Zinc-air batteries have seen significant advancements in recent years, particularly in the development of bifunctional catalysts, anode coatings, and cell architectures. Between 2010 and the present, multiple patents have been filed by key players such as NantEnergy and ZAF Energy, alongside contributions from academic institutions and other industrial entities. These innovations aim to improve the efficiency, durability, and scalability of zinc-air battery systems, addressing challenges such as oxygen reduction and evolution reaction (ORR/OER) kinetics, zinc dendrite formation, and electrolyte management.
Bifunctional catalysts are critical for zinc-air batteries because they facilitate both the oxygen reduction reaction during discharge and the oxygen evolution reaction during recharge. Early patents in this space focused on noble metal-based catalysts, such as platinum and iridium oxides, but their high cost and scarcity drove research toward non-precious alternatives. Transition metal oxides, particularly those based on manganese, cobalt, and nickel, emerged as promising candidates. For example, NantEnergy patented a class of manganese oxide-based catalysts with perovskite or spinel structures, demonstrating improved stability and activity compared to traditional noble metals. These catalysts were further optimized through doping strategies, incorporating elements like iron or copper to enhance electronic conductivity and catalytic performance.
Another notable trend in bifunctional catalyst development is the use of carbon-based materials, including nitrogen-doped graphene and carbon nanotubes. These materials offer high surface area and tunable electronic properties, making them effective supports for metal oxides or single-atom catalysts. ZAF Energy filed patents covering hybrid systems where cobalt nanoparticles are embedded in nitrogen-doped carbon matrices, achieving comparable performance to platinum-based catalysts at a fraction of the cost. Geographically, China has been a major contributor to this field, with several patents originating from universities and research institutes focusing on cost-effective synthesis methods for these advanced materials.
Anode coatings have been another focal area for zinc-air battery innovation, primarily aimed at mitigating zinc dendrite growth and improving cycling stability. Uncontrolled dendrite formation can lead to internal short circuits and capacity fade, limiting the practical lifespan of rechargeable zinc-air batteries. Patents from NantEnergy describe the use of polymer-based coatings, such as polyaniline or Nafion, which create a uniform ion flux distribution at the zinc surface. These coatings act as artificial solid-electrolyte interphases (SEIs), reducing localized current hotspots that promote dendrite nucleation. Other approaches include inorganic coatings like zinc oxide or titanium dioxide, which provide mechanical barriers while maintaining ionic conductivity.
ZAF Energy’s patents highlight the use of three-dimensional porous zinc structures combined with conductive additives like carbon or silver. These architectures increase the active surface area and reduce the effective current density, thereby delaying dendrite formation. Additionally, some patents propose electrolyte additives, such as bismuth or indium ions, which modify the zinc deposition behavior to favor planar growth over dendritic structures. The majority of these anode-related patents originate from the United States and Europe, reflecting strong industrial interest in improving the rechargeability of zinc-based systems.
Cell architecture innovations have played a crucial role in advancing zinc-air battery technology. Traditional designs faced challenges with electrolyte leakage, carbon dioxide intrusion, and inefficient oxygen diffusion. Recent patents address these issues through novel configurations, including flow-assisted systems and modular stack designs. NantEnergy’s work includes patents on air cathodes with hydrophobic layers to prevent electrolyte flooding while maintaining oxygen permeability. These designs often incorporate gas diffusion layers made of microporous polytetrafluoroethylene (PTFE) or similar materials, ensuring optimal triple-phase boundaries for ORR/OER reactions.
Another architectural advancement is the use of hybrid electrolytes, where a solid or gel electrolyte is employed at the anode side to suppress dendrites, while a liquid electrolyte facilitates oxygen reactions at the cathode. ZAF Energy has patented several designs in this category, including cells with asymmetric separator membranes that selectively control ion transport. Geographically, South Korea and Japan have been active in filing patents related to compact and flexible zinc-air battery designs, targeting applications in consumer electronics and wearable devices.
The assignee landscape for zinc-air battery patents reveals a mix of established companies and startups driving innovation. NantEnergy, formerly known as Fluidic Energy, has been a dominant player with a broad portfolio covering catalysts, electrolytes, and system integration. Their patents often emphasize scalability and cost reduction, aligning with their focus on grid-scale energy storage applications. ZAF Energy, on the other hand, has concentrated on high-performance materials and manufacturing techniques, particularly for military and aerospace applications where energy density and reliability are critical.
Academic institutions have also contributed significantly, with patents originating from universities such as MIT, Stanford, and the Chinese Academy of Sciences. These patents frequently explore fundamental material science breakthroughs, such as novel catalyst synthesis methods or advanced characterization techniques for zinc deposition. While corporate patents tend to focus on commercial viability, academic patents provide foundational knowledge that enables further industrial development.
Geographical trends in zinc-air battery patent filings show strong activity in North America, Europe, and Asia. The United States leads in system-level innovations and military applications, while China dominates in materials science, particularly for low-cost catalysts and manufacturing processes. Europe has a balanced distribution, with patents covering both fundamental research and industrial applications, often supported by government-funded initiatives. South Korea and Japan have focused on consumer electronics integration, reflecting their strong battery manufacturing ecosystems.
The evolution of zinc-air battery technology from 2010 to the present demonstrates a clear trajectory toward improved performance and commercial viability. Bifunctional catalysts have shifted from noble metals to abundant materials, anode coatings have become more sophisticated in preventing dendrites, and cell architectures have evolved to address practical challenges. Key assignees like NantEnergy and ZAF Energy have played pivotal roles in translating these advancements into patented technologies, while geographical hotspots of innovation highlight regional strengths in materials, manufacturing, and application-specific designs. As research continues, these developments are expected to further enhance the competitiveness of zinc-air batteries in the broader energy storage landscape.