☆ 4.8 Article

Synthesis, electrochemical properties, and changes in crystal and electronic structures during charge/discharge process of spinel-type cathode materials Mg4V5-xNixO12 (x=0, 0.3, 0.6, 1.0) for magnesium secondary batteries

JOURNAL OF POWER SOURCES (2020)

Journal

JOURNAL OF POWER SOURCES

Volume 455, Issue -, Pages -

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ELSEVIER

DOI: 10.1016/j.jpowsour.2020.227962

Keywords

Magnesium secondary battery; Cathode; Crystal structure; Synchrotron X-ray diffraction; Electrochemical properties; Spinel

Funding

JST ALCA-SPRING, Japan [JPMJAL1301]

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Abstract

Mg(4)V(5-x)Ni(x)O(12 )was synthesized by a solid-phase method under high vacuum. The product had a spinel structure with a space group Fd-3m based on its powder X-ray diffraction pattern. Elemental mapping by STEM-EDS showed that the particles had a uniform composition. Charge and discharge cycle tests revealed a discharge capacity exceeding 150 mAhg(-1) at 90 degrees C, and cyclability was reversible up to 14 cycles. Mg(Mg0.33V1.57Ni0.1)O-4 exhibited a high discharge capacity of 194 mAhg(-1) at a low rate of 1 mAg(-1). From a Rietveld analysis of the X-ray diffraction pattern for the electrode, the occupancies of the 8a and 16c sites increased after charging. Since the Mg occupancy at the 16c sites changed significantly after charging during the second cycle and after discharging, it is considered that the discharge capacity is largely responsible for Mg occupancy of the 16c sites. A shift towards higher energy was observed in the X-ray absorption near edge structure spectra of V and Ni. Therefore, the charge-discharge mechanism was revealed to involve a redox reaction involving V and Ni.

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Electrochemical properties and crystal and electronic structure changes during charge/discharge of spinel type cathode-materials Mg1.33V1.67-xMnxO4 for magnesium secondary batteries

Yasushi Idemoto, Mina Takamatsu, Chiaki Ishibashi, Naoya Ishida, Toshihiko Mandai, Naoto Kitamura

Summary: Mg1.33V1.67-xMnxO4 (x= 0.1 to 0.4) was synthesized for the first time using a solid-phase method under high vacuum conditions. The crystal structures were confirmed to be spinel with Fd3(-)m space group through powder X-ray diffraction analysis, and the chemical compositions were found to be uniform through STEM observation and elemental analysis. Charge and discharge cycle tests revealed that the discharge capacity depended on the cycle number, Mn composition, and working temperature. Among them, Mg1.33V1.57Mn0.1O4 (x=0.1) exhibited the highest discharge capacity of 256 mAh g(-1) at the 13th cycle, while the initial capacity was only 73 mAh g(-1) at 90 degrees C. The local structure was analyzed using EXAFS spectra, which showed that Mg1.33V1.57Mn0.1O4 had the smallest lattice distortion due to Mn at 16d sites, and XAFS spectra indicated a significant change in the oxidation state of V during the charge/discharge cycles. The particularly stable crystal structure and large contribution of charge compensation by V may contribute to the excellent charge-discharge performance of Mg1.33V1.57Mn0.1O4.

JOURNAL OF ELECTROANALYTICAL CHEMISTRY (2023)