The reuse of second-life batteries presents a significant opportunity to extend the lifecycle of energy storage systems, particularly those retired from electric vehicles. However, patent thickets—dense webs of overlapping intellectual property rights—create barriers to widespread adoption. These thickets span diagnostics, repurposing methods, and module integration, complicating efforts to commercialize second-life applications. Key IP holders dominate critical technologies, while licensing gaps stifle innovation and scalability.

Diagnostics is a critical first step in second-life battery deployment. Patents covering state-of-health (SOH) estimation, impedance spectroscopy, and machine learning-based degradation models are heavily concentrated among a few players. Major automakers and battery manufacturers hold extensive IP in this space, including methods for rapid assessment of retired batteries. For example, techniques involving hybrid models combining electrochemical impedance spectroscopy with voltage decay analysis are frequently patented. These patents often cover specific algorithms or hardware configurations, making it difficult for third-party repurposers to develop alternative solutions without infringement risks.

Repurposing methods face similar challenges. Patents cover cell sorting, reconfiguration, and capacity matching, with particular emphasis on modular designs for stationary storage. A notable thicket exists around battery pack disassembly and reassembly processes, where proprietary methods for handling degraded cells are protected. Some patents describe automated systems for testing and regrouping cells, while others focus on thermal management adaptations for second-life packs. The overlap in these claims creates uncertainty, as repurposing companies must navigate multiple patents to avoid litigation.

Module integration is another area where patent thickets hinder progress. Key patents cover voltage balancing, adaptive battery management systems (BMS), and interoperability between heterogeneous modules. Legacy automotive BMS designs often require modifications for second-life use, but many of these adaptations are patented. For instance, dynamic reconfiguration techniques that allow mixed-capacity cells to function efficiently in a single system are protected by multiple entities. This fragmentation forces second-life integrators to either license expensive technologies or develop workarounds, increasing costs and delaying deployment.

Key IP holders in this space include major automotive OEMs, battery manufacturers, and specialized energy storage firms. Companies like Toyota, BMW, and Tesla hold extensive patent portfolios covering diagnostics and repurposing. Meanwhile, firms specializing in grid storage, such as Fluence and Stem, have patented module integration solutions tailored for second-life batteries. Universities and research institutions also contribute, particularly in advanced diagnostics and predictive modeling. However, the dominance of large corporations creates an uneven playing field, where smaller innovators struggle to compete or negotiate favorable licensing terms.

Licensing gaps further exacerbate the problem. Many patents essential for second-life battery reuse are either not licensed or available only under restrictive terms. For example, proprietary BMS firmware required for module integration is often withheld, forcing repurposers to reverse-engineer solutions. Additionally, defensive patenting by some firms leads to portfolios that are neither commercialized nor accessible to others. This lack of transparency discourages investment in second-life ventures, as the risk of infringement looms large.

The impact of these thickets is measurable. Studies indicate that patent disputes and licensing complexities add 15-20% to the development costs of second-life battery systems. In some cases, projects are abandoned altogether due to uncertainty around freedom-to-operate. The slow pace of standardization in second-life applications further compounds the issue, as proprietary technologies dominate the market without clear alternatives.

Potential pathways to mitigate these challenges include patent pools and collaborative licensing frameworks. Some industry consortia have begun exploring shared IP models for second-life technologies, though progress remains slow. Policymakers could also play a role by incentivizing open licensing for critical repurposing methods. However, without systemic changes, patent thickets will continue to stifle innovation in this emerging sector.

In summary, second-life battery reuse faces significant IP hurdles. Diagnostics, repurposing methods, and module integration are all affected by dense patent landscapes controlled by a handful of key players. Licensing gaps and restrictive practices further limit scalability. Addressing these barriers will require coordinated efforts from industry, academia, and regulators to unlock the full potential of second-life energy storage.