Iron-Air Long-Duration Storage Patents: Leaders & Filing Trends 2026
- Filing has cooled since its 2023 peak. Annual filings rose from 18 in 2017 to a peak of 31 in 2023, then eased back toward the 2022 level of 25 — a flat-to-declining trend rather than accelerating growth.
- H01M dominates the IPC mix by a wide margin. All 627 records sit in H01M (batteries, cells & fuel cells), with H02J (grid/power supply) a distant second at 31 — most adjacent-system claims are still thin.
- The US is the dominant filing venue, but PCT and EPO run level. 185 US filings lead, with EPO and WIPO/PCT tied at 90 each and China at 64 — a genuinely multi-jurisdiction field rather than a single-market one.
What this landscape covers
This review tracks patent families filed against iron-air and metal-air battery constructions for long-duration storage, built around claims to the iron electrode, the air cathode, reversible oxidation chemistry and multi-day discharge cycles. The corpus spans 627 patent families published between 2015 and the 2026 data cut-off, drawn from IPC classes H01M12/06, H01M4/13 and H01M12/08.
Publication typically lags filing by around eighteen months, so the most recent year in any trend line understates real filing activity. Read the 2025-2026 figures as a floor, not a ceiling.
Let an AI agent run this analysis on your own technology
Pick a task. Every answer cites the patents behind it.
Filing trend and technology composition
Two views of the same 627-family corpus: how filing volume has moved year over year, and which IPC subclasses the claims actually sit in.
A peak in 2023, then a pullback
Filings climbed from 18 in 2017 to a peak of 31 in 2023. The 2022 figure of 25 sits below that peak, and the trajectory since has flattened rather than continued upward — consistent with a technology area where core electrode and cathode claim space is filling up faster than new entrants are arriving.
Concentrated in H01M, thin everywhere else
Every record in this set classifies under H01M. The next-largest subclasses — H02J (power supply & grid systems, 31), B60L (EV propulsion, 23), B01J (catalysis, 14) — are an order of magnitude smaller. That gap is the clearest signal in the dataset: grid-integration, thermal-management and vehicle-adjacent claims around iron-air chemistry are comparatively unclaimed.
Shares are the percentage of the 627 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Iron-Air Long-Duration Storage Landscape with Eureka
This page is one run against one query. Ask Eureka your own question about iron-air long-duration storage landscape and every answer comes back with the patent numbers behind it.
Try EurekaThe prior art doing the most work
US20130202974A1 — Air cathode, metal-air battery and method for producing air cathode for metal-air battery (Toyota, filed 2013-08-08)
An object of the present invention is to provide a metal-air battery having excellent durability and capacity by facilitating a reaction of oxygen radicals and metal ions at an air cathode. Disclosed are an air cathode used for a metal-air battery comprising an air cathode, an anode and an electrolyte layer which is present between the air cathode and the anode and which conducts metal ions between the air cathode and the anode, wherein the air cathode comprises an air cathode layer comprising at least an electroconductive material and a supporting electrolyte salt, a metal-air battery comprising the air cathode, and a method for producing the air cathode for the metal-air battery.Filed by Toyota, this record anchors one of the corpus's strongest co-assignee clusters and sits directly on the air-cathode composition claim path most new entrants will need to clear.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | WO2000036690A2 | Battery pack design for metal-air battery cells | 378 |
| 2 | US4950561A | Metal-air battery with easily removable anodes | 170 |
| 3 | US4913983A | Metal-air battery power supply | 144 |
| 4 | US6500575B1 | In-cell air management | 143 |
| 5 | US5560999A | Air manager system for recirculating reactant air in a metal-air battery | 143 |
| 6 | US4957826A | Rechargeable metal-air battery | 141 |
| 7 | US20060063051A1 | Metal-air battery with ion-conducting inorganic glass electrolyte | 137 |
| 8 | US20030186099A1 | Metal-air battery with an extended service life | 134 |
| 9 | US5554452A | Metal-air batteries having improved air access valves | 115 |
| 10 | US4177327A | Metal-air battery having electrically operated air access vent cover | 108 |
Citation counts inside a searched corpus favour older filings — treat this as a map of foundational influence, not of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
Put your own technology through the same analysis
Eureka on the web
When you want the answer in the next five minutes.
The agent works the prompt against patents and technical literature, citing every source.
Run your analysis now →MCP server & REST API
When it has to run inside your own pipeline.
Patent search, landscape analysis and assignee resolution as MCP tools. Drop them into any agent framework, or call REST directly.
Browse MCP servers →What the numbers mean for a filing decision
Four read-outs from the trend, the IPC mix and the citation table, translated into what they imply for someone deciding where to file next.
Growth has plateaued, not accelerated
The rise from 18 filings in 2017 to a 2023 peak of 31 looked like sustained growth, but the years since have not extended that curve. Combined with publication lag, the honest read is a maturing core-claim space rather than a technology still in its land-grab phase.
Core electrochemistry claims are saturated
Every record in the set classifies under H01M. New filers competing head-on for iron-electrode or air-cathode composition claims are filing into the densest part of the map, where established players already hold citation-heavy priority art.
