Encapsulation of Na3(VO)2(PO4)2F into carbon nanofiber as an superior cathode material for flexible sodium-ion capacitors with high-energy-density and low-self-discharge

Emerging Materials for Sodium-Ion Hybrid Capacitors: A Brief Review

“…Thus, the constructed hybrid capacitor could deliver an energy density of 215 Wh kg –1 with a power density of up to 5200 W kg –1 and a sustained stability for more than 10,000 cycles owing to the highly stable electrode materials (Figure ). A similar high energy density of 158 Wh kg –1 was reported by Wu et al using NVOPF@PEDOT core–shell nanorods, and a density of 182 Wh kg –1 was reported by Qiu et al using NVOPF encapsulation.…”

Aligned Arrays of Na2Ti3O7 Nanobelts and Nanowires on Carbon Nanofiber as High‐Rate and Long‐Cycling Anodes for Sodium‐Ion Hybrid Capacitors

“…Before growth of TiO 2 , the CNF membrane was first prepared according to our previous works. [ 3,11 ] In the typical synthesis of CNF, the polyacrylonitrile fibers were synthesized by electrospinning on an Al foil substrate using a mixed solution of polyacrylonitrile (1.0 g) and N,N ‐dimethylformamide (10 mL). The voltage of 15 kV was set with the distance of 20 cm, and the flow rate of the spinning solution was 1 mL h −1 .…”

“…[ 10 ] Unfortunately, the ubiquitous exploitation of lithium resources will give rise to increasing concern on the supply crisis of Li. [ 11–13 ] Considering the low cost and global abundance of sodium resources, sodium‐ion capacitors (SICs) become one promising alternative to LICs. Moreover, it is reported that the energy‐storage performance of some SICs is comparable to and even outperforms LICs.…”

Effects of Anion Carriers on Capacitance and Self‐Discharge Behaviors of Zinc Ion Capacitors

“…Thee ffects of anions on the anti-self-discharge ability was further explored. Theself-discharge curves of Zn-TiN capacitors in different electrolytes including ZnSO 4 ,z inc trifluoromethanesulfonate (ZnOTf), ZnAc 2 ,Z nCl 2 ,a nd ZnClO 4 after being charged to 1.9 Vw ere shown in Figure 5b,i 2À was more negative than others and the structure TiN-SO 4 after adsorption was more stable,w hich enable it to possess the most outstanding anti-self-discharge ability.T he comparison of capacitance retention rate between Zn-TiN capacitor with ZnSO 4 electrolyte and other supercapacitors [14,19,[51][52][53][54] were shown in Fig- ure 5d.M ost of the previously reported supercapacitors, including some zinc ion capacitors,h ave ac apacitance retention rate of less than 80 %a fter self-discharge tests of less than 300 h. TheZn-TiN capacitor showed overwhelming superiority in the ability of inhibiting self-discharge behavior, emphasizing al ong-term neglected approach to achieve enhanced anti-self-discharge capability of ac apacitor by optimizing anions.S ince the capacitors store energy through the adsorption of anions in the cathode materials when charged to the voltage range above the open-circuit voltage, the stability of the adsorbed structure such as TiN-SO 4 remarkably affect the ability of capacitors to inhibit selfdischarge behaviors.F igure 5e shows an illustration of antiself-discharge mechanism of Zn-TiN capacitors with different electrolytes,i nw hich the yellow,b lue and red balloons represented SO 4 2À ,C l À ,n dA c À anions,r espectively.T he introduction of zinc anode was al ock on the self-discharge behaviors of zinc ion capacitor,s ince zinc would not spontaneously convert to zinc ions.More importantly,the adsorption interaction between TiNa nd anions was another lock to inhibit the self-diffusion behavior of anions,inwhich the size of lock corresponded to the strength of adsorption force. Thus,Z n-TiN with ZnSO 4 electrolyte delivered the most outstanding anti-self-discharge ability.Onthe contrary,there was only one lock for TiN-based symmetrical supercapacitor, as shown in the Supporting Information, Figure S13.…”