Stabilizing Single-Crystalline Ni-Rich Cathode via Epitaxial Entropy-Assisted Surface

Single-crystalline Ni-rich LiNi x Mn y Co 1– x – y O 2 (SNCM, x ≥ 0.8) materials are regarded as next-generation cathodes for lithium-ion batteries. However, SNCM cathodes show readily low structural stability due to surface reconstruction and irreversible strain evolution during cycling at high voltages. Here, we demonstrate that Y 2 O 3 material incorporated into SNCM cathodes forms an epitaxial entropy-assisted surface layer, which acts as a highly compatible region to facilitate Li-ion transmission, suppress interface reaction and transition metal dissolution. Meanwhile, soluble Al ions are uniformly distributed in the SNCM lattice and combine with the surface Y–O bond, forming a pillaring effect to restrain irreversible strain evolution, eventually prevent the formation of gliding and nanocracks during high-voltage cycling. As a result, the SNCM cathode with a Y 2 O 3 surface and Al doping shows a high specific discharge capacity of 210.5 mAh·g –1 at 1 C within 2.75–4.4 V and a capacity retention of 86.6% after 100 cycles. This study offers a new insight into the design of a strain-retardant method for obtaining single-crystalline Ni-rich cathode materials with high performance.