Sarytogan Graphite Ltd (ASX:SGA) has successfully tested its Ultra-High Purity Fines (UHPF) as a cathode conductivity enhancer in AA alkaline batteries and in lithium monofluoride (Li/CFx) batteries.
Sarytogan plans to produce three product types in approximately equal proportions - Micro-crystalline 80-85% carbon (C) for traditional industrial uses; Uncoated Spherical Purified Graphite (USPG) for use in lithium-ion battery anodes; and UHPF for advanced industrial uses including the nuclear industry and now as a cathode conductivity enhancer.
The upstream beneficiation using grinding and flotation is planned to produce microcrystalline graphite at 80-85% C at the mine site. Around one-third of the micro-crystalline graphite will be sold for traditional industrial uses such as refractories, crucibles, foundries, friction parts, pencils and lubricants.
The other two-thirds of the flotation concentrate will be processed downstream by thermal purification and spheroidization. Sarytogan has demonstrated purification to as high at 99.9992% carbon and spheroidization at 54% yield. The resulting USPG is suitable for use in the anode of lithium-ion batteries.
The remaining 46% by-product from spheroidization is UHPF. At the very high ‘five-nines’ purity achieved, some of the UHPF may be suitable for use in the nuclear industry.
Sarytogan proposed schematic flowsheet and product mix.
UHPF graphite in Li/CFx battery market
Sarytogan has now successfully tested Sarytogan UHPF graphite in the cathode conductivity enhancer market, specifically in the Li/CFx battery market of 1 billion cells per annum and the alkaline battery market of 12 billion cells per annum.
Li/CFx batteries are primary (non-rechargeable) batteries made with a lithium metal anode and a cathode that is a blend of carbon and fluoride at variable ratios.
The Li/CFx batteries have much higher specific discharge capacity compared to lithium-ion batteries, high energy density (lightweight), long storage life, wide operating temperature range and are very rugged and reliable. They are therefore favoured in applications where charging infrastructure is not available, for example implantable medical devices, aviation and military applications.
Sarytogan UHPF was used to manufacture five Li/CFx cells. Two cells were made using the Sarytogan UHPF grading 99.998% carbon and three using Sarytogan UHPF grading 99.9992% carbon.
Both grades produced higher voltage than a control Li/CFx cell made with existing commercial graphite. The results were sensitive to purity with the higher purity Sarytogan UHPF performing better, especially during the initial discharge. The results were also highly repeatable.
Alkaline batteries
AA alkaline battery cells were manufactured by the company’s American technology partner. Sarytogan UHPF was blended with the manganese dioxide cathode and as a lining sprayed onto the inside of the metal can.
The battery produced was measured as having higher capacity than uncoated control cells and higher capacity than cells made from an existing graphite product sold for this use.
Cross section of an alkaline battery illustrating the use of Sarytogan UHPF.
“Yet another advanced use”
Sarytogan managing director Sean Gregory said: “These results demonstrate yet another advanced use for Sarytogan Graphite products. Given the giant size of the Sarytogan Graphite Deposit, the way to maximise value will be to place as many units of carbon into as many markets as possible.
“Sarytogan’s inverted flowsheet thermally purifies the graphite before rather than after spheroidization. This allows Ultra-High Purity Fines to be produced as a high-value by-product to the spherical graphite products for the rapidly growing lithium-ion battery market.”
Next steps
Sarytogen says the USPG lithium-ion cell performance has continued to cycle through repeated charges and discharges to measure long-term performance. Results after 100 cycles will enable comparison with other existing graphite products. These long-term results will be available in a few weeks.
Coated Spherical Purified Graphite (CSPG) is expected to provide even higher performance in the lithium-ion anode. CSPG has been manufactured by coating Sarytogan USPG with carbon. Battery testing of a coin cell with a Sarytogan CSPG anode will shortly commence.
These tests are all important inputs into the Pre-Feasibility Study which is on track to be completed in Q3 this year.