Lattice Engineering toward Extraordinary Structural Stability of High-Performance Single-Crystal Li-Rich Layered Oxides Cathodes

Prevailing Li-rich layered oxide cathodes (LLOs) possessing with polycrystalline morphology suffer from unsatisfactory cyclic stability due to serious structural failures including irreversible oxygen release, phase transformation, and microcrack, further limiting its commercial application for high-energy-density lithium-ion batteries. Herein, single-crystallization combining with a simple boric acid treatment strategy is applied to robust the stability of lattice structure for achieving the reversible oxygen anionic redox of LLOs. The obtained single-crystal LLOs display less grain boundaries and excellent mechanical stability, contributing to suppress the accumulation of lattice strain and microcracks. Additionally, the induced surface Li2B4O7 with spinel phase coating and bulk gradient B doping after boric acid treatment significantly inhibit the irreversible oxygen release and enhance the stability of lattice structure. Besides, lattice structure regulation also boosts the Li+ diffusion kinetics due to the existence of oxygen defects, fast Li-ion conductive coating, and enlarged Li+ layer spacing. As a result, the modified SC-LLOs showcase superior cyclic stability with a capacity retention of 87.42% after 300 cycles at 1 C and excellent rate performance with a high capacity of 144.9 mAh g-1 at 5 C. This work provides some significant references to strengthen the structural stability of single-crystal LLOs with long-term cyclic capability via lattice engineering. Single-crystallization combining with lattice regulation strategy is proposed to synthesize the well-dispersed and stable single-crystal LLOs with gradient B doping and surface structure reconstruction, contributing to the reversible anionic redox and long-term cyclic capability. image