Copper-doped Manganese Dioxide has been synthesised through a simple hydrothermal method at different doping levels. The synthesised materials have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) to determine the composition, structure, and morphology. All the Cu doped MnO are found to be single phased. Their electrochemical properties as cathode for Zinc-ion batteries are studied by cyclic voltammetry (CV), galvano-static charge / discharge (GCD) and electrochemical impedance spectroscopy (EIS), using 3 M ZnSO + 0.3 MnSO solution as the electrolyte. 3.8% Cu doped MnO has shown the highest initial capacity of 379.5 mAh g at 0.02 A·g, and 304.4 mA h g at 0.5 A g, but experienced fast fading with a poor capacity retention of 56.8% after 100 cycles. 7.4% Cu doping gives lower capacity, while 5.9% doping shows a higher discharging capacity (320.0 mAh·g at 0.02 A·g and 269.3 mAh·g at 0.5 A·g) and improved stability (85.8% capacity retention after 100 cycles), better than non-doped MnO electrode (284.4 mAh g at 0.02 A g and 252.1 mAh·g at 0.5 A g, capacity retention 76.7%). The samples show satisfactory capacity and rate capability while the cycling stability is not ideal, which may relate to the needle like morphology and nanoscale particle size. CV tests revealed that the electrochemical process is mainly diffusion controlled. The zinc ion diffusion coefficient is tested to be in the range of 10 cm·s from both CV and EIS tests and showed the same trend in their electrochemical capacity. Doping of Copper in MnO reduced the polarization on electrode, improved the electrochemical reversibility, as evidenced by the reduction of the redox peak potential difference from 0.31 to 0.24 V at 1.1 mV·s, and from 0.45 V to 0.31 V at 5 mV·s. Whilst the cell resistance of non-doped MnO increased from 1.78 Ω to 7.39 Ω after cycling, the cell resistances of all Cu-doped cathodes reduced, indicating improved electronic conductivities after cycling. These results indicate that Cu-doping is effective to increase the conductivity of the materials, reduce the polarization during charge and discharge, and improve the cycling stability of MnO cathode.

中文翻译：

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α-MnO2 中铜掺杂对水系锌离子电池正极材料的影响

通过简单的水热法合成了不同掺杂水平的铜掺杂二氧化锰。合成材料通过 X 射线衍射 (XRD) 和扫描电子显微镜 (SEM) 进行表征，以确定其成分、结构和形貌。发现所有 Cu 掺杂 MnO 都是单相的。使用 3 M ZnSO + 0.3 MnSO 溶液作为电解质，通过循环伏安法 (CV)、恒流充放电 (GCD) 和电化学阻抗谱 (EIS) 研究了它们作为锌离子电池正极的电化学性能。 3.8% Cu 掺杂的 MnO 在 0.02 A·g 下表现出最高的初始容量，为 379.5 mAh g，在 0.5 A·g 下为 304.4 mA hg，但经历了快速衰减，100 次循环后容量保持率为 56.8%。 7.4% Cu 掺杂的容量较低，而 5.9% 掺杂显示出更高的放电容量（0.02 A·g 下为 320.0 mAh·g，0.5 A·g 下为 269.3 mAh·g）和更高的稳定性（100 次循环后容量保持率为 85.8%） ，优于非掺杂MnO电极（0.02 A g-1时为284.4 mAh g，0.5 A g-1时为252.1 mAh·g，容量保持率为76.7%）。样品表现出令人满意的容量和倍率性能，但循环稳定性不理想，这可能与针状形貌和纳米级粒径有关。 CV测试表明电化学过程主要是扩散控制的。 CV和EIS测试表明锌离子扩散系数均在10 cm·s范围内，并且其电化学容量表现出相同的趋势。 MnO中铜的掺杂降低了电极的极化，提高了电化学可逆性，氧化还原峰电位差在1.1 mV·s时从0.31 V降低到0.24 V，在5 mV·s时从0.45 V降低到0.31 V。 。循环后，未掺杂 MnO 的电池电阻从 1.78 Ω 增加到 7.39 Ω，而所有铜掺杂阴极的电池电阻均降低，表明循环后电子电导率有所改善。这些结果表明，Cu掺杂可有效提高材料的电导率，减少充放电过程中的极化，并提高MnO正极的循环稳定性。