Tesla is working on cheaper, more powerful batteries for its electric cars, but many of the required innovations are still works in progress, its chief executive, Elon Musk, said Tuesday at a much anticipated presentation at the company’s California factory. The advances could ultimately cut battery costs more than 50 percent and increase the distance Tesla’s vehicles can travel by nearly as much. That would set the stage for the company to make a “compelling” $25,000 electric vehicle three years from now, Mr. Musk said, speaking to a parking lot full of Tesla owners in their vehicles, honking in approval. But Mr. Musk, who has a reputation for promising game-changing innovations that often take far longer than expected or never arrive, said the company had not yet made the advances needed to get to that point. Investors were hoping that Mr. Musk would […]