Evolution Energy Minerals Ltd (ASX:EV1) and its US technology partner have welcomed preliminary results of long-term battery cycling.
The cycle testing was conducted to gauge degradation of electrochemical performance of uncoated and coated spherical graphite. The testing found the product maintains a near-theoretical electrochemical performance at a reversible capacity of 368 mAh/g.
Cycling was performed in CR2016 coin cells, a generally accepted test vehicle for pre-qualifying graphite for use in lithium-ion battery anodes, at a C/10 rate, meaning that it takes 10 hours to charge the cell and the same to discharge. One full cycle, therefore, lasts about one day.
Easily exceeds thresholds
The testing showed that Chilalo spherical graphite easily exceeds the thresholds required by super-premium graphite in the EV and energy storage anode markets.
Testing is ongoing and seeks to verify whether the reversible capacity holds from cycle to cycle. Evaluation will gauge the degradation of electrochemical performance as a function of elapsed cycle number.
Cycle testing will continue through to 100 cycles, while the company has sufficient data to start qualification initiatives of coated spherical graphite with targeted battery manufacturers.
High purity for EV manufacturers
This latest stage in the test-work process has already demonstrated that Chilalo graphite has very low levels of molybdenum and boron, can be purified to 99.9995% C and when processed into coated spherical graphite, significantly exceeds the specifications of major EV manufacturers.
Short-term electrochemical testing has demonstrated that the uncoated Chilalo spherical graphite delivered a reversible capacity of 367.65 mAh/g with an irreversible capacity loss of 9.4%.
The surface-coated version of the same material preserved the reversible capacity level, demonstrating 367.8 mAh/g, while decreasing irreversible capacity loss to less than 7%.
In this latest test-work stage, the uncoated and coated spherical graphites were tested in a cell design engineered for long-term cycling.
The first 25 cycles have wrapped up, with more updates to come.
Very encouraging results
Managing director Phil Hoskins said: “We are extremely pleased to have started our long-term battery cycle testing program for Chilalo’s coated spherical graphite. Tests use industry-standard CR2016 battery cells and the results we are seeing to date are very encouraging.
“The surface coated graphite grade that is being tested has a mean particle size of 25 microns, which meets the specifications of at least one leading electric vehicle manufacturer and at least one world-class battery technology provider for lithium-ion cells used in utility-scale energy storage.
"We will work with these companies as intended offtake partners in the future and will be updating the market as more test data becomes available.”