Configuring hierarchical Ni/NiO 3D-network assisted with bamboo cellulose nanofibers for high-performance Ni-Zn aqueous batteries

Controllable Preparation of Hollow Spheroidal Nickel-Based Metal-Organic Frameworks Microparticles for Aqueous Nickel-Zinc Batteries

Metal-organic frameworks (MOFs) have garnered increasing interest due to their porous structure, high surface area, and rich redox active metal ions that can be exploited as good electrode materials for electrochemical energy storage. Herein, nickel-based MOFs materials with different morphological structures of solid spheres (Ni-BTC-0), hollow spheroidal microparticles (Ni-BTC-5), and hollow spheres (Ni-BTC-10) have been facilely synthesized by using water as a regulator. Among them, the unique structure of hollow spheroidal Ni-BTC-5 microparticles with the largest surface area can provide abundant channels for fast electron and electrolyte transport as well as expose more active sites. As a result, the Ni-BTC-5 electrode displays a higher specific capacity of 177.8 mA h/g than the Ni-BTC-0 (110.6 mA h/g) and Ni-BTC-10 (129.9 mA h/g) electrodes at a current density of 1.0 A/g. Furthermore, the assembled aqueous nickel-zinc battery based on the Ni-BTC-5 cathode and Zn anode delivers a high capacity of 210.6 mA h/g, a remarkable energy density of 362.3 W h/kg, and a good capacity retention rate of 80.2% over 3000 cycles. This study provides a new way to regulate the morphological structures of MOFs, also demonstrating that regulating the structure of MOFs is one of the effective approaches to improve their energy storage performances.

Recent progress and perspectives of advanced Ni-based cathodes for aqueous alkaline Zn batteries

Rechargeable aqueous alkaline Zn-Ni batteries (AZNBs) are considered a potential contender for energy storage fields and portable devices due to their inherent safety, high output voltage, high theoretical capacity and environmental friendliness. Despite the facilitated development of AZNBs by many investigations, its practical application is still restricted by inadequate energy density, sluggish kinetics, and poor stability. Therefore, Ni-based cathodes with boosted redox chemistry and enhanced structural integrity is essential for the high-performance AZNBs. Herein, this review focus on critical bottlenecks and effective design strategies of the representative Ni-based cathode materials. Specifically, nanostructured optimization, defect engineering, ion doping, heterostructure regulation and ligand engineering have been employed from the fundamental aspects for high-energy and long-lifespan Ni-based cathodes. Finally, further exploration in failure mechanism, binder-free battery configurations, practical application scenarios, as well as battery recycling are considered as valuable directions for the future development of advanced AZNBs.

Electrochemical oxidation-driven formation of nickel/nickel-based compounds on hollow carbon shells: Mechanistic insights and energy storage applications

Hydrangea-like nickel/nickel-based compounds decorated hollow carbon shells were synthesized through low-temperature calcination and a facile electrochemical oxidation process. This three-dimensional hollow hierarchical structure ensures intimate contact between the electrically conductive nickel (Ni) substrate and uniformly distributed electrochemically active nickel-based compounds. This hierarchical structure offers abundant active sites and accessible pathways, maximizing energy storage, particularly during rapid charge-discharge cycles. With 30 min of electrochemical oxidation, the optimized Ni-compound-based electrode exhibits a specific capacity of 643 C g-1 at 1 A/g. When assembled into a nickel-zinc battery cell with a zinc foil anode, the cell demonstrates swift current responses, with full capacity recovery even after a twentyfold increase in current density, followed by a return to 1 A/g. Density functional theory computations reveal that the electrochemical oxidation, conducted for an optimized duration, results in partial oxidation of Ni(OH)2, reducing the surface adsorption energy of OH- from the electrolyte and improving charge storage capacity.

Three-dimensional NiCoS nanotubes@NiCo-LDH nanosheets core-shell heterostructure for high-rate capability alkaline zinc-based batteries

Aqueous alkaline zinc-based batteries (AAZBs) are promising for large-scale applications due to their high working voltage, safety, and low cost. However, the further development of AAZBs has been significantly hindered by the low electronic conductivity and poor cycling stability of traditional nickel/cobalt-based cathode materials. In this work, a binder-free electrode was successfully designed by electrodepositing NiCo-LDH nanosheets on NiCoS nanotube arrays that were grown on nickel foam (NiCoS@NiCo-LDH). The unique three-dimensional core-shell heterostructures not only enhance electrical conductivity but also offer abundant active sites and rapid ion/electron transport channels, thereby improving its electrochemical performance. The as-fabricated NiCoS@NiCo-LDH electrode delivers a capacity of 312 mA h g-1 (0.624 mA h cm-2) at 2 mA cm-2 and exhibits high rate capability with 90% capacity retention at 10 mA cm-2. Additionally, the assembled NiCoS@NiCo-LDH//Zn battery exhibits a high energy density of 435.3 W h kg-1 at a power density of 4.1 kW kg-1 and maintains 95.9% of its capacity after 3000 cycles at a current density of 20 mA cm-2.

