Fluorinated graphene-supported Nickel-Cobalt-Iron nitride nanoparticles as a promising hybrid electrode for supercapacitor applications

Enhancing Electrochemical Performance of Aluminum-Ion Batteries with Fluorinated Graphene Cathode

In pursuit of high-performance aluminum-ion batteries, the selection of a suitable positive electrode material assumes paramount importance, and fluorinated graphene (FG) nanostructures have emerged as an exceptional candidate. In the scope of this study, a flexible tantalum foil is coated with FG to serve as the positive electrode for aluminum-ion batteries. FG positive electrode demonstrates a remarkable discharge capacity of 109 mA h g-1 at a current density of 200 mA g-1, underscoring its tremendous potential for energy storage applications. Concurrently, the FG positive electrode exhibits a discharge capacity of 101 mA h g-1 while maintaining an impressive coulombic efficiency of 95 % over 300 cycles at a current density of 200 mA g-1, which benefiting from the significant structure of FG. The results of the in-situ Raman spectroscopy signified the presence of intercalation/de-intercalation processes of AlCl4 - behavior within the FG layers.

Hierarchical CuCo2O4@CoS-Cu/Co-MOF core-shell nanoflower derived from copper/cobalt bimetallic metal-organic frameworks for supercapacitors

Rational design of composite materials with unique core-shell nanoflower structures is an important strategy for improving the electrochemical properties of supercapacitors such as capacitance and cycle stability. Herein, a two-step electrodeposition technique is used to orderly synthesize CuCo₂O₄ and CoS on Ni foam coated with Cu/Co bimetal metal organic framework (Cu/Co-MOF) to fabricate a hierarchical core-shell nanoflower material (CuCo₂O₄@CoS-Cu/Co-MOF). This unique structure can increase the electrochemically active site of the composite, promoting the Faradaic redox reaction and enhancing its electrochemical properties. CuCo₂O₄@CoS-Cu/Co-MOF shows a prominent specific capacitance of 3150 F g^-1 at 1 A g^-1, marvelous rate performance of 81.82% (2577.3 F g^-1 at 30 A g^-1) and long cycle life (maintaining 96.74% after 10,000 cycles). What is more, the assembled CuCo₂O₄@CoS-Cu/Co-MOF//CNTs device has an energy density of 73.19 Wh kg^-1 when the power density is 849.94 W kg^-1. It has unexpected application prospects.

Emerging trends in anion storage materials for the capacitive and hybrid energy storage and beyond

Electrochemical capacitors charge and discharge more rapidly than batteries over longer cycles, but their practical applications remain limited due to their significantly lower energy densities. Pseudocapacitors and hybrid capacitors have been developed to extend Ragone plots to higher energy density values, but they are also limited by the insufficient breadth of options for electrode materials, which require materials that store alkali metal cations such as Li⁺ and Na⁺. Herein, we report a comprehensive and systematic review of emerging anion storage materials for performance- and functionality-oriented applications in electrochemical and battery-capacitor hybrid devices. The operating principles and types of dual-ion and whole-anion storage in electrochemical and hybrid capacitors are addressed along with the classification, thermodynamic and kinetic aspects, and associated interfaces of anion storage materials in various aqueous and non-aqueous electrolytes. The charge storage mechanism, structure-property correlation, and electrochemical features of anion storage materials are comprehensively discussed. The recent progress in emerging anion storage materials is also discussed, focusing on high-performance applications, such as dual-ion- and whole-anion-storing electrochemical capacitors in a symmetric or hybrid manner, and functional applications including micro- and flexible capacitors, desalination, and salinity cells. Finally, we present our perspective on the current impediments and future directions in this field.

