Sb2S3-based conversion-alloying dual mechanism anode for potassium-ion batteries

The large volume expansion and sluggish dynamic behavior are the key bottleneck to suppress the development of conversion-alloying dual mechanism anode for potassium-ion batteries (PIBs). Herein, Sb2S3 nanorods encapsulated by reduced graphene oxide and nitrogen-doped carbon (Sb2S3@rGO@NC) are constructed as anodes for PIBs. The synergistic effect of dual physical protection and robust C-Sb chemical bonding boosts superior electrochemical kinetics and great electrode stability. Thus, Sb2S3@rGO@NC exhibits a high initial charge capacity of 505.6 mAh·g-1 at 50 mA·g-1 and a great cycle stability with the lifetime over 200 cycles at 200 mA·g-1. Ex situ XRD, XPS, and TEM characterizations confirm that the electrode undergoes a multielectron transfer process (Sb2S3↔ Sb + K2S ↔ KSb + K3Sb), where K-ion insert into/extract from the material via dual mechanisms of conversion and alloying. This work sheds a light on the construction of high-performance anode materials and the understanding of K-ion storage mechanism.

Phase stability of the tin monochalcogenides SnS and SnSe: a quasi-harmonic lattice-dynamics study

The tin monochalcogenides SnS and SnSe adopt four different crystal structures, viz. orthorhombic Pnma and Cmcm and cubic rocksalt and π-cubic (P2₁3) phases, each of which has optimal properties for a range of potential applications. This rich phase space makes it challenging to identify the conditions under which the different phases are obtained. We have performed first-principles quasi-harmonic lattice-dynamics calculations to assess the relative stabilities of the four phases of SnS and SnSe. We investigate dynamical stability through the presence or absence of imaginary modes in the phonon dispersion curves, and we compute Helmholtz and Gibbs free energies to evaluate the thermodynamic stability. We also consider applied pressures up to 15 GPa to obtain simulated temperature-pressure phase diagrams. Finally, the relationships between the orthorhombic crystal phases are investigated by explicitly mapping the potential-energy surfaces along the imaginary harmonic phonon modes in the Cmcm phase, and the relationships between the cubic phases are found by transition-state modelling using the climbing-image nudged elastic-band method.

Conversion-Alloying Anode Materials for Sodium Ion Batteries

The past decade has witnessed a rapidly growing interest toward sodium ion battery (SIB) for large-scale energy storage in view of the abundance and easy accessibility of sodium resources. Key to addressing the remaining challenges and setbacks and to translate lab science into commercializable products is the development of high-performance anode materials. Anode materials featuring combined conversion and alloying mechanisms are one of the most attractive candidates, due to their high theoretical capacities and relatively low working voltages. The current understanding of sodium-storage mechanisms in conversion-alloying anode materials is presented here. The challenges faced by these materials in SIBs, and the corresponding improvement strategies, are comprehensively discussed in correlation with the resulting electrochemical behavior. Finally, with the guidance and perspectives, a roadmap toward the development of advanced conversion-alloying materials for commercializable SIBs is created.

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

High-energy sodium-ion batteries have a significant prospective application as a next-generation energy storage technology. However, this technology is severely hindered by the lack of large-scale production of battery materials. Herein, a self-standing film, assembled with SnS-Sn/multiwalled carbon nanotubes encapsulated in carbon fibers (SnS-Sn/MCNTs@CFs), is prepared using ball milling and electrospinning techniques and used as sodium-ion battery anodes. To compensate the poor internal conductivity of SnS-Sn nanoparticles, MCNTs are used to interweave SnS-Sn nanoparticles to improve the conductivity. Moreover, the designed three-dimensional carbon fiber conductive network can effectively shorten the diffusion path of electron/Na⁺, accelerate the reaction kinetics, and provide abundant active sites for sodium absorption. Benefiting from these unique features, the self-standing film offers a high reversible capacity of 568 mA h g^-1 at 0.1 A g^-1 and excellent cycling stability at 1 A g^-1 with a reversible capacity of 359.3 mA h g^-1 after 1000 cycles. In the sodium-ion full cell device, the capacity is stable at 283.7 mA h g^-1 after 100 cycles at a current of 100 mA g^-1. This work provides a new strategy for electrode design and facilitates the large-scale application of the sodium-ion battery.

