Anions induced evolution of Co3X4 (X = O, S, Se) as sodium-ion anodes: The influences of electronic structure, morphology, electrochemical property

Abstract Sodium-ion batteries (SIBs) are regarded as a promising candidate for large-scale energy storage applications, however, its sluggish sodiation kinetics limit high power capabilities. First-principles density functional theory (DFT) calculations demonstrates that the replacement of large anions, within a Co3X4 (X = O, S, Se) complex, can facilitate electron transfer through the reduction of the energy band gap (Eg) and the regulation of structural, electronic and bonding properties of Co-X, suggesting that the substituted Co3X4 in the following order O   Na2S > Na2Se) with the increased active sites, which are paramount for electrochemical properties. The work in this article sheds light on the in-depth understanding of the improved sodium-storage behavior with the advancing VI group anions and provides an effective strategy for the design of high-rate electrode materials for SIBs.