This paper reports a multiscale controlled three‐dimensional (3D) electrode structure to boost the battery performance for thick electrode batteries with LiMn1.5Ni0.5O4 as cathode material, which exhibits a high areal capacity (3.5 mAh/cm2) along with a high specific capacity (130 mAh/g). This excellent battery performance is achieved by a new concept of cell electrode fabrication, which simultaneously controls the electrode structure in a multiscale manner to address the key challenges of the material. Particles with ultrathin conformal coating layers are prepared through atomic layer deposition followed by a nanoscale‐controlled, thermal diffusion doping. The particles are organized into a macroscale‐controlled 3D hybrid‐structure. This synergistic control of nano‐/macro‐structures is a promising concept for enhancing battery performance and its cycle life. The nanoscale coating/doping provides enhanced fundamental properties, including transport and structural properties, while the mesoscale control can provide a better network of the nanostructured elements by decreasing the diffusion path between. Electrochemical tests have shown that the synergistically controlled electrode exhibits the best performance among non‐controlled and selectively‐controlled samples, in terms of specific capacity, areal capacity, and cycle life.