Multilayer dodecahedrons Zn-Co sulfide for supercapacitors

A heterostructure of NiMn-LDH nanosheets assembled on ZIF-L-derived ZnCoS hollow nanosheets with a built-in electric field enables boosted electrochemical energy storage

Supercapacitors (SCs) have emerged as an efficient technology toward the utilization of renewable energy, which demands high-performance electrode materials. Transition-metal sulfides (TMSs) and layered double hydroxides (LDHs) rich in active sites and valence states are very promising electrode materials, but they still suffer from inherent defects, such as low electric conductivity, sluggish reaction kinetics and large volume change during electrochemical reactions. In this work, NiMn-LDH nanosheets are assembled on the surfaces of ZnCoS hollow nanosheet arrays derived from a zeolitic imidazolate framework-L (ZIF-L) to form a ZnCoS@NiMn-LDH heterostructure (ZCS@LDH) with a built-in electric field. The unique structure gives rise to abundant exposed active sites and improved ion diffusion. More importantly, the built-in electric field can enhance conductivity and charge transfer by modulating the electronic structures. With these merits, the optimal ZCS@LDH-6 electrode displays outstanding specific capacitance (2102.2 F g-1 at 1 A g-1) and remarkable rate performance (68.1% at 10 A g-1). The assembled asymmetric supercapacitor (ASC) using the ZCS@LDH-6 electrode shows high energy storage capacity (41.7 W h kg-1 at 850.0 W kg-1), satisfactory cycle life (92.2% capacitance retention after 10 000 cycles) and high coulombic efficiency (95.8%). This work will shed light on designing high-performance electrode materials via heterostructure and morphology engineering.

MOF-Derived Ultrathin NiCo-S Nanosheet Hybrid Array Electrodes Prepared on Nickel Foam for High-Performance Supercapacitors

At present, binary bimetallic sulfides are widely studied in supercapacitors due to their high conductivity and excellent specific capacitance (SC). In this article, NiCo-S nanostructured hybrid electrode materials were prepared on nickel foam (NF) by using a binary metal-organic skeleton as the sacrificial template via a two-step hydrothermal method. Comparative analysis was carried out with Ni-S and Co-S in situ on NF to verify the excellent electrochemical performance of bimetallic sulfide as an electrode material for supercapacitors. NiCo-S/NF exhibited an SC of 2081 F∙g^-1 at 1 A∙g^-1, significantly superior to Ni-S/NF (1520.8 F∙g^-1 at 1 A∙g^-1) and Co-S/NF (1427 F∙g^-1 at 1 A∙g^-1). In addition, the material demonstrated better rate performance and cycle stability, with a specific capacity retention rate of 58% at 10 A∙g^-1 than at 1 A∙g^-1, and 75.7% of capacity was retained after 5000 cycles. The hybrid supercapacitor assembled by NiCo-S//AC exhibited a high energy density of 25.58 Wh∙kg^-1 at a power density of 400 W∙kg^-1.

Three-dimensional hierarchical flower-like bimetallic–organic materials in situ grown on carbon cloth and doped with sulfur as an air cathode in a microbial fuel cell

Herein, the output power density produced by Zn/Co-S-3DHFLM as the cathode catalyst of an MFC was higher than that of Co-3DHFLM.

Black Phosphorus/Carbon Nanoframes for Efficient Flexible All-Solid-State Supercapacitor

A flexible all-solid-state supercapacitor with fast charging speed and high power density is a promising high-performance energy storage and sensor device in photovoltaic systems. Two-dimensional black phosphorus (BP) is a prospective electrode nanomaterial, but it struggles to fully exert its properties limited by its self-stacking. Herein, by embedding carbon nanoparticles into the interlayer of BP microplates, the designed BP/carbon nanoframe (BP/C NF) forms a certain nano-gap on the substrate for promoting the orderly transport of charges. The corresponding supercapacitor BP/C SC has a capacity of 372 F g^-1, which is higher than that constructed from BP microplates (32.6 F g^-1). Moreover, the BP/C SC exhibits good stability with a ca. 90% of capacitance retentions after 10,000 repeated bending and long-term cycles. Thus, the proposed strategy of using BP/carbon nanoframes is feasible to develop exceptional flexible energy devices, and it can guide the design of relevant two-dimensional nanocomposites.