Spray-dried assembly of 3D N,P-Co-doped graphene microspheres embedded with core-shell CoP/MoP@C nanoparticles for enhanced lithium-ion storage

The advancement of novel synthetic approaches for micro/nanostructural manipulation of transition metal phosphide (TMP) materials with precisely controlled engineering is crucial to realize their practical use in batteries. Here, we develop a novel spray-drying strategy to construct three-dimensional (3D) N,P co-doped graphene (G-NP) microspheres embedded with core-shell CoP@C and MoP@C nanoparticles (CoP@C⊂G-NP, MoP@⊂G-NP). This intentional design shows a close correlation between the microstructural G-NP and chemistry of the core-shell CoP@C/MoP@C nanoparticle system that contributes towards their anode performance in lithium-ion batteries (LIBs). The obtained structure features a conformal porous G-NP framework prepared via the co-doping of heteroatoms (N,P) that features a 3D conductive highway that allows rapid ion and electron passage and maintains the overall structural integrity of the material. The interior carbon shell can efficiently restrain volume evolution and prevent CoP/MoP nanoparticle aggregation, providing excellent mechanical stability. As a result, the CoP@C⊂G-NP and MoP@⊂G-NP composites deliver high specific capacities of 823.6 and 602.9 mA h g^-1 at a current density of 0.1 A g^-1 and exhibit excellent cycling stabilities of 438 and 301 mA h g^-1 after 500 and 800 cycles at 1 A g^-1. The present work details a novel approach to fabricate core-shell TMPs@C⊂G-NP-based electrode materials for use in next-generation LIBs and can be expanded to other potential energy storage applications.

Transition metal nitrides for electrochemical energy applications

This review comprehensively summarizes the progress on the structural and electronic modulation of transition metal nitrides for electrochemical energy applications.

Regulating the electrochemical behaviours of a hierarchically structured Co3(PO4)2/Ni-Co-O for a high-performance all-solid-state supercapacitor

Battery-type materials (e.g., transition metal phosphates) have been intensely explored in supercapacitors due to their rich electroactive sites and high theoretical capacity. Yet poor rate performance, resulting in a low energy density at high current density, limits their further applications. Herein, an improvement in rate performance resulting from enhanced surface capacitive behaviour contribution has been observed in a hierarchically structured Co3(PO4)2/Ni-Co-O@Ni foam (CPNO-12). The optimized CPNO-12 synthesized through a facile hydrothermal treatment also exhibits a striking gravimetric and areal capacity of 1410C g-1 (14 100 mC cm-2) at 5 mA cm-2 and superb cyclability (91% of retention at 50 mA cm-2 after 12 000 cycles), which can be attributed to its unique hierarchical porous structure and high mass loading per area. More importantly, a high-performance all-solid-state asymmetric supercapacitor with CPNO-12 and Fe2P/graphene hydrogel@Ni foam as positive and negative electrodes respectively has been assembled; the device delivering a maximum energy density of 95 W h kg-1 (32 mW h cm-3) and maximum power density of 4000 W kg-1 (800 mW cm-3) has the potential to power sophisticated systems. These attractive performances confirm that an enhancement of capacitive behaviour in battery-type materials holds the promise for fabricating high-performance supercapacitors.

Recent Progress in Two-Dimensional Layered Double Hydroxides and Their Derivatives for Supercapacitors

High-performance supercapacitors have attracted great attention due to their high power, fast charging/discharging, long lifetime, and high safety. However, the generally low energy density and overall device performance of supercapacitors limit their applications. In recent years, the design of rational electrode materials has proven to be an effective pathway to improve the capacitive performances of supercapacitors. Layered double hydroxides (LDHs), have shown great potential in new-generation supercapacitors, due to their unique two-dimensional layered structures with a high surface area and tunable composition of the host layers and intercalation species. Herein, recent progress in LDH-based, LDH-derived, and composite-type electrode materials targeted for applications in supercapacitors, by tuning the chemical/metal composition, growth morphology, architectures, and device integration, is reviewed. The complicated relationships between the composition, morphology, structure, and capacitive performance are presented. A brief projection is given for the challenges and perspectives of LDHs for energy research.

Lithium ferrite (α-LiFe5O8) nanorod based battery-type asymmetric supercapacitor with NiO nanoflakes as the counter electrode

The fabricated battery-type NiO//α-LiFe₅O₈ cell could deliver a specific energy of 30 W h Kg⁻¹ at a specific power of 621 W kg⁻¹ with 90.5% capacity retention at the end of 5000 GCD cycles.