March 4 (Reuters) - Canadian miner Frontier Lithium said on Monday it is forming a joint venture with Japanese trading house Mitsubishi to help advance lithium mining and processing in Ontario.

Frontier aims to become a major supplier of the commodity, a key mineral used in batteries for electric vehicles, to the North American supply chain.

The partnership will help finance Frontier's PAK Lithium Project mine in Ontario and a planned lithium chemicals conversion facility, Frontier said.

As per the terms of the agreement signed last week, Mitsubishi would buy a 7.5% stake in the project for C$25 million ($18.44 million), with an option to increase it to 25%.

The PAK Lithium project encompasses about 27,000 hectares of land in Ontario, with two spodumene-bearing lithium deposits delineated since 2013. Spodumene concentrate is a type of lithium mineral ore. ($1 = 1.3560 Canadian dollars) (Reporting by Kabir Dweit in Bengaluru; Editing by Saumyadeb Chakrabarty)