Layered-to-Layered Synthesis of High-Performance Nickel-Rich Layered Cathodes via Low-Temperature Oxidation of Layered Hydroxide Precursor

Abstract

Nickel-rich layered transition metal oxide cathodes, such as LiNi_xCo_yMn_zO₂ (LiTMO₂), are set to revolutionize the capabilities of lithium-ion batteries with their exceptional energy density. The conventional synthesis method, which entails high-temperature sintering of MO₆-structured hydroxide precursors, leads to the decomposition of the MO₆ framework to form rock salt. Although it can be reconstituted after lithiation to form a layered structure, structural defects typically remain in the final product. Hereby, a two-step, low-temperature oxidation, and lithiation process is introduced, where the MO₆ structure remains, thereby producing outstanding cathode materials. The Ni_0.9Co_0.05Mn_0.05(OH)₂ precursor is initially oxidized at ambient temperature to Ni_0.9Co_0.05Mn_0.05OOH, followed by lithiation below 90 °C. The resulting material exhibits an impressive discharge capacity of over 239.3 mAh g⁻¹ at 0.1C within 2.7–4.3 V, and an initial coulombic efficiency (ICE) of 95.76%. A subsequent high-temperature treatment significantly enhances crystallinity, further improving the material's discharge capacity, ICE, rate capability, and cycling stability, surpassing those of traditionally sintered materials. This approach is further applied to the synthesis of LiNi_0.825Co_0.115Mn_0.06O₂ and LiNiO₂, demonstrating its versatility in synthesizing nickel-rich materials. Additionally, this method helps optimize nickel-rich LiTMO₂ performance while mitigating initial irreversible reactions.