Manganese dissolution from LiMn2O4 cathodes at elevated temperature: methylene methanedisulfonate as electrolyte additive

Abstract

Diethyl carbonate (DEC) electrolyte decomposition reactions resulting from PF5 attacked produce HF by several side reaction steps. The resulting HF can dissolve the Mn from spinel-type lithium manganese oxide (LiMn2O4). To verify that methylene methanedisulfonate (MMDS) suppress Mn3+ dissolution mechanism of lithium manganese oxide spinel cathode using methylene methanedisulfonate as electrolyte additive at elevated temperature, a DEC-based electrolyte using MMDS as electrolyte additive is developed in this work. The linear sweep voltammetry (LSV) indicates the start oxidation potential of the electrolyte with 0.5 wt% MMDS is around 3.83 V (vs. Li/Li+), which is lower than the control (4.12 V). Self-discharge and inductively coupled plasma-atomic emission spectrometry (ICP-AES) reveal that Mn3+ dissolution from the spinel cathode is hindered. The results of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) demonstrate that MMDS would help to form the stable passivation film, which would effectively suppress to oxidize the control electrolyte solvents and HF generation is suppressed, and result in less Mn3+ dissolution from the spinel cathode.