Lignin-Based Semi-Interpenetrating Polymer Network as a Binder for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs) have emerged as strong contenders for next-generation energy storage technologies owing to their exceptionally high energy density. To address the challenges of high crystallinity, poor adhesion, and severe capacity fading associated with conventional poly(vinylidene fluoride) (PVDF) binders in LMBs, we designed a lignin-based semi-interpenetrating polymer network (SIPN) binder, synthesized by grafting polyethylene glycol methacrylate (PEGMA) and glycerol carbonate methacrylate (GCMA) onto lignin-based chain transfer agents (L-CTA) using reversible addition–fragmentation chain transfer (RAFT) polymerization, followed by polyamine cross-linking and integrating with PVDF. The SIPN binder reduced the crystallinity of PVDF, provided excellent adhesion strength and efficient ionic conductivity pathways, and improved cycling stability. The cathode using SIPN-5 binder maintained 96% of its original capacity, significantly outperforming the PVDF binder, which retained only 78% after 500 cycles at 2 C. These findings highlight the potential of lignin-based SIPN as multifunctional, sustainable binder materials for high-performance LMBs.