Nanocomposite Engineering of a High‐Capacity Partially Ordered Cathode for Li‐Ion Batteries

Abstract

AbstractUnderstanding the local cation order in the crystal structure and its correlation with electrochemical performances has advanced the development of high‐energy Mn‐rich cathode materials for Li‐ion batteries, notably Li‐ and Mn‐rich layered cathodes (LMR, e.g., Li1.2Ni0.13Mn0.54Co0.13O2) that are considered as nanocomposite layered materials with C2/m Li2MnO3‐type medium‐range order (MRO). Moreover, the Li‐transport rate in high‐capacity Mn‐based disordered rock‐salt (DRX) cathodes (e.g., Li1.2Mn0.4Ti0.4O2) is found to be influenced by the short‐range order of cations, underlining the importance of engineering the local cation order in designing high‐energy materials. Herein, the nanocomposite is revealed, with a heterogeneous nature (like MRO found in LMR) of ultrahigh‐capacity partially ordered cathodes (e.g., Li1.68Mn1.6O3.7F0.3) made of distinct domains of spinel‐, DRX‐ and layered‐like phases, contrary to conventional single‐phase DRX cathodes. This multi‐scale understanding of ordering informs engineering the nanocomposite material via Ti doping, altering the intra‐particle characteristics to increase the content of the rock‐salt phase and heterogeneity within a particle. This strategy markedly improves the reversibility of both Mn‐ and O‐redox processes to enhance the cycling stability of the partially ordered DRX cathodes (nearly ≈30% improvement of capacity retention). This work sheds light on the importance of nanocomposite engineering to develop ultrahigh‐performance, low‐cost Li‐ion cathode materials.