Construction of CoP@C embedded into N/S-co-doped porous carbon sheets for superior lithium and sodium storage

Construction of N-doped carbon encapsulated CoP hollow nanofibers as multifunctional electrode materials for potassium-ion and lithium-sulfur batteries

Herein, a composite of N-doped carbon coated phosphating cobalt hollow nanofibers (N/C@CoP-HNFs) was synthesized by electrospinning, phosphating, and carbon coating processes. When employed as multifunctional electrode materials for potassium-ion batteries (PIBs) and lithium-sulfur (Li-S) batteries, the N/C@CoP-HNFs demonstrated notable electrochemical properties. Specifically, it delivered an initial specific capacity of 420.4 mA h g-1 at a current density of 100 mA g-1, with a sustained capacity of 190.8 mA h g-1 after 200 cycles in PIBs, and a specific capacity of 1448 mA h g-1 at a current density of 0.5C in Li-S batteries, which is considered relatively high for these types of battery technology. This good performance may due to the combination of the carbon nitrogen layer and cobalt phosphide bilayer hollow tube structure, which is conducive to telescoping the diffusion length of ions and electrons and buffer volume variation, and effectively inhibits the shuttle effect. Density functional theory (DFT) calculations were also used to explore the energy storage mechanism of the material. The possible adsorption sites and corresponding adsorption energy of K+ were analyzed, and the advantages of the material were explored by calculating the diffusion barrier and state density. The theoretical simulations further validated the strong adsorption capability of CoP for polysulfides. This work is expected to provide new ideas for new energy storage materials.

Oxygen vacancies synergistic cobalt phosphide electron bridge modulated bismuth oxychloride/carbon nitride Z-scheme junction for efficient carbon dioxide reduction coupled with tetracycline oxidation

Although great progress has been made with respect to electron bridges, the electron mobility of the state-of-the-art electron bridges is far from satisfactory because of weak electrical conductivity. To overcome the above issue, cobalt phosphide (CoP), as a model electron bridge, was modified by superficial oxygen vacancies (OVs) and embedded into a defective bismuth oxychloride/carbon nitride (BiO1-xCl/g-C3N4) Z-scheme heterojunction to obtain atomic-level insights into the effect of surface OVs on CoP electron bridges. Compared to BiO1-xCl/g-C3N4 and bismuth oxychloride/cobalt phosphide/carbon nitride (BiOCl/CoP/g-C3N4) composites, the defective bismuth oxychloride/cobalt phosphide/carbon nitride (BiO1-xCl/CoP/g-C3N4) heterojunction exhibited remarkable photocatalytic redox performance, indicating that the surface OVs-assisted CoP electron bridge effectively boosted electrical conductivity and yielded ultrafast electron transfer rates. The theoretical and experimental results demonstrate that the surface OVs play a critical role in improving the electrical conductivity of the CoP electron bridge, thereby accelerating electron mobility. This research provides insights into interfacial OVs-modified transition metal phosphide (TMP) electron bridges and their potential application in heterojunctions for energy crisis mitigation and environmental remediation.

Spaced-Confined Janus Engineering Enables Controlled Ion Transport Channels and Accelerated Kinetics for Secondary Ion Batteries

The large grain boundary resistance between different components of the anode electrode easily leads to the low ion transport efficiency and poor electrochemical performance of lithium-/sodium-ion batteries (LIBs/SIBs). To address the issue, a Janus heterointerface with a Mott-Schottky structure is proposed to optimize the interface atomic structure, weaken interatomic resistance, and improve ion transport kinetics. Herein, Janus Co/Co2P@carbon-nanotubes@core-shell (Janus Co/Co2P@CNT-CS) refined urchin-like architecture derived from metal-organic frameworks is reported via a coating-phosphating process, where the Janus Co/Co2P heterointerface nanoparticles are confined in carbon nanotubes and a core-shell polyhedron. Such a Janus Co/Co2P heterointerface shows the strong built-in electric field, facilitating the controllable ion transport channels and the high ion transport efficiency. The Janus Co/Co2P@CNT-CS refined urchin-like architecture composed of a core-shell structure and the grafting carbon nanotubes enhances the structure stability and electronic conductivity. Benefiting from the spaced-confined Janus heterointerface engineering and synergistic effects between the core-shell structure and the grafting carbon nanotubes, the Janus Co/Co2P@CNT-CS refined urchin-like architecture demonstrates the fast ion transport rate and excellent pseudocapacitance performance for LIBs/SIBs. In this case, the Janus Co/Co2P@CNT-CS refined urchin-like architecture shows high specific capacities of 709 mA h g-1 (200 cycles) and 203 mA h g-1 (300 cycles) at a current density of 500 mA g-1 for LIBs/SIBs, respectively.

