When you switched the phone off correctly, it knows that it
power will be shut down shortly.That means, all the
applications and the operating system get the chance to
save whatever needs to be saved and to go through their
proper shut-down process.
Removing the battery without switching the phone off will
immediately crash every running applications as well as the
It’s just like unplugging your system while it’s running. You
can do it, but it’s not advice-able, a bad idea though.Other
thing is that While switching off your device, the operating
system will make sure that every thing connected to the
phone’s memory and external memory is properly and
carefully closed.If you remove the battery before switching
off your phone, you may corrupt the memory which may
lead to unexpected behavior.
To summarize everything, Please always switch off your
phone before removing the battery.