The leading assignee in this dataset holds 812 of the 16,145 records in scope, with the fifth-ranked company at 389 and the tenth at 265. That said, the top five together account for only 17.4% of all records, and the ranked list runs to 100 distinct companies, so no single filer controls the field. A freedom-to-operate review needs to look well beyond the top few names.

Filings peaked in 2017 at 524 and have declined since; the most recent complete three-year window, 2021 to 2024, shows annual volume falling from 401 to 279, a 30% drop. However, publication lags filing by roughly 18 months, so the 2025 and 2026 figures in any dataset are still incomplete and should not be read as evidence the field is dying. The pattern reads more like a maturing core claim space than an abandoned one.

Nearly all records — 99.5% of the 16,145 in scope — carry an H01M battery and fuel cell classification, which is expected given the search scope. Beyond that, electrolytic production of compounds (9.1%), inorganic compound chemistry (6.4%) and ceramics processing (6.0%) are the next largest overlaps, followed by smaller shares in catalysis, separation processes, coatings and alloys. Each of these secondary areas sits in single digits, meaning materials and process claims are more distributed than concentrated.

The United States receiving office carries the largest volume at 4,997 records, followed by the European Patent Office at 3,509 and the WIPO PCT route at 1,579. South Korea, Canada and Germany each carry four-figure counts as well, reflecting the jurisdictions where stationary power generation and fuel cell vehicle programmes are most active. Filers targeting global protection typically combine a US or EPO first filing with a PCT route into these secondary markets.

US20100136380A1, filed by Topsoe Fuel Cell A/S and published in 2010, describes a solid oxide cell built by depositing a fuel electrode on a support layer, adding a stabilised-zirconia electrolyte, optionally pre-sintering that half-cell, then depositing an oxygen electrode layer that includes a lanthanum-strontium-manganite and stabilised-zirconia composite. It matters as a representative filing because the layered fabrication sequence and the specific oxygen electrode composite are exactly the kind of construction detail that later filings in this space have to design around or license.