Due to the suitability to balance the intermittency in decentralized systems with renewable sources, electrochemical energy storage possibilities have been analyzed in several studies, all highlighting the need for improvements in relevant techno-economic parameters. Particularly a reduction in the costs per cycle is much needed, which could either come from innovation in more cost-efficient manufacturing methods, a higher endurance of charge/discharge sequences or higher capacities. Looking at patent applications as a metric allows us to determine whether the necessary technological progress is indeed occurring, as the mandatory publication of the underlying inventions provides access to otherwise hidden R&D activities. Our paper contributes to the literature with a compilation of technological classes related to important battery types in the novel Cooperative Patent Classification (CPC), which can be used to identify relevant patent applications of the competing technologies. Using the worldwide patent statistical database (PATSTAT), we find that promising technologies have been showing increasing patent counts in recent years. For example, the number of patent applications related to regenerative fuel cells (e.g. redox flow batteries) doubled from 2009 to 2011. Nevertheless, the volume of patent filings in technologies related to lithium remains unchallenged. Patent applications in this area are still growing, which indicates that the introduction of improved modules will continue. Using citation analysis, we have identified important patents and organizations for relevant candidate technologies. Our study underlines that electrochemical storage, and in particular lithium-based technologies, will play an increasingly important role in future energy systems.