High-performance quasi-solid-state flexible supercapacitors based on a flower-like NiCo metal–organic framework

Abstract

The flower-like NiCo MOF prepared by a hydrothermal has a specific capacitance of 927.1 F g−1 at 1 A g−1 and a capacitance retention of 69.7% from 1 A g−1 to 10 A g−1, showing excellent electrochemical performance.

Ligand-Controlled Growth of Different Morphological Bimetallic Metal–Organic Frameworks for Enhanced Charge-Storage Performance and Quasi-Solid-State Hybrid Supercapacitors

“…The similar XRD spectra of NiCo MOFs confirm that the addition of different ligands altered the morphology and not caused much change in crystallinity. According to the literature, the peaks are well matched with the Ni-MOF (Ni 3 (OH) 2 (C 8 H 4 O 4 ) 2 (H 2 O) 4 , PDF #985792), Co-MOF (Co 2 (OH) 2 C 8 H 4 O 4 , PDF #153067), C 8 H 6 NiO 5 H 2 O (PDF #35-1677), and C 8 H 6 Co 2 O 6 (PDF #34-1897). − The sharp and clear peaks at 2θ = 9.3 and 12.9° for all the NiCo MOF correspond to the (100) and (010) crystal planes for Ni-MOF and Co-MOF, respectively, demonstrating excellent crystallinity. , Additional peaks observed for NiCo MOF_BDC at 15.7, 18.3, and 23.9° correspond to the (10-1), (200), and (020) crystal planes of Ni-MOF, respectively . Also, the peaks at 12.9° (010) and 25.6° (110) indicate d -spacings of 0.68 and 0.34 nm, respectively, suggesting a layered NiCo coordinated structure .…”

“…The NiCo MOF_BTC inherits a high surface area and pore volume that facilitate exposing more electroactive sites for mass transport and redox reaction and provide better ion diffusion channels for electrochemical reactions, thereby helping to improve the charge-storage performance. 45,46,54 The TEM images of as-prepared NiCo MOF_BTC further prove the nanosheet-assembled flower-like structure (inset of Figure 4a). Again, the magnified images confirm the nanosheets (Figure 4a,b) and extremely porous nature (Figure 4c) of the structure that match well with the SEM and BET results.…”

“…The Ragone plot of energy density and power density for different structured NiCo MOF-based devices and the fabricated ASC device in this work is depicted in Figure h, where eqs and are used for the calculation. Interestingly, the nanosheet-assembled flower-like sphere NiCo MOF_BTC//PVA + KOH//AC ASC device possesses a high energy density of 78.1 Wh kg –1 at a power density of 750 W kg –1 and even retains 47.5 Wh kg –1 at a power density of 3750 W kg –1 , which is higher than the reported NiCo MOF-based materials, such as hydrangea-like NiCo MOF//AC (45.3 Wh kg –1 at 847.8 W kg –1 ), flower-like NiCo MOF//AC (28.5 Wh kg –1 at 400.5 W kg –1 ), layered sheet-like NiCo MOF//rGO-CNT (55.5 Wh kg –1 at 175 W kg –1 ), sheet-like NiCo MOF//AC (66.1 Wh kg –1 at 800 W kg –1 ), nanosheet-assembled hollow sphere-like NiCo MOF//AC (20.94 Wh kg –1 at 750.84 W kg –1 ), sheet-like NiCo MOF//AC (50.25 Wh kg –1 at 300 W kg –1 ), and flower-like NiCo MOF//AC (77.7 Wh kg –1 at 450 W kg –1 ) (comparison is tabulated in Table ). The NiCo MOF_BTC//AC device maintains excellent cycle stability with 88% compared to its initial capacitance after 5000 charge–discharge cycles at a current density of 10 A g –1 and the Coulombic efficiency is about 90% (Figure i).…”

“…Distinctly, the NiCo MOF_BTC delivers the highest specific capacity and is superior to the prepared NiCo MOF_BDC and NiCo MOF_2-Melm. Also, the synthesized nanosheet-assembled flower-like NiCo MOF using trimesic acid as the ligand exhibits a higher specific capacitance of 2942.8 F g −1 than the already reported different morphological structured NiCo MOFs, i.e., flower-like NiCo MOF (927.1 F g −1 @ 1 A g −1 ), 45 nanosheet-assembled hollow sphere-like NiCo MOF (1126.7 F g −1 @ 0.5 A g −1 ), 40 and hydrangea-like NiCo-MOF (1665.2 F g −1 @ 1 A g −1 ). 39 The comparison of NiCo MOF-based electrode energy storage performance is given in Table 1.…”

“…The BJH pore volumes of NiCo MOF_BDC, NiCo MOF_2-Melm, and NiCo MOF_BTC are calculated as 0.08, 0.17, and 0.35 cm 3 g –1 , respectively. The NiCo MOF_BTC inherits a high surface area and pore volume that facilitate exposing more electroactive sites for mass transport and redox reaction and provide better ion diffusion channels for electrochemical reactions, thereby helping to improve the charge-storage performance. ,, …”