aa battery.New progress in research on metal selenide anode materials for sodium batteries

　　Recently, the internationally renowned journals "Advanced Materials" (IF=21.95) and "Advanced Energy Materials" (IF=21.875) have published a series of research work on metal selenide anode materials for sodium batteries by the team of Professor Ji Xiaobo from the School of Chemistry and Chemical Engineering of Central South University. Professor Ji Xiaobo is the corresponding author of the paper, and Ge Peng, a 2016 doctoral student, is the first author of the paper. Professor Ji Xiaobo’s team has long been committed to the research of new battery materials. Research has found that the conversion reaction, one of the three major reaction mechanisms, has a volume expansion smaller than the alloying reaction and a larger sodium storage capacity than the intercalation reaction. It is currently considered a new battery material system with great potential. This type of materials mainly includes metal oxides, sulfides, selenides, phosphides, etc. Due to the toxicity of raw materials and the limitations of synthesis methods of phosphides, the current main conversion materials are mainly concentrated on metal-based sixth main group compounds. Among them, due to the strong electronic conductivity (1×10-5Sm-1) and weak electronegativity (2.5) of the Se element, metal selenide has the potential to become a material with excellent charge-discharge specific capacity and cycle stability. . Professor Ji Xiaobo's team has made new progress in designing and regulating the interface properties of metallic selenium-based materials and carbon matrices. Linear basic nickel carbonate (Ni-Pr) was designed and synthesized by means of self-assembly, and its large specific surface area was used to adsorb pyrrole monomer into it for polymerization reaction. Using Se element and the Kirkendall effect at high temperature, a carbon-coated multi-level hollow structure was successfully generated. The system successfully introduced the metal oxygen-carbon bond and the derived double carbon layer structure, which effectively improved the reaction reversibility of the material, alleviated the volume expansion of the material, and deepened the depth of the electrochemical reaction. Demonstrating excellent performance in the field of sodium ion energy storage, this work has important guiding significance for the design and derivation of metal-based materials. The research results were recently published in Advanced Energy Materials (2018, DOI: 10.1002/adma.201803035) (IF=21.875). New progress has been made in the research on metal selenide anode materials for sodium batteries. In addition, the team found that the iron-based Prussian blue-like structure has the characteristics of wide sources of raw materials and simple production processes. However, the material itself has internal interstitial crystal water and relatively weak oxidation and reduction. The electric pair Fe2+/Fe3+ results in poor cycle stability and rate performance of this type of material. Replacement of some iron-based elements by cations (cobalt, nickel, manganese) affects the crystallinity, particle size, and electrochemical performance of Prussian blue-like materials. Carry out a series of effective controls. Thanks to the excellent physical and chemical stability, enhanced kinetic coefficient and "zero strain" structure, the prepared Ni-FePBAs can still maintain a capacity of 81mAhg-1 at a current density of 1.0Ag-1. In addition, a double carbon layer core-shell structure nickel-iron-based selenide was further derived through pyrolytic selenization, showing excellent cycle stability and rapid charge and discharge capabilities. Using nickel-based Prussian blue and the corresponding derived selenide as positive and negative electrode materials, the corresponding all-electric system is assembled, showing an outstanding charge-discharge specific capacity of 302.2mAhg-1 (1.0Ag-1). The research results were recently published in Advanced Materials (2018, DOI: 10.1002/adma.201806092) (IF=21.95).

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