Artificial Graphite Powder
Graphite is an extremely soft and highly conductive mineral. Depending on its purity, it can be used for lubricants and paints, stove polishes, lead pencils, electrodes, brake linings, batteries (acid and lithium ion), powder metallurgy and as an additive to polymers. Its high ductility helps ensure good molding properties and low spring-back.
Natural graphite, which is mined through open pit and underground methods, usually requires beneficiation to remove unwanted impurities. This can be done by hand-picking the material and hand-screening it or by crushing the rock and floating off the graphite. The disadvantage of flotation is that the soft graphite “marks” or coats particles of the gangue minerals and they also float off, yielding an impure concentrate. Alternatively, the rock may be leached by acid (using hydrofluoric or hydrochloric acids) to separate the graphite from the gangue.
Often, both natural and synthetic graphite are used to manufacture battery anodes. To maximize the energy density, cycle durability and lower expansion rate of anode electrodes, it is important to have an understanding of the rheology of the raw materials. Characterizing the shear strength of the raw material through TA Instruments’ Powder Rheology Accessory on the Discovery HR 30 rheometer can help manufacturers optimize manufacturing and handling to avoid abrasion and other defects in anode coating. This in turn can reduce the cost of production and improve battery performance. Combined with other graphite slurry measurements such as viscoelasticity and yield stress, a battery manufacturer can optimize the anode formula and process to maximize battery capacity.