Green Fabrication of Amorphous Fepo4/Carbon Nanotube Electrodes Via Electrophoretic Deposition for Sodium-Ion Batteries

The conventional fabrication of electrodes for sodium-ion batteries involves mixing the active material with additives and tape casting on metallic current collectors. In this work, an electrophoretic deposition (EPD) method has been developed to fabricate composite electrodes without using volatile and toxic solvents as well as binders. The approach is based on the EPD of amorphous FePO4 and multi-wall carbon nanotube (MWCNT) from aqueous suspensions. The fabrication of FePO4 suspensions containing MWCNT, and controlled co-deposition of both materials is crucial for the EPD of composites. Multiple dispersants with different properties are investigated as the dispersing, charging and film-forming agents. The deposition yield of EPD films is measured under various conditions. The atomic force microscopy analysis, engaged with thermogravimetric tests, provides evidence of the formation of adhesive and conductive FePO4/MWCNT films. The dispersant concentration is optimized in order to achive high capacity. The composite electrode, prepared by EPD, delivers a discharge capacity of 142.2 mAh g-1 at the current of 10 mA g-1. Another important finding is the possibility to fabricate full-cell sodium-ion batteries, containing pre-sodiated hard carbon as the anode and deposited FePO4/MWCNT cathode. The electrodes and devices show adequate capacitance retention as charge-discharge current increased and stable cycling performance.