AbstractA main challenge that significantly impedes REBa₂Cu₃O_x (RE = rare earth) coated conductor applications is the low engineering critical current density J _e because of the low superconductor fill factor in a complicated layered structure that is crucial for REBa₂Cu₃O_x to carry supercurrent. Recently, we have successfully achieved engineering critical current density beyond 2.0 kA/mm² at 4.2 K and 16 T, by growing thick REBa₂Cu₃O_x layer, from ∼1.0 μm up to ∼3.2 μm, as well as controlling the pinning microstructure. Such high engineering critical current density, the highest value ever observed so far, establishes the essential role of REBa₂Cu₃O_x coated conductors for very high field magnet applications. We attribute such excellent performance to the dense c-axis self-assembled BaZrO₃ nanorods, the elimination of large misoriented grains, and the suppression of big second phase particles in this ~3.2 μm thick REBa₂Cu₃O_x film.