No single jurisdiction dominates outright
The US leads at 185 filings, but EPO and WIPO/PCT are tied at 90 each and China follows at 64. A filing strategy built around the US alone misses roughly half the disclosed activity in this field.
Foundational battery-pack art still anchors the field
WO2000036690A2, on metal-air battery pack design, carries far more citations than any other record in the table. Citation weight here reflects age and foundational status, not that the claim remains commercially central today.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to iron-air long-duration storage landscape, with the prior art for and against each one.
Who holds the claim space, and where it thins out
Recent-year filing activity across the named assignees in this corpus has gone quiet across the board, which points to either a consolidation phase or a shift in filing strategy toward continuations rather than new priority claims.
Recent-year filing has gone quiet
Every assignee tracked for recent-year momentum — including Fuen Energy at a -100% YoY drop — shows zero filings in the latest year. That is consistent with publication lag rather than an actual halt, but it means the visible pipeline looks thinner than real activity likely is.
A small number of tight filing partnerships
Ten co-assignee pairs appear in the corpus, with the strongest — Electric Fuel and Yaron Shrim — filing together 11 times. Toyota's pairing with the University of St Andrews Court follows at 10. These are narrow, repeat collaborations rather than a broad ecosystem.
Mixed corporate and academic filers
The assignee list mixes automotive OEMs such as Toyota with dedicated battery ventures and university research-funding bodies, such as the Florida university research foundation. That spread suggests the field still draws foundational research funding alongside applied corporate R&D.
| Assignee | Recent year | YoY |
|---|---|---|
| AER Energy Resources, Inc. | 0 | — |
| Electric Fuel Ltd. | 0 | — |
| The Gillette Company | 0 | — |
| Finergy Ltd. | 0 | — |
| Fuen Energy Corporation | 0 | -100% |
| University of Florida Research Foundation, Inc. | 0 | — |
| Alcan International Limited | 0 | — |
| Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation) | 0 | — |
Where to take this analysis
The trend and assignee data here narrow down where to look; the next steps depend on whether you need freedom-to-operate confidence or a filing strategy.
Run a freedom-to-operate check on air-cathode claims
Air-cathode composition sits at the densest point of this landscape. Before committing to a specific electroconductive-material or electrolyte-salt formulation, check it against the active claim scope held around records like US20130202974A1.
Explore Eureka for FTO analysisMap the under-claimed grid-integration branch
H02J filings sit at a fraction of H01M's volume. If your work touches grid dispatch or multi-day discharge control alongside the cell chemistry, that branch has room for a first-mover claim.
Explore Eureka for white-space mappingWatch for the publication-lag catch-up
Recent-year filings across every tracked assignee read as zero, which is almost certainly a lag artefact rather than a real stop. Re-run this landscape in six to twelve months to see which filers resume.
Set up monitoring in EurekaCommon questions on this landscape
The corpus shows filing concentrated among a mix of dedicated battery ventures, automotive OEMs such as Toyota, and university research-funding bodies. No single assignee dominates the full 627-family set; instead there is concentration at the top around a handful of repeat filers and a long tail of single-filing entrants. Co-assignee data also shows a small number of tight, repeat filing partnerships rather than a broad multi-party ecosystem, which is useful context when assessing how defensible any one player's position really is.
Filing volume rose from 18 in 2017 to a peak of 31 in 2023, but the trend has flattened since, with 2022 sitting at 25 and no clear continued acceleration. Because publication lags filing by roughly eighteen months, the very latest years in any such trend will always look lower than they eventually turn out to be. Taken together, the honest read is a technology whose core claim space is maturing rather than one still in an early land-grab phase.
Nearly all activity in this dataset — all 627 records — classifies under H01M, the battery, cell and fuel-cell class, specifically around iron electrode, air cathode and reversible oxidation subclasses. Adjacent classes appear at far lower volume: H02J for power supply and grid systems, B60L for EV propulsion, and B01J for catalysis-related processes. That gap between core and adjacent classes is the clearest indicator of where claim space remains open.
US20130202974A1 claims an air cathode for a metal-air battery, comprising an air cathode layer with at least an electroconductive material and a supporting electrolyte salt, together with the anode, an ion-conducting electrolyte layer, and a method for producing that cathode. Filed by Toyota and dating to 2013, it sits squarely on the air-cathode composition claim path that most later entrants working on oxygen-radical and metal-ion reactions at the cathode will need to review. Its practical effect is to constrain certain electroconductive-material-plus-electrolyte-salt cathode formulations rather than the iron-electrode or overall cell architecture.
The clearest gaps sit outside core H01M electrochemistry: grid-scale thermal buffering, multi-day discharge control electronics, and air-cathode catalyst regeneration cycles all show materially thinner claim density than the iron-electrode and air-cathode composition space itself. Vehicle-adjacent thermal management, which overlaps with B60H filings elsewhere in the corpus, is another area with limited direct iron-air-specific claim coverage. These branches are worth scouting first, since a first claim there faces far less prior art than a new air-cathode composition filing would.
Research Iron-Air Long-Duration Storage Landscape in depth with Eureka
Go past this page: query the whole iron-air long-duration storage landscape corpus yourself, in your own scope.
Every answer comes back with patent numbers you can open.
Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.