Evidence for transition from polaron to bipolaron conduction in LixCr0.11V2O5.16: a dynamic study from 10 to 10^10 Hz
Résumé
This paper presents a study on the electrical transport properties of lithiated Cr0.11V2O5.16, which can be used as a rechargeable cathodic material in lithium batteries. Dielectric and conductivity spectra of Li,Cr0.11V2O5.16 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 Cr0.11V2O5.16.