Synthesis of polyvalent ion reaction of MoS2/CoS2-RGO anode materials for high-performance sodium-ion batteries and sodium-ion capacitors

MoS2/SnS/CoS Heterostructures on Graphene: Lattice-Confinement Synthesis and Boosted Sodium Storage

The development of high-efficiency multi-component composite anode nanomaterials for sodium-ion batteries (SIBs) is critical for advancing the further practical application. Numerous multi-component nanomaterials are constructed typically via confinement strategies of surface templating or three-dimensional encapsulation. Herein, a composite of heterostructural multiple sulfides (MoS2/SnS/CoS) well-dispersed on graphene is prepared as an anode nanomaterial for SIBs, via a distinctive lattice confinement effect of a ternary CoMoSn-layered double-hydroxide (CoMoSn-LDH) precursor. Electrochemical testing demonstrates that the composite delivers a high-reversible capacity (627.6 mA h g-1 after 100 cycles at 0.1 A g-1) and high rate capacity of 304.9 mA h g-1 after 1000 cycles at 5.0 A g-1, outperforming those of the counterparts of single-, bi- and mixed sulfides. Furthermore, the enhancement is elucidated experimentally by the dominant capacitive contribution and low charge-transfer resistance. The precursor-based lattice confinement strategy could be effective for constructing uniform composites as anode nanomaterials for electrochemical energy storage.

Bonding iron chalcogenides in a hierarchical structure for high-stability sodium storage

Owing to price-boom and low-reserve of Lithium ion batteries (LIBs), cost-cutting and well-stocked sodium ion batteries (SIBs) attract a lot of attention, aiming to develop an effective energy storage and conversion equipment. As a typical anode for SIBs, Iron sulfide (FeS) is difficult to maintain the high theoretical capacity. Structural instability and inherent low conductivity limit the cyclic and rate performance of FeS. Herein, hierarchical architecture of FeS-FeSe₂ coated with nitrogen-doped carbon (NC) is obtained by single-step solvothermal method and two-stage high-temperature treatments. Specifically, lattice imperfections provided by heterogeneous interfaces increase the Na⁺ storage sites and fasten ion/electron transfer. Synergistic effect induced by the hierarchical architecture effectively enhances the electrochemical activity and reduces the resistance, which contributes to the transfer kinetics of Na⁺. In addition, the phenomenon that heterogeneous interfaces provide more active site and extra migration Na⁺ path is also proved by density functional theory (DFT). As an anode for SIBs, FeS-FeSe₂/NC (FSSe/C) delivers highly reversible capacity (704.5 mAh·g^-1 after 120 cycles at 0.2 A·g^-1), excellent rate performance (326.3 mAh·g^-1 at 12 A·g^-1) and long-lasting durability (492.3 mAh·g^-1 after 1000 cycles at 4 A·g^-1 with 100 % capacity retention). Notably, the full battery, assembled with FSSe/C and Na₃V₂(PO₄)₃/C (NVP/C), delivers reversible capacity of 252.1 mAh·g^-1 after 300 cycles at 1 A·g^-1. This work provides a facile method to construct a hierarchical architecture anode for high-performance SIBs.

Induced Bimetallic Sulfide Growth with Reduced Graphene Oxide for High-Performance Sodium Storage

Metal sulfide has been considered an ideal sodium-ion battery (SIB) anode material based on its high theoretical capacity. Nevertheless, the inevitable volume expansion during charge-discharge processes can lead to unsatisfying electrochemical properties, which limits its further large-scale application. In this contribution, laminated reduced graphene oxide (rGO) successfully induced the growth of SnCoS₄ particles and self-assembled into a nanosheet-structured SnCoS₄@rGO composite through a facile solvothermal procedure. The optimized material can provide abundant active sites and facilitate Na⁺ ion diffusion due to the synergistic interaction between bimetallic sulfides and rGO. As the anode of SIBs, this material maintains a high capacity of 696.05 mAh g^-1 at 100 mA g^-1 after 100 cycles and a high-rate capability of 427.98 mAh g^-1 even at a high current density of 10 A g^-1. Our rational design offers valuable inspiration for high-performance SIB anode materials.

