A bettery, from the viewpoint of a circuit, is just another source. So we could call them chemical electricity generators, if we're brave enough to indulge the confusion
I still don't quite understand it. Where does the battery get the energy? I understand that there's no difference in a circuit, but why is this comparison relevant? Many power sources are way less efficient that using a battery, but we need to charge the battery.
For low-enough-power applications and sufficiently long-lasting batteries, charging is just another step in production.
Betavotaic generators usually produce extremely low power. A similarly sized battery can last for decades at the same power output.
Alkaline batteries are never charged, per se. The energy comes from the one-way chemical breakdown of cathode and the anode.