Evidence for transition from polaron to bipolaron conduction in electroactive LixCr0.11V2O5.16 powders: A dynamic study from 10 to 10 Hz

This paper presents a study on the electrical transport properties of lithiated Cr_0.11V₂O_5.16, which can be used as a rechargeable cathodic material in lithium batteries. Dielectric and conductivity spectra of Li_xCr_0.11V₂O_5.16 powders (x=0, 0.05, 0.40 and 1.20) were recorded in a broad frequency range of 10-10¹⁰ Hz at temperature varying between 300 and 400 K. Complex resistivity diagrams have enabled to obtain thermal behaviors of bulk dc-conductivity. Dielectric relaxations were found, attributed to small polarons and (intersite) bipolarons hopping. The transport properties are shown to be consistent with small polaron and bipolaron conduction models. The change from polaronic to bipolaronic conduction has been evidenced with the increase of the lithium content x from 0.40 to 1.20. This work opens up new prospects for a more fundamental understanding of the electronic transport in relation with the electrochemical properties of Cr_0.11V₂O_5.16.