So much roof space, so little PV. I guess in China they don't do rooftop PV as much because the regulations allow for cheaper installations somewhere on a meadow?

Since most solar panels, charging equipment, inverters and batteries are made in China, I would be very surprised if they did not utilize it on their own buildings, provided that they have sufficient money to fund it.

That being said, China still has very high air pollution levels, especially in the urban areas. As a result, it might not be as economical to build solar power installations in there.

China has more distributed/rooftop solar than the US, percentage-wise. It's hardly like every big building in the US has rooftop solar, and Zhengzhou is more to the north of the country where there is less incident light.

That said a battery factory is a good place to put solar. The final stage of battery manufacturing is several priming charge/discharge cycles which build up resilient layers inside the battery. You can push power into/out of the grid (or use discharging batteries to charge other cells) but having a big DC source nearby is still going to be convenient.

they do a lot of rooftop PV in china. maybe not on this one factory but it's extremely common and even mandatory for all new industrial developments in some chinese cities now