As I mentioned in the article, the slide deck from which the chart is borrowed http://gcep.stanford.edu/pdfs/events/workshops/Barnhart_NEA%20Stanford%20April%202015.pdf is based on the average emissions intensity of the US power supply networks. Yes, logically, if a battery factory is powered from non-fossil energy sources then the embodied emissions will decrease. Despite the amazing build of renewable and nuclear energy in China, however, odds are any such factory will go the other way due to the continued dominance of coal.

The slide deck also provides the assumptions for storage media lifespan, which is 6000 cycles for Li ion i.e. over 16 years of daily cycling. More rigorous experimentation from NREL suggests degradation to 70% in about 5 years for the NMC chemistry used in Tesla’s powerpack https://www.nrel.gov/docs/fy17osti/67102.pdf We are still several years away from seeing real operational results, of course.