The lowly chemical storage battery is slow to charge and slow to release energy into the load.
The capacitor is relatively fast at both.................
plus they go pop when you plug them into the wall outlet
But, as the article explains: “They have a weakness, however, in the relatively low quantity of energy that they can store, a property known as their energy density.”
The energy density disparity is huge for standard capacitors compared to physical batteries. You expect a battery to supply power for a matter of hours. Capacitors, on the other hand take on chores like taking the voltage ripple out of power supplies by charging and discharging over 100 times a second.
Even though these guys are improving the energy density, it is going to be a far cry from being able to supplant batteries for long haul operations.