Electrochemical reactivity and passivation of organic electrolytes at spinel MgCrMnO4 cathode interfaces for rechargeable high voltage magnesium-ion batteries

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2024-08, Vol.12 (33), p.22220-22232
• Main Authors: Yang, Zhenzhen, Cai, Jiyu, Wang, Evelyna, Sultanov, Maksim, Gao, Lihong, Wu, Xianyang, Liao, Chen, Chen, Zonghai, Wen, Jianguo, Trahey, Lynn, Ingram, Brian J
• Format: Article
• Language: English
• Subjects: Anions; Batteries; Cathodes; Decomposition reactions; Electrochemistry; Electrode materials; Electrolytes; High voltage; High voltages; Interface stability; Leakage current; Magnesium; Nonaqueous electrolytes; Passivity; Photoelectron spectroscopy; Photoelectrons; Solvents; Transition metal oxides; Voltage; X ray photoelectron spectroscopy
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta03765k

Magnesium transition metal oxides such as MgCr2−xMnxO4 are promising high-voltage and high-capacity cathode materials for rechargeable magnesium batteries (RMBs). Understanding and improving the chemical and electrochemical stability of the cathode–electrolyte interface (CEI) has been the primary technical emphasis to enable this category of cathode materials, which has been significantly underexplored. Herein, in this study, we focus on investigating the fundamental mechanism of parasitic reactions at the charged surface of the high-voltage MgCrMnO4 model cathode with different organic electrolytes. The aim is to reveal the underlying effect of anions and solvents responsible for the passivation behavior of the cathode by using three exemplary anions: [(CF3SO2)2N]− (TFSI−), Al[OC(CF3)3]4− (TPFA−), and [CB11H12]− (MC) and three solvents: diglyme (G2), triglyme (G3), and 3-methoxypropylamine (MPA). High precision leakage current measurements during potentiostatic hold reveal that the electrolyte solvent chemistry has a more profound impact than anion's on the passivation of the MgCrMnO4 cathode surface during deintercalation of Mg2+. X-ray photoelectron spectroscopy exhibits the differences in CEI composition. Amine solvents like MPA show poor passivation due to a higher degree of solvent decomposition, while the thin and anion-derived CEI in glyme-based electrolytes is directly linked with the better passivation behavior on the cathode. Furthermore, we leverage the knowledge from these findings to modify the electrolyte structure by adding a solvent additive, with the goal of reducing the parasitic reaction.