Sustainable lithium-ion batteries based on metal-free tannery waste biochar

In the present study, we tackle the sustainable batteries topic by addressing its most defining aspects, namely what kind of waste material should be employed and its treatment for realizing performant battery anodes. In this regard, we focus on leather shaving waste (LSW), as it is an important waste element in many economies, hence resulting in an advantageous choice both from an environmental point of view and in terms of circular economy. Herein, especially metal-free LSW is used to introduce an innovative kind of eco-friendly anode for lithium-ion batteries (LIBs). A pyrolysis process of the waste material is adopted to form biochar, followed by its texture engineering through either steam or CO2, both of them recognized as safe and environmentally friendly procedures. Indeed, these procedures develop hierarchical micro/mesopores in the biochar and modify the amount of oxygen-containing functional groups on its surface, which can lead to high performance anodes. In this respect, when water-based solvent and carboxymethyl cellulose (CMC) binder are employed, the fabricated electrode discloses high initial capacities and remarkable electrochemical stability in lithium-metal half-cells. In particular, the steam-activated electrode demonstrates a specific discharge capacity of 735 mAh g-1 after 1000 charge and discharge cycles at 0.5 A g-1. This anode electrode also secures an excellent initial capacity and acceptable cycling stability in full-cell LIBs where a high mass LiFePO4 loading cathode is employed. The results reported here represent a noticeable improvement with respect to the state of the art, hence demonstrating the enormous potential associated with the green re-use of wasting materials in important sectors such as energy storage.