Kinetic Insight into the Electrochemical Lithium Insertion Process in the Puckered-Layer γ’-V2O5 Polymorph

International audienceCycling properties, rate capability performance and kinetic parameters for Li insertion in the puckered γ'-V2O5 host lattice are reported here in the 4.0 V-2.5 V voltage window corresponding to 0 ≤ x ≤ 1 in γ-LixV2O5. Whereas a high reversible behavior and good cycling performance are achieved (135 mAh g−1 after 50 cycles at C/10), the rate capability study shows a rapid increase in the discharge-charge hysteresis with the current density, impeding the recovering of high capacity values even at C/2 rate. The kinetics of the electrochemical lithium insertion reaction in γ'-V2O5 has been investigated by ac impedance spectroscopy and discussed in the light of the structural mechanism. The chemical diffusion coefficient DLi is found constant in the 0 ≤ x < 0.4 biphasic region while lithium ions more rapidly diffuse in the solid solution domain 0.4 ≤ x ≤ 1 with greater DLi values by one or two orders of magnitude (around 10−9 cm2 s−1). An increase in charge transfer resistance and cathode impedance characterizes nevertheless the second part of the discharge. These findings explain the limitations in the reaction kinetics in the micrometric γ'-V2O5 cathode material and give directions toward improved performance