This analysis of over 90,000 secondary battery innovations (measured by international patent families) provides a comprehensive account of the long-run progress of a knowledge base with a key role in the transition to a transformative, closed-loop, Circular Economy. Innovation accelerated globally from 2000 to 2019, a sustained dynamic mostly originating in Asia. Patterns of less toxicity and more diversity in technological trajectories are detected and found to bear evidence of pro-circularity. We find a number of emergent technological trajectories, such as solid-state, lithium–sulfur, redox-flow and sodium-ion batteries, each one with a different potential to push ahead the circularity pathway, and which allow for the detection of country clusters. Through a methodology that can be of interest for further research, we examine the extent to which batteries have circular characteristics.