On the Beneficial Effect of MgCl₂ as Electrolyte Additive to Improve the Electrochemical Performance of Li₄Ti₅O₁₂ as Cathode in Mg Batteries

• Main Authors: Marta Cabello, Gregorio F. Ortiz, Pedro Lavela, José L. Tirado
• Format: Article
• Language: English
• Published: MDPI AG 2019-03-01
• Series: Nanomaterials
• Subjects: Li₄Ti₅O₁₂; magnesium batteries; cathodes; MgCl₂
• Online Access: https://www.mdpi.com/2079-4991/9/3/484

Magnesium batteries are a promising technology for a new generation of energy storage for portable devices. Attention should be paid to electrolyte and electrode material development in order to develop rechargeable Mg batteries. In this study, we report the use of the spinel lithium titanate or Li₄Ti₅O₁₂ (LTO) as an active electrode for Mg²⁺-ion batteries. The theoretical capacity of LTO is 175 mA h g^−1, which is equivalent to an insertion reaction with 1.5 Mg²⁺ ions. The ability to enhance the specific capacity of LTO is of practical importance. We have observed that it is possible to increase the capacity up to 290 mA h g^−1 in first discharge, which corresponds to the reaction with 2.5 Mg²⁺ ions. The addition of MgCl₂·6H₂O to the electrolyte solutions significantly improves their electrochemical performance and enables reversible Mg deposition. Ex-situ X-ray diffraction (XRD) patterns reveal little structural changes, while X-ray photoelectron spectrometer (XPS) (XPS) measurements suggest Mg reacts with LTO. The Ti³⁺/Ti⁴⁺ ratio increases with the amount of inserted magnesium. The impedance spectra show the presence of a semicircle at medium-low frequencies, ascribable to Mg²⁺ ion diffusion between the surface film and LTO. Further experimental improvements with exhaustive control of electrodes and electrolytes are necessary to develop the Mg battery with practical application.