Synergistic Zr/Zn Dual Doping Enhances the Performance of Cobalt-Free Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries

Cobalt-free nickel-rich layered oxide cathode materials exhibit high specific capacity and cost-effectiveness, making them promising cathode candidates in next generation of lithium-ion batteries (LIBs). However, increasing the Ni content in layered cathodes comes at the expense of accelerated structural degradation and undesirable side reactions. This study reports the doping of Zr/Zn ions into lithium nickel manganese oxide (LNMO). By exploiting the similarity in ionic radii between zinc ions (Zn²⁺) and lithium ions (Li⁺), Zn²⁺ effectively substitutes for Li⁺ and incorporates into the Li layer of the LNMO lattice. Meanwhile, due to its larger ionic radius, Zr⁴⁺ is incorporated into the transition metal-oxygen (TM-O) layers, thereby not only expanding the c-axis lattice spacing but also enhancing the stability of lattice oxygen through the formation of strong Zr–O bonds. Notably, this approach effectively suppresses the undesirable H3 phase transitions and mitigates lattice oxygen loss. Comprehensive characterizations combined with density functional theory (DFT) calculations confirm that the dual-element doping with Zr/Zn effectively increases the Li⁺/Ni²⁺ mixing energy and oxygen release energy, stabilizes the lattice structure, and enhances the electrochemical performance. Furthermore, the 2-NMZZ demonstrates a high capacity retention of 95.36% after 150 cycles at 0.5C, compared to only 66.91% for the pristine P-NM. By simultaneously addressing the critical challenges of bulk and interfacial instability, this dual-site doping strategy offers a novel and effective approach for the application of LNMO in LIBs, underscoring its significant potential for designing high-performance cobalt-free, nickel-rich cathodes.