Wu Fan, Ma He, Ye Xin, Wu Shaoyang, Zhang Haodong, Liang Kang, Li Jianbin, Ren Yurong, Wei Peng
School of Materials Science and Engineering, Jiangsu Province Engineering Research Center of Intelligent Manufacturing Technology for the New Energy Vehicle Power Battery, Changzhou University, Changzhou 213164, China.
School of Materials Science and Engineering, Jiangsu Province Engineering Research Center of Intelligent Manufacturing Technology for the New Energy Vehicle Power Battery, Changzhou University, Changzhou 213164, China.
J Colloid Interface Sci. 2025 Feb;679(Pt A):132-140. doi: 10.1016/j.jcis.2024.09.206. Epub 2024 Sep 27.
Mixed iron-based phosphate NaFe(PO)PO/C (NFPP) has gradually emerged as a promising cathode material for sodium-ion batteries (SIBs) owing to its affordability and convenient preparation. However, poor electrical conductivity and inadequate sodium-ion diffusion limit the exertion of its electrochemical properties. Herein, a structural modulation strategy based on Cd doping is applied to NFPP to address the above limitations. In situ X-ray diffraction analysis reveals that Cd-doped NFPP (NFCPP) undergoes an incomplete solid-solution reaction driven by Fe/Fe redox. Cd doping effectively stabilises the crystal structure, resulting in a minimal 1 % change in unit cell volume during cycling. Density of state calculations indicate that Cd doping reduces the band gap, increases the local electron density and significantly improves electron conductivity. Benefitting from the enhanced electrochemical kinetics and intercalation pseudocapacitance, the optimised NaFeCd(PO)PO/C (NFCPP@3%) exhibits exceptional rate performance (capacity of 62 mAh/g at 20 C) and ultra-long cycling life (82.7 % after 6000 cycles at 20 C). A full SIB prepared using NFCPP@3% and hard carbon, display a 91 % capacity retention rate at a current density of 130 mA g over 200 cycles. This work demonstrates that doping can effectively enhance electrochemical performance and offers insights into future development of SIBs.
混合铁基磷酸盐NaFe(PO)PO/C（NFPP）因其价格低廉且制备方便，已逐渐成为一种有前景的钠离子电池（SIBs）正极材料。然而，其较差的导电性和不足的钠离子扩散限制了其电化学性能的发挥。在此，基于Cd掺杂的结构调制策略被应用于NFPP以解决上述限制。原位X射线衍射分析表明，Cd掺杂的NFPP（NFCPP）经历了由Fe/Fe氧化还原驱动的不完全固溶反应。Cd掺杂有效地稳定了晶体结构，导致循环过程中单位晶胞体积变化最小，仅为1%。态密度计算表明，Cd掺杂降低了带隙，增加了局部电子密度，显著提高了电子导电性。受益于增强的电化学动力学和嵌入赝电容，优化后的NaFeCd(PO)PO/C（NFCPP@3%）表现出优异的倍率性能（在20 C时容量为62 mAh/g）和超长循环寿命（在20 C下6000次循环后为82.7%）。使用NFCPP@3%和硬碳制备的全电池SIB在130 mA g的电流密度下经过200次循环后容量保持率为91%。这项工作表明掺杂可以有效地提高电化学性能，并为SIBs的未来发展提供了见解。
