Graphite products from the Kazakhstan project of Sarytogan Graphite Ltd (ASX:SGA) continue to demonstrate high-performance capabilities for use in the all-important anodes of lithium-ion batteries.
The company is highly encouraged by the high-value potential being demonstrated by Sarytogan Graphite in testing, with Coated Spherical Purified Graphite (CSPG) being the latest product to show its mettle, including:
- Coin-cell batteries manufactured from CPSG have now cycled 100 times;
- Coating has significantly improved lithium-ion battery performance; and
- Coating improves market pricing from approximately US$2,500 per tonne to US$8,000 per tonne.
The CSPG testing will now form a component of a pre-feasibility study (PFS), which is on track for completion no later than September 2024.
“Premium-priced element”
Sarytogan managing director Sean Gregory said: “We are delighted with the high performance demonstrated by Sarytogan Graphite in lithium-ion battery anodes.
"The successful demonstration of coating adds a premium-priced element to our battery product offering and opens the door to future direct relationships with battery manufacturers and OEMs.
"Coating has therefore been added to the flowsheet for the pre-feasibility study which is progressing well and is on track for completion no later than September this year.”
The company previously reported strong battery performance of lithium-ion batteries made with Uncoated Spherical Purified Graphite (USPG).
Performance exceeded all expectations with the reversible capacity of 342-347 mAh/g being superior to many synthetic graphite products used as the anode in lithium-ion batteries for electric vehicles.
Coating
Spherical graphite is routinely coated for improved performance as the anode in lithium-ion batteries for use in electric vehicles.
Five Nines Sarytogan Graphite was spheroidized and wet classified. A representative classified fraction was coated with soft carbon giving ideal spheres with a d50 size of 14 micron and tap density of 0.95 g/cc.
The main objective of the coating is to smooth the surface of the spheres. In this case, the surface area was reduced to 6.7 m2/g measured by the BET method.
Strong performance
Coin cell batteries were manufactured with Sarytogan CSPG. These batteries have been charged and discharged over a 10-hour cycle 100 times.
The Irreversible Capacity Loss (ICL), a measure of the difference between the capacity of the first charge and first discharge, is reported as 11%. This is a good result for the first attempt at coating, being only just above the industry benchmark of 10% for high-performing lithium-ion batteries.
A thicker coating of soft carbon will be added in future optimisation tests to further reduce the surface area and ICL.
The results have realised a significant improvement in the reversible capacity to 354 mAh/g, well above the values of many synthetic graphite products used in the anodes of lithium-ion batteries for EVs.
This performance has endured with 98.9% capacity still available after 100 cycles. Extrapolating this result, more than 1,600 cycles are expected before the typical useful threshold of 80% capacity is reached.
Product mix
Sarytogan plans to produce three product types to get as many units of carbon into as many markets as possible from its giant and exceptionally high-grade mineral resource.
The upstream beneficiation using grinding and flotation is planned to produce microcrystalline graphite at 80-85% Carbon (C) at the mine site.
Some of the micro-crystalline graphite will be diverted for sale into traditional industrial uses such as refractories, crucibles, foundries, friction parts, pencils and lubricants.
The rest of the flotation concentrate is planned to be processed downstream by thermal purification to Ultra High Purity Fines (UHPF) for advanced industrial uses. Spheroidization then shapes the graphite to USPG and now coating produces CSPG for lithium-ion battery anodes for electric vehicles and other advanced applications.
CSPG a value-add
USPG is predominantly sold to China, South Korea and Japan where it is normally coated for use in high-performing lithium-ion batteries.
The addition of CSPG to Sarytogan’s product offering is expected to facilitate the establishment of direct relationships with battery manufacturers and OEMs in Europe and America.
Furthermore, the market price for CSPG is approximately US$8,000/tonne, a significant value-add over the pricing of USPG at approximately US$2,500/tonne.
Therefore, coating has been added to the flowsheet for the PFS.