The future of batteries, sought for decades by academics, startups, and corporate R&D armies is—quite possibly—just a slender sheet of ceramic material that’s supple enough to bend between two fingers. But no one outside of a Silicon Valley startup is allowed to know what it’s made of. Even the color of this man-made substance is a closely held secret, so of course it’s never been independently analyzed. And this battery material has already made Jagdeep Singh a billionaire, long before it makes its way into a single electric vehicle. His company, QuantumScape Corp., came out of stealth mode late last year for a public stock listing backed by promising data but no commercial product and zero revenue. In no time, the company briefly surpassed the valuation of Ford Motor Co., which sold more than half a million cars and trucks […]