Ultrathin Al2O3 layer modified LiNi0.6Co0.2Mn0.2O2 with Al-doping for high performance lithium ion batteries

Ni-rich oxide materials suffer poor rate capability and rapid capacity fading, which seriously hinder its further commercialization. In this study, an ultrathin Al2O3 coating layer on surface of the LiNi0.6Co0.2Mn0.2O2 (NCM) material was prepared with Al(OC4H9)4 in organic medium; the process followed by heat treatment achieves Al doping. The synergistic effect of surface modification and Al doping significantly enhances the capacity retention and rate performance, while the resistance to moisture is also improved. The coated sample with 2wt% Al2O3 shows superior electrochemical performances with an initial capacity of 175 mAh g−1 at 1 C and a retention of 80% after 500 cycles, which is 10% higher than the uncoated raw materials. In addition, it delivers 152 mAh g−1 at 10 C, suggesting an excellent rate capability. The substitution of Al3+ and the Al2O3 protective layer facilitates ion diffusion dynamic characteristic and improves electrochemical stability.