Slight Multielement Doping-Induced Structural Order–Disorder Transition for High-Performance Layered Na-Ion Oxide Cathodes

Abstract

To realize concurrently the high-energy density and excellent cycling stability, maximum utilization of redox couple, minimization of detrimental phase transition, and structural degradation of O3-type layered oxide cathodes are critical for developing Na-ion batteries. Ni2+/Ni4+ redox couple showing multielectron reaction and higher redox potential is favorable to increase the energy density. However, the Jahn-Teller distortion of Ni3+ generated upon (dis)­charging results in a strong anisotropy in the local crystal structure that causes irreversible interlayer bending and chemo-mechanical cracks of the cathode particles, compromising the electrochemical properties eventually. In this work, we show a slight multielement doping strategy that enlarges the amount of active redox components while minimizing the inactive contents. The results show that the uniform distribution of multiple components can help increase the disorder degree of atom arrangement and alleviate the structural changes and detrimental anisotropy cracks. As a proof of concept, a multielement-doped O3-type Na0.9Ni0.25Cu0.05Mg0.05Zn0.05Fe0.05Al0.05Mn0.40Ti0.05Sn0.05O2 oxide is rationally prepared that presents better chemo-mechanical stability and delayed O3-P3 phase transition behavior. Compared to the high Ni-content Na0.9Ni0.35Fe0.2Mn0.45O2 cathode, this as-prepared multielement material delivers a reversible capacity of about 120 mAh/g in the voltage range of 2–4.0 V, superior cycling stability with 90% of capacity retention after 500 cycles, and excellent rate capability (more than 70% of initial capacity at 5.0 C). This work indicates that the multielement doping method is highly suitable for the development of advanced Na-ion layered oxide cathodes.

Predominant P3-Type Solid–Solution Phase Transition Enables High-Stability O3-Type Na-Ion Cathodes

“…The preparation process of positive electrodes, the fabrication procedure, and the measurement method of coin-type cells were in agreement with those reported in the previous work, as shown in the Supporting Information.…”

“…The preparation process of positive electrodes, the fabrication procedure, and the measurement method of coin-type cells were in agreement with those reported in the previous work, 29 as shown in the Supporting Information. We speculated that adjusting the P2-type composition with intermediate Na content can pass through the division between O3-and P2-type structures, promoting the attainment of an O3-type structure with P-type structural characteristics.…”

Application and Prospects of Ni–Mn-Based Layered Oxide Cathodes for Sodium-Ion Batteries

“…Moreover, the Coulombic efficiency remained approximately 99.9% throughout the cycling process. In a similar vein, Guo et al employed a high-entropy strategy to design and synthesize multielement-doped O3-type Na 0.9 Ni 0.25 Cu 0.05 Mg 0.05 Zn 0.05 Fe 0.05 Al 0.05 Mn 0.40 Ti 0.05 Sn 0.05 O 2 , which exhibited a reversible capacity of approximately 120 mAh/g over the 2.0–4.0 V voltage range and demonstrated superior cycling stability with a capacity retention of 90% after 500 cycles . These studies collectively highlight the efficacy of the multidoping strategy in achieving high capacity and stable cycling performance, making it a promising avenue for practical applications.…”

Doping Engineering in Electrode Material for Boosting the Performance of Sodium Ion Batteries

“…In comparison to the high Ni-content Na 0.9 Ni 0.35 Fe 0.2 Mn 0.45 O 2 cathode, this doped material demon-within the voltage range of 2−4.0 V. Moreover, it displays superior cycling stability with 90% capacity retention after 500 cycles and excellent rate capability, retaining over 70% of the initial capacity at 5.0 C. This study underscores the efficiency of the multielement doping method for advancing the development of advanced Na-ion layered oxide cathodes. 33 Similarly, Chae et al introduced doping with Al and F in Na 0.44 MnO 2 to enhance its electrochemical performance. This resulted in a modified crystal structure with the chemical formula Na 0.46 Mn 0.93 Al 0.07 O 1.79 F 0.21 , deviating from the tunneltype manganese oxide structure.…”