It is grammatically correct, but indeed not very tidy. The pronoun and contracted verb it's could simply be elided and the sentence would remain perfectly correct:
The company is planning to introduce its SUV Model X next month, designing its Model 3 car, building a huge battery factory near Reno, Nevada, and scaling up its grid battery business, which will sell batteries to utilities, companies and homeowners to connect to the power grid.
Stilistic errors are not "wrong" grammatically, but the fact that we call them "errors" shows that there are better ways to write sentences like this.
Additionally, the repetition of it's is not the only thing that could be changed in order to improve this sentence in my humble opinion. The sentence could be split into two and fiddled around with a bit in order to improve its readability, but all this is just a matter of personal preference and the writer is free to phrase his words as he pleases or as he thinks they should be phrased for his public to be willing to read his text.