Self-Standing Film Assembled using SnS-Sn/Multiwalled Carbon Nanotubes Encapsulated Carbon Fibers: A Potential Large-Scale Production Material for Ultra-stable Sodium-Ion Battery Anodes

Novel Electrospun Sn-Based Composite Cathodes Exhibiting Extended Cycle Life for Hybrid Magnesium-Lithium Batteries

In this study, we present a strategic approach for the structural design and composite modification of one-dimensional Sn-based nanocomposites to enhance the overall electrochemical performance of hybrid magnesium-lithium batteries (MLIBs), which are emerging as promising successors to lithium-ion batteries. By using electrospinning technology, we successfully synthesized NST-SnO2, NST-SnO2-NiO, Sn-CNF, and Ni3Sn2-CNF composite cathodes, as well as analyzed the synthesis mechanism of the four Sn-based cathodes. The 100-cycle testing at a current density of 500 mA·g-1 revealed that NST-SnO2 maintained a discharge specific capacity of 129.8 mA h·g-1 with a retention rate of 90.76%, while NST-SnO2-NiO achieved a higher capacity of 147.4 mA h·g-1 and an 88.05% retention rate. Notably, Sn-CNF and Ni3Sn2-CNF exhibited initial discharge capacities of 66.7 and 79.6 mA h·g-1, respectively, coupled with exceptional cycle stability, evidenced by retention rates of 104.19 and 102.38%. The remarkable cycling stability observed in these novel cathodes is attributed to their robust structural integrity, thus demonstrating the potential for an extended cycle life in MLIBs. This work provides significant advancement in the development of high-performance electrode materials for next-generation hybrid magnesium-lithium energy storage systems.

An Ultra-Flexible Sodium-Ion Full Cell with High Energy/Power Density and Unprecedented Structural Stability

Futuristic wearable electronics desperately need power sources with similar flexibility and durability. In this regard, the authors, therefore, propose a scalable PAN-PMMA blend-derived electrospinning protocol to fabricate free-standing electrodes comprised of cobalt hexacyanoferrate nanocube cathode and tin metal organic framework-derived nanosphere anode, respectively, for flexible sodium-ion batteries. The resulting unique inter-networked nanofiber mesh offers several advantages such as robust structural stability towards repeated bending and twisting stresses along with appreciable electronic/ionic conductivity retention without any additional post-synthesis processing. The fabricated flexible sodium ion full cells deliver a high working voltage of 3.0 V, an energy density of 273 Wh·kg-1 , and a power density of 2.36 kW·kg-1 . The full cells retain up to 86.73% of the initial capacity after 1000 cycles at a 1.0 C rate. After intensive flexibility tests, the full cells also retain 78.26% and 90.78% of the initial capacity after 1000 bending and twisting cycles (5 mm radius bending and 40o axial twisting), respectively. This work proves that the proposed approach can also be employed to construct similar robust, free-standing nanofiber mesh-based electrodes for mass-producible, ultra-flexible, and durable sodium ion full cells with commercial viability.

Flexible, recoverable, and efficient photocatalysts: MoS2/TiO2 heterojunctions grown on amorphous carbon-coated carbon textiles

Most traditional powder photocatalysts are not easily recovered. Herein, we report a flexible and recoverable photocatalyst with superior photocatalytic activity, in which MoS2/TiO2 heterojunctions are grown on amorphous carbon-coated carbon textiles (CT@C-MoS2/TiO2). Recoverable CT@C-MoS2/TiO2 textile was used to degrade 10 mg L-1 rhodamine B, leading to a degradation rate of up to 98.8 % within 30 min. Such a degradation rate is much higher than that of most of the reported studies. A density functional theory (DFT) calculation results illustrate charge transfer mechanism inside TiO2-C, MoS2-C, and MoS2/TiO2 heterojunctions, which shows that CT@C-MoS2/TiO2 textile with three electron separation channels has a high photogenerated carrier separation rate, which remarkably enhances the photocatalytic activity. Our work provides a novel strategy to design an efficient and recoverable photocatalyst with high activity.

Hybridization of Layered Titanium Oxides and Covalent Organic Nanosheets into Hollow Spheres for High-Performance Sodium-Ion Batteries with Boosted Electrical/Ionic Conductivity and Ultralong Cycle Life

While development of a sodium-ion battery (SIB) cathode has been approached by various routes, research on compatible anodes for advanced SIB systems has not been sufficiently addressed. The anode materials based on titanium oxide typically show low electrical performances in SIB systems primarily due to their low electrical/ionic conductivity. Thus, in this work, layered titanium oxides were hybridized with covalent organic nanosheets (CONs), which exhibited excellent electrical conductivity, to be used as anodes in SIBs. Moreover, to enlarge the accessible areas for sodium ions, the morphology of the hybrid was formulated in the form of a hollow sphere (HS), leading to the highly enhanced ionic conductivity. This synthesis method was based on the expectation of synergetic effects since titanium oxide provides direct electrostatic sodiation sites that shield organic components and CON supports high electrical and ionic conductivity with polarizable sodiation sites. Therefore, the hybrid shows enhanced and stable electrochemical performances as an anode for up to 2600 charge/discharge cycles compared to the HS without CONs. Furthermore, the best reversible capacities obtained from the hybrid were 426.2 and 108.5 mAh/g at current densities of 100 and 6000 mA/g, which are noteworthy results for the TiO₂-based material.

