All that would do is offset things so that we can pollute more. Not to mention the CO2 and other emissions from such a project. And it would ruin a huge amount of space because of course this would run into “not in my neighborhood”. It’s far better to fix the problem than to paint over it.
Interesting, but even if we solved the temperature problem, we would still have the issue of the acidification of the oceans due to excess CO2. In the end we must remove CO2 from the atmosphere one way or another.
So we'd only have to paint 1/80 of the Earth. That's ~6.4mln km2, or 2/3 the area of the USA. Still a lot, but not impossible.
I'm sure paint manufacturing scales better than li-ion batteries, and those more than doubled in production volume over the last decade.