Battery Separator Membrane Patents: Who Leads, Trends 2026
- Filings have cooled since 2018. the peak year (173 filings) is behind us, and the 2022 midpoint of 124 shows a plateau rather than continued growth.
- The foundational art is old and heavily cited. the most-cited record in the corpus dates to a 1960s-era trilayer/shutdown lineage still cited hundreds of times, meaning new filers are working around, not into, empty space.
- Filing is concentrated in three offices. the United States, Europe and PCT filings together account for the large majority of receiving-office activity, with China, Japan and South Korea each holding a smaller but material share.
Filing growth compares 2021 (132 records) with 2024 (62) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 3,571 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This dataset tracks 3,571 patent families filed between 2015 and mid-2026 that combine battery separator or ceramic-coated separator claims with technical criteria on porosity, shutdown temperature, thermal shrinkage, wettability or wet-process manufacture, classified under H01M50, C08J9 or B01D67. It is a narrow, functionally defined slice of the broader battery patent space: the search string requires both a separator-membrane subject and a named physical property or process, which excludes generic electrode or electrolyte filings that happen to mention a separator in passing.
Because publication typically lags filing by around 18 months, counts for the most recent one or two years in any trend line are understated and should not be read as a real slowdown in R&D activity — only as an artefact of the data cut-off.
Filing trend and technology composition
The two views below show when separator-membrane patent families were filed and which adjacent technology classes they draw on most heavily.
Filings by year
Filings rose to a peak of 173 in 2018, held near the 2022 midpoint of 124, and the partial 2026 count reflects publication lag rather than an actual drop-off. Read the plateau as claim space that is already well populated rather than a technology in decline.
IPC subclass composition
Nearly every record sits in H01M (batteries, cells and fuel cells), as the search design requires, but secondary classification is instructive: C08J (polymer processing) and B32B (laminates) each appear in several hundred families, confirming that most inventive activity is in materials and layer construction rather than pure electrochemistry. B01D (separation processes) and D04H (nonwovens) are present but thinner, marking narrower but still active sub-fields.
Shares are the percentage of the 3,571 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Battery Separator Membranes with Eureka
This page is one run against one query. Ask Eureka your own question about battery separator membranes and every answer comes back with the patent numbers behind it.
Try EurekaThe foundational art and a representative recent filing
Microporous membranes, separators, lithium batteries, and related methods (US20200067046A1)
Filed by Celgard, LLC, this application covers ionized-radiation-treated microporous polyolefin separators, including polyethylene and polyethylene/polypropylene blends, for secondary lithium batteries, along with methods of making and using them. It sits squarely in the polyolefin shutdown-separator lineage that dominates the most-cited records in this dataset.Abstract trimmed for length; see full text for complete claim scope.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US3351495A | Battery separator | 477 |
| 2 | US4650730A | Battery separator | 251 |
| 3 | US5691077A | Shutdown, trilayer battery separator | 245 |
| 4 | US6080507A | Trilayer battery separator | 231 |
| 5 | US5952120A | Method of making a trilayer battery separator | 222 |
| 6 | JP1999144700A | Porous membrane, battery separator comprising porous membrane, and manufacture thereof | 215 |
| 7 | US6602593B1 | Battery separators with reduced splitting propensity | 202 |
| 8 | US3972759A | Battery separators made from polymeric fibers | 193 |
| 9 | US6328770B1 | Method of making multi-layer electrochemical cell devices | 151 |
| 10 | US4923650A | Breathable microporous film and methods for making it | 148 |
Citation counts accumulate over time and favour older filings; a high count signals influence on the field's foundational claim language, not current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once the raw counts are set against filing dates and classification.
Growth has plateaued, not accelerated
The peak year of 173 filings (2018) has not been exceeded since; the 2022 figure of 124 sits below peak, and the shape is flat-to-declining once the reporting lag is accounted for. This is a mature filing area, not an emerging one.
The oldest trilayer/shutdown patents still anchor the field
The five most-cited records in the corpus are all trilayer or shutdown-separator patents, one carrying 477 citations. New filings in this lineage are almost certainly designing around claims that have already been tested for decades.
Materials and lamination, not electrochemistry, drive filings
With H01M present in nearly the entire corpus by search design, the more informative split is secondary classification: C08J (polymer processing) and B32B (laminates) each cover a substantial share, pointing to coating chemistry and layer architecture as the active battlegrounds.
Filing is concentrated in three gateways
The United States, Europe and the PCT route together receive the bulk of filings in this dataset, with China, Japan and South Korea trailing at more moderate volumes despite their manufacturing weight in battery production.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to battery separator membranes, with the prior art for and against each one.
