Yes! All plugged in Z-Wave devices automatically extend your Z-Wave range. Battery powered devices save energy by not constantly listening for other devices' signals and transmitting them to the primary controller. Plugged in devices, however, don't have to worry about draining their battery, so they constantly listen for signals and repeat them back to the controller.
When planning your Z-Wave network, make sure all of your devices (or "nodes" in the network) have multiple paths for the signal to travel back to the primary controller. For example, if a motion detector is at the other end of your home from your controller, make sure there are at least two plugged-in devices between the motion detector and the primary controller, in case one of them loses connectivity due to temporary obstacles, loss of power, etc. Also, Z-Wave signals can only "hop" a maximum of four times from the controller, and it's best to keep it to two hops if possible.