Synthesizing glassy materials using LiMn2O4 as cathode powder from Li-ion batteries and P2O5

Abstract

The making of glasses using lithium manganese(III,IV) oxide as cathode-active material of lithium-ion batteries and phosphorus pentoxide as glass former is herein reported for the first time. The raw materials LiMn₂O₄ and P₂O₅ were mixed in various proportions and melted in ambient atmosphere directed by xLiMn₂O₄-(100 − x)P₂O₅ with x = 15 mol%, 20 mol%, 25 mol%, 30 mol% and 35 mol% nominal compositions. The materials obtained were subsequently characterized by X-ray diffraction (XRD), density, Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), optical absorption, and photoluminescence (PL) spectroscopy measurements with decay kinetics analysis. The XRD data supported vitrification in the explored compositional range wherein the density tended to increase with LiMn₂O₄ concentration. The FT-IR spectra indicated that adding LiMn₂O₄ at the expense of P₂O₅ leads to a network depolymerization effect evidenced largely by the upsurge of the v_as(PO₃²⁻) band of end-of-chain PO₄ tetrahedra. DSC results showed that the glass transition temperature increased steadily while glass stability decreased with increasing LiMn₂O₄ content. The optical absorption measurements showed increasingly the presence of both Mn²⁺ and Mn³⁺ ions leading to the development of intense purple hues consistent with LiMn₂O₄ decomposition in the melts. The PL assessment then scrutinized the manifestation of red-emitting Mn²⁺ ions wherein an emission suppression trend was observed. The decay dynamics evaluation revealed the shortening of the Mn²⁺ decay times harmonizing with the PL quenching effect. The original work carried out stimulates additional research regarding the potential of vitrification with P₂O₅ for the management or upcycling of lithium battery components.