Chemistry: Anode

Graphite Basic Technology And Information Graphite is the industry standard anode active material AAM) for Li-ion batteries LIBs Graphite, an allotrope of carbon, occurs naturally but can also be synthesized. Lithium ions intercalate into its layered structure. Fully lithiated graphite LiC6) offers a theoretical maximum capacity of 372 mAh/g. Fully processed natural graphite for AAM is called uncoated spherical purified graphite USPG. Carbon coating, applied to both natural and synthetic graphite, enhances electrical conductivity, minimizes surface reactions, and boosts coulombic efficiency during cycling.

NATURAL GRAPHITE

Production process: Mining of flake graphite, grinding, beneficiation (e.g. flotation), purification and spheroidization to produce USPG.

+ Capacity and rate capability can be slightly better than synthetic graphite. – Mining can cause environmental degradation. Chemical purification (e.g. HF) can be hazardous. SYNTHETIC GRAPHITE

Production process: Carbonaceous precursors (e.g. petroleum coke and coal tar) are processed at high temperatures and refined.

+ Cycle life and thermal stability can be slightly better than USPG. – Energy-intensive production process. Precursors are byproducts of the petrochemical industry. Sources: Jakob Asenhaeur et al 2020 The success story of graphite as a lithium-ion anode material... Sustainable Energy & Fuels, 411, 53875416. K Zaghib et al 2003 Purification process of natural graphite... Journal of Power Sources, 119121, 815. Seong Jin An et al 2016 The state of understanding of the lithium-ion-battery graphite solid electrolyte interphase... Carbon, 105, 5276.

SUPPLIERS Leading suppliers of both natural and synthetic graphite include BTR, Shanshan and Putailai China, Posco Korea, and Resonac Japan.

ALTERNATIVES Blending natural graphite and synthetic graphite, and sometimes incorporating a small amount of silicon monoxide SiOx, is common. Other forms of silicon, blended with graphite or as a replacement, are in limited use but under extensive development.

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