Full Potential Catalysis of Co0.4Ni1.6P-V/CNT with Phosphorus Vacancies for Li2S1-2 Deposition/Decomposition and S8/Li2Sn (3 ≤ n ≤ 8) Conversion in Li-S Batteries

The slow kinetics of polysulfide conversions hinders the commercial progress of Li-S batteries. The introduction of high-efficiency catalysts accelerates heterogeneous reactions and enhances the utilization of S. The full potential of the Co0.4Ni1.6P-V/CNT-modified separator catalyzes the all-process reactions of the S electrode and increases the rates and cycling lives of the batteries. The two-site synergistic effect of Co0.4Ni1.6P-V/CNT regulates the catalytic activity, and the phosphorus vacancies enrich the active sites. The higher electron density at the Co and Ni double sites increases chemisorption of the Co0.4Ni1.6P-V/CNT on Li2Sn (1 ≤ n ≤ 4), stretches and breaks the Li-S and Ni-S bonds during Li2S decomposition, and reduces the energy barrier for Li2S decomposition. The cyclic voltammograms of the asymmetric batteries demonstrated that Co0.4Ni1.6P-V/CNT also catalyzed the Li2Sn ⇌ S8 (3 ≤ n ≤ 8) reaction, realizing the full catalytic potential of the Li-S batteries. Increased Li+ diffusion/migration in the Co0.4Ni1.6P-V/CNT-modified separator ensured fast electrochemical reactions. The excellent catalytic effect of Co0.4Ni1.6P-V/CNT provided smaller polarization and superior rate performance, which led to high discharge specific capacities of 1511.9, 1172.6, 1006.0, 881.0, and 785.7 mA h g-1 at current densities of 0.1, 0.2, 0.5, 1, and 2 mA cm-2 with sulfur loadings of 7.98 mg cm-2, respectively. This approach involving simple crystal modulation and introduction of defects provides a new way to achieve the full catalytic potential of Li-S batteries.

Surface engineered hollow Ni-Co-P@TiO2-x nanopolyhedrons as high performance anode material for sodium storage

With the proposal of carbon peaking and carbon neutrality goals, clean energy storage is attracting more and more attentions. In view of the lack of lithium resource in our earth, sodium-ion batteries are considered as the emerging and promising next-generation energy storage devices. Appropriate high-performance anode materials play a vital role in the development of sodium-ion batteries. Here, a core-shell hollow Ni-Co-P nanopolyhedron interconnected by oxygen defect TiO₂ (Ni-Co-P@TiO_2-x) is reported, which is synthesized by ion etching-hydrolysis and subsequent phosphatization/hydrogenation treatment using ZIF-67 as template and hybrid carbon source. The achieved Ni-Co-P@TiO_2-x material has several distinct advantages including hollow core-shell structure, flexible conductive carbon matrix, stable electroactive coating layer, and efficient pseudocapacitive behavior, resulting in high reversible capacities, remarkable rate capability and excellent cycle stability. The synergetic battery-capacitor characteristic of Ni-Co-P@TiO_2-x material makes it become a promising anode for sodium-ion batteries.

In-situ synthesis of FeS/N, S co-doped carbon composite with electrolyte-electrode synergy for rapid sodium storage

Pyrrhotite (FeS) is extensively investigated as the anode for low-cost sodium-ion batteries (SIBs) due to their natural abundance and high theoretical capacity. However, it suffers from significant volume expansion and poor conductivity. These problems can be alleviated by promoting sodium-ion transport and introducing carbonaceous materials. Here, FeS decorated on N, S co-doped carbon (FeS/NC) is constructed through a facile and scalable strategy, which is the best of both worlds. Moreover, to give full play to the role of the optimized electrode, ether-based and ester-based electrolytes are used for matching. Reassuringly, the FeS/NC composite displays a reversible specific capacity of 387 mAh g^-1 after 1000 cycles at 5A g^-1 in dimethyl ether electrolyte. The even distribution of FeS nanoparticles on the ordered framework of carbon guarantees a fast electron/Na-ion transport channel, and the reaction kinetics can be further accelerated in the dimethyl ether (DME) electrolyte, ensuring the excellent rate capability and cycling performance of FeS/NC electrodes for sodium-ion storage. This finding not only provides a reference for the introduction of carbon via in-situ growth protocol, but also demonstrates the necessity for electrolyte-electrode synergy in realizing efficient sodium-ion storage.

Rational construction of yolk-shell CoP/N,P co-doped mesoporous carbon nanowires as anodes for ultralong cycle life sodium-ion batteries

Owing to the natural abundance and low-cost of sodium, sodium-ion batteries offer advantages for next-generation portable electronic devices and smart grids. However, the development of anode materials with long cycle life and high reversible capacity is still a great challenge. Herein, we report a yolk–shell structure composed of N,P co-doped carbon as the shell and CoP nanowires as the yolk (YS–CoP@NPC) for a hierarchically nanoarchitectured anode for improved sodium storage performance. Benefitting from the 1D hollow structure, the YS–CoP@NPC electrode exhibits an excellent cycling stability with a reversibly capacity of 211.5 mA h g⁻¹ at 2 A g⁻¹ after 1000 cycles for sodium storage. In-depth characterization by ex situ X-ray photoelectron spectroscopy and work function analysis revealed that the enhanced sodium storage property of YS–CoP@NPC might be attributed to the stable solid electrolyte interphase film, high electronic conductivity and better Na⁺ diffusion kinetics.

