Ultra-dispersed nickel-cobalt sulfides on reduced graphene oxide with improved power and cycling performances for nickel-zinc batteries

Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N2C1MS0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g-1 at a current density of 1 A g-1. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N2C1MS0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg-1 at a power density of 800 W kg-1, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.

Bi-Interlayer Strategy for Modulating NiCoP-Based Heterostructure toward High-Performance Aqueous Energy Storage Devices

Nickel-cobalt (NiCo) phosphides (NCPs) possess high electrochemical activity, which makes them promising candidates for electrode materials in aqueous energy storage devices, such as supercapacitors and zinc (Zn) batteries. However, the actual specific capacitance and rate capability of NCPs require further improvement, which can be achieved through reasonable heterostructural design and loading conditions of active materials on substrates. Herein, novel hierarchical Bi-NCP heterogeneous structures with built-in electric fields consisting of bismuth (Bi) interlayers (electrodeposited on carbon cloth (CC)) are designed and fabricated to ensure the formation of uniform high-load layered active materials for efficient charge and ion transport. The resulting CC/Bi-NCP electrodes show a uniform, continuous, and high mass loading (>3.5 mg) with a superior capacitance reaching 1200 F g-1 at 1 A g-1 and 4129 mF cm-2 at 1 mA cm-2 combined with high-rate capability and durable cyclic stability. Moreover, assembled hybrid supercapacitors (HSCs), supercapatteries, and alkaline Zn-ion (AZBs) batteries constructed using these electrodes deliver high energy densities of 64.4, 81.8, and 319.1 Wh kg-1, respectively. Overall, the constructed NCPs with excellent aqueous energy storage performance have the potential for the development of novel transition metal-based heterostructure electrodes for advanced energy devices.

Bi Nanosheets on Porous Carbon Cloth Composites for Ultrastable Flexible Nickel-Bismuth Batteries

The use of bismuth (Bi) as an anode material in nickel-metal batteries has gained significant attention due to its highly reversible redox reaction and suitable operating conditions. However, the cycling stability and flexibility of nickel-bismuth (Ni//Bi) batteries need to be further improved. This paper employs a facile electrodeposition technique to prepare Bi nanosheets uniformly grown on a porous carbon cloth (PCC), denoted as Bi-PCC electrodes. The Bi-PCC electrode portrays a specific surface area and good wettability that enable fast charge transfer and ion transport channels. Consequently, the Bi-PCC electrode demonstrates a high specific capacity of up to 297.1 mAh g^-1 at 2 A g^-1, with a capacity retention of up to 71.5% at 2-40 A g^-1 and an impressive capacity retention of 79.9% after 1000 cycles at 2-40 A g^-1. More importantly, the flexible rechargeable Ni//Bi battery (denoted as Ni(OH)₂-PCC//Bi-PCC) with Bi-PCC as the anode and Ni(OH)₂-PCC as the cathode has excellent electrochemical performance. The Ni(OH)₂-PCC//Bi-PCC battery boasts a remarkable capacity retention of 93.6% after 3000 cycles at 10 A g^-1. Further, the cell presents a maximum energy density of 73.1 Wh kg^-1 and an impressive power density of 11.9 kW kg^-1.

Heterogeneous Ni-Co phosphide/phosphate with a specific hollow sea-urchin-like structure for high-performance hybrid supercapacitor and alkaline zinc-metal battery applications

Constructing well-defined nanostructures consisting of the multiple components with distinctive features are a promising but challenging strategy to develop advanced electroactive materials for energy storage applications. Herein, heterogeneous Ni-Co phosphide/phosphate with a specific hollow sea-urchin-like structure has been synthesized as advanced electroactive materials for both hybrid supercapacitor (HSC) and alkaline zinc-metal battery (AZB) applications. The heterogeneous Ni-Co phosphide/phosphate combines the merits of improved electrolyte interfacial property from the specific hollow sea-urchin-like structure, high electron-conductivity of phosphide, and better ion adsorption and solid diffusion property of phosphate. As a result, the Ni-Co phosphide/phosphate achieves a high capacity to 180.7 mA h g^-1 at 1 A g^-1, excellent rate capability of 51% capacity retention when the specific current increases by 50 times, and stable cycling stability of 85% capacity retention when cycled for 1000 cycles. Ex situ test was conducted to investigate the formation mechanism for the hollow and sea-urchin-like structure, which can be ascribed to the anion exchange reaction between pre-formed hydroxide and CO₃^2- ions. When used to assemble HSCs with reduced graphene oxide (RGO), the HSCs exhibit a high specific energy of 49.4 W h kg^-1, an ultrahigh specific power to 11.7 kW kg^-1, and an eminent cycling stability over 10,000 cycles. Meanwhile, Ni₂Co-P/PO_x-based AZB also achieves both high-energy and high-power performance with the specific energy of 308.0 W h kg^-1 at 828.4 W kg^-1 and 117.4 W h kg^-1 at 30.8 kW kg^-1. These results above suggest that heterogeneous Ni-Co phosphide/phosphate has great potential to be used as a candidate for both HSC and AZB applications.

Facile Synthesis of NixCo3-xS4 Microspheres for High-Performance Supercapacitors and Alkaline Aqueous Rechargeable NiCo-Zn Batteries

Electrochemical energy storage devices (EESDs) have caused widespread concern, ascribed to the increasing depletion of traditional fossil energy and environmental pollution. In recent years, nickel cobalt bimetallic sulfides have been regarded as the most attractive electrode materials for super-performance EESDs due to their relatively low cost and multiple electrochemical reaction sites. In this work, NiCo-bimetallic sulfide Ni_xCo_3-xS₄ particles were synthesized in a mixed solvent system with different proportion of Ni and Co salts added. In order to improve the electrochemical performance of optimized Ni_2.5Co_0.5S₄ electrode, the Ni_2.5Co_0.5S₄ particles were annealed at 350 °C for 60 min (denoted as Ni_2.5Co_0.5S₄-350), and the capacity and rate performance of Ni_2.5Co_0.5S₄-350 was greatly improved. An aqueous NiCo-Zn battery was assembled by utilizing Ni_2.5Co_0.5S₄-350 pressed onto Ni form as cathode and commercial Zn sheet as anode. The NiCo-Zn battery based on Ni_2.5Co_0.5S₄-350 cathode electrode delivers a high specific capacity of 232 mAh g^-1 at 1 A g^-1 and satisfactory cycling performance (65% capacity retention after 1000 repeated cycles at 8 A g^-1). The as-assembled NiCo-Zn battery deliver a high specific energy of 394.6 Wh kg^-1 and long-term cycling ability. The results suggest that Ni_2.5Co_0.5S₄-350 electrode has possible applications in the field of alkaline aqueous rechargeable electrochemical energy storage devices for supercapacitor and NiCo-Zn battery.

The in-situ construction of oxygen vacancies-rich NiCo2S4@NiMoO4/Ni2P multilevel nanoarray for high-performance aqueous Zn-ion batteries

The development of active and durable cathode materials is the key to achieving high-performance water-based zinc-ion batteries. In this work, the NiCo2S4@NiMoO4/Ni2P nanoarray was employed by hydrothermal and subsequent phosphine...