FILE PHOTO: An electric vehicle charging station is seen at the Volkswagen display during media day at the Canadian International AutoShow in Toronto, Ontario, Canada, February 14, 2019. REUTERS/Chris Helgren/File Photo

BEIJING (Reuters) - China's Tianqi Lithium Corp 002466.SZ, one of the world's biggest lithium producers, said on Tuesday that its Australian unit had signed a long-term supply agreement with Swedish battery maker Northvolt.

Tianqi Lithium Kwinana, which recently launched a processing plant in Western Australia, will supply lithium hydroxide, a chemical used in electric vehicle (EV) batteries, to Northvolt Ett from 2020-25, Tianqi said in a filing to the Shenzhen Stock Exchange.

Northvolt Ett is the name of Northvolt's planned lithium-ion battery plant in northern Sweden. What will be Europe's largest such plant is due to begin production in 2021 and counts German automakers Volkswagen VOWG.DE and BMW BMWG.DE among its investors.

The filing gave no absolute tonnage figure for the deal but said that the volume supplied each year would be no lower than 6-10% of Tianqi Kwinana’s annual capacity.

The deal marks the second major customer win for Tianqi in a little more than a month. The company announced on Aug. 22 that it had signed up South Korea's LG Chem 051910.KS on a three-year deal covering 2020-22 for no less than 15% of Kwinana's annual capacity.

Tianqi Lithium Kwinana started production of lithium hydroxide this month, with its first phase output to ramp up to the full 24,000 tonnes a year over the next 12-18 months.

Capacity will double to 48,000 tonnes with a second stage, though Tianqi has put that on hold until the ramp-up of the first phase is complete because lithium prices remain depressed.

Amid a wave of new supply and adjustments to EV subsidies in China, lithium hydroxide prices AM-LIOH0002-LHM, as assessed by industry information provider Asian Metal, have fallen by 36.8% this year to 67,000 yuan ($9,428.25) a tonne.