Electrochemical mechanism and effects of Fe doping and grinding process on the microstructural and electrochemical properties of Na2Co1-xFexSiO4 cathode material for sodium-ion batteries

Abstract

Sodium-based orthosilicates are considered promising candidates as positive electrode materials for rechargeable sodium-ion batteries (SIBs). Na2Co1-xFexSiO4 (NCFS), with x = 0.1 and 0.2 cathode materials have been synthesized by low cost method (improved solid-state). The effects of Fe substitution and grinding process on the structural, morphological, and electrochemical properties of Na2Co0.9Fe0.1SiO4 (NCFS1) and Na2Co0.8Fe0.2SiO4 (NCFS2) are deeply investigated. The prepared Na2Co1-xFexSiO4 cathodes are indexed based on the orthorhombic system with Pca21 space group with a slight difference in lattice parameters. The morphological properties are strongly determined by the suspension formalism, which has an impact on the electrochemical performances. The ball-milling process leads to enhanced electrochemical performance and higher reversible capacity although with capacity fading after 100 cycles. Na2Co0.8Fe0.2SiO4 demonstrated an initial discharge capacity at C/50 of 131.4 mAh.g−1 (1C= 272.7 mA.g−1) that is two times higher than that of the Na2Co0.9Fe0.1SiO4 (54.6 mAh.g−1 (1C= 272.27 mA.g−1)). All the above features and insights make the new materials highly promising for use as potential cathode material for SIBs.