V2O5 As the Cathode for Mg2+-Ion Batteries, Preparation and Characterization

Portable electronics and their commercial use are strongly dependent on the prize, performance and life cycle of the rechargeable batteries. This is even truer for the use in electric vehicles. Currently used Li⁺-ion batteries represent the state of art technology but there still is a strong demand for further improvement [1,2]. Low abundance and thus high costs for lithium have initiated intensive research for the possible replacement of lithium by other more abundant metals such as magnesium and sodium [3]. Ionic, electronic and chemical characteristics of Li⁺-, Na⁺- and Mg²⁺-ions are different and therefore host materials appropriate for Li⁺-ions intercalation are not necessarily suitable for Mg²⁺ and Na⁺ ions – as well known for the case of graphite anodes. The cathode material V₂O₅ is one candidate which already showed good performance not just for Li⁺ but also for Mg²⁺ and Na⁺ions [4,5].

Since the morphology and structure of the host materials strongly influence the intercalation process, in this study efforts have been done to synthesize V₂O₅ with different morphology by applying different synthetic routes and choosing the best material for the metal ion intercalation. V₂O₅ was prepared by means of sonochemical modification of commercial V₂O₅ powder, anodization of V metal, electrochemical deposition and hydrothermal synthesis. The obtained materials were characterized by means of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The sonochemical treatment and electrochemical deposition yielded V₂O₅-nanofibers, the anodization method V₂O₅-nanotubes and the hydrothermal synthesis hollow nanospheres of V₂O₅. The performance of the obtained materials was tested by several electrochemical techniques such are cyclic voltammetry, potentiostatic intermittent titration technique (PITT) and galvanostatic charge/discharge cycles. Li, Na and Mg intercalation were studied. For Li, the rate capability of the sonochemically prepared material was clearly improved compared to commercial, microcrystalline V₂O₅, but the available voltage at a given discharge capacity was less. The electrodeposited material showed a rather poor performance, while the hollow nanospheres behaved very promising. Also for Na intercalation the latter material showed reasonable performance. First measurements for Mg insertion are shown as well.

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[4] Gershinsky G. et al., Electrochemical and Spectroscopic Analysis of Mg²⁺ Intercalation into Thin Films Electrodes of Layered Oxides: V₂O₅ and MoO₃, Langmuir 29 (2013) 10964

[5] Su D. W. et al., Hierarchical orthorhombic V₂O₅hollow nanospheres as high performance cathode materials for sodium-ion batteries, J. Mater. Chem. 2 (2014) 11185