High energy density sodium-ion capacitors through co-intercalation mechanism in diglyme-based electrolyte system

• Published in: Journal of power sources 2015-11, Vol.297, p.457-463
• Main Authors: Han, Pengxian, Han, Xiaoqi, Yao, Jianhua, Zhang, Lixue, Cao, Xiaoyan, Huang, Changshui, Cui, Gunglei
• Format: Article
• Language: English
• Subjects: Co-intercalation; Diglyme; Energy storage; Sodium ion capacitor
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2015.08.011

A novel sodium-ion capacitor (NIC) was assembled using graphitic mesocarbon microbead anode and activated carbon cathode in diglyme-based electrolyte. Charge/discharge tests indicate that sodium ions can reversibly co-intercalated with diglyme solvent into graphite anode and show good rate performance. The energy densities of the NICs are as high as 93.5 and 86.5 Wh kg−1 at 573 and 2832 W kg−1 (equal to 4 C and 50 C) in the voltage window at 1–4 V, respectively. By optimizing the voltage ranges, the capacity retention of the NIC at 20 C is 98.3% even after 3000 cycles. Such superior electrochemical performance should be attributed to the reversible intercalated/deintercalated reaction of sodium ions and the formation of ternary graphite intercalation compounds in diglyme-based electrolyte. The present work pioneers new realms of hybrid energy storage system with high energy density, high power density and long cycle life. [Display omitted] •A NIC is constructed with graphitic MCMB anode and activated carbon cathode.•The sodium ions can reversibly intercalate into MCMB in diglyme-based electrolyte.•The optimized NIC delivers a maximum energy density of 93.5 Wh kg−1 at 573 W kg−1.•The NIC still reaches 86.5 Wh kg−1 at 2832 W kg−1.•The NIC retains 98.3% after 3000 cycles at a rate of 20 C.