From DID:

As the successor to the 102,000 ton Nimitz Class super-carriers, the CVN-21 program aimed to increase aircraft sortie generation rates by 20%, increase survivability to better handle future threats, require fewer sailors, and have depot maintenance requirements that could support an increase of up to 25% in operational availability. The combination of a new design nuclear propulsion plant and an improved electric plant are expected to provide 2-3 times the electrical generation capacity of previous carriers, which in turn enables systems like an Electromagnetic Aircraft Launching System (EMALS, replacing steam-driven catapults), Advanced Arresting Gear, and integrated combat electronics that will leverage advances in open systems architecture. Other CVN-21 features include an enhanced flight deck, improved weapons handling and aircraft servicing efficiency, and a flexible island arrangement allowing for future technology insertion. This graphic points out many of the key improvements.