Tuned Bimetallic Fe–Ni Thiophosphides as Advanced Battery Materials for Asymmetric Electrochemical Supercapacitors with Outstanding Energy Density

Abstract

The facile fabrication of functional supercapacitor electrodes with desirable characteristics is a bottleneck challenge to advance the supercapacitor industry. Among those functional materials, metal phosphides and sulfides have been explored separately with various pros and cons. Herein, we report a facile one-step electrodeposition method for the preparation of bimetallic thiophosphide (FNSP) based electrodes that comprise the advantages of both sulfides and phosphides simultaneously. Upon use as a supercapacitor electrode, FNSP shows an exceptionally high specific capacity of 1415.20 C/g at 1 A/g. Moreover, the assembled AC//FNSP asymmetric device reveals outstanding performance with a high energy density of 52.42 Wh/kg corresponding to a power density of 1.70 kW/kg at 2 A/g with superior Coulombic efficiency and cycling stability over 10 000 cycles. The obtained performance metrics demonstrate the superb performance of the fabricated AC// FNSP device over the sulfide or phosphide alone based devices reported so far. The exceptional specific capacitance of the FNSP electrode is attributed to the synergy between S and P in the fabricated electrode that improves the conductivity and provides more electrochemical active sites.

NiFeZnP Nanosheets with Enriched Phosphorus Vacancies for Supercapattery Electrodes

“…This positive shift is consistent with a recent DFT study, which predicted that P v resulted in higher electron distribution in the Ni 3d band due to the weakening in the hybridization between Ni 3d and P 2p orbitals . Additionally, the characteristic peak of the Ni–P bond vanishes, indicating that phosphorus is significantly reduced on the NiFeZnP surface after NaBH 4 reduction. , …”

“…All these data indicate that the loss of P element during the reduction reaction of NiFeZnP resulted in a large amount of P v on P v -NiFeZnP, where NaBH 4 was used as the reductant. It is an important strategy to create abundant phosphorus vacancies on NiFeZnP via removing the oxidized P–O. , …”

“…It is an important strategy to create abundant phosphorus vacancies on NiFeZnP via removing the oxidized P−O. 13,20 The surface composition and chemical oxidation states of the electrode elements before and after reduction were elucidated via the XPS technique (Figure 2). In the highresolution Ni 2p 3/2 XPS spectrum of the pristine NiFeZnP electrode, the characteristic peak of the Ni−P bond is observed at 853.1 eV.…”

“…29 Additionally, the characteristic peak of the Ni−P bond vanishes, indicating that phosphorus is significantly reduced on the NiFeZnP surface after NaBH 4 reduction. 13,20 The Fe 2p XPS spectrum was decomposed to the characteristic peak of the Fe−P bond at 707 eV (Figure 2b). 33 Moreover, two defined peaks appeared at 712.8 and 728.4 eV, corresponding to Fe 2+ 2p 3/2 and Fe 2+ 2p 1/2 , respectively.…”

“…17 Additionally, a Ni-Zn-Fe LDH//AC asymmetric device delivered an energy density of 14.9 W h kg −1 at a power density of 1077.6 W kg −1 , 18 whereas the ASC NiCo 2 S 4 // porous carbon produced an energy density of 22.8 W h kg −1 at 1 mA cm −2 . 19 Another comparative study illustrated that NiFeP and NiFeS electrodes exhibited specific capacitances of 522 and 287 F g −1 at a current density of 2 A g −1 , respectively, 20 further demonstrating the superiority of phosphides over sulfides and oxides. Not only the use of TMP is important, but also the choice of specific transition metals is crucial.…”