In Situ Chelating Synthesis of Hierarchical LiNi Co Mn O Polyhedron Assemblies with Ultralong Cycle Life for Li-Ion Batteries.

Layered lithium transition-metal oxides, with large capacity and high discharge platform, are promising cathode materials for Li-ion batteries. However, their high-rate cycling stability still remains a large challenge. Herein, hierarchical LiNi Co Mn O polyhedron assemblies are obtained through in situ chelation of transition metal ions (Ni , Co , and Mn ) with amide groups uniformly distributed along the backbone of modified polyacrylonitrile chains to achieve intimate mixing at the atomic level. The assemblies exhibit outstanding electrochemical performances: superior rate capability, high volumetric energy density, and especially ultralong high-rate cyclability, due to the superiority of unique hierarchical structures. The polyhedrons with exposed active crystal facets provide more channels for Li diffusion, and meso/macropores serve as access shortcuts for fast migration of electrolytes, Li and electrons. The strategy proposed in this work can be extended to fabricate other mixed transition metal-based materials for advanced batteries.