Power cell is a popular name for advanced supercapacitors commonly used in our setting. (Some other SF settings have called these “batacitors” because they combine the best features of capacitors and chemical batteries.) They can be charged quickly, given a powerful enough energy source, and they can be discharged either quickly or slowly. These are used to power everything from small devices – like flashlights or datapads – to automobiles and skycars. They are sometimes used as power sources in buildings (particularly hospitals) in case of power failure.
A power cell can store more energy than lithium-ion batteries (which are now mostly obsolete), but not as much energy as a tank of liquid fuel. Thus, vehicles which require long range without recharging, or which have to operate away from the electrical grid, are often hybrid designs.
Power cells have some safety issues. If the energy content is released quickly enough, they can explode. They can also cause electrical shock. Most power cells are carefully designed, armored and compartmentalized, to prevent these types of accidents as much as possible – however, if you crush a power cell, the energy has to go somewhere.