Recent Advancements in Chalcogenides for Electrochemical Energy Storage Applications

Energy storage has become increasingly important as a study area in recent decades. A growing number of academics are focusing their attention on developing and researching innovative materials for use in energy storage systems to promote sustainable development goals. This is due to the finite supply of traditional energy sources, such as oil, coal, and natural gas, and escalating regional tensions. Because of these issues, sustainable renewable energy sources have been touted as an alternative to nonrenewable fuels. Deployment of renewable energy sources requires efficient and reliable energy storage devices due to their intermittent nature. High-performance electrochemical energy storage technologies with high power and energy densities are heralded to be the next-generation storage devices. Transition metal chalcogenides (TMCs) have sparked interest among electrode materials because of their intriguing electrochemical properties. Researchers have revealed a variety of modifications to improve their electrochemical performance in energy storage. However, a stronger link between the type of change and the resulting electrochemical performance is still desired. This review examines the synthesis of chalcogenides for electrochemical energy storage devices, their limitations, and the importance of the modification method, followed by a detailed discussion of several modification procedures and how they have helped to improve their electrochemical performance. We also discussed chalcogenides and their composites in batteries and supercapacitors applications. Furthermore, this review discusses the subject’s current challenges as well as potential future opportunities.

Nanohybridization of CoS2 /MoS2 Heterostructure with Polyoxometalate on Functionalized Reduced Graphene Oxide for High-Performance LIBs

To address the poor cycling stability and low rate capability of MoS₂ as electrode materials for lithium-ion batteries (LIBs), herein, the CoS₂ /MoS₂ /PDDA-rGO/PMo₁₂ nanocomposites are constructed via a simple hydrothermal process, combining the advantages of all three, namely, CoS₂ /MoS₂ heterojunction and polyoxometalates (POMs) provide abundant catalytically active sites and increase the multi-electron transfer ability, and the positively charged poly(diallyldimethylammonium chloride) modified reduced graphene oxide (PDDA-rGO) improve electronic conductivity and effectively prevent the aggregation of MoS₂ , meanwhile stabilize the negatively charged [PMo₁₂ O₄₀ ]^3- . After the electrochemical testing, the resulting CoS₂ /MoS₂ /PDDA-rGO/PMo₁₂ nanocomposite achieved 1055 mA h g^-1 initial specific capacities and stabilized at 740 mA h g^-1 after 150 cycles at 100 mA g^-1 current density. And the specific capacities of MoS₂ , MoS₂ /PDDA-rGO, CoS₂ /MoS₂ , and CoS₂ /MoS₂ /PDDA-rGO were 201, 421, 518, and 589 at 100 mA g^-1 after 150 cycles, respectively. The fact of the greatly improving capacity of MoS₂ -based nanocomposites suggests its potential for high performance electrode materials of LIBs. Moreover, the lithium storage mechanism of CoS₂ /MoS₂ /PDDA-rGO/PMo₁₂ has been discussed on the basis of cyclic voltammetry with different scan rates.

Boosting Fast Sodium Ion Storage by Synergistic Effect of Heterointerface Engineering and Nitrogen Doping Porous Carbon Nanofibers

Heterointerface engineering with multiple electroactive and inactive supporting components is considered an efficient approach to enhance electrochemical performance for sodium-ion batteries (SIBs). Nevertheless, it is still a challenge to rationally design heterointerface engineering and understand the synergistic effect reaction mechanisms. In this paper, the two-phase heterointerface engineering (Sb₂ S₃ and FeS₂ ) is well designed to incorporate into N-doped porous hollow carbon nanofibers (Sb-Fe-S@CNFs) by proper electrospinning design. The obtained Sb-Fe-S@CNFs are used as anode in SIBs to evaluate the electrochemical performance. It delivers a reversible capacity of 396 mA h g^-1 after 2000 cycles at 1 A g^-1 and exhibits an ultra-long high rate cycle life for 16 000 cycles at 10 A g^-1 . The admirable electrochemical performance is mainly attributed to the following reasons: The porous carbon nanofibers serve as an accelerator of the electrons/ions and a buffer to alleviate volume expansion upon long cyclic performance. The abundant phase boundaries of Sb₂ S₃ /FeS₂ exert low Na⁺ adsorption energy and greatly promote the charge transfer in the internal electric field calculated by first-principle density functional theory. Therefore, the as-prepared Sb-Fe-S@CNFs represents a promising candidate for an efficient anode electrode material in SIBs.

Hierarchical CoS2/MoS2 flower-like heterostructured arrays derived from polyoxometalates for efficient electrocatalytic nitrogen reduction under ambient conditions

Electrochemical nitrogen reduction reaction (NRR) has been identified as a prospective alternative for sustainable ammonia production. Developing cost-effective and highly efficient electrocatalysts is critical for NRR under ambient conditions. Herein, the hierarchical cobalt-molybdenum bimetallic sulfide (CoS₂/MoS₂) flower-like heterostructure assembled from well-aligned nanosheets has been easily fabricated through a one-step strategy. The efficient synergy between different components and the formation of heterostructure in CoS₂/MoS₂ nanosheets with abundant active sites makes the non-noble metal catalyst CoS₂/MoS₂ highly effective in NRR, with a high NH₃ yield rate (38.61 μg h^-1 mg_cat.^-1), Faradaic efficiency (34.66%), high selectivity (no formation of hydrazine) and excellent long-term stability in 1.0 mol L^-1 K₂SO₄ electrolyte (pH = 3.5) at -0.25 V versus the reversible hydrogen electrode (vs. RHE) under ambient conditions, exceeding much recently reported cobalt- and molybdenum-based materials, even catch up with some noble-metal-based catalyst. Density functional theory (DFT) calculation indicates that the formation of N₂H* species on CoS₂(200)/MoS₂(002) is the rate-determining step via both the alternating and distal pathways with the maximum ΔG values (1.35 eV). These results open up opportunities for the development of efficient non-precious bimetal-based catalysts for NRR.

