Lattice plainification flattens the crystal structure of nickel-rich layered cathodes

Abstract

The extremely fast charging/discharging of nickel-rich LiNi_xCo_yMn_1−x−yO₂ (NCM) cathodes has raised concerns about rapid capacity decay. The birth defects and fragile lattice result in the sluggish Li⁺ diffusion kinetics and unfavorable structural degradation. Moreover, lattice strain, mechanical failures, surface reconstruction, and interfacial side reactions accelerate the decay process. Here, a proof-of-principle study of the lattice plainification (LP) strategy in a high-nickel NCM cathode is reported. The introduction of Al and Zr in transition metal layers by a wet chemistry and calcination method enables the simplification of the complex lattice structures to obtain an order phase and repair the various defects of NCM, thereby enhancing the lithium-ion transport. The modified LP-NCM exhibits a high initial discharge capacity of 157.3 mAh g⁻¹ with a capacity retention of 81% after 300 cycles at a 5C rate, significantly outperforming the pristine counterpart (50.9%). The LP-NCM/Gr pouch cells presented impressive cycling performance, achieving 80% capacity retention over 1000 cycles at 1C, which far surpasses the performance of the pristine NCM. Our method eliminates the rocksalt and disordered phases, and suppresses oxygen, lithium, and transition metal vacancies, as well as Li/Ni mixing. LP-NCM after cycling exhibits nanopores rather than cracks of pristine NCM. Our investigations reveal that the lattice plainification design approach flattens and toughens up the crystal lattice, which contributes to robust structural stability and improves the structure degradation, mechanical failures, and gas release. Our findings underscore the importance of lattice engineering and demonstrate the potential of the lattice plainification strategy for designing high-performance cathodes.