A sustainable hard carbon 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 technology 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, as for the other perfluorinated alkylated substances (PFAS), in terms of high environmental impact. 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 currently poorly valorized. A one-step pyrolysis of holm-oak waste followed by acid leaching were 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 has been extracted from holm oak waste feedstock through an organosolv process with a binary mixture of γ-valerolactone and water, obtaining a lignin with high level of purity. The obtained materials were combined to prepare a bio-based anode materials for SIBs, exhibiting around 200 mAh g-1 reversible capacity 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 Hard Carbon substrate, reflecting into electrodes with long cycle life and capacity retention.
- This article is part of the themed collection: Green and Sustainable Batteries