The plastic sheet invented by Stanford University chemical engineer Zhenan Bao and her colleagues can be inserted in lithium-ion batteries to avoid overheating. Zheng Chen/Courtesy of Zhenan Bao hide caption

toggle caption Zheng Chen/Courtesy of Zhenan Bao

Jim and Lyn Schneider installed solar panels and batteries because bringing grid power to their house in central Wyoming was going to cost around $80,000. Leigh Paterson/Wyoming Public Radio hide caption

toggle caption Leigh Paterson/Wyoming Public Radio

Smart watches based on Qualcomm chipsets are displayed at CES — but do consumers want them? Jae C. Hong/AP hide caption

toggle caption Jae C. Hong/AP

A prototype of a flexible battery from Imprint Energy, one of 40 companies working on battery technology in the San Francisco Bay Area. Imprint Energy hide caption

toggle caption Imprint Energy