Graphite As Anode for Li-Ion Batteries
The anode, made of natural graphite or synthetic graphite based on petroleum coke, is the key raw material in lithium-ion batteries. It is responsible for the characteristic parameters of battery performance such as energy density and rate capability – both factors determine the lifetime of the battery. The purity of the graphite and its optimization with EC are essential to achieve the desired battery properties. With its unique production know-how and its high quality graphite products, SGL Carbon is a competent partner in the field of battery-grade graphite for Li-ion batteries. We use our extensive experience to develop graphite tailored to the special cell design and test it in our Battery Application Laboratory.
Graphite anodes have been commercially available since 1940. They are manufactured by bonding carbonaceous fillers with carbon-yielding binders (coal tar pitch), extruding them into rods and baking them at 1000degC to carbonize the pitch binder. After cooling in a reducing atmosphere, the anodes are placed in electric graphite furnaces and reheated to above 250degC to complete the graphitization process, which gives the anodes crystalline properties and improved electrical and thermal conductivity.
The primary disadvantage of graphite anodes in Li-ion batteries is their relatively poor rate capability and first cycle irreversible capacity loss (Cirr) which result from the reductive electrolyte decomposition and consumption of the lithium metal charge carrier. While there is considerable room for further improvement in the former aspect, particularly considering that the Li-ion kinetics can be significantly enhanced by adding EC as an electrolyte additive, the latter remains a significant industrial challenge and is one of the main areas of research focus (see figure below). It is important to reduce Cirr, not only to increase the battery’s energy density but also to improve cycling stability. A promising approach for lowering Cirr is the modification of the graphite surface prior to electrode preparation and cell assembly.
