Sodium-Ion Hybrid Capacitor of High Power and Energy Density

• Published in: ACS central science Vol. 4; no. 9; pp. 1261 - 1265
• Main Authors: Yuan, Yue, Wang, Chenchen, Lei, Kaixiang, Li, Haixia, Li, Fujun, Chen, Jun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.09.2018
• ISSN: 2374-7943; 2374-7951
• DOI: 10.1021/acscentsci.8b00437

Sodium-ion hybrid capacitors (NHCs) have been attracting research interest in recent years. However, NHCs suffer from slower redox reaction kinetics of electrodes as compared to non-Faradaic capacitive counterparts. Herein, a high-performance NHC using porous NaBi as anode, activated carbon (AC) as cathode, and 1.5 M of NaPF6 in diglyme as electrolyte is reported. In a charging process, Na+ is inserted into NaBi to form Na3Bi, and PF6 – is stored in the electric double layers of the AC cathode; in a reverse process, the Na3Bi is desodiated to NaBi and eventually Bi, and the adsorbed PF6 – is released into the electrolyte in the first cycle. The NHC exhibits a capacity of ∼298 mA h gBi –1, capacity retention of 98.6% after 1000 cycles at 2 A gBi –1, and Coulombic efficiency of >99.4%. The achievable power and energy density are as high as 11.1 kW kgtotal –1 and 106.5 W h kgtotal –1, respectively. The superior electrochemical performance is ascribed to the gradually formed three-dimensional (3D) porous and stable networks of the anode, ensuring its comparable fast reaction kinetics and cycle stability to the AC cathode.