Battery is used in families and machines. The chemicals inside it produce electricity. It's quite convenient for humans' lives. Now an old battery is getting a makeover (改造) and can give electric cars more energy to run. The nickel-iron (镍铁) battery was created over 100 years ago and now scientists in Harvard University have improved it to give off energy quickly. This can help electric cars run faster. What's more, this kind of battery is less harmful than the common (平常) ones. This new kind of battery hasn't been used in daily lives, but people are all interested in it. Scientists say they are working hard to put it into market as soon as possible. They believe that the battery will make another great change for people's lives.