Developing electrode materials with high energy and power densities holds the key for satisfying the urgent demand for energy storage. Addressing at this issue, we herein report a nanophase MnV 2 O 4 material as a novel anode material for lithium-ion batteries. Nanoscale V 2 O 3 precursor was employed as raw material and successfully limited the diameter of the MnV 2 O 4 particles. Nanoscale MnV 2 O 4 with carbon coating behaves an ideal electrochemical performance, and its initial capacity and Coulombic efficiency are 736.9 mAh g −1 under 50 mA g −1 and of 83.17%, respectively. Besides, the MnV 2 O 4 also shows the high lithium-ion storage capacity and excellent cycling stability under high current density, indicating potential application in energy storage devices.
Shuyue Li,Qianru Mi,Liangliang Wang,Yong Li,Liping Chen,Juan Wang
Aqueous zinc-ion batteries (AZIBs) have received comprehensive attention as promising candidates for large-scale energy storage owing to high security, low cost, and environmental friendliness. Developing appropriate cathode materials is of great significance for high-efficiency Zn 2+ storage. Herein, we proposed an efficient in-situ electrochemical pretreatment strategy to unlock the potential of non-electrochemically active spinel MnV 2 O 4 via an irreversible phase reconstruction from crystalline structure to short-range ordered amorphous state. Specifically, the reconstructed electrodes not only deliver abundant active sites for Zn 2+ ions accommodation, but also shorten diffusion paths for rapid reaction kinetics, thus achieving superior electrochemical properties . As revealed, the optimized electrodes present a prominent specific capacity of 445 mA h g −1 at 0.1 A g −1 , a high capacity retention of 73.1 % over 2000 cycles at 5 A g −1 , as well as exceptional energy density of 335 W h kg −1 and power density of 176 W kg −1 based on the mass of cathode. In addition, the reaction mechanism during Zn 2+ ions storage process is systematically investigated by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. This in-situ electrochemical conversion mechanism sheds light on a new methodology of designing desirable cathode materials for aqueous ion batteries.
By annealing [Mn(phen)H 2 O][V 2 O 6 ] (phen = 1,10-phenanthroline) in the presence of graphite template, MnV 2 O 4 /C microparticles are obtained, in which MnV 2 O 4 particles with one-layer or few-layer coating of graphene are anchored on the graphite sheets. The optimal sample, MnV 2 O 4 (p)/C-700 with a high carbon content (35.3 at. %) can deliver a large specific capacity of 410 mAh g −1 at 0.1 A g −1 with a high capacity retention of 94.3% over 1000 discharge/charge cycles at 20 A g −1 as cathode in zinc-ion battery. Ex situ X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectra, as well as elemental mappings and X-ray photoelectron spectroscopy of MnV 2 O 4 (p)/C-700 discern the partial phase transformation mechanism of MnV 2 O 4 →Zn 3 (OH) 2 V 2 O 7 (H 2 O) 2 during discharge/charge process. It is because the rich oxygen defects of MnV 2 O 4 can improve electrical conductivity, favor the electron transfer from V→Mn/O, thus facilitate the binding of Zn 2+ , and the captured Zn 2+ cannot be extracted, as evidenced by density functional theory calculations. Furthermore, it is found that O-deficiency can capture the water shell from the hydrated Zn 2+ , then the dehydrated Zn 2+ is easy to insert into MnV 2 O 4 with lower migration barrier of Zn 2+ (0.84 eV), leading to the structural reversibility of MnV 2 O 4 in cycling test.
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