In this dataset, thermal propagation testing covers methods for deliberately triggering thermal runaway in a single cell — typically by nail penetration or heater — and measuring whether and how it spreads to neighbouring cells in a pack. Claims in scope include trigger-method comparability (how a heater trigger compares to a nail trigger), instrumentation and temperature mapping used to record the event, and pass/fail criteria such as warning-time requirements before propagation reaches a passenger compartment. The field sits at the intersection of test-method engineering and pack-level safety standards, which is why IPC classes for material testing (G01N) show up alongside battery hardware classes (H01M) in the data.

The ranked assignee set covers 100 companies, with the leader holding 4,064 records and a fifth-place holder at 2,328. Importantly, the top 5 assignees combined account for only 7.0% of the 220,940 records in scope, and the top 10 combined reach 11.1% — this is not a field with one or two companies controlling the claim space. Recent-year momentum data also shows that several companies with large historic totals have gone quiet in the latest tracked year, so cumulative rank and current activity are not the same thing.

Filing peaked in 2020 at 971 records, held roughly steady through 2022 (893), and has declined since. The 2026 count of 54 looks dramatic but is partial, since publication typically lags actual filing by around 18 months — so the true 2026 total will be higher once later publications catch up. Even accounting for that lag, the trend from 2017 through 2022 already suggests a plateau rather than sustained growth, which matters for anyone deciding whether this is a space worth heavy new investment or one that is settling into mature practice.

This CATL filing, published 2026-07-30, describes a nail penetration test method and device where the penetrating nail is controlled to move into a battery cell, and penetration to a predetermined depth continues once the voltage between the nail and a first electrode terminal exceeds a preset threshold. The specific mechanism worth noting is the voltage-trigger condition governing depth control, rather than a fixed-speed or fixed-depth test protocol. Anyone designing a nail-penetration rig with voltage-based depth control should review this filing's claim scope directly rather than relying on the abstract alone.

Based on IPC composition and filing density, warning-time threshold standardisation, multi-point temperature mapping arrays, and trigger-method comparability protocols (correlating heater-trigger results to nail-trigger results) all show thinner claim density than core nail-penetration hardware claims in this corpus. These are procedural and instrumentation-adjacent branches rather than core cell-hardware claims, which is consistent with a field where the physical trigger mechanism is well-trodden but the surrounding test-standardisation methodology is less fully claimed. A focused prior-art search on these specific sub-areas, rather than the broad topic, is the more productive next step.