Abstract:

Alloy-type materials are promising anode materials for lithium/sodium ion batteries owing to their high specific capacity and suitable lithium/sodium intercalation potential. Compared with the control of the morphology and structure of alloy materials, micron alloy materials are more cost effective. This article reviews the research progress in optimizing electrolyte to stabilize micro-alloy materials, and reveals the relationship between volume effect and the stability of micro-alloy electrodes. In the traditional electrolyte system, the volume expansion causes the alloy electrode exposed the fresh interface, which leading the fast decomposition of the electrolyte, but the volume effect is only a phenomenon, not the root cause of the failure of the alloy material. The decomposition of electrolyte can form an electronically insulating SEI on the surface of the pulverized alloy material (leading the alloy material lack of electrical contact), this is the root cause of the failure. At the same time, this article also compares the difference between the alloy electrodes in lithium storage and sodium storage, where sodium ions have lower desolvation energy than lithium ions, which makes it easy to complete the desolvation process at the interface of alloy electrodes. Also, the absolute potential of the alloying reaction between sodium ions and the alloy electrode is higher. These two advantages can improve the stability of the electrolyte (reducing the reduction and decomposition of the electrolyte), so based on the sodium storage mechanism of micron alloy electrode, the choice of electrolyte is wider. At the same time, this article also looks forward to the development direction of using electrolyte to stabilize micron alloy electrodes: increasing the voltage resistance window of ether solvents, and developing high-voltage lithium (sodium) ion full batteries based on the micron alloy electrodes.

Key words: alloy materials, electrolyte, volume change, Li/Na-ion battery