Dual carbon-confined Sb2Se3 nanoparticles with pseudocapacitive properties for high-performance lithium-ion half/full batteries

Transition metal selenides have attracted enormous research attention as anodes for lithium-ion batteries (LIBs) due to their high theoretical specific capacities. Nevertheless, the low electronic conductivity and dramatic volume variation in electrochemical reaction processes result in rapid capacity fading and poor rate capability. Herein, a metal-organic framework is used as a template to in situ synthesize Sb₂Se₃ nanoparticles encapsulated in N-doped carbon nanotubes (N-CNTs) grafted on reduced graphene oxide (rGO) nanosheets. The synergistic effects of N-doped carbon nanotubes and reduced graphene oxide nanosheets are beneficial for providing good electrical conductivity and maintaining the structural stability of electrode materials, leading to stable cycling performance and superior rate performance. Kinetic analysis suggests that the electrochemical reaction kinetics is dominated by pseudocapacitive contribution. Notably, a high discharge capacity of 451.1 mA h g^-1 at a current density of 2.0 A g^-1 is delivered after 450 cycles. Even at a high current density of 10.0 A g^-1, a discharge capacity of 192.6 mA h g^-1 is maintained after 10 000 cycles. When coupled with a commercial LiFePO₄ cathode, the full batteries show an excellent discharge specific capacity of 534.5 mA h g^-1 at 0.2 A g^-1. This work provides an effective strategy for constructing high-performance anodes for Li⁺ storage.

Sulfur vacancies and morphology dependent sodium storage properties of MoS2-x and its sodiation/desodiation mechanism

Creating rich vacancies and designing distinct micro-morphology are considered as effective strategies for boosting the electrochemical performances of sodium ion battery (SIB) electrode materials. In this paper, a variety of MoS₂ nanostructures with different sulfur vacancies concentration and morphologies are successfully constructed by a hydrothermal method combined with various-temperature calcination treatment in a Ar/H₂ mixed atmosphere. Employed as a free-standing anode for SIBs, the flower-like MoS_2-x microspheres assembled by the intertwined nanosheet arrays (MoS_2-x-800) delivers highest specific capacity of 525.3 mAh g^-1 and rate capability, as well as extraordinarily stable cycle life with almost no loss of capacity after 420 cycles. The favorable sodium storage properties are mainly ascribed to the cooperated effects of superior intrinsic conductivity and richer active sites generated by sulfur vacancies, and numerous interspace achieved by the intersection of neighbouring nanosheets. Meanwhile, through ex situ analyses, the reversible charge/discharge mechanism of the obtained MoS_2-x-800 is revealed reasonably. This work not only brings new insights into the design of high-performance electrode materials for SIBs, but also makes a great step forward in the practical applications of transition metal sulfides in energy storage systems.

Electrospun hetero-CoP/FeP embedded in porous carbon nanofibers: enhanced Na+ kinetics and specific capacity

The practical application of transition metal phosphides has been hampered by the inferior rate capability and large volume change during charging and discharging processes. To address this, the construction of metal phosphide heterostructures combined with a porous carbon skeleton is a promising strategy for providing fast charge transfer kinetics. Herein, hetero-CoP/FeP nanoparticles embedded in porous carbon nanofibers (CoP/FeP@PCNFs) are obtained by coaxial electrospinning and low-temperature phosphorization processes. By employing CoP/FeP@PCNFs as the anode for sodium-ion batteries, a large reversible specific capacity (459 mA h g-1 at 0.05 A g-1), excellent rate performance (46.4% capacity retention rate at 10 A g-1 relative to 0.05 A g-1) and long-term cycling stability (208 mA h g-1 at 5 A g-1 over 1000 cycles and 73.5% capacity retention) can be obtained. By virtue of the porous structure and heterogeneous structure, the electrochemical performance of the CoP/FeP@PCNF sample was greatly improved. The porous structure can promote the ion transport and accommodate the volume expansion. Density functional theory calculation confirms that the constructed heterostructure can generate a built-in electric field and facilitate the reaction kinetics of Na+. This work provides the basic guidance for the future development of energy storage materials by designing heterostructures with a porous structure.