SAN FRANCISCO (Reuters) - Tesla Motors <TSLA.O> Chief Executive Elon Musk is buying $65 million of bonds from SolarCity Corp <SCTY.O> in the latest debt offering by the solar panel company that Tesla plans to acquire for $2.6 billion, according to a filing on Tuesday.

Musk's purchase of the so-called "solar bonds" comes after money-losing SolarCity last week said it would cut operating costs to bring expenses in line with its reduced solar installation outlook.

SolarCity Chief Executive Lyndon Rive and Chief Technology Officer Peter Rive are each buying another $17.5 million of the $124 million offer, according to the SolarCity filing.

It appeared to be the first time Musk has directly purchased SolarCity bonds, although his rocket-making and space transport services company SpaceX has bought them in the past. He is the largest shareholder in Tesla and SolarCity and a cousin of the Rives.

Also on Tuesday, Tesla said an improved battery for the performance version of its Model S all-electric sedan would allow it to accelerate from 0-60 miles per hour in just 2-1/2 seconds.

(Reporting by Noel Randewich; Editing by Tom Brown)