A Fast-Charging Cathode for Na-Ion Hybrid Supercapacitor

Abstract

Iron-based phosphate (Na 3 Fe 2 (PO 4 )P 2 O 7 ) cathode have been regarded as a potential cathode for sodium-ion batteries (SIBs), but the poor-rate capability restricts their fast charging performance. In this work, we have synthesized a mesoporous Na 3 Fe 2 (PO 4 )P 2 O 7 (M-NFPP) material and employed them in rechargeable sodium-ion batteries. The mesopores are produced by the decomposition carbonization of polyvinyl alcohol, which enlarges reactive sites and accelerates Na ion migration. As a result, the reversible specific capacity maintains at 81 mAh g - 1 (72.5% of 0.1 C reversible specific capacity) under an ultra-high C-rate of 40 C (equal to 1.5 mins), and than 1000 cycles life. A Na-ion hybrid supercapacitor using M-NFPP as cathode and active carbon as an anode can achieve a maximum energy and power density of 48 Wh kg - 1 and 1350 W kg - 1 with a capacity retention rate of 92% after 500 cycles at 20 C.

Keywords: energy storage, sodium-ion batteries, Sol-Gel Method, Iron-based phosphate, Cathode material