Analysis of Charged State Stability for MonoclinicLiMnBO3Cathode.

The stability ofthe charged state of monoclinic LiMnBO3has been analyzedto better understand its electrochemical cyclingbehavior in this work. First-principles calculations indicate thatdelithiated monoclinic Li1–xMnBO3becomes unstable for x≥ 0.625. Resultsobtained from ex-situX-ray diffraction on chargedelectrodes and chemically oxidized powder confirm the phase decompositionof the LiMnBO3phase when a significant amount of Li isextracted. Energy-dispersive X-ray spectroscopy and X-ray diffractionanalysis also reveal Mn dissolution from the cycled LiMnBO3cathodes and chemically delithiated LiMnBO3specimen.Based on these results, we consider the cycling performance of monoclinicLiMnBO3to be primarily limited by its charged state instability.To overcome this limitation, we partially substituted Mn with Mg tomaintain structural integrity of the phase and reduce capacity fadingover multiple cycles. [ABSTRACT FROM AUTHOR]