Sn‐Driven Grain Boundary Elimination for Single‐Crystalline Ni‐Rich Cathodes with Superior High‐Voltage Stability in Lithium‐Ion Batteries

ABSTRACT Single‐crystalline Ni‐rich cathodes are regarded as promising candidates for high‐energy‐density lithium‐ion batteries (LIBs), providing superior mechanical and structural stability compared to polycrystalline counterparts. In this work, we present a low‐temperature grain‐boundary‐elimination approach to synthesize single‐crystalline LiNi 0.9 Co 0.08 Al 0.02 O 2 (SC‐NCA) through Sn‐assisted modification. Beyond enabling low‐temperature synthesis, the integrated Sn serves a dual‐protective function. Bulk Sn doping robustly pins lattice oxygen and mitigates harmful irreversible phase transitions, preserving structural integrity. Simultaneously, the residual formation of a highly conductive Li 2 SnO 3 surface layer accelerates Li + diffusion kinetics and robustly passivates the cathode‐electrolyte interphase against parasitic degradation. Consequently, this dual‐site modified SC‐Sn‐NCA90 cathode exhibits exceptional electrochemical performance, delivering a remarkable capacity retention of 86.7% after 500 cycles at 1 C (2.8–4.5 V), vastly eclipsing the 40.8% retention of the polycrystalline benchmark. This work presents a low‐temperature strategy for synthesizing SC‐NCA combined with Sn doping, facilitating the development of Ni‐rich layered cathodes for high‐energy‐density LIBs.