Surface Degradation of Lithium–Manganese Spinel in Contact with Lithium-Hexafluorophosphate-Containing Electrolyte Solution

Abstract

A set of computational and experimental methods is used in the study of chemical side interactions in the LiMn₂O₄-based lithium-ion cathodic half-cell over the 25–60°C temperature range. The degradation of LiMn₂O₄-spinel-based electrodes is shown to start upon the LiMn₂O₄ granules contacting the standard (basic) electrolyte solution (1 m LiPF₆ in a mixture of ethylene carbonate and dimethyl carbonate (1 : 1, by wt)). It is established that under current-less conditions, the degradation of the LiMn₂O₄-based electrode is caused by the mutual thermodynamic instability between LiMn₂O₄ and the LiPF₆ lithium salt. The equilibrium interaction products are determined, and the mechanism of the critical temperature influence on the degradation of lithium-ion batteries with lithium–manganese spinel is refined. A model is proposed for the primary surface layer at the LiMn₂O₄/electrolyte interface formation and evolution, which explains the distinctive features of the degradation processes in this system.