AbstractFor cuprate superconductors, a high critical transition temperature (T_c) can be realized in compounds containing multiple CuO₂ layers in the unit cell, while a high critical current density (J_c) is rarely sustained above liquid nitrogen temperature. The CuBa₂Ca₃Cu₄O_10+δ (Cu-1234) superconductors synthesized under high oxygen pressure incredibly exhibit high T_c (~117 K) and high J_c (>10⁴ A/cm², 100 K) values. Here, the “double high” traits of Cu-1234 were investigated with advanced scanning transmission electron microscopy. It was revealed that ordering vacancies and plate-like 90° microdomains induced efficient microstructure pinning centers that suppressed vortex flux flow and enhanced J_c. Furthermore, metallic charge-reservoir blocks [Ba₂CuO_3+δ] were composed of unique compressed [CuO₆] octahedra, which induced many holes with 2p_z symmetry that significantly decreased the superconducting anisotropy and dramatically enhanced the interlayer coupling that guaranteed a high J_c. On the other hand, optimally doped CuO₂ planes inside the thick superconducting blocks [Ca₃Cu₄O₈] maintained a high T_c. Our results are applicable to design and synthesis of new superconductors with “double high” traits.