Defect controlled diffusion of lithium ions in Mn doped V2O5 for potential applications as cathode material

Abstract

With a motivation to unravel the effect of cation (Mn) doping-induced modifications in structure, charge transfer resistance, and Li-ion diffusion in V2O5 a systematic study using X-ray diffraction (XRD), Raman Spectroscopy and electrochemical impedance spectroscopy (EIS) has been employed using three electrodes configuration. Structural investigations using XRD suggest the selective diffusion of Mn ion towards the c-axis at a low doping percentage. Raman spectroscopy suggests the shift in 994 cm-1 modes which substantiates the uniaxial diffusion of Mn ions. Nyquist plots show that interfacial charge transfer resistance is highest for the lowest doping i.e., 1% Mn-doped V2O5 and exhibits the lowest diffusion coefficient as compared to other doped V2O5 samples. Specific capacitance calculated from cyclic voltammetry is found to be highest for the 4% Mn-doped V2O5 sample. Moreover, diffusion of Lithium ions improves with an increase in doping concentration due to higher concentration of defects as evident from Δd/d and Nelson–Riley factor (NRF) for pure V2O5 and Mn-doped V2O5.