K/F 共掺杂实现具有优异倍率性能的高压层状锰基氧化物阴极,ACS Applied Energy Materials

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K/F 共掺杂实现具有优异倍率性能的高压层状锰基氧化物阴极
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2023-02-06 , DOI: 10.1021/acsaem.2c03613
Rihuang Nie ₁ , Hongxia Chen ₁ , Yutian Yang ₁ , Cheng Li ₁ , Hongming Zhou ₁

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P型层状锰基材料在4.2 V左右易发生晶格氧氧化并伴有氧层滑移，甚至发生不利的相变，导致放电容量迅速下降，结构稳定性差，限制了其工作电压和能量密度. _{在这里，我们提出了层状 Na 0.67} MnO ₂的改性策略材料与K/F共掺杂，从而在4.4 V的高截止电压下达到晶格氧氧化行为和结构稳定性的优化。结合X射线粉末衍射精修结果，非原位X射线光电子能谱分析，高分辨率透射电子显微镜和电化学表征，我们的工作表明适量的K / F共掺杂对良好可逆晶格氧氧化行为的形成和Na层间距的改善具有有利影响。由于钾和氟原子的协同作用，初始放电容量在0.1 C时高达210.2 mA hg ^{–1 ，在1 C时高达140.2 mA}^hg –1，100次循环后容量保持73%，放电容量高达115.0 mA汞柱^–1在 5 C 下，68.1 mA hg ^–1在 200 次循环后保留。动力学分析表明，最优的K _0.05 Na _0.62 MnO _1.95 F _0.05样品表现出最大的钠离子扩散系数和最小的电化学极化，为层状锰基氧化物在高压正极材料中的应用铺平了道路。钠离子电池。

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High-Voltage Layered Manganese-Based Oxide Cathode with Excellent Rate Capability Enabled by K/F Co-doping

P-type layered manganese-based materials are prone to undergo lattice oxygen oxidation accompanied by oxygen layer slipping and even unfavorable phase transitions at around 4.2 V, giving rise to rapid discharge capacity decline and inferior structural stability, which restricts their operating voltage and energy density. Here we propose a modification strategy for layered Na_0.67MnO₂ material with K/F co-doping so as to reach the optimization of lattice oxygen oxidation behavior and structural stability at a high cut-off voltage of 4.4 V. Combining X-ray powder diffraction refinement results, ex situ X-ray photoelectron spectrometry analysis, high-resolution transmission electron microscopy, and electrochemical characterization, our work demonstrates that an appropriate amount of K/F co-doping has a favorable effect on the formation of well-reversible lattice oxygen oxidation behavior and the improvement of Na layer spacing. Owing to the synergetic effect of potassium and fluorine atoms, the initial discharge capacity is up to 210.2 mA h g^–1 at 0.1 C and 140.2 mA h g^–1 at 1 C with 73% capacity retention after 100 cycles and high discharge capacity of 115.0 mA h g^–1 at 5 C, with 68.1 mA h g^–1 retained after 200 cycles. The kinetic analysis shows that the optimal K_0.05Na_0.62MnO_1.95F_0.05 sample exhibits the largest sodium ion diffusion coefficient and the smallest electrochemical polarization, which paves a novel path for the application of layered manganese-based oxides in high-voltage cathode materials for sodium-ion batteries.

更新日期：2023-02-06

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