Fe‐Doped CoP Flower‐Like Microstructure on Carbon Membrane as Integrated Electrode with Enhanced Sodium Ion Storage

Flexible free-standing Fe-CoP-NAs/CC nanoarrays for high-performance full lithium-ion batteries

In this study, a flexible, free-standing Fe-doped CoP nanoarrays electrode for superior lithium-ion storage has been successfully fabricated. The electrode combines the advantages of a Fe-doping and a flexible carbon cloth (CC) support, resulting in a high specific capacity (1356 mAh/g at 0.2 A/g) and excellent cycling stability (1138 mAh/g after 100 cycles). The cyclic voltammetry (CV) curves at different scan rates investigate the outstanding lithium storage behavior of Fe-CoP-NAs/CC which indicates a combined influence of diffusion behavior and capacitance behavior on the electrochemical process. The galvanostatic intermittent titration technique (GITT) analyzes the diffusion kinetics of Li+ which indicates the fast diffusion kinetics in the Fe-CoP/NAs/CC anode. The assembled Fe-CoP-NAs/CC//LiFePO4 battery exhibits a remarkable capacity of 325.2 mAh/g even at 5 A/g. And the battery also has good cycle stability, and still provides 498.1 mAh/g specific capacity after 200 cycles. Moreover, the Fe-CoP-NAs/CC//LiFePO4 soft-pack battery can continuously power the LEDs when it is bent at various angles which demonstrates its potential for use in wearable devices.

Boosting sodium-ion battery performance with binary metal-doped Na3V2(PO4)2F3 cathodes

Na3V2(PO4)2F3 (NVPF), recognized for its Na superionic conductor architecture, emerges as a promising candidate among polyanion-type cathodes for sodium ion batteries (SIBs). However, its adoption in practical applications faces obstacles due to its inherently low electronic conductivity. To address this challenge, we employ a binary co-doped strategy to design Na3.3K0.2V1.5Mg0.5(PO4)2F3 cathode with nitrogen-doped carbon (NC) coating layer. This configuration enhances electronic conductivity and reduces diffusion barriers for sodium ion (Na+). The strategy of incorporating nitrogen-doped carbon coating not only facilitates the formation of a porous structure but also introduces additional defects and active sites. Such modifications accelerate the reaction kinetics and augment electrolyte interaction through an expanded specific surface area, thus streamlining the electrochemical process. Concurrently, strategic heteroatom substitution leads to a more efficient engagement of Na+ in the electrochemical activities, thereby bolstering the cathode's structural integrity. The vanadium fluorophosphate Na3.3K0.2V1.5Mg0.5(PO4)2F3@NC exhibits an electrochemical performance, including a high discharge specific capacity of 124.3 mA h g-1 at 0.1C, a long lifespan of 1000 cycles with a capacity retention of 93.1 % at 10C, and a rate property of 73.2 mA h g-1 at 20C. This research provides a method for preparing binary doped NVPF for energy storage electrochemistry.

Superlong cycle-life sodium-ion batteries supported by electrode/active material interaction and heteroatom doping: Mechanism and application

To achieve both the capacity and stability of metal sulfides simultaneously remains a significant challenge. In this study, we have synthesized the manganese-doped copper sulfide three-dimensional (3D) hollow flower-like sphere (M/CuS-NSC), encapsulated in a nitrogen and sulfur co-doped carbon. The hollow lamellae structure allows the rational self-aggregation process of numerous active surface area enlarged nanosheets, thereby enhancing electrochemical activity. The subsurface framework characterized by CSC bonds enhances the pseudo-capacitive properties. Furthermore, the transformation of sulfur and the isomerization of carbon contribute to the enhancement of sodium ion storage. The incorporation of Mn into CuS lattice increases the interplanar distance, providing additional space for the accommodation of sodium ions. Mn doping facilitates the localization of electrons near the Fermi level, thereby improving conductivity. Additionally, Cu foils coated with M/CuS-NSC-2 engage with the electrolyte and sulfur, initiating the reaction sequence through the formation of Cu9S8. Consequently, M/CuS-NSC-2 exhibits highly reversible capacities of 676.24 mAh g-1 after 100 cycles at 0.1 A g-1 and 511.52 mAh g-1 after 10000 cycles at 10 A g-1, with an average attenuation ratio of only 0.009 %. In this study, we propose an effective strategy that combines structural design with heteroatom doping, providing a novel approach to enhance the electrochemical performance of monometallic sulfide.

