A sustainable anode for Na-ion batteries based on holm oak waste-derived hard carbon and lignin binder
Abstract
Sodium-ion batteries (SIBs) represent one of the key-enabling technologies for the ongoing energy transition. However, the economic success of SIBs relies on sustainable and low-cost electrode materials, such as the bio-derived ones. Particularly, it is important to find an environmentally friendly alternative to the commercial binder polyvinylidene fluoride, which currently poses several concerns in terms of environmental impact together with the other perfluorinated alkylated substances (PFAS). In this context, a holm oak waste biomass was used both for the production of hard carbon and as a source of lignin (a natural binder that is currently poorly valorized). A one-step pyrolysis of holm-oak waste followed by acid leaching was performed to obtain a hard carbon with low amount of impurities, good interlayer spacing and well-developed microporosity and surface area. On the other hand, lignin was extracted from holm oak waste feedstock through an organosolv process with a binary mixture of γ-valerolactone and water, obtaining a lignin with a high level of purity. The obtained materials were combined to prepare bio-based anode materials for SIBs, exhibiting a reversible capacity of around 200 mA h g−1 in Na half-cells cycled at 300 mA g−1, with promising rate capability and long cycling stability even at high current rates. The electrochemical results combined with the interfacial and post-mortem SEM analysis demonstrated the ability of lignin binder to ensure longstanding adhesion with the hard carbon substrate, reflecting in electrodes with long cycle life and capacity retention.
- This article is part of the themed collection: Green and Sustainable Batteries