What determines the cost decline of batteries?

“the largest share of cost reduction, was driven by public and private R&D, which we estimate contributed a majority of the observed cost reduction, with a lower contribution of cost reduction coming from expanding economies of scale. Moreover, it is found that the majority of the R&D contribution can be attributed to advancements in chemistry and materials science.”

Reference:

https://pubs.rsc.org/en/content/articlelanding/2021/ee/d1ee01313k