There are some 12 volt heaters and defrosters you put in your vehicle to defrost your windshield in your vehicle and to warm the interior of the vehicle faster than your normal heater that runs off the engine would while the engine is warming up.
But those 12 volt heaters would not keep your house warm at all or warm you very much during a power outage or anything.
So other than that it would be impossible to have a battery powered space heater that runs off of normal household batteries since space heaters require a lot of power to heat up the elements and would drain the batteries within a few seconds.
Best thing to do is to have a wall mounted natural gas heater or a floor furnace that runs without electricity to keep your house warm during a power outage.
Another option of emergency heat is to have a wood burning stove installed in your home and get some free firewood or even purchase some firewood to have on hand so you can have your house heated really warm during a power outage.
Wood stoves give off lots of heat and will warm your home really quick.
I burn wood a lot even when I have power because I love the feel of the wood burning stove and I can get lots of firewood for free.