Highly Conducting Li(Fe_1−<i>x</i>Mn_<i>x</i>)_0.88V_0.08PO₄ Cathode Materials Nanocrystallized from the Glassy State (<i>x</i> = 0.25, 0.5, 0.75)

Abstract

This study showed that thermal nanocrystallization of glassy analogs of LiFe1−xMnxPO4 (with the addition of vanadium for improvement of glass forming properties) resulted in highly conducting materials that may be used as cathodes for Li-ion batteries. The glasses and nanomaterials were studied with differential thermal analysis, X-ray diffractometry, and impedance spectroscopy. The electrical conductivity of the nanocrystalline samples varied, depending on the composition. For x=0.5, it exceeded 10−3 S/cm at room temperature with an activation energy as low as 0.15 eV. The giant and irreversible increase in the conductivity was explained on the basis of Mott’s theory of electron hopping and a core-shell concept. Electrochemical performance of the active material with x=0.5 was also reported.

Keywords

• nanocrystallization
• high conductivity
• electron hopping
• olivine
• cathode materials