Upcycling sodium lignosulfonate into a carbon anode with an inorganic-rich interphase by potential regulation for lithium-ion batteries

Abstract

The conversion of industrial lignocellulosic waste into high-valued battery materials is important for sustainable electrochemistry. Lignocellulosic waste is a good precursor for hard carbon (HC), which is a promising anode for Li-ion batteries, considering its high specific capacity and low cost. However, the solid electrolyte interphase (SEI) formed on HC usually suffers from sluggish Li⁺ diffusion and irreversible Li⁺ loss. Herein, we present a strategy to transform sodium lignosulfonate (LS), a major by-product of the paper industry, into a high-performance HC. Furthermore, we engineer a highly stable artificial SEI rich in inorganics with fast Li⁺ transfer at the surface through a green overpotential-tailoring method. This strategy constructs an artificial SEI with a gradient inorganic composition, where an inner Li₃PO₄ layer serves as an ion-conductive layer with high Li⁺ conductivity and the Li₂CO₃-dominated outer layer formed by the selective decomposition of ethylene carbonate features a lower energy barrier for Li⁺ transfer and shields the anode from continuous side reactions. With the combined effects, the artificial SEI helps the HC anode exhibit a remarkable initial coulombic efficiency of 94.4% (78.5% for pure LS) and a high reversible capacity of 346.9 mAh g⁻¹ with 82.5% capacity retention (32.7% for LS) after 200 cycles at 0.1 A g⁻¹. This work not only provides a scalable method for designing high-performance HC anodes but also establishes a strategy for upcycling industrial waste into green battery materials.