Bill Joy is a legendary computer scientist—a co-founder of Sun, a co-inventor of Java, and a visionary who was working on the Internet of Things two decades ago. Today, he’s the driving force behind a new battery technology that could revolutionize the renewable energy economy. The new battery combines the advantages of the familiar alkaline batteries (cheap, safe, and reliable) with those of the more powerful and expensive, fire-prone lithium batteries in our computers and phones. In this interview with Wired, Joy explains the groundbreaking new technology.