Amin M, Yamauchi Y, Xu M, Pan L. MoS2 Nanosheets with Expanded Interlayer Spacing for Ultrastable Aqueous Mg-Ion Hybrid Supercapacitor

Aqueous magnesium ion supercapacitors (MISs) have attracted attention due to their safety, low cost and environmental friendliness. However, the cycling stability of MISs is usually not ideal due to magnesium...

The intergrated nanostructure of bimetallic CoNi-based zeolitic imidazolate framework and carbon nanotubes as high-performance electrochemical supercapacitors

In this study, a series of one-dimensional (1D)/two-dimensional (2D) heterostructure hybrids were fabricated through the in situ growth of a Co and Ni bimetallic zeolitic imidazolate framework (CoNi-ZIF) around N-doped carbon nanotubes (N-CNTs). The hybrids were further exploited as effective supercapacitor materials. The N-CNTs were prepared by carbonizing a mixture of glucose and the melamine-cyanuric acid complex at a high temperature (900 °C) under N₂ atmosphere and applied as the template for the in situ synthesis of CoNi-ZIF nanosheets (NSs). The 1D N-CNTs in the hybrids can act as the high-way for charge transfer to boost the faradaic reactions. Changing the usage of metal precursors not only provided abundant redox reaction sites in 2D CoNi-ZIF NSs but also modulated the microstructures and chemical components of the hybrids. The integration of the features of N-CNTs and CoNi-ZIF NSs can result in a synergistic effect between N-CNTs and CoNi-ZIF NSs. Therefore, the obtained CoNi-ZIFs and N-CNTs hybrid (CoNi-ZIF@N-CNT) exhibited superior electrochemical capacitive performance. Comparison revealed that the CoNi-ZIF@N-CNT-2 hybrid, which was prepared with a 1:1 mass ratio of Co(NO₃)₂·6H₂O and Ni(NO₃)₂·6H₂O, displayed the largest specific capacitance of 1118F g^-1 at 1 A g^-1, which was higher than the capacitance of most reported metal-organic framework (MOF)-based supercapacitor electrodes. Moreover, the asymmetric supercapacitor based on the CoNi-ZIF@N-CNT-2 electrode exhibited a high energy density of 51.1 Wh kg^-1 at the power density of 860.1 W kg^-1 and good cycle stability. This work can provide a facile and effective way for the fabrication of heterostructured 1D/2D nanostructures based on 2D MOFs for advanced energy storage.

Controllable architecture of the NiCoZnS@NiCoFe layered double hydroxide coral-like structure for high-performance supercapacitors

The rational design of the morphological structure of electrode materials is considered as an important strategy to obtain high-performance supercapacitors. So, NiCoZnS materials with different Ni/Co/Zn molar ratios on Ni foam (NF) were synthesized, in which the Ni/Co/Zn molar ratio plays a key role in the morphological structure and electrochemical performances. Furthermore, the pre-prepared NiCoZnS materials act as substrates to guide the self-assembling of NiCoFe layered double hydroxide (LDH) nanosheets on the substrate surface to form core-shell electrode materials (NiCoZnS@NiCoFe-LDH) with a 3D mesoporous hierarchical network structure for further improving electrochemical performances. The unique interconnected coral-like NiCoZnS₁@NiCoFe-LDH with a large specific surface area (93.1 m² g^-1) and high specific capacitance is achieved at the Ni/Co/Zn molar ratio of 1 : 1 : 1. Benefiting from the unique structural feature and respective merits of the NiCoZnS and NiCoFe-LDH, the NiCoZnS₁@NiCoFe-LDH demonstrates an ultrahigh specific capacitance of 1524.0 C g^-1 (3386.7 F g^-1) at 1.0 A g^-1 and excellent 95.0% capacitance retention at 10 A g^-1 after 5000 cycles. As for practical application, the assembled NiCoZnS₁@NiCoFe-LDH//AC delivers a favorable energy density of 66.25 W h kg^-1 at 1500 W kg^-1 and a long-term cycling lifetime (86.04% retention at 5.0 A g^-1 after 10 000 cycles), which suggests promising potential in energy storage and conversion.