Impact of binder content on particle fracture and microstructure of solvent-free electrodes for Li-ion batteries

Journal article

The fraction of polytetrafluoroethylene (PTFE) binder in solvent-free electrodes for Li-ion batteries, also known as dry-processed electrodes, is shown to have a dramatic impact on their processability, microstructural evolution and electrochemical performance. We show experimentally that increasing the binder fraction from 0.5 to 4 wt% transformed the electrode microstructure from an effective, open structure containing PTFE nano-fibrils to a compact morphology with fragmented active material and porosity blocked by PTFE agglomerates. The solvent-free electrodes showed a classic visco-elastic response during compression, comprising three distinct regions of deformation. The electrode stiffness and yield strength increased non-linearly with binder fraction such that for higher binder contents (>2 wt%), there was extensive LiNi0.6Co0.2Mn0.2O2 (NMC) particle fracture during the calendering process, with cracks propagating along the grains of polycrystalline NMC particles. Conversely at lower binder fraction (<2 wt%), PTFE readily fibrillated into highly textured (100) crystalline nano-fibrils and NMC particles remained largely intact. These electrodes showed superior electrochemical performance due to higher ionic mobility through the open nano-fibrillar microstructure and intact NMC particles.

Authors: Matthews, G; Meyer, B; Doerrer, C; Ramírez-González, J; Darnbrough, E

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry
• Journal: Journal of Materials Chemistry A
• Volume: 13
• Issue: 24
• Pages: 18283-18291
• Publication date: 2025-05-08
• Acceptance date: 2025-05-06
• DOI: 10.1039/d5ta01950h
• EISSN: 2050-7496
• ISSN: 2050-7488
• Language: English