Enhanced cycling stability of silicon electrode for lithium-ion batteries by dual hydrogen bonding mediated by carboxylated carbon nanotube

Abstract

Carbon nanotubes (CNTs) are being used as high-performance conductive agents for fast electron transport and effective suppression of volume change in silicon (Si) electrode. However, utilization of CNTs has significant challenges, including poor dispersibility and weak interaction with Si particles. Herein, carboxylated CNTs (CNT-COOH) are employed as a mediator to form dual hydrogen bonds with the tannic acid-coated Si particles (Si@TA) and carboxymethyl cellulose (CMC) binder, through which all the constituents (active material, conductive agent, and binder) comprising the electrode are strongly connected. Also, CNT-COOH strongly attaches to Si@TA via π-π conjugation. Furthermore, the TA-coating layer serves as a protective layer from the electrolyte. As a result, the Si@TA/CNT-COOH composite electrode shows excellent cycling stability delivering a discharge-specific capacity of 1287 mAh g^-1 after 200 cycles at 2 A g^-1 and retains 1916 mAh g^-1 even at high current density of 10 A g^-1. The structural integrity of the Si@TA/CNT-COOH electrode is also confirmed by less deformation and thickness change after cycling.