Metal-air batteries represent a promising frontier in energy storage due to their high theoretical energy density, which exceeds that of conventional lithium-ion batteries. The technology leverages the reaction of metal with oxygen from the air, making it lightweight and potentially cost-effective for applications such as electric vehicles, grid storage, and portable electronics. The intellectual property landscape for metal-air batteries is dynamic, with key players and emerging innovators driving advancements through patents. This article surveys the patent trends, dominant entities, and technological innovations shaping the field.

The patent landscape for metal-air batteries reveals a concentration of activity around materials, cell design, and system integration. Major corporations, academic institutions, and startups have filed patents covering fundamental aspects of the technology, including anode materials, air cathodes, electrolytes, and sealing mechanisms to prevent electrolyte evaporation and carbon dioxide intrusion.

Zinc-air batteries dominate the early patent filings due to their relative simplicity, safety, and established manufacturing processes. Companies like Electric Fuel Limited (now part of Phinergy) and ZAF Energy Systems have pioneered patents on zinc-air systems, focusing on improving rechargeability and cycle life. Early patents often addressed mechanical recharge mechanisms, where spent zinc anodes are replaced manually or through automated systems. More recent filings emphasize electrochemical rechargeability, with innovations in bifunctional air electrodes that catalyze both oxygen reduction and evolution reactions.

Lithium-air batteries, though more challenging to commercialize due to their sensitivity to moisture and carbon dioxide, have attracted significant patent activity from academic and industrial researchers. IBM, Toyota, and PolyPlus Battery Company hold key patents in this space. IBM’s early work focused on organic electrolytes and protective membranes to stabilize the lithium metal anode. Toyota’s patents highlight hybrid electrolytes and nanostructured cathodes to enhance energy efficiency. PolyPlus has pioneered protected lithium electrodes (PLE) with glass-ceramic membranes, enabling operation in aqueous and non-aqueous environments.

Aluminum-air batteries, while less common in patent filings, show potential for high energy density and low cost. Phinergy and Alcoa have developed patents addressing anode corrosion inhibition and air cathode catalysts to improve performance. Recent filings explore alloying aluminum with other metals to reduce parasitic reactions and extend shelf life.

Emerging innovations in metal-air batteries are reflected in patents filed over the past decade. A notable trend is the integration of advanced catalysts for air electrodes, such as transition metal oxides, perovskites, and carbon-based materials doped with heteroatoms. These materials aim to reduce overpotentials and improve round-trip efficiency. For example, patents from the University of Waterloo and MIT describe cobalt-oxide and manganese-oxide catalysts with enhanced durability and activity.

Another area of intense patent activity is electrolyte formulation. Non-aqueous electrolytes for lithium-air batteries often feature organic solvents like ethers and ionic liquids, paired with lithium salts to enhance conductivity and stability. Patents from Samsung and LG Chem detail hybrid electrolytes that combine solid and liquid phases to mitigate dendrite formation and extend cycle life. Aqueous electrolytes for zinc-air and aluminum-air batteries are also a focus, with additives to suppress hydrogen evolution and improve ionic transport.

Sealing and air management systems are critical for metal-air batteries, as uncontrolled exposure to ambient air can lead to electrolyte degradation and performance loss. Patents from Bosch and Panasonic describe modular designs with selective oxygen diffusion membranes and moisture scavengers. These innovations aim to balance oxygen access for the cathode while excluding contaminants.

Startups and academic spin-outs are increasingly active in the patent landscape, often targeting niche applications or novel materials. Companies like NantEnergy (formerly Fluidic Energy) have patented zinc-air systems for off-grid energy storage in emerging markets. Academic institutions, such as the University of Oxford and Stanford University, hold patents on advanced cathode architectures and machine learning-driven optimization of battery parameters.

The geographic distribution of metal-air battery patents reflects regional strengths and market priorities. China leads in the number of filings, driven by government support for energy storage technologies and a strong academic-industrial collaboration framework. Japan and South Korea follow, with a focus on lithium-air systems for electric vehicles. The United States and Europe show a balanced portfolio, with patents spanning zinc-air, lithium-air, and aluminum-air technologies.

Key players in the metal-air battery patent landscape can be categorized into three groups: established battery manufacturers, automotive OEMs, and specialized startups. Established players like Panasonic, LG Chem, and Samsung leverage their expertise in lithium-ion batteries to explore metal-air systems. Automotive OEMs, including Toyota, BMW, and Hyundai, file patents targeting electric vehicle applications. Startups such as Phinergy and NantEnergy focus on commercializing metal-air batteries for specific use cases, often with unique IP strategies.

The evolution of metal-air battery patents indicates a shift from fundamental material discoveries to system-level innovations. Early patents emphasized individual components, while recent filings integrate multiple advancements into functional prototypes. For example, a 2022 patent from Toyota describes a lithium-air battery pack with thermal management and gas recirculation systems, highlighting the move toward practical implementation.

Despite progress, challenges remain in the patent landscape. Many metal-air battery patents are still in the early-stage or proof-of-concept phase, with limited commercialization. The high number of academic filings suggests a gap between research and industrial adoption. Additionally, overlapping patents in catalyst materials and electrolyte systems indicate potential licensing complexities.

The future of metal-air battery patents will likely focus on overcoming technical barriers to commercialization. Key areas include improving cycle life, reducing costs, and scaling production. Patents on recycling and second-life applications are also emerging, addressing sustainability concerns. As the technology matures, cross-licensing and collaboration between stakeholders may increase to accelerate deployment.

In summary, the patent landscape for metal-air batteries is characterized by diverse innovations, with dominant players and new entrants contributing to advancements. Zinc-air, lithium-air, and aluminum-air systems each have unique IP trends, reflecting their respective challenges and opportunities. The field is poised for growth, driven by the demand for high-energy-density storage solutions and the continuous flow of inventive ideas protected by intellectual property.