Elon Musk’s Tesla was the clear global leader in electric vehicle sales at the start of 2022, powered by booming demand and profit from the fast-growing Chinese market. But in the first six months of the year, China-based BYD is emerging as a formidable new competitor with total sales—including plug-in hybrid models—that topped the U.S. EV pioneer. BYD, which counts Warren Buffett’s Berkshire Hathaway as a longtime investor, delivered 641,350 EVs and plug-in hybrids to customers in the first half, up 315% from a year ago, compared with Tesla’s 564,743, up 46% . Tesla’s sales of battery-only models kept it...