Plymouth-based electric vehicle startup Rivian Automotive LLC has netted a $350 million investment from Atlanta-based Cox Automotive as the automaker readies to produce its first vehicles.

The investment announced Tuesday follows $500 million from Ford Motor Co., and $700 million from Amazon.com Inc. earlier this year. Rivian aims to launch its first electric pickup truck and electric SUV by 2021. The automaker is currently renovating an old Mitsubishi plant in central Illinois where it plans to start building those vehicles late next year.

The automaker has grabbed the attention of big-name investors and the public for its vision of rugged, longer-range electric vehicles that can go off-road, haul, and stand up to wear and tear that electric vehicles aren't currently known for. The automaker has poached engineers and other minds from the Detroit Three, including a designer who worked on Ford's forthcoming Bronco SUV.

The Cox Automotive investment would drive partnerships in service operations, logistics and digital retailing, according to a statement.

"We are building a Rivian ownership experience that matches the care and consideration that go into our vehicles," said RJ Scaringe, founder and CEO of Rivian, in a statement. "As part of this, we are excited to work with Cox Automotive in delivering a consistent customer experience across our various touchpoints."

The quiet startup aims to launch a five-passenger electric R1T pickup and a seven-passenger R1S SUV with a more-than 400-mile range and off-road capability in late 2020. The Plymouth-based start-up made waves late last year when it unveiled the sleek products — hardly anyone had heard of Rivian. The company didn't even have signs on its buildings last November, shortly after it stole the show at the Los Angeles auto show.

Ford and Rivian have said the companies are exploring partnerships on a product for the North American market. Ford plans to launch an electric crossover next year; it's also working on an electric F-150. Ford CEO Jim Hackett said recently that the Rivian-Ford product won't necessarily be a truck.

The Cox and Amazon partnerships explore a different space that looks to be focused on fleets and possible delivery vehicles, among other things.

"With the electrification of vehicles set to play a significant role in the new mobility future, this partnership opens another channel of discovery and learning for Cox Automotive," said Joe George, president of Cox Automotive Mobility Group, in a statement. "Advancements in battery technology and the electrification of fleets are two of our primary focus areas, and we believe this relationship will prove to be mutually beneficial."

ithibodeau@detroitnews.com

Twitter: @Ian_Thibodeau