The mining newspaper for Alaska and Canada's North
The mining newspaper for Alaska and Canada's North
Graphite Creek's STAX material excels as anode in lithium-ion batteries
The more that is known about Graphite Creek, the more this enormous deposit in western Alaska seems ideally suited to fill the growing need for graphite in electric vehicle batteries and other technology applications.
Though Graphite One Resources Inc. has only systematically drilled a small section of the 11 miles of known near-surface mineralization at Graphite Creek, the Vancouver B.C.-based company has already outlined 17.95 million metric tons of indicated resource grading 6.3 percent graphitic carbon and 154.36 million metric tons of inferred resource at 5.7 percent at this deposit located about 35 miles north of Nome.
Establishing that the Graphite Creek deposit is so massive that a mine could ship out 50,000 metric tons of graphite per year for centuries, Graphite One is working with TRU Group Inc. – a technology metals consultant with expertise along the entire graphite-graphene supply chain – to find out if this massive store of graphite could efficiently be transformed into carbon-coated spherical graphite needed for the anodes of lithium-ion batteries used in electric vehicles.
Graphite One and TRU Group has just released the final results from a five-phase program that indicates the graphite not only meets the criteria but has unique characteristics that sets it above any known deposit of natural graphite on the planet.
STAX advantage
When TRU Group first began examining Graphite Creek material late in 2014, its technicians immediately recognized it was different. These distinguishing features can be described as spheroidal, thin, aggregate and expanded. The graphite specializing consultant postulated that these distinctive characteristics could lend to different specialized applications with minimal processing.
These unique and naturally occurring properties have prompted Graphite One to apply for the trademark, STAX, an acronym to describe Graphite Creek graphite.
“From the time we identified the unique mineralization of our STAX graphite, we’ve observed a number of potential performance advantages,” said Huston.
During the initial three phases of the program aimed to confirm these advantages by producing and testing the performance of carbon-coated spherical graphite, TRU tested various means of milling and purifying Graphite Creek STAX material, all of which resulted in creating graphite purities above the 99.95 percent requirement for battery quality graphite.
John Roumeliotis, TRU Group Vice President and manager of the Graphite Creek tests, said the material was really easy to air mill, requiring about one-third of the air pressure typically needed.
To efficiently pack graphite into the anodes of lithium-ion batteries, it first must be transformed into roughly potato-shaped spheroids. This seems to be where the STAX graphite really stands above any other of its competitors.
TRU found that more than 74 percent of the STAX flake graphite could be turned into spherical graphite without milling. This is a monumental achievement considering that only about 40 percent of the best-performing flake graphite found in any other known deposit can be converted to spherical graphite, even using high-end equipment.
“This is another unique result that we can attribute to the STAX graphite,” Roumeliotis explained.
Battery tests
In the final two phases of testing, TRU Group measured the performance of the spheroidized graphite produced from STAX material in coin cells typically used in watches and similar devices.
During the fourth phase, uncoated spherical graphite produced during the testing were used as the anode in five battery cells.
Three of the cells demonstrated a first discharge capacity that approached natural graphite’s theoretical maximum of 372 ampere hours per kilogram.
Discharge capacity is a measure of a battery’s energy storage capability once first charged.
The top three performing cells – 1203, 1207 and 1208 – used air-milled and spheroidized graphite.
The first-discharge capacity of the best-performing cell, 1203, equaled the theoretical discharge capacity of natural graphite.
Cell 1209, which was loaded with un-milled but spheroidized graphite, had a first-discharge capacity of 369.1, still within 1 percent of the theoretical maximum.
The lowest performing coin cell, 1211, had a first discharge capacity of 361 ah/kg, or about 3 percent below the theoretical maximum. Even this lowest performing cell is on par with the roughly 360 ah/kg average first discharge capacity of lithium ion batteries currently being manufactured.
“The STAX graphite is performing robustly and in the manner in which we had predicted during TRU’s initial investigation of the Graphite Creek deposit. It was anticipated that the morphology observed in the drill core samples would translate into processing and performance gains over conventional flake graphite,” said Roumeliotis.
In addition to first discharge capacity, the phase 4 tests also provided an early indication of the ability of the STAX graphite to achieve similar discharge capacity in repeated, subsequent charging-discharging cycles. This behavior was evident in both the highest-performing and lowest-performing cells.
“These results support our material having demonstrated superior first discharge capacity for uncoated graphite, while the continuous cycling test shows the potential for our SPG (spheroidized graphite) to be used in EV (electric vehicle) applications,” said Graphite One CEO Huston.
In addition to being spheroidized, the graphite loaded into the cells of commercially produced lithium ion batteries is coated with a layer of carbon that extends the lifetime of the battery.
Spheroidized graphite typically trades some of it high-performance for extended durability. The coating applied to the Graphite Creek test material, however, only slightly lowered the reversible discharge capacity of the coin cells while increasing the efficiency, measured in terms of reduced irreversible capacity loss.
In the final phase of testing, TRU Group loaded batteries with coated spherical STAX graphite.
The highest ranking reversible discharge capacity for a coin cell loaded with coated spherical graphite was 370.1 Ah/kg – 0.5 percent less than the theoretical maximum for natural graphite. The irreversible capacity loss for this cell was 6.3 percent, which is about par with synthetic graphite currently being loaded into lithium ion batteries.
The other two cells had 367.9 and 364.1 Ah/kg reverse discharge capacity and 7.8 percent and 9.2 percent irreversible capacity loss.
“These first coated coin cell results indicate that our C-SPG maintained high reversible capacity, while improving efficiency as measured by ICL”, said Huston.
Dual characteristics
Up to this point, the testing has been completed on surface samples collected at Graphite Creek. During the next battery of tests, Graphite One and TRU Group will use material from the near-surface high-grade zone where mining would begin.
In addition to reproducing the high-performance achieved thus far, TRU believes the unique attributes of STAX graphite could deliver both high-energy and high-power as an anode material in lithium-ion batteries.
“Because of the particle sizes we do observe in the graphite, and how we believe the spherical graphite is being formed, we could possibly achieve dual characteristics of both high-power and high-energy,” Roumeliotis explained. “This could certainly translate into an advantage for Graphite One.”
“Up to this point, EV battery end-users have had to make a choice between systems that deliver high-power and high-energy. Based on these new results and observations made when processing STAX graphite, we will focus our development work on determining whether our STAX-derived SPG can deliver both high-energy and high-power performance,” Huston added.
While the battery tests look promising, the economics of developing a mine at Graphite Creek have yet to be evaluated. The first look at the viability of mining the STAX graphite at the Northwest Alaska project will be available in a preliminary economic assessment due to be completed in the third quarter of this year.
Over his more than 16 years of covering mining and mineral exploration, Shane has become renowned for his ability to report on the sector in a way that is technically sound enough to inform industry insiders while being easy to understand by a wider audience.
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