お知らせ • Jul 19
Evolution Energy Minerals Limited Announces Exceptional Performance of Coated Spherical Graphite
Evolution Energy Minerals Limited reported the results of testwork aimed at the production of uncoated and coated spherical graphite from thermally purified graphite from the Company's Chilalo Graphite Project in Tanzania. The testwork builds upon earlier tests that confirmed thermal purification could produce an ultra-high purity of 99.9995 wt% C prior to milling and shaping. Highlights: Electrochemical results indicate that Chilalo spherical graphite can be produced into the super- premium class of active anode materials for lithium-ion batteries in the EV and energy storage sectors - this class of active anode materials sells for USD 18,000 - USD 22,000 per tonne. Superior battery electrochemical performance of Chilalo coated spherical graphite, including: Reversible capacity (the measure of specific capacity rating) of 368 mAh/g1 - this is near theoretical capacity of 372 mAh/g; and Irreversible capacity loss (essentially demonstrating the retention of specific capacity from charge to charge) is < 7%. These results exceed the specifications of the major EV manufacturers and basically mean that lithium-ion batteries using Chilalo coated spherical graphite will have exceptional cycle life and very high recharge efficiency compared to competing products (ie. represent a premium product). Unoptimised testwork delivered exceptional 64% yields into usable spherical graphite (compared to industry average of ~40%) - this will substantially enhance the economics of Evolution's battery anode materials production plant. These results provide compelling justification for Evolution to advance the feasibility and construction of a battery anode materials production facility either in parallel with the development of Chilalo or soon thereafter. Evolution has produced sufficient data during this program to immediately commence qualification initiatives for its coated spherical graphite with leading battery manufacturers. Further processing and battery testing of the purified, non-spherical by-product from the spheroidisation process is ongoing to determine suitability as conductivity enhancement in battery cathodes and electrically conductive coatings - successful results would further enhance the economics of the planned battery anode materials plant. Testwork Stages: Evolution is working with a US technology partner, an established manufacturer of advanced battery materials and experienced graphite supplier to the battery industry, on a series of tests to determine the suitability of Chilalo's fines product for downstream processing into higher value battery anode materials. The initial testwork stage established that graphite from Chilalo contained extremely low amounts of Molybdenum and Boron. Elemental analysis of impurities in Chilalo's 95% C flake graphite fines concentrate identified extremely low levels of naturally occurring Molybdenum and Boron, opening the pathway to premium performance batteries, and nuclear-grade graphite. The second testwork stage involved thermal purification of the graphite to achieve battery grade (>99.95% C). This purification resulted in an extremely high purity of 99.9995% C, which exceeds the purity requirements of both the battery and the very high value nuclear sector. Evolution adopted an `inverted' flow sheet whereby the purification step is undertaken prior to milling and shaping into spheroids, which is the opposite of the traditional approach. This current testwork stage took the 99.9995% C thermally purified graphite and undertook a process of shaping and milling, otherwise known as spheroidisation. Traditional flow sheets that mill and shape first generally have a yield of ~40%, with the 60% rejected suitable only for low value by-products. Evolution's process has resulted in significantly higher yields, with the rejected material potentially being suitable for high- value by-product applications due to its very high purity. Following spheroidisation, the uncoated spheroidal material was then subjected to a proprietary coating process with soft carbon, with the resulting carbon coated spherical graphite having properties that meets the specification of some of the leading EV battery producers in the world. The shaping precursor was thermally-purified graphite with an initial purity of 99.9995% C, tap density of 0.67 g/cm3, and surface area of 1.99 m2/g. Energy dispersive scan (EDS) analysis of this precursor material reveals extremely pure flake with no notable foreign impurities. The concentration of iron, which is one of the main deleterious elements in batteries, was measured by ICP-OES as 0.97ppm. Testwork of non-spherical `rejects' or by-products: Conventional spherical graphite flowsheets typically produce: ~35-40% yield into saleable coated spherical graphite; and ~60-65% `rejects' representing a 94% C, non-spherical, low value by-product. In contrast, Evolution has achieved: 64% yield into a premium quality coated spherical graphite; and Evolution's US technology partner is conducting a series of demonstration projects to process the 36% non-spherical, high-purity by-product into both: battery cathode conductivity enhancement materials; and premium-performance electrically conductive coatings. Positive results from the demonstration projects on the non-spherical by-product would significantly enhance the economics of Evolution's proposed downstream battery anode plant by producing high- value products from 100% of the fine flake feedstock. Conventional technologies process spherical graphite at a starting purity of approximately 94-95% C. A cascade milling circuit, typically consisting of 21-23 pin mills outfitted with air classifiers, is employed. As the predominant impurities in flake graphite are iron oxides, alumina, and silica, impurities have a significant abrasive effect on mill parts. Evolution's flowsheet realizes a number of benefits by spheroidising ultrapure flake, with its impurity-free graphite acting as a dry film lubricant, as opposed to being abrasive, on the mill components. The resultant carbon- coated spherical graphite had the following properties: tap density of 0.95 g/cm3, d503 of 25 µm, and BET surface area of 2.8 m2/g, which already meets the specification of some of the leading EV battery producers in the world. Milling process adjustments can easily result in the production of spheroidal carbon-coated graphite with a finer particle size, in order to meet the requirements of other EV manufacturers in the future. The stated capacities were achieved at a C/10 formation rate, meaning that the cell was charged and discharged over ten hours for each part of the cycle. Long-term cycle testwork is ongoing, with further results expected in the coming weeks. The Company also expects to finalise the demonstration projects on the non-spherical by-product, aiming to produce battery cathode conductivity enhancement materials and premium performance electrically conducting coatings.