NIO Inc., the Chinese electric-car maker backed by Tencent Holdings Ltd., is planning a U.S. initial public offering that would give it a valuation topping $8 billion as it gears up to take on the likes of Tesla Inc. The company is aiming to raise as much as $1.3 billion, offering 160 million American depositary shares at $6.25 to $8.25 each, according to a regulatory filing Tuesday in the U.S. That would give the company a market capitalization of about $6.4 billion to $8.5 billion.