Who is filing, and where the collaboration exists
Assignee activity in this corpus is led by a handful of established separator and materials manufacturers, with momentum data suggesting the leaders' filing pace has slowed in the most recent reported year.
Recent-year filings are down across the leaders
Every assignee tracked for recent-year momentum shows either a sharp year-on-year decline or zero filings in the latest partial year. This is consistent with the corpus-wide plateau and with publication lag rather than a sudden exit from the field.
Co-filing is limited but concentrated
Only ten co-assignee pairings appear in the dataset, and the strongest of them links a materials manufacturer with a technical-research partner at 22 shared filings — evidence of a small number of durable joint-development relationships rather than broad industry-wide co-filing.
Filing strategy favours multi-jurisdiction coverage
The spread across the United States, Europe, PCT, China, Japan and South Korea indicates that leading assignees pursue parallel protection in major manufacturing and consumption markets rather than concentrating in a single home jurisdiction.
| Assignee | Recent year | YoY |
|---|---|---|
| SK Innovation (Skaid Corporation) | 1 | -90% |
| Toray Tonen Specialty Separator GK | 0 | — |
| Daramic, LLC | 0 | -100% |
| Sumitomo Chemical Co., Ltd. | 0 | — |
| Toray Industries, Inc. | 0 | — |
| Tonen Chemical Corporation | 0 | — |
| Nitto Denko Corporation | 0 | — |
| W.R. Grace & Co. | 0 | — |
Where to take this analysis
The filing plateau and concentrated foundational art suggest three practical follow-ups for teams evaluating freedom to operate or new filing strategy in this space.
Map claims against the trilayer/shutdown lineage
Before filing in shutdown or thermal-safety separator claims, check new drafts against the most-cited trilayer patents in this corpus, since their claim language has already shaped decades of subsequent filings.
Explore prior art in EurekaProbe the thinner IPC branches for open claim space
B01D and D04H carry meaningfully lower filing counts than the core H01M and C08J classes, which may indicate room for narrower, well-drafted claims in separation-process or nonwoven-substrate approaches.
Run a white-space search in EurekaTrack momentum before committing R&D budget
With every tracked assignee showing flat or declining recent-year filings, confirm whether that reflects genuine slowdown or publication lag before assuming the technology is winding down.
Monitor assignee activity in EurekaCommon questions about battery separator membrane patents
The most-cited records in this corpus are trilayer and shutdown-separator patents, including one cited 477 times, that established the core polyolefin shutdown mechanism used across the industry. These foundational patents are decades old, and most current filers are building narrower claims around coating chemistry, porosity control or thermal-shrinkage additives rather than the base shutdown mechanism itself. Checking a new filing against this trilayer/shutdown lineage is a reasonable first step in any freedom-to-operate review in this space.
No, based on this dataset filing activity peaked in 2018 at 173 families and had settled to 124 by the 2022 midpoint, indicating a plateau rather than continued growth. The most recent year shows only a handful of filings, but that reflects the roughly 18-month lag between filing and publication rather than an actual collapse in R&D activity. Overall the shape is flat to slightly declining across the observed period.
Relative to the dominant H01M and C08J classifications, the B01D (separation processes) and D04H (nonwovens and felts) subclasses carry noticeably lower filing counts in this corpus. That does not guarantee an easy path to allowance, but it does suggest these branches, along with capacitor-grade separator adaptation under H01G, carry thinner prior art density than core shutdown or coating claims. Any freedom-to-operate or white-space search should still be run against the specific claim language rather than relying on subclass counts alone.
The United States receives the largest share of filings in this dataset at 1,280, followed by Europe at 831 and the PCT route at 312, with China, Japan and South Korea each contributing more moderate volumes. This pattern suggests assignees are prioritising the US and European markets for direct filing while also using PCT applications to preserve options in additional jurisdictions. It is worth noting that manufacturing concentration in Asia does not automatically map onto the same concentration of filings in this corpus.
US20200067046A1, assigned to Celgard, LLC, covers ionized-radiation-treated microporous polyolefin separators, including polyethylene and polyethylene-polypropylene blends, for secondary lithium batteries. It sits within the same polyolefin shutdown-separator lineage as the most-cited foundational patents in this corpus, meaning any new filing using radiation-treated polyolefin chemistry for shutdown behaviour should be checked against its specific claim scope. It is a representative example rather than the single most influential record, so it should be read alongside the older trilayer patents rather than in isolation.
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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.