I think you misread. It has 85MW output power and stores 8.5GWh of energy. It literally says so in the article.
Watt-hours and Watt is not the same
8.5 GWh / 85 MW = 100 hours, or around 4 days. If they can build it cheap enough, this is the kind of battery we would need to replace nuclear for dealing with the day-to-day variability of renewables.
Nuclear doesn’t work that way, it’s not really compatible with renewables because it’s generating as close to 24/7 as possible. You can’t ramp it up and down to accommodate the variable output from renewables because it’s slow to react when compared to battery, pumped hydro, or NG peaker plants and because a nuclear plant is so expensive that having it not generating 24/7 means it’s not making the money it needs to be worth the initial investment.
