Abstract

LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathode materials are susceptible to irreversible phase changes and surface side reactions between electrode materials and electrolyte during charging and discharging, which represent a severe danger to the safety and electrochemical performance of batteries. Li\(_{{1.06-x}}\)Na_xNi_0.5Co_0.2Mn_0.3O\(_{{2-y}}\)Cl_y cathode materials co-doped with Na⁺ and Cl^– were prepared by a simple co-precipitation method. The effects of crystal structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and charge-discharge performance tests. The results show that the doping of Na⁺ and Cl^– reduces the mixing of cations and expands the diffusion channels of Li⁺. Currently, the doped 1%-NCM has a high charge-discharge capacity and the best cycling performance (187.56 mA h g^–1 at 1 C with the highest capacity retention at 76.29% after the first cycle). After 50 cycles, the specific capacity retention was 138.33 mA h g^–1, which increased the capacity retention by 18.58% compared with the unmodified material, indicating that the co-doping of anions and cations improved the Li⁺ de-embedding ability as well as the specific capacity.

中文翻译：

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Na、Cl共掺杂LiNi0.5Co0.2Mn0.3O2正极材料的制备及电化学研究

摘要

LiNi_0.5Co_0.2Mn _0.3O₂ (NCM523) 正极材料容易发生不可逆相变和表面副反应充放电过程中电极材料与电解液之间发生化学反应，对电池的安全性和电化学性能构成严重威胁。李\(_{{1.06-x}}\)Na_x镍_0.5Co_0.2Mn_0.3O\(_{{2-y}}\)Cl_y共掺杂Na⁺和Cl^{正极材料–} 是通过简单的共沉淀方法制备的。通过X射线衍射（XRD）、扫描电子显微镜（SEM）、电化学阻抗谱（EIS）和充放电性能测试研究了晶体结构、形貌和电化学性能的影响。结果表明，Na⁺和Cl^–的掺杂降低了阳离子混合并扩大Li⁺的扩散通道。目前，掺杂的 1%-NCM 具有较高的充放电容量和最佳的循环性能（1 C 时为 187.56 mA h g^–1，最高第一次循环后容量保持率为 76.29%）。 50次循环后，比容量保持率为138.33 mA h g^–1，与未改性材料相比，容量保持率提高了18.58%，表明阴离子和阳离子的共掺杂提高了Li⁺的去嵌入能力以及比容量。