Synergistic Protecting-Etching Synthesis of Carbon Nanoboxes@Silicon for High-Capacity Lithium-Ion Battery

Silicon (Si) is considered as the most likely choice for the high-capacity lithium-ion batteries owing to its ultrahigh theoretical capacity (4200 mA h g^-1) being over 10 times than that of traditional graphite anode materials (372 mA h g^-1). However, its widespread application is limited by problems such as a large volume expansion and low electrical conductivity. Herein, we design a hollow nitrogen-doped carbon-coated silicon (Si@Co-HNC) composite in a water-based system via a synergistic protecting-etching strategy of tannic acid. The prepared Si@Co-HNC composite can effectively mitigate the volume change of silicon and improve the electrical conductivity. Moreover, the abundant voids inside the carbon layer and the porous carbon layer accelerate the transport of electrons and lithium ions, resulting in excellent electrochemical performance. The reversible discharge capacity of 1205 mA h g^-1 can be retained after 120 cycles at a current density of 0.5 A g^-1. In particular, the discharge capacity can be maintained at 1066 mA h g^-1 after 300 cycles at a high current density of 1 A g^-1. This study provides a new strategy for the design of Si-based anode materials with excellent electrical conductivity and structural stability.