Graphene Manufacturing Group (GMG) has reported no measurable capacity loss from its 1Ah graphene aluminium-ion pouch cells after 489 fast charge-discharge cycles.
The G Cells were charged and discharged at 10C, with each operation completed in six minutes. Testing was carried out by the Battery Innovation Center (BIC) in Indiana, US, which manufactured the cells using materials developed and supplied by GMG from its battery development centre in Brisbane, Australia.
The cycling remains ongoing. Data collected up to 4 September showed no reduction in cell capacity after 489 cycles (fig. 1).
A lithium titanate oxide (LTO) cell tested using the same cycling profile retained 86% of its original capacity after 64 cycles. GMG said its cell had therefore completed more than seven times as many cycles under the test conditions without measurable degradation.
Voltage and capacity data showed a relatively flat voltage curve through around 80% of the G Cell discharge cycle (fig. 2). GMG said this characteristic could make it easier to control constant-power discharge.
The G Cells recorded a gravimetric energy density of 39Wh/kg under 10C charging and discharging, compared with 37Wh/kg for the LTO reference cell (fig. 3). This is below the 49Wh/kg at 10C that GMG reported in April 2026. The company described the latest cells as unoptimised and said it believed energy density could be restored to around 50Wh/kg through further development.
The graphene aluminium-ion cells had a measured internal resistance of approximately 5mΩ and reached 29°C from an ambient temperature of 25°C. The LTO cells recorded resistance of up to 30mΩ and reached 44°C under testing.
Bob Galyen, GMG director and former chief technology officer of CATL, said: “The cycling stability we are seeing from these G Cells is genuinely exceptional.
“The very low internal resistance of around 5mΩ, and the resulting 4-degree temperature rise above ambient, tells me GMG’s material science is translating into real, measurable cell-level performance rather than just laboratory promise.”
He acknowledged that further work was required to improve energy density and scale up the cell format.
The 1Ah cells are currently produced in pouch format (see main picture). GMG is developing the chemistry with the University of Queensland and UniQuest under a joint development agreement with mining company Rio Tinto. The technology does not use lithium or rare-earth materials and remains at battery technology readiness level four.
