Gradient doping Mg and Al to stabilize Ni-rich cathode materials for rechargeable lithium-ion batteries

Nickel-rich layered oxides are attracting extensive interest as cathode materials to build high-energy lithium-ion batteries, but their intrinsic structural instability and interfacial parasitic reactions deteriorate the cycling performance. Herein, we report concentration-gradient Mg and Al doped LiNi0.95Co0.03Al0.01Mg0.01O2 (NCAMg) as a stable and high-capacity cathode material. The obtained NCAMg microparticles exhibit outstanding cyclability (capacity retention of 95.6% after 100 cycles) and remarkable rate capability (172.9 mAh g−1 at 10 C). The gradient Mg and Al doping boosts the electrochemical performance by restraining the undesirable H2–H3 phase conversion and the anisotropic volume change. Moreover, the enrichment of Mg and Al at particle shell enhances the Li-ion diffusivity, inhibits the growth of microcracks, and significantly improves the thermal stability over LiNiO2. The results indicate that Mg and Al gradient co-doping is an efficient and practical route to upgrade Ni-rich layered oxide cathode materials for LIBs.