Al/Zr synergetic modification tailored low-cobalt single crystal LiNi0.72Co0.05Mn0.23O2 cathode for high-performance lithium-ion battery

Nickle (Ni)-rich layered oxides as promising candidate of high-capacity cathode materials have aroused extensive concern primarily regarding their higher specific capacity. However, the major hurdle of Ni-rich cathodes (Ni content ≥0.7) is their poor cycling stability, which often suffers from the release of oxygen, structural degradation and increased impedance during cycling, especially at high voltage or high temperature. Herein, we demonstrated a feasible solid phase method for easy industrialization based on the Al3+/Zr4+ co-doping in LiNi0.72Co0.05Mn0.23O2 (AXZY-NCM) single-crystal cathode. The optimized A0.5Z0.5-NCM single-crystal material exhibited greatly enhanced structural and thermal stability. XRD refinement results indicated that both Al3+ and Zr4+ were mainly located in transition metal (TM) sites, strengthening the layered structure through strong M-O bonds and inhibiting cation mixing. In-situ XRD revealed that the synergistic rivet effect of Al/Zr co-doping alleviates anisotropic lattice stress-strain during charge/discharge process. Accordingly, the A0.5Z0.5-NCM cathode can output a high initial capacity of 177.3 mAh g-1 at 1 C, and captured a more desirable capacity retention of 85.10% than that of U-NCM (74.33%) at 1 C over 200 cycles. Even at a high voltage of 4.5 V, its capacity retention can still reach 82.37%, significantly surpassing the unmodified U-NCM (31.0%). The above results demonstrated that well-designed dual doping is highly effective for strengthen structure stability and cycling performance of Ni-rich cathodes.