The batteries made with graphite from the Lac Guéret deposit, in the anode, maintained 86% of their original capacity after 470 cycles of charge and discharge, said the company.
"This a remarkable performance, considering that for such prototype batteries, the target in the electric vehicle application is a minimum of 80% of retention after typically 500 cycles," it added.
The batteries were charged and discharged at the conditions typically used for electric vehicles - a rate of C/3, meaning three hours to charge, three hours to discharge.
"After many years of work and based on our industrial approach, the experience and expertise of our team allowed us to reach excellent results with our coated spherical graphite project," said Gilles Gingras, chairman of the board of directors.
"That these results have been obtained with samples produced at the pilot scale, and not laboratory scale, clearly demonstrates how advanced our project is."
Mason Graphite plans a new pilot production campaign of coated spherical graphite early 2021, which should be followed by a new sequence of cycling tests.
The total measured and indicated mineral resources of Lac Guéret are 65.5 million tonnes grading 17.2% Cg (carbon in graphite form), according to a December 2018 press release. This includes 19.0Mt of measured resources grading 17.9% Cg and 46.5 Mt of indicated resources grading 16.9% Cg.
The prototype full pouch cell type batteries were assembled on the new prototyping line of NRC in Boucherville, Quebec, Canada - a long-term partner of the company for the development of its spherical graphite grades, and tested in NRC's laboratories