an electric graphite furnace after cooling and reheated to over 250 degC (480 degF) completing the graphitization process. The result is a porous, stable and low-cost graphite material that performs well in Li-ion batteries.
Typical anode manufacturing processes include coating the anode with a wax, linseed oil or resin. This treatment seals the porosity of the anode, improving its performance and life. It also reduces the tendency for electrochemical activity to occur within the pores of the anode. Additionally, it provides protection from moisture intrusion which can cause deterioration of the anode.
A recent development in graphite anode technology is the introduction of silicon (Si) into the electrode. This approach increases the energy density of the anode by utilizing nanotechnology to fuse Si onto commercial graphite powders. This enables a significant increase in battery energy density and lowers the cost per kWh of the resulting Li-ion batteries.
