(444b) Micron Size NaCrO2 Particles Enable High Loading Dry-Process Electrode for Sodium Ion Batteries

Traditional sodium-ion battery (SIB) electrode fabrication typically relies on a wet slurry process involving N-methyl-2-pyrrolidone (NMP), a solvent known for its high cost, environmental harm, and toxicity. As an alternative, dry-process fabrication using polytetrafluoroethylene (PTFE) is emerging as a preferred method due to its cost efficiency, eco-friendliness, and potential to achieve higher energy densities. While numerous studies have demonstrated the high loading compatibility of the dry process method compared to the traditional slurry method, there remains a gap in understanding the critical material parameters necessary for producing high mechanical property films and enhancing their electrochemical performance. In this study, two different sizes of NaCrO₂ particles noted as S-NCO (300-600 nm) and L-NCO (5-20 µm) were synthesized to investigate the impact of particle size on dry film fabrication. Our findings reveal that electrodes made with larger L-NCO particles exhibit significantly higher high tensile strength of around 24 kPa over S-NCO film (less than 10 kPa) at the same PTFE binder ratio, as well as enhanced electronic conductivity and electrochemical performance when the same carbon ratio is added. These improvements are primarily attributed to the low porosity of L-NCO film induced by higher tapped density and reduced surface area of L-NCO powder. Notably, a full cell incorporated with a high-loading L-NCO film electrode (45 mg/cm² or 5.4 mAh/cm²) demonstrates exceptional cycling performance (80% capacity retention over 300 cycles) compared with S-NCO film electrodes, highlighting the potential advantages of using larger particle sizes in dry film electrode fabrication. These results provide insights regarding the design and fabrication of PTFE-based cathode dry-process film electrode and promote the high-loading and high-performance electrodes for future energy storage applications.