CR927 battery.Summary of the latest research progress on sodium-ion batteries and lithium-sulfur batteries

　　1. Angew.Chem.Int.Ed.: Singlet Oxygen in Aprotic Sodium-Oxygen Battery Cycles

　　Aprotic sodium-oxygen batteries require the reversible formation/dissolution of sodium superoxide (NaO2) during cycling. Poor cycle life related to collateral chemistry should be attributed to the reaction of the electrolyte and electrode with NaO2, a strong nucleophile and base. However, its reactivity cannot account for side effects and irreversibility simultaneously. Recently, Dr. Stefan A. Freunberger (corresponding author) of the Technical University of Graz, Austria, and others confirmed that singlet oxygen (1O2) is formed at all stages of the cycle and is the main driving force of incidental chemistry. The capture agent and 1O2 quickly and selectively form a stable adduct for in-situ or ex-situ detection. 1O2 formation includes proton-mediated superoxide dismutation during discharge, pause, charging below 3.3V and direct electrochemical production of 1O2 at about 3.3V. The trace amounts of water required for high volumes are also a driving force for incidental chemistry. Controlling highly reactive singlet oxygen is therefore key to highly reversible battery operation.

　　2. Angew.Chem.Int.Ed.: Ultra-high capacity organic thiocarboxylate electrodes for room temperature sodium ion batteries

　　Organic battery electrodes are expected to replace traditional metal oxide electrode materials due to their advantages of low cost, no heavy metals, and easily adjustable structures. Carboxylates and carbonyl compounds have been widely studied as organic room temperature sodium battery electrodes. For the first time, Professor Du Yaping and Professor He Gang (co-corresponding author) of Xi'an Jiaotong University gradually replaced the oxygen atoms of the carboxyl group in sodium terephthalate with sulfur atoms and used it as a sodium ion battery electrode, which can improve electron delocalization, conductivity and sodium absorption capacity. . The above general strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon skeleton. After introducing two sulfur atoms into the carboxylate skeleton, the molecular solid reversible capacity reaches 466mAh·g-1 at a current density of 50mA·g-1. After introducing four sulfur atoms, the capacity increased to 567mAh·g-1 at a current density of 50mA·g-1, which is the highest capacity of an organic sodium-ion battery anode so far.

　　3.NanoEnergy: Research on the reaction mechanism of SnF2@C nanocomposite as anode material for high-capacity sodium-ion battery

　　As a rechargeable battery anode with extremely high theoretical energy storage capacity, tin-based materials have attracted the attention of many researchers. Professor KyungYoonChung (corresponding author) of the Korea Institute of Science and Technology and others prepared a nanocomposite based on SnF2 and acetylene black and used it as an anode material for high-performance sodium ion batteries, and studied its electrochemical properties and related energy storage mechanisms. . Compared with the reversible capacity of micron-sized pure SnF2 electrode (323mAh·g-1), the reversible capacity of nanocomposite electrode (563mAh·g-1) is greatly improved. The nanocomposite electrode shows superior rate performance, and the reversible capacity can reach 191mAh·g-1 at a high current density of 1C, while the pure electrode has a lower capacity. In-situ XRD was used to observe changes in the crystal structure, and the results showed that there were solid solutions of two or more substances during the charge/discharge process.

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