Glycine-Nitrate Process for Synthesis of Na₃V₂(PO₄)₃ Cathode Material and Optimization of Glucose-Derived Hard Carbon Anode Material for Characterization in Full Cells

Abstract

Cost-effective methods need to be developed to lower the price of Na-ion battery (NIB) materials. This paper reports a proof-of-concept study of using a novel approach to the glycine-nitrate process (GNP) to synthesize sodium vanadium phosphate (Na3V2(PO4)3 or NVP) materials with both high-energy (102 mAh g−1 at C/20) and high-power characteristics (60 mAh g−1 at 20 C). Glucose-derived hard carbons (GDHCs) were optimized to reduce both sloping and irreversible capacity. The best results were achieved for electrodes with active material heat treated at 1400 °C and reduced Super P additive. Sloping region capacity 90 mAh g−1, irreversible capacity 47 mAh g−1, discharge capacity 272 mAh g−1 (of which plateau 155 mAh g−1) and 1st cycle coulombic efficiency (CE) 85% were demonstrated. GDHC||NVP full cell achieved 80 mAh g−1 (reversible) by NVP mass out of which 60 mAh g−1 was the plateau (3.4 V) region capacity. Full cell specific energy and energy density reached 189 Wh kg−1 and 104 Wh dm−3, respectively. After 80 cycles, including rate testing from C/20 to 10 C, the cell cycled at 65 mAh g−1 with 99.7% CE. With further optimization, this method can have very high industrial potential.

Keywords

• NVP
• Na-ion battery
• glycine-nitrate process
• hard carbon
• solution combustion
• sodium