Nanometer-Thick Gallic Acid Coatings Enhance the Electrochemical Performance of Silicon Anodes

Due to the drawbacks of huge volume expansion upon lithiation/delithiation and surface corrosion by the electrolyte, silicon (Si) anodes for lithium ion batteries (LIBs) suffered from rapid capacity degradation. Herein, nano-Si was simply treated with a gallic acid (GA) solution to cover the Si surface with a nanometer-thick GA-layer. During surface treatment, GA formed an irreversible cross-linking structure, and it can be bonded to the surface of nano-Si via hydrogen bonds. The resulted nano-Si@GA-1 sample (mSi/mGA = 10:1) exhibited an initial coulombic efficiency as high as 89.8% and a high charge capacity of 2979 mA h g–1 at a current density of 100 mA g–1. It can be demonstrated by the facilitated Li+ diffusion and reduced Li+ consumption by the surface GA-layer containing immense −OH and −COOH groups, acting as an artificial solid–electrolyte interface (SEI) film. Moreover, the formed GA-layer also effectively suppressed volume expansion and delamination of the Si electrode, leading to the superior stability of nano-Si@GA. A charge capacity of 1567 mA h g–1 was retained after 300 cycles tested at 1 A g–1 for the nano-Si@GA-1 electrode, among the best values of reported Si materials. Overall, our prepared nano-Si@GA via a facile route is promising for the practical application of LIBs as an anode material.