Enhancing the Integral Structural and Thermal Stability of Ultrahigh-Ni Cathodes via Morphology Refinement and In Situ Interfacial Engineering.

Nickel-rich layered oxides are promising cathodes in commercial materials for lithium-ion batteries. However, the increase of the nickel content leads to the decay of cyclic performance and thermal stability. Herein, in situ surface-fluorinated W-doping LiNi 0.90 Co 0.05 Mn 0.05 O 2 cathodes enhance integral lithium-ion migration (transfer in bulk and diffusion in the interface) kinetics by synergistically solving the problems of bulk and interface structural degradation. Owing to the introduction of tungsten, the growth of primary particles is regulated toward the (003) crystal plane and with the acicular structure, which further stabilizes the bulk structure during cycling. Moreover, the LiF coating layer on the cathode/electrolyte interface physically isolates the attack of the electrolyte on the surface cathodes and accelerates the lithium-ion diffusion rate, ultimately ameliorating the interfacial dynamics and structural stability. Dual-modified LiNi 0.90 Co 0.05 Mn 0.05 O 2 exhibits superior electrochemical properties, especially more remarkable cyclic retention (88.16% vs 70.44%) after 100 cycles at 1 C and more outstanding high current rate properties (173.31 mAh·g -1 vs 135.97 mAh·g -1 ) at 5 C than the pristine one. This work emphasizes the probability of an integrated optimization strategy for Ni-rich materials, which provides an innovative idea for ameliorating (bulk and interfacial) structure degradation and promoting the diffusion of lithium ions during cycling.