A sulfur-doped porous functional layer derived from lignin with hydrophobic and zincophilic properties for stable zinc metal anodes

Although aqueous zinc-ion batteries (ZIBs) have demonstrated great potential for large-scale energy storage, the poor chemical stability of Zn metal in aqueous electrolyte leads to irreversible side reactions, restricting widespread utilization of ZIBs. Herein, a hydrophobic-zincophilic bi-functional layer (NLC) derived from paper mill waste lignosulfonate is designed to separate the solid and liquid phases to enhance the performance and stability of zinc anodes in batteries. The abundant C-SO₃H groups in lignosulfonate undergo pyrolysis and in-suit doping into the carbon skeleton to transform into C-S-C bridges, C–S bonds and some C-SO₃H groups during carbonization, which coordinate with Zn²⁺ and reduce the nucleation overpotential of Zn²⁺ to facilitate the de-solvation process and induce uniform deposition. Additionally, the honeycomb hydrophobic carbon skeleton effectively inhibits the corrosion by preventing Zn metal from directly contacting electrolyte and alleviates structural stress during cycling. As a result, the lifespan of symmetrical cells with NLC900@Zn is prolonged to 1000 h at a current density of 1 mA·cm⁻² and 1 mAh·cm⁻². Importantly, the full battery coupled with MnO₂/CNT shows a higher capacity retention of 89.06% after 500 cycles at 0.5 A·g⁻¹, which is higher than that of bare Zn anode (39.76%). This work achieves the combination of waste recycling and zinc ion battery modification, paving a new way for the application of lignin in the field of energy storage.