Biomimetic\nSn₄P₃ Anchored on\nCarbon Nanotubes as an Anode for High-Performance Sodium-Ion Batteries

Abstract

Recently, Sn₄P₃ has emerged as a promising\nanode for sodium-ion batteries (SIBs) due to the high specific capacity.\nHowever, the use of Sn₄P₃ has been impeded by\ncapacity fade and an inferior rate performance. Herein, a biomimetic\nheterostructure is reported by using a simple hydrothermal reaction\nfollowed by thermal treatment. This bottlebrush-like structure consists\nof a stem-like carbon nanotube (CNT) as the electron expressway and\nmechanical support; fructus-like Sn₄P₃ nanoparticles\nas the active material; and the permeable stoma-like thin carbon coating\nas the buffer layer. Having benefited from the biomimetic structure,\na superior electrochemical performance is obtained in the SIBs. It\nexhibits a high capacity of 742 mA h g^–1 after 150\ncycles at 0.2C, and superior rate performance with 449 mA h g^–1 at 2C after 500 cycles. Moreover, the sodium storage\nmechanism is confirmed by cyclic voltammetry and <i>ex situ</i> X-ray diffraction and transmission electron microscopy. <i>In situ</i> electrochemical impedance spectroscopy was adopted\nto analyze the reaction dynamics. This research represents a further\nstep toward figuring out the inferior electrochemical performance\nof other metal phosphide materials.