Gradient Micro‐Structure Design Enabling Mechanochemically Durable Single‐Crystalline Ni‐Rich Layered Oxides for Advanced Lithium‐Ion Batteries

Abstract

Ni‐rich layered oxides are promising positive electrode materials for lithium‐ion batteries (LIBs) owing to their high energy density and cost efficiency. Nevertheless, the intrinsic chemicophysical instability of Ni‐rich layered oxides severely limits the massive application. Herein, a unique gradient structure design from coherent rock‐salt phase surface structure to quasi super‐lattice matrix on the sub‐surface of single‐crystalline LiNi0.83Co0.11Mn0.06O2 (GS‐SC‐NCM) is proposed to improve their stability. The introduced Ti4+/Nb5+/Zr4+ ions are able to alleviate the overlay of O 2p and Ni 3d bands at the highly delithiated state, remarkably improving the stability of anion skeleton. Moreover, intragranular cracks and undesired lattice shrinkage during the H2‐H3 phase transition are greatly suppressed due to the ultra‐stable gradient structure design. In addition, the inert rock‐salt‐like phase on the surface of GS‐SC‐NCM hinders continuous evolution of interphase. Consequently, the superior cycling stability of GS‐SC‐NCM with high capacity retention of 92.9% after 150 cycles is achieved. Moreover, an Ah‐level pouch cell consisting of GS‐SC‐NCM positive electrode and commercial graphite negative electrode exhibits extraordinary cycling stability at 1C with 89.8% capacity retention after 450 cycles. This work represents significant progress in stabilizing single‐crystalline Ni‐rich layered oxides for an advanced secondary battery system, which is pivotal for accelerating the current electrification process.