Species-Dependent Nanostructured Diatom-SiO₂ Anodes: A Sustainable Option for Optimizing Electrode Performance

Abstract

SiO 2 structures show great promise for increasing the energy density of anodes for next-generation lithium-ion batteries (LIBs). However, high control of the area, porosity, and morphology of SiO 2 particles is critical to optimize anodes electrochemical performance, and the lack of sustainable methods for producing SiO 2 particles with tailored properties at the nanoand microscale represents a serious challenge. Exoskeletons of diatoms (microalgae) display nanoporous structures made of SiO 2 , and each diatom species grows SiO 2 exoskeletons with unique morphology. In this work, we show that by performing the first comparative analysis of the species-dependent electrochemical performance of diatom-based anodes, we are introducing a new concept in which single-species diatoms with preferred physical and textural properties can be carefully chosen and cultivated to develop anode materials with optimized electrochemical performance for next-generation LIBs. SiO 2 anodes made using SiO 2 exoskeletons from two cultured diatom species, Nitzschia sp. and Craspedostauros sp., with diatomaceous earth as the active material are presented. Pristine micron-sized frustules exhibiting areas of 85.4, 47.1, and 2.0 m 2 g −1 displayed specific capacities of 811, 747, and 520 mAh g −1 , respectively, after 100 cycles at 100 mA g −1 and capacity retention up to ∼97% after 200 cycles. Results show that significant improvement on specific capacity, cycle life, and rate capability of SiO 2 anodes can be achieved by selecting diatom species growing desired SiO 2 structures. The presented results aim to unveil the potential of the wide variability of diatom exoskeletons physical properties to optimize anode performance, opening the path for the sustainable production of outperforming Si-based anodes for next-generation LIBs.