Capacitive Deionization Patents: Who Leads, Where the Gaps Are 2026
- 32.5% concentration at the top. The top 5 assignees hold 86 of 265 records in scope — dense enough that a new entrant should expect to design around incumbent claims, not file into open space.
- Filing has cooled from its 2018 peak. 18 filings that year against 8 in 2021 and 5 in 2024, a documented -38% over that span; 2025-2026 figures are still filling in given normal publication lag.
- Water treatment framing dominates over energy storage framing. 85.3% of records sit in C02F (water treatment) versus 22.3% in H01G (capacitors) and 12.1% in H01M (batteries) — CDI is claimed mostly as a water process, not a storage device.
Filing growth compares 2021 (8 records) with 2024 (5) — 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 265 records in scope (CR5), not by the ranked leaders only.
What the capacitive deionization patent record shows
Capacitive deionization (CDI) removes ions from water by applying a voltage across porous electrodes rather than forcing water through a membrane under pressure, which is the reason its patent activity straddles water treatment and electrochemistry classifications at once. The 265 records in scope span 2015 through the current filing year, concentrated in claims around electrode carbon material, salt adsorption capacity, charge efficiency and regeneration cycle design — the operating variables that determine whether a CDI system is commercially competitive against reverse osmosis or ion exchange.
The foundational patents in this field date back to the 1990s methods for capacitive deionization and electrochemical regeneration of electrodes, and those early filings remain the most-cited records in the corpus today. That citation weight reflects influence on later filers, not current technical relevance — most of the recent claim activity sits in narrower territory: electrode surface modification, flow-through cell geometry, and membrane-assisted (MCDI) variants.
Filing trend and technology composition
Two views of the same 265-record dataset: how filing activity has moved year over year, and which IPC subclasses the claims actually sit in.
Filing trend, 2017-2026
Filings ran from 15 in 2017 to a peak of 18 in 2018, then eased to 8 by 2021 and 5 by 2024 — a documented -38% over that three-year span. 2025 and 2026 counts (3 so far in 2026) are undercounted because publication typically lags filing by around 18 months; they should not be read as a continued decline until later data fills in.
IPC technology composition
C02F (water and wastewater treatment) covers 85.3% of the 265 records, confirming CDI is filed primarily as a water treatment process. H01G (capacitors) at 22.3% and H01M (batteries, cells and fuel cells) at 12.1% mark the electrochemical-storage crossover claims, while B01D (separation processes) at 18.1% and C25B (electrolytic production) at 6.4% mark adjacent process claims. Because records can carry multiple IPC codes, these shares sum to more than 100% of the record total.
Shares are the percentage of the 265 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Capacitive Deionization Systems with Eureka
This page is one run against one query. Ask Eureka your own question about capacitive deionization systems and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited foundational patents
US10793450B2 — Potential of zero charge-based capacitive deionization
The invention is a capacitive, aka electrostatic, deionization apparatus and method that solves the problem of short lifetime of conventional capacitive deionization (CDI) and of membrane capacitive deionization (MCDI) devices and methods by shifting the Potential of Zero Charge of electrode surfaces through surface modifications. Such electrode surface modifications provide very long lifetime capacitive deionization devices and methods.Filed by University of Kentucky Research Foundation, granted 2020-10-06 — a device-lifetime fix rather than a new removal mechanism.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US6309532B1 | Method and apparatus for capacitive deionization and electrochemical purification and regeneration of electro… | 368 |
| 2 | US5425858A | Method and apparatus for capacitive deionization, electrochemical purification, and regeneration of electrodes | 301 |
| 3 | US5954937A | Method and apparatus for capacitive deionization and electrochemical purification and regeneration of electro… | 268 |
| 4 | US6346187B1 | Alternating-polarity operation for complete regeneration of electrochemical deionization system | 106 |
| 5 | US20140346046A1 | Polarized Electrode for Flow-through Capacitive Deionization | 76 |
| 6 | US6580598B2 | Deionizers with energy recovery | 63 |
| 7 | US6661643B2 | Deionizers with energy recovery | 60 |
| 8 | US20080198531A1 | Capacitive deionization system for water treatment | 53 |
| 9 | US7138042B2 | Alternating-polarity operation for complete regeneration of electrochemical deionization system | 46 |
| 10 | US6761809B2 | Alternating-polarity operation for complete regeneration of electrochemical deionization system | 44 |
Citation counts favour older records simply by virtue of having been available longer to cite — read this table as a map of foundational influence, not current-state importance.
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
Three readings of the dataset that matter more than the raw counts on their own.
The top of the field is dense, the tail is long
86 of 265 records sit with the five leading assignees, and 146 — 55.1% of the field — sit with the ranked top 10. Below that the ranking runs to 100 companies with a long tail of single- or low-count filers, typical of a field where a handful of early movers set the claim boundaries and later entrants file narrow improvement patents around them.
Activity has cooled from its 2018 peak
Filings peaked at 18 in 2018 and had fallen to 5 by 2024, a -38% move over the 2021-2024 window. That is a real slowdown in the last complete years of data, not an artifact of recency — but 2025 and 2026 figures are still incomplete due to normal publication lag and should not be added to the trend yet.
