KiCad: Power with hierarchical sheets
The solution that you have on your pictures will work fine. I have checked the Battery element in the library editor and it has both pins as a passive pins, so ERC wont complain. 

If you want to use +9 V and GND elements from Power library, then you also need to add a power flag. In the reference they say:


  It is common to have an error or a warning on power pins, even though all seems normal. This happens because, in most designs, the power is provided by connectors, that are not power sources (like regulator output, which is declared as Power out).
  The ERC thus won’t detect any Power out pin to control this wire and will declare them not driven by a power source.
  To avoid this warning you have to place a “PWR_FLAG” on such a power port. 


So, using the power flags, you can make following configuration:



Regarding the hierarchical sheets, take a look at this video to learn more (browse the channel, there are lots of very useful videos for KiCad).