(1) A three-dimensional representative volume element is employed to describe the composite cathode microstructure, as shown in Fig. and Supplementary Fig. . NMC secondary particles synthesized by the co-precipitation method typically consist of many randomly oriented primary particles . However, modifying the surface energies through a boron doping strategy can induce the directional growth of primary particles, resulting in NMC secondary particles with radially aligned primary particles . In this study, an isolated Ni-rich NMC811 polycrystal particle, consisting of 200 randomly oriented primary particles, is embedded in the uniform solid electrolyte.