Advances in Cellulose-Based Composites for Energy Applications

The various forms of cellulose-based materials possess high mechanical and thermal stabilities, as well as three-dimensional open network structures with high aspect ratios capable of incorporating other materials to produce composites for a wide range of applications. Being the most prevalent natural biopolymer on the Earth, cellulose has been used as a renewable replacement for many plastic and metal substrates, in order to diminish pollutant residues in the environment. As a result, the design and development of green technological applications of cellulose and its derivatives has become a key principle of ecological sustainability. Recently, cellulose-based mesoporous structures, flexible thin films, fibers, and three-dimensional networks have been developed for use as substrates in which conductive materials can be loaded for a wide range of energy conversion and energy conservation applications. The present article provides an overview of the recent advancements in the preparation of cellulose-based composites synthesized by combining metal/semiconductor nanoparticles, organic polymers, and metal-organic frameworks with cellulose. To begin, a brief review of cellulosic materials is given, with emphasis on their properties and processing methods. Further sections focus on the integration of cellulose-based flexible substrates or three-dimensional structures into energy conversion devices, such as photovoltaic solar cells, triboelectric generators, piezoelectric generators, thermoelectric generators, as well as sensors. The review also highlights the uses of cellulose-based composites in the separators, electrolytes, binders, and electrodes of energy conservation devices such as lithium-ion batteries. Moreover, the use of cellulose-based electrodes in water splitting for hydrogen generation is discussed. In the final section, we propose the underlying challenges and outlook for the field of cellulose-based composite materials.

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...

Synthesis of NiSe nanorod array structure as a binder-free cathode for an aqueous rechargeable Ni–Zn battery

Co0.33Ni0.67Se nanorod array electrode synthesized by a simple two-step solvothermal method on Ni foam and demonstrated good electrochemical performances for supercapacitor and aqueous rechargeable Ni–Zn battery.

Engineering oxygen vacancies and surface chemical reconstruction of MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays for advanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) are emerging as promising alternatives among various energy storage devices. However, the lack of research on cathode materials with both high capacity and electrochemical stability restricts widespread applications of ZIBs. Herein, surface chemical reconstruction and partial phosphorization strategies are employed to synthesize MOF-derived hierarchical CoO/Ni₂P-Co₂P nanosheet arrays on Ni foam substrates as cathodes for ZIBs. The unique hierarchical nanostructure and multiple components with exposed surfaces and rich oxygen vacancies accelerate charge transfer and ion diffusion, expose more active sites, and promote the accessibility between the active materials and electrolyte. The oxide/phosphide composites obtained by novel partial phosphorization achieve a common improvement of performance and stability. As expected, the CoO/Ni₂P-Co₂P electrode delivers a high specific capacity (370.4 mA h g^-1 at 3 A g^-1) and excellent rate performance (63.3% retention after a six-fold increase in the current density). Moreover, when employed as the cathode of the CoO/Ni₂P-Co₂P-30//Zn battery, the assembled battery exhibits a superior specific capacity (322.8 mA h g^-1 at 2 A g^-1), a long cycle life (104.9% retention after 6000 cycles), a favorable energy density (547.5 W h kg^-1) and power density (9.7 kW kg^-1). Therefore, this study provides a suitable candidate which meets the requirements of high-performance cathode materials for ZIBs.

Towards advanced aqueous zinc battery by exploiting synergistic effects between crystalline phosphide and amorphous phosphate

High-performance aqueous zinc batteries are expected to be realized, rooting from component synergistic effects of the hierarchical composite electrode materials. Herein, hierarchical crystalline Ni-Co phosphide coated with amorphous phosphate nanoarrays (C-NiCoP@A-NiCoPO₄) self-supporting on the Ni foam are constructed as cathode material of an aqueous zinc battery. In this unique core-shell structure, the hexagonal phosphide with high conductivity offers ultra-fast electronic transmission and amorphous phosphate with high stability, and open-framework provides more favorable ion diffusivity and a stable protective barrier. The synergistic effects of this intriguing core-shell structure endow the electrode material with outstanding reaction kinetics and structural stability, which is theoretically confirmed by density functional theory (DFT) calculations. As a result, the C-NiCoP@A-NiCoPO₄ electrode exhibits a higher specific capacity of 350.6 mA h g^-1 and excellent cyclic stability with 92.6% retention after 10 000 cycles. Moreover, the C-NiCoP@A-NiCoPO₄ is coupled with Zn anode to assemble an aqueous pouch battery that delivers ultra-high energy density (626.33 W h kg^-1 at 1.72 kW kg^-1) with extraordinary rate performance (452.05 W h kg^-1 at 33.56 kW kg^-1). Moreover, the corresponding quasi-solid flexible battery with polyacrylamide hydrogel electrolyte exhibits favorable durability under frequent mechanical strains, which indicates the great promise of crystalline/amorphous hierarchical electrodes in the field of energy storage.

