含氧氧化还原反应过程的P2-型层状氧化物正极由于具有高容量在钠离子电池中受到广泛关注。然而，由于这些材料在高电压下发生不可逆的氧氧化还原反应和相变过程，通常电化学性能较差，因而阻碍了它们的大规模应用。
近日，太原理工大学张献明教授、段小川教授和武汉工程大学张鼎教授等人在Science China Materials发表研究论文，揭示了通过掺杂铜使无Co/Ni的Na0.75Li0.25–2/3xCuxMn0.75–1/3xO2循环稳定性和速率性能显著提高的机理。
本文要点
1) 非原位XPS显示，掺入Cu可减少循环过程中引发Jahn-Teller效应的Mn3+的量。此外，Cu周围氧的电子富集可以减轻氧的不可逆氧化，从而抑制因O–O之间静电排斥的快速减弱而产生的相变。2) 原位XRD结果证实，Na0.75Li0.19Cu0.09Mn0.72O2在充放电过程中保持了P2相结构，从而实现了1.9%的近零应变特性。3) 优化后的正极在0.1 C时的可逆容量高达194.9 mAh g−1，在5 C时循环100次后的容量保持率高达88.6%。与商用硬碳负极配对的全电池可提供240 Wh kg−1的能量密度。这项研究为设计低成本、高能量密度的新型钠离子电池插层正极材料提供了思路。Figure 1. Structural characterization of cathode materials. XRD Rietveld refinement of (a) NLMO and (b) NLC9MO. (c) Crystal structure of NLC9MO. SEM images of (d) NLMO and (e) NLC9MO. (f) HR-TEM image of NLC9MO. (g) EDS mappings of NLC9MO.Figure 2. Electrochemical properties of NLMO and NLC9MO materials at 1.5–4.4 V. The first three cycles of charge-discharge curves of (a) NLMO and (b) NLC9MO at 0.1 C (1 C = 200 mA g−1). CV curves of (c) NLMO and (d) NLC9MO. (e) Calculated log(DNa+) for NLMO and NLC9MO at each voltage. (f) The comparison of rate performances between NLMO and NLC9MO. (g) Output potential versus cycle number. (h) Cycling performance of NLMO and NLC9MO at 5 C.Figure 3. Structural changes in NLMO and NLC9MO materials. In-situ XRD patterns during the initial cycle at 0.1 C of (a) NLMO and (b) NLC9MO. Asterisks indicate diffraction peaks from the Al collector. Changes in single-cell parameters a/b, c and volume of (c) NLMO and (d) NLC9MO. (e) Schematic representation of the structural changes of NLMO and NLC9MO during the first charge/discharge process. (f) Schematic representation of irreversible oxygen redox reduction in relation to interlayer slip.Figure 4. Performance of the full cell composed of P2-NLC9MO cathode//hard carbon anode. (a) Schematic of the full cell structure. (b) Hard carbon charge-discharge profile. (c) Optimized voltage window depicted by the CV profile. (d) Constant-current charge-discharge profile of the full cell. (e) Cycling performance in a voltage window of 1.4–4.4 V at 0.5 C (based on the active mass of cathode).Hai-Xia Zhang, Lin-Rong Wu, Hao-Rui Wang, Dong-Zheng Wu, Shao-Hui Guo, Ding Zhang, Xiao-Chuan Duan, Xian-Ming Zhang. Stabilizing oxygen redox reaction in phase-transition-free P2-type Co/Ni-free cathode via Cu doping for sodium-ion batteries. Sci. China Mater. (2024).https://doi.org/10.1007/s40843-024-3081-9
![]()
点击左下角“阅读原文”，阅读以上文章PDF原文
![]()
