Diatom-Based Artificial Anode—Uniform Coating of Intrinsic Carbon to Enhance Lithium Storage

Pursuing improved electrode materials is essential for addressing the challenges associated with large-scale Li-ion battery applications. Specifically, silicon oxide (SiOx) has emerged as a promising alternative to graphite anodes, despite issues related to volume expansion and rapid capacity degradation. In this study, we synthesized carbon-coated SiOxusing diatom biomass derived from artificially cultured diatoms. However, the inherent carbon content from diatoms poses a significant challenge for the electrochemical performance of diatom-based anodes in large-scale applications. Subsequently, we conducted further research and demonstrated excellent performance with a carbon content of 33 wt.% as anodes. Additionally, real-time characterization of the carbonization process was achieved using thermogravimetry coupled with infrared spectroscopy and gas chromatography mass spectrometry (TG-FTIR-GCMS), revealing the emission of CO and C3O2during carbonization. Furthermore, electrochemical tests of the processed diatom and carbon (PD@C) anode exhibited outstanding rate capability (~500 mAh g−1at 2 A g−1), high initial Coulomb efficiency (76.95%), and a DLi+diffusion rate of 1.03 × 10−12cm2s−1. Moreover, structural characterization techniques such as HRTEM-SAED were employed, along with DFT calculations, to demonstrate that the lithium storage process involves not only reversible transport in Li2Si2O5and Li22Si5, but also physical adsorption between the PD and C layers. Exploring the integration of diatom frustules with the intrinsic carbon content in the fabrication of battery anodes may contribute to a deeper understanding of the mechanisms behind their successful application.