The short answer is that supercapacitors can't replace batteries in most applications, just as batteries usually can't replace supercapacitors, but why?.
What is a rechargeable battery and a supercapacitor?
In a rechargeable battery, those ions can regain electrons and return to the start, ready to have those new electrons skimmed off in a new cycle. A supercapacitor is a newer concept that combines the design of a battery with the physics of a capacitor.
What is the difference between a supercapacitor and a battery?
Supercapacitors and batteries, they are both storage methods. If we look at lithium-ion batteries, they rely entirely on chemical reactions. They consist of a positive and negative side, technically called an anode and a cathode.
Supercapacitors may replace coin cell batteries in many applications, such as memory backup power. The Eaton KVR-5R0C155-R (Figure 2, right) is a 1.5 F supercapacitor rated at a maximum working voltage of 5 volts. Its package dimensions are similar to those of a 20 mm coin cell. It can deliver a peak power of 0.208 watts.
The same goes for voltage delivery. A 12V battery might only provide 11.4V in a few years, but a supercapacitor will provide the same voltage after more than a decade of use.
Are supercapacitors better than lithium ion batteries?
The biggest drawback compared to lithium-ion batteries is that supercapacitors can't discharge their stored power as slowly as a lithium-ion battery, which makes it unsuitable for applications where a device has to go long periods of time without charging.
Could supercapacitors replace bulky batteries in future electric vehicles?
These factors are a given-it is a Supercapacitor after all. This study makes this study unique and interesting because the researchers suggest that the new, thinner Supercapacitors could replace bulkier batteries in future electric vehicles.