Does a 100A outlet for a car charger need a dedicated disconnect?
Receptacle plugs can serve as a means to disconnect an appliance.  

If there is no receptacle, but is instead direct-wired, appliances rated over 300 volt-amperes require a disconnect.  If the breaker box is within sight and is 50 ft or less the breaker can serve as the disconnect.  If it is not within sight, then a means to lock the breaker in the off position can suffice as a disconnect.

Addendum: There is a small section in the code that talks about car charging disconnects.  As mentioned by another post, 2011 625.23 says greater than 60A or 150 volts to ground requires a disconnect --  That section was moved to 625.42 in the 2014, and to 625.43 in 2017.  

That being said, 60A or less can use a receptacle plug as a disconnect if listed by the manufacture, and with residential 150V to ground is not an concern.