Shirley Meng, seen with students in a UC San Diego lab, studies power technology. She says researchers are expected to double the energy density of lithium ion batteries over the next five years, making them last longer between charges. Lithium ion batteries are common in consumer electronics.

Shirley Meng, seen with students in a UC San Diego lab, studies power technology. She says researchers are expected to double the energy density of lithium ion batteries over the next five years, making them last longer between charges. Lithium ion batteries are common in consumer electronics. Photo by Photo courtesy of Jacobs School of Engineering, UC San Diego

The trick of extending battery life on smartphones and tablets is “a big problem and a big opportunity,” said Rick Cooper, a San Diego-based venture capitalist and treasurer for the Tech Coast Angels...