Metal Phosphide Anodes in Sodium-Ion Batteries: Latest Applications and Progress

Sodium-ion batteries (SIBs), as the next-generation high-performance electrochemical energy storage devices, have attracted widespread attention due to their cost-effectiveness and wide geographical distribution of sodium. As a crucial component of the structure of SIBs, the anode material plays a crucial role in determining its electrochemical performance. Significantly, metal phosphide exhibits remarkable application prospects as an anode material for SIBs because of its low redox potential and high theoretical capacity. However, due to volume expansion limitations and other factors, the rate and cycling performance of metal phosphides have gradually declined. To address these challenges, various viable solutions have been explored. In this paper, the recent research progress of metal phosphide materials for SIBs is systematically reviewed, including the synthesis strategy of metal phosphide, the storage mechanism of sodium ions, and the application of metal phosphide in electrochemical aspects. In addition, future challenges and opportunities based on current developments are presented.

Prussian Blue Analogue-Derived Fe-Doped CoS2 Nanoparticles Confined in Bayberry-like N-Doped Carbon Spheres as Anodes for Sodium-Ion Batteries

Obvious volume change and the dissolution of polysulfide as well as sluggish kinetics are serious issues for the development of high performance metal sulfide anodes for sodium-ion batteries (SIBs), which usually result in fast capacity fading during continuous sodiation and desodiation processes. In this work, by utilizing a Prussian blue analogue as functional precursors, small Fe-doped CoS2 nanoparticles spatially confined in N-doped carbon spheres with rich porosity were synthesized through facile successive precipitation, carbonization, and sulfurization processes, leading to the formation of bayberry-like Fe-doped CoS2/N-doped carbon spheres (Fe-CoS2/NC). By introducing a suitable amount of FeCl3 in the starting materials, the optimal Fe-CoS2/NC hybrid spheres with the designed composition and pore structure exhibited superior cycling stability (621 mA h g−1 after 400 cycles at 1 A g−1) and improved the rate capability (493 mA h g−1 at 5 A g−1). This work provides a new avenue for the rational design and synthesis of high performance metal sulfide-based anode materials toward SIBs.

LDH-derived phosphide/N-doped graphene oxide hierarchical electrocatalyst for enhanced oxygen evolution reaction

A hierarchical electrocatalyst Fe-Ni2P/N-GO was successfully synthesized via a facile method combining solvothermal and phosphorization, which shows excellent OER performance in alkaline solution.

Construction of Fe-doped CoP with hybrid nanostructures as a bifunctional catalyst for overall water splitting

Due to their open skeleton structures, adjustable active sites and homogeneous catalytic centers, PBA-based materials have promising applications in electrochemical water splitting. Herein, we report a PBA derived Fe_0.25-CoP electrocatalyst with a hybrid nanostructure, which offered a large specific surface area and active sites for the HER and OER, respectively. The as-synthesized Fe_0.25-CoP catalyst exhibits remarkable catalytic performance and durability at overpotentials of 262 mV for the OER and 111 mV for the HER, requiring a voltage of merely 1.57 V to achieve a current density of 10 mA cm^-2 for the electrocatalytic water splitting process. The preeminent activity of Fe_0.25-CoP was mainly ascribed to the framework structures of Co-PBA and appropriate doping of Fe³⁺ which regulated the electronic structures and morphology of Fe_0.25-CoP. In addition, the partial phosphating strategy retained the active centers for the OER in Co-PBA, which were further enhanced by the catalysis of Fe³⁺. In short, the rational design and regulation of catalyst structures and compositions is a promising approach for the development of highly efficient water splitting catalysts.

Co-Salen Complex-Derived CoP Nanoparticles Confined in N-Doped Carbon Microspheres for Stable Sodium Storage

The poor rate and cycle performance rooting from the inferior electrical conductivity and large volume change are bottlenecks for further application of the potential anode material in sodium-ion batteries. To address this problem, homogeneous CoP nanoparticles enwrapped in the N-doped carbon (CoP/NC) microspheres are synthesized by the simultaneous carbonization and phosphorization of Co-salen complex microspheres for the first time. The N-doped carbon enhances its conductivity and diminishes the volume stress, and the dispersed CoP nanoparticles in carbon provide more reaction sites, resulting in a superior sodium storage performance. CoP/NC microspheres exhibit the capacity of 373 mA h g^-1 at 0.1 A g^-1 after 100 cycles. Even at 2 A g^-1 for 2000 cycles, the capacity of 195 mA h g^-1 is also achieved. This work provides an excellent reference for the design and synthesis of sulfide, selenide, and other transition-metal composites. It is also beneficial to expand the application of salen complexes in the design and synthesis of catalysts and energy storage materials.

