3. What type of carbon materials are used in Li-ion batteries?
As we mentioned above, graphite is the most commonly used anode active material in Li-ion batteries. Graphite is the most stable form of carbon and is the same type of carbon that we find in pencils. Because of its light weight, conductive properties and long-term cycle stability, it is an ideal anode material. Both natural, and synthetic (from petroleum coke) graphite are used for Li-ion anodes, typically in the form of powder or flakes. For optimal battery performance, properties of the graphite are often tailored, including crystallinity, particle size, morphology, and surface chemistry.
Other carbon-based anode materials that may further enhance the performance of Li-ion batteries due to improved electrical, mechanical and thermal properties, but have not yet found commercial use, are graphene and carbon nanotubes (CNTs).
In addition to constituting the anode active material, carbon materials are also used to improve the electrical conductivity of both the positive and negative electrodes, without being involved in the electrochemical redox process, which delivers the energy of the electrochemical cell. These are typically nanosized carbon particles like carbon black and carbon nanofibres, but also include the afore-mentioned graphene, carbon nanotubes and fine graphite powder. Common to all these conductive carbon additives are superior properties of low weight, high chemical inertia and high specific surface area.