Flat-Zigzag Interface Design of Chalcogenide Heterostructure toward Ultralow Volume Expansion for High-Performance Potassium Storage

Heterostructure construction of layered metal chalcogenides can boost their alkali-metal storage performance, where the charge transfer kinetics can be promoted by the built-in electric fields. However, these heterostructures usually undergo interface separation due to severe layer expansion, especially for large-size potassium accommodation, resulting in the deconstruction of heterostructures and battery performance fading. Herein, first a stable interface design strategy where two metal chalcogenides with totally different layer-morphologies are stacked to form large K⁺ transport channels, rendering ultralow interlayer expansion, is presented. As a proof of concept, the flat-zigzag MoS₂ /Bi₂ S₃ heterostructures stacked with zigzag-morphology Bi₂ S₃ and flat-morphology MoS₂ present an ultralow expansion ratio (1.98%) versus MoS₂ (9.66%) and Bi₂ S₃ (9.61%), which deliver an ultrahigh potassium storage capacity of above 600 mAh g^-1 and capacity retention of 76% after 500 cycles, together with the built-in electric field of heterostructures. Once the heterostructures are used as an anode for potassium-based dual-ion batteries (K-DIBs), it achieves a superior full-cell capacity of ≈166 mAh g^-1 with a capacity retention of 71% after 400 cycles, which is an outstanding performance among the reported K-DIBs. This proposed interface stacking strategy may offer a new way toward stable heterostructure design for metal ions storage and transport applications.

Dual Regulation of Metal Doping and Adjusting Cut-Off Voltage for MoSe2 to Achieve Reversible Sodium Storage

MoSe₂ , as a typical 2D material, possesses tremendous potential in Na-ion batteries (SIBs) owing to larger interlayer distance, more favorable band gap structure, and higher theoretical specific capacity than other analogs. Nevertheless, the low intrinsic electronic conductivity and irreversible conversion of discharged products of Mo/Na₂ Se to MoSe₂  seriously hamper its electrochemical performance. Herein, through a facile hydrothermal method combined with calcination process, Sn-doped MoSe₂  nanosheets grown on graphene substrate in the vertical direction are fabricated. Benefiting from the improved electronic conductivity contributed by the abundant defects and expanded interlamellar spacing of MoSe₂  originated from Sn doping, combined with a smart strategy of raising discharge cut-off voltage to 0.2 V during the actual performance testing for SIBs, the as-fabricated anode material delivers superior Na-ions storage performance in terms of electrons/ions transfer, reversible sodium storage as well as cycle stability. An ultra-stable reversible specific capacity of 268.5 mAh g^-1 at 1 A g^-1 can be maintained after 1600 cycles. Moreover, the great sodium storage property in the SIB full-cell system of the as-obtained nanocomposite illustrates practical potential. Density functional theory calculation and in situ/ex situ measurements are employed to further reveal the storage mechanism and process of Na-ions.

Nano and Battery Anode: A Review

Improving the anode properties, including increasing its capacity, is one of the basic necessities to improve battery performance. In this paper, high-capacity anodes with alloy performance are introduced, then the problem of fragmentation of these anodes and its effect during the cyclic life is stated. Then, the effect of reducing the size to the nanoscale in solving the problem of fragmentation and improving the properties is discussed, and finally the various forms of nanomaterials are examined. In this paper, electrode reduction in the anode, which is a nanoscale phenomenon, is described. The negative effects of this phenomenon on alloy anodes are expressed and how to eliminate these negative effects by preparing suitable nanostructures will be discussed. Also, the anodes of the titanium oxide family are introduced and the effects of Nano on the performance improvement of these anodes are expressed, and finally, the quasi-capacitive behavior, which is specific to Nano, will be introduced. Finally, the third type of anodes, exchange anodes, is introduced and their function is expressed. The effect of Nano on the reversibility of these anodes is mentioned. The advantages of nanotechnology for these electrodes are described. In this paper, it is found that nanotechnology, in addition to the common effects such as reducing the penetration distance and modulating the stress, also creates other interesting effects in this type of anode, such as capacitive quasi-capacitance, changing storage mechanism and lower volume change.