Shuying Zhen,Wang Sun,Peiqian Li,Guangze Tang,David Rooney,Kening Sun,Xinxin Ma
In this work Cu 1.4 Mn 1.6 O 4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD . XPS results confirm that mixed Cu + /Cu 2+ and Mn 3+ /Mn 4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm −1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc 2 O 3 stabilized ZrO 2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm 2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm −2 at 800 °C under H 2 (3% H 2 O) as the fuel and ambient air as the oxidant. These results indicate that Cu 1.4 Mn 1.6 O 4 is a superior and promising cathode material for IT-SOFCs.
Manganese oxides with high theoretical capacity and natural abundance are promising cathode materials for aqueous zinc-ion batteries (ZIBs), yet their intrinsic Jahn–Teller distortion and the strong Zn2+–cathode electrostatic interactions tend to trigger rapid capacity degradation and inferior rate performance. Herein, we propose a high-electronegativity substitution doping strategy to enhance the electrochemical kinetics and stability of manganese oxide cathodes. Manganese oxide materials doped by a trace amount of high-electronegativity Ru atoms are synthesized, for which the Ru dopant substituting Mn atoms not only improves the electronic conductivity of manganese oxides but also induces the compression of [MnO6] octahedra to strengthen the Mn–O bonds, effectively improving ion diffusion capability and mitigating Jahn–Teller distortion-associated lattice expansion during the Zn2+ storage process to improve the electrochemical kinetics and stability of the high-electronegativity Ru-doped manganese oxides. As a result, the synthesized Ru-doped MnO2 cathode possessing a high specific capacity of 230 mAh/g presents good rate performance and attractive cycling stability with a stable average output voltage of 1.34 V and an energy efficiency of over 84%, notably superior to those of currently reported manganese oxide cathode materials. This work provides new insights for designing stable Zn2+ storage cathode materials and is believed to promote the development of ZIBs.
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