Pomegranate like silicon–carbon composites prepared from lignin-derived phenolic resins as anode materials for lithium-ion batteries

Abstract

Silicon-based materials are considered to be potential anode materials for Li-ion batteries due to their high electrochemical capacity, but their high volume change during charging and discharging, bad cycle life and low first Coulombic efficiency are the major problems that prevent their commercialization. Carbon materials have excellent electrical properties and can be used to cushion the expansion of silicon volume while simultaneously strengthening the electrical conductivity of the cathode material, which can secure a very high specific capacity while also increasing its cycling stability. In this study, a lignin-based phenolic resin (deep eutectic solvent-treated alkaline lignin) was used as the carbon source and Si nano-powder as the silicon source. The lignin-based phenolic resin was coated on the surface of silicon nanoparticles, and the carbon layer was obtained by carbonizing the outer layer of the resin through high-temperature calcination. The morphological composition of carbon and silicon was tested using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, and the carbon layer was found to be uniformly coated on the surface of the silicon nanoparticles. The electrochemical properties of the samples were also tested. Compared with pure phenolic resin-coated silicon, the cycling performance of lignin-based phenolic resin-coated silicon nanoparticles was significantly improved, with the best electrochemical performance of Si/C-LPR with an initial specific capacity of 782.45 mA h g⁻¹ and a specific capacity of 605.43 mA h g⁻¹ after 100 cycles (0.5 A g⁻¹).