Australian lithium miner Pilbara Minerals on Tuesday said it had signed an additional deal with Chinese automaker Great Wall Motor Co to supply spodumene concentrate, a key mineral for electric vehicles.

Deliveries under the six-year deal will begin in August, with 20,000 dry metric tons of concentrate to be shipped annually.

The West-Perth based company's shares reversed course to rise as much as 13.7 percent after the announcement, their sharpest gain in over three months.

In 2017, Great Wall Motor took a 3.5 percent stake in Pilbara and signed an off-take deal that would provide it with 75,000 tons of spodumene concentrate each year for an initial five-year period. 

Pilbara said it shipped 43,214 dry metric tons of concentrate in the June quarter, higher than the previous quarter's figure of 38,562 dry metric tons.

The miner expects sales in the three months ending in September to be in the range of 35,000-48,000 dry metric tons of concentrate, affected by a 14-day planned shutdown at its Pilgangoora project.

Sales are anticipated to be in the range of 65,000-80,000 dry metric tons of concentrate in the December quarter as production returns to full capacity.