By virtue of high specific capacity, LiNi_0.8Co_0.15Al_0.05O₂ (NCA) is considered to have a promising application in all-solid-state lithium batteries (ASSLB) using sulfide electrolyte. However, the interfacial instability between NCA cathode and sulfide electrolyte is still a serious problem, leading to poor rate and cycle performances of NCA cathode. To boost the interfacial instability and boost the rate and cycle performances of NCA cathode, a novel double buffer layer strategy is constructed in this paper. Firstly, NCA is designed as a core-shell structure to achieve self-coating, in which Ni-rich core LiNi_0.85Co_0.15O₂ can provide high capacity, and Al-rich shell LiNi_0.6Co_0.15Al_0.25O₂ as the first buffer layer can provide the complete coating on the Ni-rich core. Secondly, a thin inactive LiNbO₃ layer as the second buffer layer is coated on the core-shelled NCA (CS-NCA) particles to increase the interface stability. As expected, LiNbO₃-coated CS-NCA (CS-NCA@LiNbO₃) cathode displays high discharge capacity (184.1 mAh g⁻¹ at 0.06 C), excellent initial coulombic efficiency (90.2%, 0.06 C), outstanding rate performance (130 mAh g⁻¹ at 4.2 C) and cycle performance (capacity retention of 89.4% after 400 cycles at 0.3 C) at 60 °C. The results indicate that this novel double buffer layers strategy is effective to boost rate and cycle performances of NCA cathode for ASSLB using sulfide electrolyte.