Surface Doping to Enhance Structural Integrity and Performance of Li-Rich Layered Oxide

The Li-rich layer-structured oxides are regarded as one of the most promising cathode materials for their high energy density but suffer from severe problems such as capacity fading, poor rate performance, and continuous potential dropping. These issues are addressed here by surface doping of niobium (Nb) and other heavy ions in a Li-rich Mn-based layered oxide, Li1.2Mn0.54Ni0.13Co0.13O2. The doped ions are verified to be located in the Li-layer near the oxide surface; they bind the slabs via the strong Nb-O bonds and inactivate the surface oxygen, enhancing the structural stability. The specific capacity of the modified oxide reaches 320 mAh g(-1) in the initial cycle, 94.5% of which remains after 100 cycles. More importantly, the average discharge potential drops only by 136 mV in this process. The findings of this study illustrate the importance of inactivating the surface oxygen in suppressing the cation mixing in the bulk, providing an effective strategy for designing high-performance Li-rich cathode materials.