May 22 (Reuters) - Canada's Nemaska Lithium said on Tuesday it had secured funding of up to C$402 million ($314 million) from investors, which it plans to use to build a mine and processing plant to produce lithium, the key ingredient for rechargeable batteries.

This brings to more than C$1.1 billion the amount of money Nemaska has raised this year for its proposed operations, as the Quebec-based company rides a wave of interest in lithium for batteries used in electric vehicles and mobile phones.

"Today marks a big day in the life of Nemaska Lithium, as we are announcing the last piece of financing required to start the commercial development of the Whabouchi lithium mine project," Nemaska Chief Executive Guy Bourassa said in a statement.

Nemaska is developing the Whabouchi hard rock lithium project in Quebec, one of North America's largest spodumene deposits.

Under the deal announced on Tuesday, Nemaska said National Bank Financial, BMO Ca pital Markets and Cantor Fitzgerald Canada had agreed to purchase 280 million of its shares at C$1 each in a bought deal. They have the option to increase this by C$42 million.

In addition, Nemaska has agreed to do a private placement of 80 million shares at C$1 each with an unnamed institutional investor. Nemaska's shares closed at C$1.18 on the Toronto Stock Exchange on Tuesday, down 9 Canadian cents.

In April, Nemaska said Japan's SoftBank Group Corp would invest in its shares. It has also done a stream financing and a bond offering.

($1 = 1.2813 Canadian dollars) (Reporting by Nicole Mordant in Vancouver, Editing by Rosalba O'Brien)