CDI is claimed as water treatment, not storage
The overwhelming majority of records classify under C02F (water and wastewater treatment) rather than H01M (batteries) or H01G (capacitors), even though the underlying electrochemistry overlaps with supercapacitor and battery electrode work. Filers pursuing electrode-material claims should expect prior art searches to need both water-treatment and electrochemical-storage classifications.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to capacitive deionization systems, with the prior art for and against each one.
| Assignee | Co-assignee | Shared families |
|---|---|---|
| TALLON REBECCA M | BOEDEKER BRETT A | 13 |
| TALLON REBECCA M | AVERBECK DAVID J | 13 |
| BOEDEKER BRETT A | AVERBECK DAVID J | 13 |
| Unilever NV | Unilever PLC | 9 |
| TALLON REBECCA M | Pentair Residential Filtration LLC | 7 |
| BOEDEKER BRETT A | Pentair Residential Filtration LLC | 7 |
| AVERBECK DAVID J | Pentair Residential Filtration LLC | 7 |
| The Regents of the University of California | FARMER JOSEPH C | 2 |
Ten co-assignee pairs appear in the data, with the strongest three pairs each linked on 13 shared records — a small, tightly connected inventor group rather than broad industry co-filing.
Who holds the claim space, and where it thins out
The ranked field runs to 100 assignees, but activity is heavily front-loaded: the leader alone accounts for 20 records, more than the entire tenth-place position combined with several others below it.
A clear single leader
The top assignee holds 20 of the 265 records in scope, ahead of a fifth-place position at 15 and a tenth-place position at 10 — a steep drop-off that marks this as a leader-plus-tail structure rather than a flat competitive field.
Consolidation thickens by tenth place
By the tenth ranked position, cumulative share reaches 146 records — 55.1% of all 265 in scope. Anyone benchmarking freedom-to-operate against only the top few names is missing over half the documented activity.
Several established names show no recent filings
A number of assignees with meaningful historical counts, including university and multinational-consumer filers, show zero filings in the latest year captured. That is consistent with the broader post-2018 slowdown rather than exit from the field, since 2025-2026 data is still incomplete.
| Assignee | Recent year | YoY |
|---|---|---|
| The Regents of the University of California | 0 | — |
| Unilever NV | 0 | — |
| Unilever PLC | 0 | — |
| EnPar Technologies | 0 | — |
| Stockholm Water Tech AB | 0 | — |
| TALLON REBECCA M | 0 | — |
| BOEDEKER BRETT A | 0 | — |
| AVERBECK DAVID J | 0 | — |
Where to take this analysis
The dataset points to specific next steps depending on whether the goal is freedom-to-operate, licensing, or new claim drafting.
Screen the under-claimed branches
Energy recovery, co-ion expulsion and power-supply integration show comparatively thin filing density against the 85.3% concentration in core water-treatment claims — worth a focused prior-art pull before drafting there.
Run a white space search in EurekaTrack the leader-plus-tail structure
With 55.1% of records held by the ranked top 10 and a long tail below, ongoing monitoring should watch both the leading assignees and new entrants filing narrow improvement patents around their claims.
Set up assignee monitoring in EurekaCommon questions about capacitive deionization patents
The tracked dataset for this landscape contains 265 published records dated 2015 through the current filing year, covering capacitive and membrane capacitive deionization claims tied to salt adsorption capacity, electrode carbon material, charge efficiency, regeneration cycles, co-ion expulsion and energy recovery. This is a defined search scope, not every CDI-related filing ever made, since broader or differently worded searches will return different counts. Patent families are the more reliable unit here than raw document counts because they neutralise continuation filings and multi-jurisdiction duplicates.
The ranked field covers 100 assignees, with a clear single leader holding 20 of the 265 records and a steep drop to 15 records at fifth place and 10 at tenth. The top 5 assignees combined account for 32.5% of all records in scope, and the top 10 combined account for 55.1% — meaning the majority of documented activity sits with a relatively small group even though the full ranking runs to 100 names. Recent-year filings have slowed across several of these historically active assignees, though that partly reflects publication lag in the newest years rather than confirmed exit from the field.
Based on complete-year data, filing activity peaked in 2018 at 18 records and had fallen to 5 by 2024, a documented -38% decline between 2021 and 2024. Figures for 2025 and 2026 are still incomplete because patent publication typically lags the filing date by roughly 18 months, so the most recent years will understate true activity until later data fills in. Treat 2024 as the last year you can compare against with confidence.
Most records classify under C02F, water and wastewater treatment, covering 85.3% of the 265 records in scope, confirming that CDI is claimed primarily as a water process. Meaningful secondary classifications include H01G capacitors at 22.3%, B01D separation processes at 18.1%, and H01M batteries and fuel cells at 12.1%, reflecting the electrochemical overlap between CDI electrodes and energy-storage electrode research. Because a single record can carry several IPC codes, these percentages sum to more than 100% of the record total and should not be read as mutually exclusive categories.
US10793450B2, assigned to University of Kentucky Research Foundation and granted in October 2020, claims a method of extending capacitive deionization device lifetime by shifting the Potential of Zero Charge at the electrode surface through surface modification. It addresses a specific durability failure mode in conventional CDI and MCDI systems rather than the core ion-removal mechanism itself, so it constrains surface-modification approaches to that specific problem rather than blocking capacitive deionization broadly. Anyone drafting electrode-longevity claims in this space should review its scope directly rather than assume it covers all electrode surface treatment methods.
Research Capacitive Deionization Systems in depth with Eureka
Go past this page: query the whole capacitive deionization systems 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.