Lignin-Based Separators for Lithium-Ion Batteries via a Dry Fibrillation Method

This study reports the development of a sustainable single-layer lignin-based separator for lithium-ion batteries (LIBs), produced using a dry fibrillation method. The approach converts lignosulfonate — a biorefinery byproduct — into ultrathin (≈15 µm) films exhibiting excellent mechanical strength, thermal stability, and electrolyte wettability. The sulfonate functional groups promote formation of stable, low-resistance cathode and anode interphases (CEI/SEI), improving cycle life and safety in both graphite||NMC811 and Si-Gr||NMC811 cells. The dry fibrillation process achieved near-100% material conversion efficiency with minimal energy input, establishing a scalable pathway for eco-friendly, high-performance LIB separators.