Investigation of the high-rate Na ion storage property in bulk Cu2-xSe plates

The traditional views hold the conversion and intercalation compounds without nanostructure used in ion batteries could not afford high-rate performance. This study demonstrated a bulk material of hexagonal plate-like Cu2-xSe with exposed (111) plane exhibits an ultrahigh rate performance without any assistance of high conducting graphene or carbon nanotube, et.al. The bulk Cu2-xSe plates, used as the anode of sodium ion battery, deliver a high capacity of 377.6 mA h g-1 at 0.1 A g-1 and maintain a capacity retention rate of 83.5% at 10 A g-1, as well as a long cycle life of 93.2% after 1000 cycles at 5 A g-1. Density functional theory analysis confirms that the (111) faceted Cu2-xSe plates with reduced migration energy for Na ion across the Cu2-xSe can enhance its electrochemical reaction kinetics. Moreover, the detailed Na ion insertion/extraction mechanism was demonstrated by combining the in situ and ex situ measurement technologies. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study demonstrates the high-rate performance of hexagonal plate-like Cu2-xSe bulk material in sodium ion batteries without the need for high conducting materials like graphene or carbon nanotubes. Density functional theory analysis confirms the enhanced electrochemical reaction kinetics of (111) faceted Cu2-xSe plates, while in situ measurement technologies reveal the detailed Na ion insertion/extraction mechanism.