Abstract
More than 40 m length of drill cores were collected from four boreholes drilled by Geological Survey of Finland (GTK) and Outokumpu Oy in high-grade metamorphic rocks of Rautalampi and Käypysuo, Central Finland. The hosted rocks of the graphite mineralization were mica–quartz schist and biotite gneiss. The graphite-bearing rocks and final concentrated graphite powder were studied with petrographic microscope, scanning electron microscope (SEM-EDS), Raman spectroscopy, and X-ray analysis (XRD and XRF). A majority of the studied graphite had a distinctly flakey (0.2–1 mm in length) or platy morphology with a well-ordered crystal lattice. Beneficiation studies were performed to produce high-purity graphite concentrate, where rod milling and froth flotation produced a final concentrate of 90% fixed carbon with recoveries between 67% and 83%. Particle size reduction was tested by a ball and an attritor mill. Graphite purification by alkaline roasting process with 35% NaOH at 250 °C and leached by 10% H2SO4 solution at room temperature could reach the graphite purity level of 99.4%. Our analysis suggested that purifying by multistage flotation processes, followed by alkaline roasting and acid leaching, is a considerable example to obtain high-grade graphite required for lithium-ion battery production.
Highlights
Graphite occurs naturally in the Earth’s crust in schist and gneiss metamorphic rocks
The graphite-bearing rocks and final concentrated graphite powder were studied with petrographic microscope, scanning electron microscope (SEM-EDS), Raman spectroscopy, and
Beneficiation studies were performed to produce high-purity graphite concentrate, where rod milling and froth flotation produced a final concentrate of 90% fixed carbon with recoveries between 67% and 83%
Summary
Graphite occurs naturally in the Earth’s crust in schist and gneiss metamorphic rocks. The graphite can have a microcrystalline structure and flaky morphology, displaying a polymorphic phase with hexagonal and rhombohedra layers. Based on its structure properties, graphite is applied in a variety of technological applications including lithium-ion batteries, fuel cells, two-dimensional grapheme, electronics, fiber optics, electrical vehicles, and so forth. Graphite is an essential component of commercial lithium-ion batteries in the near-to-mid-term future. The vast majority of lithium-ion (Li-ion) batteries use graphite powder as an anode material. Graphite anodes meet the voltage requirements of most Li-ion cathodes, as they are relatively affordable, extremely light, porous, and durable. Natural graphite has been considered as a promising anode material due to its high reversible capacity, cycle stability, higher purity, and more suitable particle size distribution [1,2]
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