I need to know for Xbee Series 2 as well as for Xbee Series 1.
If its less, how can i scale it up for up-to 100 end devices per coordinator
For the 802.15.4 product, there is no limitation implemented with in the Code for the total number of end devices. So in this case it is a function of how many 16 bit addresses that can be assigned out.
As for the Zigbee product, depending on the specific version of the hardware and firmware you are using, a parent node such as a Coordinator or router can each support up to 10 - 12 End device children.
In series 2 how can i overcome this limit.
You can’t. If you need more sleeping end devices, you have to add more parent routers to your network. That is your only option.