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

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 LiNi0.9Co0.08Al0.02O2 (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 Li2SnO3 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.