Supercapacitors power the Note 9 stylus — but are they ready to replace batteries?

Samsung’s latest Galaxy Note 9 has a nifty new feature: for the first time, the S Pen stylus has Bluetooth and can be charged instantly using a supercapacitor. Sticking the S Pen into the phone for 40 seconds gives it enough juice for 30 minutes of use, so battery life should no longer be a worry. But how exactly does this technology work? And what else could we use supercapacitors for?Supercapacitors (or ultracapacitors) store energy and, in some ways, are the opposite of batteries. Batt