Sacrificial Additive\nC<sub>60</sub>-Assisted Catholyte\nBuffer Layer for Li<sub>1+<i>x</i></sub>Al<sub><i>x</i></sub>Ti<sub>2–<i>x</i></sub>(PO<sub>4</sub&g

All-solid-state batteries with oxide electrolytes and\nhigh-nickel\nlayered oxide cathodes (LiNi<sub><i>x</i></sub>Co<sub><i>y</i></sub>Mn<sub><i>z</i></sub>O<sub>2</sub> and\nLiNi<sub><i>x</i></sub>Co<sub><i>y</i></sub>Al<sub><i>z</i></sub>O<sub>2</sub>, <i>x</i> + <i>y</i> + <i>z</i> = 1, <i>x</i> ≥\n60%) have received widespread attention owing to their high energy\ndensity and high safety. However, they generally suffer from interfacial\nstructural instability when coupled with solid-state electrolytes,\nwhich strongly diminishes the longevity of the battery. In this work,\nwe propose adding a sacrificial additive C<sub>60</sub> to the catholyte\nbuffer layer between Li<sub>1.4</sub>Al<sub>0.4</sub>Ti<sub>1.6</sub>(PO<sub>4</sub>)<sub>3</sub> (LATP) and LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> (NCM811) to enhance the electrochemical\nstability under high-voltage operating conditions. A uniform and robust\ncathode–electrolyte interphase (CEI) film enriched with Li<sub><i>x</i></sub>PO<sub><i>y</i></sub>F<sub><i>z</i></sub>, LiP<sub><i>x</i></sub>F<sub><i>y</i></sub>, and C<sub>60</sub>F<sub><i>n</i></sub> is spontaneously\nformed on the surface of the cathode particles. In addition, the NCM811/Li\nsolid-state battery delivers a discharge capacity of 150.3 mAh g<sup>–1</sup> with a retention of 85% after 200 charge–discharge\ncycles at 0.5 C. This study offers a practical approach toward realizing\nLATP-based all-solid-state high-voltage batteries characterized by\nexceptional cycling stability.