Hironobu Minowa, who demonstrated the battery at NTT’s R&D Forum in Tokyo this week NTT DATA

A transparent battery could replace glass in windows. The battery still has a low output, but could eventually add extra energy storage to smart glasses or cars.

Most battery research focuses on increasing power output or energy density, a measure of how much energy can be stored in a certain volume. But Hironobu Minowa and his colleagues at Japanese communications giant NTT decided instead to focus on making a battery that is as inconspicuous as possible.

The team had to create new …