Hydrothermal Synthesis of Hybrid Rod‐Like Hollow CoWO₄/Co_1−xS for High‐Performance Supercapacitors

Abstract

A rod‐like hollow cobalt tungstate/non‐stoichiometric cobalt sulfide (CoWO4/Co1−xS) hybrid is successfully grown in situ on nickel foam through a simple two‐step hydrothermal process. Owing to the unique hollow structure, the as‐synthesized CoWO4/Co1−xS hybrid electrode possesses a large surface area and delivers a high specific capacitance of 1894.5 F ⋅ g−1 at a current density of 1 A ⋅ g−1. By using the CoWO4/Co1−xS hybrid electrode as the anode and an activated carbon (AC) electrode as the cathode, an asymmetric supercapacitor of CoWO4/Co1−xS//AC exhibits a high capacitance of 103.1 F ⋅ g−1 and high specific capacitance retention of 87.27 % after 5000 cycles. Furthermore, the asymmetric supercapacitor demonstrates a maximum power density of 4000 W ⋅ kg−1 at an energy density of 22.5 Wh ⋅ kg−1. The superior performance of the device can be ascribed to distinctive structure and positive synergistic effects in the hybrid. The facile preparation process and excellent performance presented here indicate the CoWO4/Co1−xS hybrid to be a promising candidate electrode material for supercapacitor applications.

Bottom‐up Approach for Designing Cobalt Tungstate Nanospheres through Sulfur Amendment for High‐Performance Hybrid Supercapacitors

“…S−CoWO 4 //AC HSC exhibited an specific energy of 63.03 Wh kg −1 at 1066.66 W kg −1 specific power and it remained 21 Wh kg −1 at 8000 W kg −1 . These obtained results of the S−CoWO 4 //AC HSC are superior to those of the reported tungstate‐based HSC devices, such as CoMoO 4 ‐3D graphene//AC (21.1 Wh kg −1 at 300 W kg −1 ), [34] NiWO 4 ‐CoWO 4 //AC (30.1 Wh kg −1 at 200 W kg −1 ), [35] 3D‐H CoWO 4 /NF//AC (29 Wh kg −1 at 400 W kg −1 ), [36] CoWO 4 /Co 1‐ x S//AC (22.5 Wh kg −1 at 4000 W kg −1 ), [37] Ni−NiWO 4 @NiS/NS−C (43.68 Wh kg −1 at 850 W kg −1 ), [38] CoWO 4 /Co 3 O 4 //AC (57.8 Wh kg −1 at 750 W kg −1 ), [39] 3DCoWO 4 /Co 3 O 4 //PC (45.6 Wh kg −1 at 750 W kg −1 ), [40] Ni−Co−S−W (40 min)/NF//AC/NF (55.1 Wh kg −1 at 799.8 W kg −1 ), [41] or NiSe//WO 3 @PPy (37.3 Wh kg −1 at 1249 W kg −1 ) [42] …”

Review on Recent Progress in the Development of Tungsten Oxide Based Electrodes for Electrochemical Energy Storage

“…Ge et al. synthesized a rod‐like hollow CoWO 4 –Co 1− x S hybrid on Ni foam through a two‐step hydrothermal method . The prepared CoWO 4 –Co 1− x S hybrid electrode had a huge surface area and demonstrated a specific capacitance of 1894.5 F g −1 at a current density of 1 A g −1 .…”

“…The CoWO 4 //AC ASCs delivered a high energy density of 48 Wh kg −1 at a power density of 365 W kg −1 , and still maintained a value of 28.4 Wh kg −1 at a power density of 3.65 kW kg −1 . Moreover, the ASCs fabricated with CoWO 4 −Co 1− x S and AC as positive and negative electrodes, respectively, showed a specific capacitance of 103.1 F g −1 and a high capacity retention of 87.27 % over 5000 cycles . The ASCs fabricated by Chen et al., with the NiCo 2 O 4 −NiWO 4 hybrid as the positive electrode and AC as the negative electrode in 6 m KOH electrolyte showed a high energy density of 41.5 Wh kg −1 at a power density of 760 W kg −1 .…”

Enhancing the Kinetic Process in Biphasic Crystalline NiWO4/Amorphous Co‐B Electrode Materials toward Energy Storage with Ultrahigh Rate Performance

“…In Figure 2e, the EDS spectrum shows the Co−B sample is composed of Co and B elements, and the detected O element is caused by oxygen on the surface of Co−B in the air. In the Co core energy level spectrum (Figure 2h), the two diffraction peaks at 805.2 and 787.5 eV are the satellite peaks, the two characteristic peaks at 802.5 eV in Co 2p 1/2 and 783.5 eV in Co 2p 3/2 are corresponding to Co 2+ , the two characteristic peaks at 797.5 eV in Co 2p 1/2 and 781.4 eV in Co 2p 3/2 are corresponding to Co 3+ [26] . The B 1s spectrum in Figure 2k shows the unique characteristic peak at 192 eV, which is attributed to the B−O bond [27] .…”