Abstract: Nickel-rich layered oxides (NRLOs) are regarded as ideal cathode materials for high-energy-density all-solid-state lithium-ion batteries (ASSLIBs). However, their practical application is hindered by structural instability and interfacial reactions with sulfide solid-state electrolytes, which lead to rapid performance degradation. To address these challenges, a synergistic stabilization strategy has been developed, simultaneously reinforcing the bulk lattice of NRLOs and suppressing surface side reactions. In this approach, high-valence W⁶⁺ ions were incorporated into the lattice of LiN_i0.94Co_0.05Mn_0.01O₂ to enhance bulk-phase stability (W-NCM94), while excess W⁶⁺ ions segregated on the NCM94 surface, forming a protective Li_xW_yO_z passivation layer that effectively inhibits interfacial reactions. ASSLIBs fabricated with W-NCM94 cathodes exhibit superior electrochemical performance, delivering an initial capacity of 145.7 mAh·g⁻¹ at 0.2 C with outstanding cycling stability (>80% capacity retention after 230 cycles). Notably, at an elevated cut-off voltage of 4.5 V, the cells achieve an impressive initial capacity of 167.6 mAh·g⁻¹. This innovative strategy combining bulk doping with surface segregation provides new insights for designing stable, high-performance NRLOs-based ASSLIBs, paving the way for their practical implementation in next-generation energy storage systems.