Sheet-to-layer structure of SnSe2/MXene composite materials for advanced sodium ion battery anodes

The synergistic SnSe₂/MXene composite was synthesized through electrostatic assembly and exhibits a good electrochemical performance for use in a sodium-ion battery.

Sulfur-Mediated Interface Engineering Enables Fast SnS Nanosheet Anodes for Advanced Lithium/Sodium-Ion Batteries

Interface design is generally helpful to ameliorate the electrochemical properties of electrode materials but challenging as well. Herein, in situ sulfur-mediated interface engineering is developed to effectively raise the kinetics properties of the SnS nanosheet anodes, which is realized by a synchronous reduction and carbon deposition/doping process. The sulfur in the raw SnS₂ directly induces the sulfur-doped amorphous carbon layer onto the in situ reduced SnS nanosheet. In situ and ex situ electrochemical characterizations suggest that the sulfur-mediated interface layer can enhance the reversibility and kinetics properties, promote the ion/electron swift delivery, and maintain the configurational wholeness of the SnS nanosheet anodes. Consequently, a relatively high Li-storage capacity of 922 mAh g^-1 and Na-storage capacity of 349 mAh g^-1 at 1.0 A g^-1 even after 1000 and 300 long-term cycles are achieved, respectively. The facile method and excellent performance suggest the effective interface tuning for developing the SnS-based anodes for batteries and beyond.

Synthetic method, growth mechanism and electrochemical properties of PbSnS2 nanosheets for supercapacitors

Facile hydrothermally synthesized PbSnS₂ nanosheets with various morphologies were developed to obtain high performance electrode materials for supercapacitors. A precipitation-dissolution mechanism was proposed to demonstrate the growth process of PbSnS₂. The as-prepared nanosheets exhibited superior capacitance (678.8 F g^-1 at 50 mV s^-1) and a long cycle life (95.5% capacitance retention after 100 000 cycles at 5 A g^-1).

Ultrasmall SnS Quantum Dots Anchored onto Nitrogen-Enriched Carbon Nanospheres as an Advanced Anode Material for Sodium-Ion Batteries

Structural pulverization of metal chalcogenides such as Sn-based compounds is a serious issue for development of high-performance anode materials and results in serious capacity fading during continuous charge and discharge cycles. In this work, we synthesize ultrasmall SnS quantum dots (QDs) anchored onto nitrogen-enriched carbon (NC) nanospheres through facile hydrothermal and carbonization processes to prepare a progressive anode material for sodium-ion batteries. The optimized SnS QDs@NC electrode delivered an initial discharge capacity of 281 mAh g^-1 at 100 mA g^-1 and exhibited excellent cycling stability with a capacity retention of 75% after 500 cycles at a high current density of 1000 mA g^-1. Ex situ XRD, XPS, FE-SEM, TEM measurements, and kinetics study were performed to unveil the sodium storage mechanism of the SnS QDs@NC electrode. A sodium-ion full cell assembled with an SnS QDs@NC anode and a Na₃V₂(PO₄)₃ cathode exhibited high capacity and good cycling stability. Such a superior electrochemical performance of SnS QDs@NC can be attributed to the synergistic effects of NC and SnS QDs where NC serves as a conducting matrix to support SnS QDs and helps avoid structural degradation. This work provides a promising strategy to resolve the pulverization issue of alloying and conversion-type anode materials.

Copper sulfide nanostructures and their sodium storage properties

Hexagonal CuS nanosheets and microspheres composed of numerous flakes were successfully prepared by sonochemical and solvothermal methods, respectively.