In Situ Constructing Ultrastable Mechanical Integrity of Single‐Crystalline LiNi_0.9Co_0.05Mn_0.05O₂ Cathode by Interior and Exterior Decoration Strategy

Abstract

Planar gliding along with anisotropic lattice strain of single‐crystalline nickel‐rich cathodes (SCNRC) at highly delithiated states will induce severe delamination cracking that seriously deteriorates LIBs’ cyclability. To address these issues, a novel lattice‐matched MgTiO3 (MTO) layer, which exhibits same lattice structure as Ni‐rich cathodes, is rationally constructed on single‐crystalline LiNi0.9Co0.05Mn0.05O2 (SC90) for ultrastable mechanical integrity. Intensive in/ex situ characterizations combined with theoretical calculations and finite element analysis suggest that the uniform MTO coating layer prevents direct contact between SC90 and organic electrolytes and enables rapid Li‐ion diffusion with depressed Li‐deficiency, thereby stabilizing the interfacial structure and accommodating the mechanical stress of SC90. More importantly, a superstructure is simultaneously formed in SC90, which can effectively alleviate the anisotropic lattice changes and decrease cation mobility during successive high‐voltage de/intercalation processes. Therefore, the as‐acquired MTO‐modified SC90 cathode displays desirable capacity retention and high‐voltage stability. When paired with commercial graphite anodes, the pouch‐type cells with the MTO‐modified SC90 can deliver a high capacity of 175.2 mAh g−1 with 89.8% capacity retention after 500 cycles. This lattice‐matching coating strategy demonstrate a highly effective pathway to maintain the structural and interfacial stability in electrode materials, which can be a pioneering breakthrough in commercialization of Ni‐rich cathodes.

Enhanced Li-ion intercalation kinetics and lattice oxygen stability in single-crystalline Ni-rich Co-poor layered cathodes

“…It is noteworthy that the extent of changes in both peak potential and intensity during cycling was not as significant for BA-NCM85 as it was for NCM85. 37,38 This phenomenon testifies that the Ba–Al dual-doped can visibly enhance the electrochemical reversibility and electrode kinetics of the Ni-rich single-crystalline cathode. Fig.…”

“…4e). 38,39 In contrast, the single-crystalline particles in the pure NCM85 displayed severe slippage and evident crack (Fig. 4f), while the HRTEM images showed that NCM85 existed a large number of rock-salt phase structures from the surface to the bulk phase, and the local layered structure was severely disorganized (Fig.…”