3D Carbon Networks: Design and Applications in Sodium Ion Batteries

As the key component of a new generation for low-cost energy storage systems, sodium-ion batteries (SIBs) have attracted enormous attention and research due to its promising potentiality in large-scale electrochemical energy storage. For practical application of SIBs, carbonaceous materials have been considered to be one of the best choices for electrodes in virtue of their abundant reserves, low cost, easy availability, and environmental friendliness. 3D carbon network (3D-carbon) is of particular interests, which has displayed outstanding features, including abundant active sites, interconnected multi-level pore structures, high electronic conductivity, and excellent mechanical stability. Herein, we review the structural advantages of 3D-carbon and its preparation methods, and then discuss recent progress in 3D carbon materials and their composites for SIBs. The superior functionalities of 3D-carbon are emphasized as support templates or encapsulation shell membranes. Finally, we summarize and outline the challenges and future prospects of 3D-carbon in SIBs.

Crystal Phase-Controlled Synthesis of the CoP@Co2P Heterostructure with 3D Nanowire Networks for High-Performance Li-Ion Capacitor Applications

The paramount focus in the construction of lithium-ion capacitors (LICs) is the development of anode materials with high reversible capacity and fast kinetics to overcome the mismatch of kinetics and capacity between the anode and cathode. Herein, a strategy is presented for the controllable synthesis of cobalt-based phosphides with various morphologies by adjusting the time of the phosphidation process, including 3D hierarchical needle-stacked diabolo-shaped CoP nanorods, 3D hierarchical stick-stacked diabolo-shaped Co₂P nanorods, and 3D hierarchical heterostructure CoP@Co₂P nanorods. 3D hierarchical nanostructures and a highly conductive project to accommodate volume changes are rational designs to achieve a robust construction, effective electron-ion transportation, and rapid kinetics characteristics, thus leading to excellent cycling stability and rate performance. Owing to these merits, the 3D hierarchical CoP, Co₂P, and CoP@Co₂P nanorods demonstrate prominent specific capacities of 573, 609, and 621 mA h g^-1 at 0.1 A g^-1 over 300 cycles, respectively. In addition, a high-performance CoP@Co₂P//AC LIC is successfully constructed, which can achieve high energy densities of 166.2 and 36 W h kg^-1 at power densities of 175 and 17524 W kg^-1 (83.7% capacity retention after 12000 cycles). Therefore, the controllable synthesis of various simultaneously constructed crystalline phases and morphologies can be used to fabricate other advanced energy storage devices.

A Low-Cost and High-Capacity SiO x /C@graphite Hybrid as an Advanced Anode for High-Power Lithium-Ion Batteries

Silicon suboxide (SiO _x ) is one of the most promising anodes for the next-generation high-power lithium-ion batteries because of its higher lithium storage capacity than current commercial graphite, relatively smaller volume variations than pure silicon, and appropriate working potential. However, the high cost, poor cycling stability, and rate capability hampered its industrial applications due to its complex production process, volume changes during Li⁺ insertion/extraction, and low conductivity. Herein, a low-cost and high-capacity SiO _x /C@graphite (SCG) hybrid was designed and synthesized by a facile one-pot carbonization/hydrogen reduction process of the rice husk and graphite. As an advanced anode for lithium-ion batteries, the SiO _x /C@graphite hybrid delivers a high reversible capacity with significantly enhanced cycling stability (842 mAh g^-1 after 300 cycles at 0.5 A g^-1) and rate capability (562 mAh g^-1 after 300 cycles at 1 A g^-1). The great improvement in performances could be attributed to the positive synergistic effect of SiO _x nanoparticles as lithium storage active materials, the in situ-formed carbon matrix network derived from biomass functioning as an efficient three-dimensional conductive network and spacer to improve the rate capability and buffer the volume changes, and graphite as a conductor to further improve the rate capabilities and cycling stability by increasing the conductivity. The low-cost and high-capacity SCG derived from rice husk synthesized by a facile, scalable synthetic method turns out to be a promising anode for the next-generation high-power lithium-ion batteries.