Optimization of grain size and interface structure of Li-rich cathodes based on various lithium contents

Abstract

Li-rich Mn-based layered oxides (LMLOs) have been considered as the potential cathode materials to develop high-energy density lithium-ion batteries (LIBs) due to the lower cost and higher capacity. Whereas, LMLOs still face challenges of multiphase interfacial side reaction, structure transformation and microcrack growth, especially the polycrystalline particles. Herein, a high-performance submicron single-crystal-like Li-rich Mn-based layered material was obtained by optimizing lithium content to regulate crystal structure and interface chemistry. Detailed characterization indicates that the regulation of lithium content has a profound effect on the grain size, crystal structure and crystallinity. And the submicron LMLOs with appropriate lithium content exhibit a composite crystal structure composed of long-range ordered layered bulk phase and spinel heterogeneous surface layer, which combines the advantages of structural stability in single-crystal particles and rapid kinetic behavior in polycrystalline particles. Hence, the optimized submicron single-crystal-like LMLOs possess remarkable reversible capacity of 257.7 mAh/g and 143.2 mAh/g at 0.1 C and 10 C, respectively, corresponding to the capacity retention of 85.72% and voltage decay of 1.77 mV/cycle after 200 cycles at 1 C, which provides a new insight for the optimization and development of cathodes for rechargeable secondary battery.