Synthesis of 3D stacked silicon nanosheets via electrochemical reduction of attapulgite in molten salt for high-performance lithium-ion batteries anode

Silicon has attracted widespread attention as one of the most promising anode materials for next-generation lithium-ion batteries. Herein, we report a scalable method for synthesizing the stacked Si nanosheets (s-SiNS) in molten salt by electro-deoxidation of attapulgite followed by an acid etching process. The s-SiNS consists of 3D stacked silicon nanosheets and abundant voids between them, which can accommodate volume expansion during lithiation/delithiation process. Ex-situ X-Ray powder diffraction and scanning electron microscope reveal that the formation of s-SiNS microstructure involved the stratified Ca3Si3O9 intermediate and etching of unreacted SiOx by HF. Owing the typical void-contained 3D architecture, the s-SiNS anode delivers a high specific capacity of 3046 mAh g-1 with a high initial coulombic efficiency of 82.5% at 0.2 A g-1, and a high rate capability of 700 mAh g-1 at 4 A g-1. The s-SiNS anode also possesses good cyclability and can deliver a satisfying reversible specific capacity of 1205 mAh g-1 at 0.5 A g-1 after 200 cycles with a high capacity retention of 60.2%. More importantly, the results of this study provide a new strategy for scalable synthesizing void-contained 3D Si architecture with abundant attapulgite as feedstock, and might shed light on the high-value utilization of resourceful attapulgite.