Synthesis of nickel-copper composite with controllable nanostructure through facile solvent control as positive electrode for high-performance supercapacitors

Development of 3D compound structures and highly wettable carbonate hydroxide electrodes for high-performance supercapacitors

A facile hydrothermal method was employed to fabricate tailored NiCo(CO3)(OH)2 electrodes for high-performance supercapacitors. Ni and Co ions, transition metals with versatile oxidation states, were used, promoting redox reactions. Additionally, a comparative analysis of the characteristics and electrochemical properties between electrodes fabricated with 3D Ni foam substrates and those without substrates was conducted. This comparison emphasizes the critical role of 3D substrate selection in enhancing electrochemical performance during electrode fabrication. Furthermore, carbonate/hydroxide-based transition metal electrodes have been fabricated. Carbonate-based transition metals can substantially increase the wettability of the electrode surface due to their hydrophilicity, which has proven beneficial in aqueous electrolytes. The NiCo(CO3)(OH)2 electrodes with Ni foam substrates and without Ni foam substrates exhibit impressive specific capacitances of 2576.4 and 1460.2 F g-1, respectively, at 3 A g-1. Furthermore, an asymmetric supercapacitor configuration is introduced, utilizing the NiCo(CO3)(OH)2 electrode with a Ni foam substrate and graphene as positive and negative electrodes, respectively. A remarkable energy density of 35.5 W h kg-1 and a power density of 2555.6 W kg-1 at a current density of 2 A g-1 are exhibited by this configuration. Notably, excellent cycling stability is displayed by the asymmetric supercapacitor, with approximately ∼71.3% of its capacity retained after 10 000 cycles. These results highlight the promising potential of the fabricated electrodes and asymmetric supercapacitor configuration for practical energy storage applications.

Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g-1 at 5 mV s-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g-1 at a current density of 1 A g-1. At a power density of 749 W kg-1, a satisfactory energy density of 26.3 W h kg-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.

Three-dimensional ternary NixCuyZnz(CO3)(OH)2 electrodes for supercapacitors: electrochemical properties and applications

Transition metal-based binary and ternary compound arrays were directly grown on a porous Ni foam substrate using a facile one-step hydrothermal method. Transition metals are considered ideal electrode materials for faradaic capacitors because they exhibit a wide range of oxidation states enabling effective redox charge transfer. Furthermore, compounds in which two or more transition metals react can help increase the number of active sites for charge-discharge reactions and provide more valence changes for improved charge transfer. In this work, we fabricated ternary electrodes with Ni, Cu, and Zn ions, exhibiting a larger surface area and higher entropy than those made with binary compounds. The Ni_xCu_yZn_z-based ternary electrode had a shorter diffusion path for the electrolyte ions owing to its larger surface area. Ternary compounds can increase the entropy of the electrode because of the reaction between atoms of different sizes, bringing about a synergistic effect for high characteristic electrochemical values. The optimized Ni_xCu_yZn_z(CO₃)(OH)₂ compound showed a maximum specific capacity of 344 mA h g^-1 at a current density of 3 A g^-1, which was remarkably higher than that of the binary electrode, and a cycling stability of 84.9% after 5000 cycles. An asymmetric supercapacitor produced with this compound as the positive electrode and graphene as the negative electrode exhibited a high energy density of 36.2 W h kg^-1 at a power density of 103.1 W kg^-1 and a current density of 2 A g^-1. The asymmetric supercapacitor fabricated using the Ni_xCu_yZn_z(CO₃)(OH)₂ compound as the positive electrode exhibited excellent electrical properties when used in an illuminated LED device.

Metal-organic-framework derived hollow manganese nickel selenide spheres confined with nanosheets on nickel foam for hybrid supercapacitors

Metal-organic framework (MOF) derived nanoarchitectures have special features, such as high surface area (SA), abundant active sites, exclusive porous networks, and remarkable supercapacitive performance when compared to traditional nanoarchitectures. Herein, we propose a viable strategy for the synthesis of hollow manganese nickel selenide spheres comprising nanosheets supported on the nickel foam (denoted as MNSe@NF) from the MOF. The MNSe nanostructures can demonstrate enriched active sites, and shorten the ion-electron diffusion pathways. When the MNSe@NF electrode is used as a cathode electrode for a hybrid supercapacitor, the electrode reflected impressive supercapacitive properties with a high capacity of 325.6 mA h g-1 (1172.16 C g-1) at 2 A g-1, an exceptional rate performance of 86.6% at 60 A g-1, and remarkable longevity (3.2% capacity decline after 15 000 cycles). Also, the assembled MNSe@NF∥AC@NF hybrid supercapacitors employing activated carbon on the nickel foam (AC@NF, anode electrode) and MNSe@NF (cathode electrode) revealed an impressive energy density of 66.1 W h kg-1 at 858.45 W kg-1 and an excellent durability of 94.1% after 15 000 cycles.