Na-doped Ni-rich LiNi_0.5Co_0.2Mn_0.3O₂ cathode material with both high rate capability and high tap density for lithium ion batteries

Na-doped Ni-rich LiNi_0.5Co_0.2Mn_0.3O₂ cathode material, Li_0.97Na_0.03Ni_0.5Co_0.2Mn_0.3O₂, is synthesized by a hydroxide co-precipitation route. The structural characterization reveals that the substitution of Na for Li results in a more ordered α-NaFeO₂ structure, enlarges Li layer spacing, and reduces the degree of cation mixing. The Li_0.97Na_0.03Ni_0.5Co_0.2Mn_0.3O₂ material has a high tap density of 2.17 g cm^-3 that meets the commercial requirement in lithium ion batteries (LIBs). The galvanostatic charge/discharge results show that the electrochemical performance of the Li_0.97Na_0.03Ni_0.5Co_0.2Mn_0.3O₂ is significantly improved. At 0.2, 1, 10, 30 and 50 C, the specific capacities of the Li_0.97Na_0.03Ni_0.5Co_0.2Mn_0.3O₂ are 228.43, 163.12, 121.43, 95.56 and 60.09 mA h g^-1, respectively, which are superior to those of the undoped LiNi_0.5Co_0.2Mn_0.3O₂ due to the enlargement of Li layer spacing, the decreased degree of cation mixing, and the rapid diffusion of Li-ion in the bulk lattice after the substitution of Na for Li. Therefore, the Na-doped Ni-rich LiNi_0.5Co_0.2Mn_0.3O₂ material is a promising cathode candidate for the next generation of LIBs.