Towards Scalable Production of Sodium-Ion Batteries: Solvent-Free Layered-Oxide Cathodes and Aqueous-Processed Hard Carbon Anodes for Cost-Effective Full-Cell Manufacturing

Abstract

Achieving commercial viability for more sustainable sodium-ion batteries (SIB) necessitates reducing the environmental impact of production, particularly originating from electrode drying and the use of toxic solvents like N-methyl-2-pyrrolidone (NMP). This study presents the dry-processing of commercial P2-type Na_0.75Ni_0.25Fe_0.25Mn_0.50O₂ (NFM) via the DRYtraec® process, aiming to lower the binder content of 1 wt.% polytetrafluoroethylene (PTFE) and eliminating the need for electrode drying and NMP recovery. Assessments of electrode morphology and active material crystallinity were conducted to gauge the effects of mechanical stress during processing. The resulting cathodes, loaded at a commercially relevant 2.3–2.7 mAh cm⁻² loading, were successfully paired with aqueous-processed hard carbon (HC) anodes, demonstrating stable performance in full-cells. Comparative analysis with entirely wet-processed electrodes revealed comparable capacity accessibility and comparable long-term stability. This showed the competitiveness of dry-processed cathodes. Finally, the integration of NMP-free, dry-processed cathodes and aqueous-processed anodes was scaled to the commercially relevant prototype pouch-cell. The cell demonstrates stable cycling for 400 cycles with an energy density of 102 Wh kg⁻¹ as well as reduced processing costs and environmental footprint.