Owing to the natural abundance and low-cost of sodium, sodium-ion batteries offer advantages for next-generation portable electronic devices and smart grids.

Ion/Electron Redistributed 3D Flexible Host for Achieving Highly Reversible Li Metal Batteries

3D carbon frameworks are promising hosts to achieve highly reversible lithium (Li) metal anodes, whereas insufficient effects are attributed to their single electron conductivity causing local aggregating of electron/Li⁺ and uncontrollable Li dendrites. Herein, an ion/electron redistributed 3D flexible host is designed by lithiophilic carbon fiber cloth (CFC) modified with metal-organic framework (MOF)-derived porous carbon sheath with embedded CoP nanoparticles (CoP-C@CFC). Theory calculations demonstrate the strong binding energy and plenty of charge transfer from the reaction between CoP and Li atom are presented, which is beneficial to in situ construct a Li₃ P@Co ion/electron conductive interface on every single CoP-C@CFC. Thanks to the high ionic conductive Li₃ P and electron-conductive Co nanoparticles, the rapid dispersion of Li⁺ and obviously reduced local current density can be achieved simultaneously. Furthermore, in situ optical microscopy observations display obvious depression for volume expansion and Li dendrites. As expected, a miraculous average Coulombic efficiency (CE) of 99.96% over 1100 cycles at 3 mA cm^-2 and a low overpotential of 11.5 mV with prolonged cycling of over 3200 h at 20% depth of discharge are successfully obtained. Consequently, the CoP-C@CFC-Li||LiFePO₄ full cells maintain a capacity retention of 95.8% with high CE of 99.96% over 500 cycles at 2 C and excellent rate capability.

In Situ Fabrication of Porous Cox P Hierarchical Nanostructures on Carbon Fiber Cloth with Exceptional Performance for Sodium Storage

Superior high-rate performance and ultralong cycling life have been constantly pursued for rechargeable sodium-ion batteries (SIBs). In this work, a facile strategy is employed to successfully synthesize porous Co_x P hierarchical nanostructures supported on a flexible carbon fiber cloth (Co_x P@CFC), constructing a robust architecture of ordered nanoarrays. Via such a unique design, porous and bare structures can thoroughly expose the electroactive surfaces to the electrolyte, which is favorable for ultrafast sodium-ion storage. In addition, the CFC provides an interconnected 3D conductive network to ensure firm electrical connection of the electrode materials. Besides the inherent flexibility of the CFC, the integration of the hierarchical structures of Co_x P with the CFC, as well as the strong synergistic effect between them, effectively help to buffer the mechanical stress caused by repeated sodiation/desodiation, thereby guaranteeing the structural integrity of the overall electrode. Consequently, Co_x P@CFC as an anode shows a record-high capacity of 279 mAh g^-1 at 5.0 A g^-1 with almost no capacity attenuation after 9000 cycles.

Rationally integrated nickel sulfides for lithium storage: S/N co-doped carbon encapsulated NiS/Cu2S with greatly enhanced kinetic property and structural stability

Nickel sulfides are promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities but suffer from the sluggish kinetic process and poor structural stability. Herein, we develop...

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.

Facile synthesis of a rod-like porous carbon framework confined magnetite nanoparticle composite for superior lithium-ion storage

This work demonstrates a streamlined method to engineer a rod-like porous carbon framework (RPC) confined magnetite nanoparticles composite (Fe₃O₄/RPC) starting from metallic iron and gallic acid (GA) solution. First, a mild redox reaction was triggered between Fe and GA to prepare a rod-shaped metal-organic framework (MOF) ferric gallate sample (Fe-GA). Then, the Fe-GA sample was calcinated to obtain a prototypic RPC supported metal iron nanoparticle intermediate sample (Fe/RPC). Finally, the Fe₃O₄/RPC composite was synthesized after a simple hydrothermal reaction. The Fe₃O₄/RPC composite exhibited competitive electrochemical behaviors, which has a high gravimetric capacity of 1140 mAh·g^-1 at a high charge and discharge current of 1000 mA·g^-1 after 300 cycles. The engineered RPC supportive matrix not only offers adequate voids to buffer the volume expansion from inside well-dispersed Fe₃O₄ nanoparticles, but also facilitates both the ionic and electronic transport during the electrochemical reactions. The overall material synthesis involves of no hazardous or expensive chemicals, which can be regarded to be a scalable and green approach. The obtained samples have a good potential to be further developed for wider applications.