Sacrificial Additive C₆₀-Assisted Catholyte Buffer Layer for Li_1+xAl_xTi_2–x(PO₄)₃-Based All-Solid-State High-Voltage Batteries

All-solid-state batteries with oxide electrolytes and high-nickel layered oxide cathodes (LiNi x Co y Mn z O 2 and LiNi x Co y Al z O 2, x + y + z = 1, x ≥ 60%) have received widespread attention owing to their high energy density and high safety. However, they generally suffer from interfacial structural instability when coupled with solid-state electrolytes, which strongly diminishes the longevity of the battery. In this work, we propose adding a sacrificial additive C 60 to the catholyte buffer layer between Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) to enhance the electrochemical stability under high-voltage operating conditions. A uniform and robust cathode–electrolyte interphase (CEI) film enriched with Li x PO y F z, LiP x F y, and C 60 F n is spontaneously formed on the surface of the cathode particles. In addition, the NCM811/Li solid-state battery delivers a discharge capacity of 150.3 mAh g –1 with a retention of 85% after 200 charge–discharge cycles at 0.5 C. This study offers a practical approach toward realizing LATP-based all-solid-state high-voltage batteries characterized by exceptional cycling stability.