High mass loading NiCo-OH nanothorns coated CuO nanowire arrays for high-capacity nickel-zinc battery

The rational design of cathode materials with core-shell heterostructures is significant to develop a Ni//Zn battery with both high gravimetric and areal energy density under high mass loading. In this work, the NiCo-OH nanothorns with a mass loading of 11.6 mg cm^-2were coated on CuO nanowire arrays via a chemical bath deposition method. Thanks to the construction of 3D core-shell nanowire arrays and appropriate cobalt doping, as-fabricated Ni//Zn battery based on the NiCo-OH as cathode achieved the maximum specific capacity of 383 mAh g^-1at 5 mA cm^-2with high energy density of 649 Wh kg^-1at 0.73 kW kg^-1, indicating good energy storage performance in Ni//Zn battery.

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

Rechargeable alkaline nickel-zinc (Ni-Zn) batteries are attracting increased attention owing to their exceptional inherent safety and high specific capacity. Unfortunately, the limited power and cycling performances of these Ni-Zn batteries are still challenging. Herein, bimetal nickel-cobalt sulfide/ reduced graphene oxide (NiCo-S/RGO) composites with tunable compositions are synthesized by rational designing precursor and subsequent sulfidation treatment. NiCo-S is evenly anchored on RGO surface, resulting in increased number of electrochemical active sites, accelerated electrolyte ion diffusion, and enhanced electrical conductivity. Particularly, by tuning the Ni and Co composition ratios in NiCo-S, NiCo-S/RGO with a Ni to Co ratio of 2:1 (NiCo-S-2/RGO) shows a specific capacity of 145.7 mA h g^-1 at 1 A g^-1 and long-life cycling retention of 84.7% after 1000 cycles, and the above performances are superior than the controlled samples with other Ni to Co ratios. Furthermore, the as-assembled alkaline zinc batteries of NiCo-S-2/RGO//Zn deliver an impressive specific energy of 333.2 W h kg^-1, showing great potential in practical applications. This experiment hopefully provides new idea for construction of high-performance electrodes of aqueous rechargeable batteries.

Ni3S2 Nanocomposite Structures Doped with Zn and Co as Long-Lifetime, High-Energy-Density, and Binder-Free Cathodes in Flexible Aqueous Nickel-Zinc Batteries

Flexible rechargeable Zn//Ni batteries are attractive owing to their high energy density, good safety, inexpensive cost, and simple manufacturing process. However, the effects of metal doping on the properties of Ni₃S₂ cathodes in Zn/Ni batteries are not well understood. Herein, a binder-free Ni₃S₂ electrode is doped with Zn and Co and the nanocomposite structures are prepared on nickel foam (named ZCNS/NF) by a simple two-step hydrothermal technique. The ZCNS/NF//Zn battery delivers excellent electrochemical performance such as a working voltage window can be as high as 2.05 V, a capacity of 2.3 mAh cm^-2 at 12 mA cm^-2, and 82% retention going through 2000 cycles at 20 mA cm^-2. The battery has a maximum output area energy density of 1.8 mWh cm^-2 (462 Wh kg^-1) and a power density of 36.8 mW cm^-2 (9.2 kW kg^-1). In addition, the flexible battery remains operational while being bent at a large angle and even punctured. The high performance and robustness of the composite cathode suggest that the design principle and materials have large commercial potential in Ni//Zn batteries.

Engineering Hierarchical Co@N-Doped Carbon Nanotubes/α-Ni(OH)2 Heterostructures on Carbon Cloth Enabling High-Performance Aqueous Nickel-Zinc Batteries

Searching for high-performance Ni-based cathodes plays an important role in developing better aqueous nickel-zinc (Ni-Zn) batteries. For this purpose, herein, we demonstrate the design and synthesis of ultrathin α-Ni(OH)₂ nanosheets branched onto metal-organic frameworks (MOFs)-derived 3D cross-linked N-doped carbon nanotubes encapsulated with tiny Co nanoparticles (denoted as Co@NCNTs/α-Ni(OH)₂), which are directly supported on a flexible carbon cloth (CC). An aqueous Ni-Zn battery employing the hierarchical CC/Co@NCNTs/α-Ni(OH)₂ as the binder-free cathode and a commercial Zn plate as the anode is fabricated, which displays an ultrahigh capacity (316 mAh g^-1) and energy density (540.4 Wh kg^-1) at 1 A g^-1 as well as excellent rate capability (238 mAh g^-1 at 10 A g^-1) and superior cycling performance (about 84% capacity retention after 2000 cycles at 10 A g^-1). The impressive electrochemical performance might benefit from the rich active sites, rapid electron transfer, cushy electrolyte access, rapid ion transport, and robust structural stability. In addition, the quasi-solid-state CC/Co@NCNTs/α-Ni(OH)₂//Zn batteries are also successfully assembled with polymer electrolyte, indicating the great potential for portable and wearable electronics. This work might provide important guidance for constructing carbon-based hybrid materials directly supported on conductive substrates as high-performance electrodes for energy-related devices.