BEIJING -- Daimler AG Chief Executive Dieter Zetsche says he'd never disregard an idea from Tesla Motors Inc. CEO Elon Musk. But Daimler won't be an investor in Mr. Musk's concept of building a huge, electric car battery "giga-factory," Mr. Zetsche said.

Daimler owns a small stake in Tesla, and has worked with the Silicon Valley luxury car maker on battery technology.

But...