It appears that WeLion has been more successful in developing the new battery type because NIO filed to use its semi-solid-state battery cells in three EV models. The filing was revealed as China's Ministry of Industry and Information Technology released a catalog with the latest models allowed to be sold in China. The same catalog lists various specification changes made by carmakers to their current lineups. This is required by law so that people can submit feedback before the models are approved for selling in China.
NIO has no new models, but it listed three models with new specifications related to using semi-solid-state batteries. The three models are only listed by their model numbers, but a quick search reveals that they refer to two versions of the ES8 SUV and the ET7 sedan. This makes sense, considering the ET7 was the first model announced with the new battery tech. The ES8 and ET7 share similar dimensions, and it's fair to assume they will use the same battery pack, especially as this will be swappable.
The 150-kWh capacity represents 50% more than the current biggest battery packs both models use, thanks to the improvements in energy density afforded by the semi-solid-state battery tech. NIO said the new batteries have an energy density of 360 Wh/kg, which seems appropriate for the task. After all, being a swappable battery pack, it should remain compatible with the existing packs and car models.
The same filing reveals that the new battery is heavier than the current packs. Specifications listed in the catalog show the car models fitted with semi-solid-state batteries weigh 20 kg (44 lbs.) more than before. The new packs should become available this summer and will initially be available for rent only. NIO will also offer them for sale in the future, but we don't have a timeframe for that.
Considering the new technology and huge capacity, buying outright will probably be too costly. Previous rumors indicated that the new pack could be as expensive as a NIO ET5 sedan. It will take a long time before the new technology will reach price parity with the current liquid Li-ion batteries.