High-nickel layered oxide LiNi 0.9 Co 0.1 O 2 is a promising cathode material for lithium-ion batteries due to its high specific capacity and low cost. However, the internal stress generated during deep delithiation can cause microcracks, giving rise to rapid capacity decay and deteriorated thermal stability. In this work, Mg and Al ions are incorporated into the bulk phase of LiNi 0.9 Co 0.1 O 2 via high-temperature solid-state reaction. We demonstrate that Al 3+ doping enhances charge transfer between transition metal (TM) and oxygen layers, strengthening TM-O bonds and stabilizing the structure, thereby alleviating structural distortions under deep delithiation. More impressively, Mg 2+ doping significantly improves structural stability through a pillaring effect, effectively suppressing irreversible phase transitions during charge-discharge cycling. Consequently, Mg-Al co-doping optimizes the overall structural integrity of the high-nickel cathode, enhances its stability, and inhibits lattice oxygen release during long-term cycling. The Mg-Al co-doped LiNi 0.9 Co 0.1 O 2 delivers a remarkable capacity of 177.3 mAh g −1 after 100 cycles with capacity retention of 93.5 %, demonstrating outstanding cyclability. This Mg-Al co-doping strategy provides a simple and practical approach to enhance the electrochemical performance of high-nickel layered cathode materials.
Shuai Zhao,Hai-lin Ren,Yang Su,Cheng-wei Li,Xiao-min Wang
High-nickel layered cathode materials for lithium-ion batteries have received widespread attention in new energy vehicles for their excellent specific energy and cost advantages, and are considered to be the most promising cathode materials for high-energy density lithium-ion batteries. Despite its many advantages, poor thermal stability and rapid capacity degradation have greatly limited its large-scale application. Ion doping is considered to be an effective way to improve its drawbacks, and in this paper, a series of W-doped LiNi 0.9 Co 0.1 O 2 cathode materials were prepared using WO 3 as a tungsten source. Among them, 1 mol% W doping was the most effective, and its reversible capacity of 204.44 mA g −1 still had 93.25 % capacity retention after 100 this cycles at 1C. Combined with DFT calculations , it is found that the introduction of W does not change the original layered structure and the material transitions from semi-metallic to metallic at lower doping concentrations, resulting in more electrons occupying the Fermi energy levels to enhance its electrical conductivity and leading to an elevated spin state and a lower oxidation state of Ni.
Elevating the nickel (Ni) content within layered cathodes constitutes a straightforward and effective approach to enhance the energy density of lithium-ion batteries (LIBs). However, the phase transition from H2 to H3 introduces substantial alterations in lattice volume, leading to structural degradation and diminished electrochemical performance . This study employs density functional theory (DFT) calculations to determine that the formation energy for Nb 5+ occupied at Li 3 b sites is lower compared to that of Ni 3 a and Co 3 a sites, yet higher than that of Mn 3 a sites. This suggests a preference for Nb 5+ doping within the Li layer of Mn-free cathodes. Motivated by these DFT results, we show the viability of high-valence Nb 5+ as a stable pillar in the compositionally optimized binary oxide LiNi 0.9 Co 0.1 O 2 . The inclusion of this Nb 5+ pillar in the Li layer of Ni/Co-based oxide significantly enhances the reversibility of the H2–H3 redox couple and mitigates microcrack formation in polycrystalline cathodes. As a result, the Nb-doped Ni/Co-based cathode exhibits an extended cycling lifespan, elevated rate capability, and increased thermal stability compared to the undoped. This investigation achieves precise control over doping sites by optimizing the chemical composition of Ni-rich cathodes and provides novel insights into advancing their electrochemical performance for high-energy LIBs.
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