Co-free Ni-rich layered oxide cathodes need urgent development due to the continuously increasing demand for high-performance lithium-ion batteries. Here, the cathode materials of LiNi_0.60Mn_0.40O₂ (NM) and Fe-doped LiNi_0.60Mn_0.40–xFe_xO₂ (NMFe, x = 0.01–0.05) were prepared via a coprecipitation method associated with a high shear mixer, and the corresponding electrochemical performance was assessed. The optimal Fe-doped sample (NMFe-3) exhibits a discharge capacity of 185.3 mAh·g^–1 (0.1C), higher than that of NM (182.5 mAh·g^–1) at 2.8–4.5 V and 25 °C. Characterization based on XRD, XPS, HRTEM, EIS, CV, and GITT tests illustrates the presence of LiFeO₂ crystal planes inside the NMFe samples, the lower values of the electrode/electrolyte interface impedance of the Fe-doped samples, and the charge-transfer impedance of the electrodes, as well as higher Li⁺ diffusion rate during charge/discharge processes. In situ XRD tests confirm that NMFe-3 exhibits excellent reversible phase transition during the charge/discharge process. DFT calculations disclose that Fe dopants would make Li layer spacings enlarged and lower the energy barrier of Li⁺ diffusion. This work provides a facile route to synthesize Fe-substituted Co-free Ni-rich cathode materials with excellent electrochemical performance for lithium-ion batteries.

中文翻译：

---

Fe掺杂增强LiNi0.60Mn0.40O2正极材料的电化学性能


由于对高性能锂离子电池的需求不断增加，无钴富镍层状氧化物正极亟待开发。这里，正极材料为LiNi _0.60 Mn _0.40 O ₂ (NM)和Fe掺杂LiNi _0.60 Mn _0.40–x O ₂ (NMFe, x = 0.01–0.05) 通过与高剪切混合器相关的共沉淀方法制备，并评估了相应的电化学性能。最佳Fe掺杂样品（NMFe-3）的放电容量为185.3 mAh·g ^–1 （0.1C），高于NM的放电容量（182.5 mAh·g ^–1 ）在 2.8–4.5 V 和 25 °C 下。基于 XRD、XPS、HRTEM、EIS、CV 和 GITT 测试的表征表明 NMFe 样品内部存在 LiFeO ₂ 晶面，Fe 掺杂的电极/电解质界面阻抗值较低样品的电荷转移阻抗，以及充电/放电过程中较高的Li ⁺ 扩散速率。原位 XRD 测试证实 NMFe-3 在充电/放电过程中表现出优异的可逆相变。 DFT计算表明，Fe掺杂会使Li层间距增大，降低Li ⁺ 扩散的能垒。这项工作为合成具有优异锂离子电池电化学性能的铁取代无钴富镍正极材料提供了一条简便的途径。