Traditional heterogeneous polycrystalline layered oxides suffer from serious chemo-mechanical degradations, which is extremely true in nickel-rich cathodes under high-voltage operation. Although single-crystalline structure is proved to be able to withstand anisotropic lattice strain and prevent cracks formation, the long cycle stability at high-voltage in all-solid-state batteries (ASSBs) with nickel-rich layered oxides as the cathode are still far from commercial applications. Herein, we synthesize a micro-sized single-crystalline nickel-rich oxides LiNi0.83Co0.11Mn0.06O2 (SC–N83) to eliminate the chemo-mechanical failures. The well-dispersed SC-N83 in the ASSBs delivers an excellent cyclic stability under high-voltage (4.4 V vs Li/Li+) operation, which shows a capacity retention of 85.1% after 500 cycles at 0.5C. Even at high active areal loading of 22.6 cm−2 (corresponding to an initial areal capacity of 4.19 mAh cm−2) and high temperature of 50 °C, the SC-N83 cathodes can still maintain 75.5% discharge capacity after 200 cycles at 0.5C. The high cycling stability is further proved to be attributed to dramatically suppressed mechanical failure caused by the build-up of strain and stress. This proposed strategy with highly dispersed single-crystalline nickel-rich oxides paves the way to develop advanced high-capacity and high-voltage operating ASSBs.