Iron substitution in Na4VMn(PO4)3 as a strategy for improving the electrochemical performance of sodium-ion batteries

P Lavela,M.A Hidalgo,R Klee,J.L Tirado

doi:10.1016/j.jelechem.2021.115533

Abstract

Six NASICON type samples with Na4-xVFexMn1-x(PO4)3 (0 ≤ x ≤ 1) stoichiometry are examined as positive electrodes for sodium-ion batteries. The structural, morphological, and chemical state of elements in raw samples is unveiled by XRD diffraction, electron microscopy, and Raman and XPS spectroscopies. The effect of the dual Fe/Mn substitution is examined by electrochemical tests using both voltammetric and galvanostatic methods. The results reveal the beneficial effect of the iron substitution, justified by an improvement of the kinetic response, and supported by the calculation of the apparent diffusion coefficients and internal cell resistance.

Highlights

Electrochemical sodium-ion storage is attracting more attention as a serious competitor of lithium-ion batteries
We aim to evaluate the effect of the replacement of vanadium by different Fe/Mn ratios in the Na4-xVFexMn1-x(PO4)3 (0 ≤ x ≤ 1) series as cathode materials for sodium-ion batteries
The narrow reflections were suitably indexed in the R-3c space group of the trigonal system

Summary

Introduction

Electrochemical sodium-ion storage is attracting more attention as a serious competitor of lithium-ion batteries. Numerous objections were raised about the intrinsic larger ion size and lower output voltage of sodium than lithium. Crucial benefits as the high crust and ocean abundance, the homogeneous distribution of resources, and environmental benignity of sodium have been pointed out as essential aspects to be considered in the case of limited lithium resource supply [1,2,3,4,5,6]. The desolvation energy for these alkaline ions has been reported to be is roughly 30% smaller than for lithium in several organic solvents, diminishing the charge transfer resistance and enhancing the electrode kinetics [7,8]. Sodiumion batteries are nowadays envisaged for their applicability as largescale stationary batteries supporting energy storage from renewable resources [9,10]

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