Growth of Bouquet-like Zn2GeO4 Crystal Clusters in Molten Salt and Understanding the Fast Na-Storage Properties

The exploration of high-performance anode materials is imperative for the development of sodium-ion batteries (SIBs). Herein, a molten-salt-assisted approach is developed to prepare crystallized Zn2GeO4 clusters constructed by interconnected nanorods, and the Na-ion storage mechanism is studied systemically through in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, and high-resolution transmission microscopy associated with galvanostatic intermittent titration technique. The Zn2GeO4 anode undergoes conversion reactions followed by the alloying reaction. The large channel in the Zn2GeO4 crystal structure ensures insertion of sodium ions. The amorphous transformation during the initial discharge process increases the active site for the fast electrochemical reaction. As the anode for SIBs, the Zn2GeO4 cluster exhibits good rate capability with a capacity retention of 111.1 mA h g(-1) at 20 A g(-1) in half cells and 118.9 mA h g(-1) at 2 A g(-1) in full cells, associated with a capacity of 184.2 mA h g(-1) at 0.5 A g(-1) after 500 cycles. The ex situ scanning electron microscopy images of the electrode material disclose that the hierarchical structure can accommodate the volume variation of Zn2GeO4 during discharge/charge cycling, facilitating long cycling stability. The investigation of Zn2GeO4 provides new insight for the development of high-rate anode materials for SIBs.