Dual-buffered SnSe@CNFs as negative electrode with outstanding lithium storage performance

Optimized crystal orientation for enhanced reaction kinetics and reversibility of SnSe/NC hollow nanospheres towards high-rate and long-term lithium/sodium storage

The development of anode materials with high theoretical capacity and cycling stability is very important for the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, SnSe/NC hollow nanospheres with different crystal orientations were prepared by regulating the high-temperature selenization of the PDA@SnO2 precursor for lithium/sodium storage. In SnSe/NC hollow nanospheres, the physical buffering and chemical bonding of the nitrogen carbon matrix and SnSe nanoparticles could inhibit volume expansion and polyselenide loss, thus maintaining long-term structural stability. More importantly, electrochemical tests and DFT calculations show that the diffusion energy barrier of Li+/Na+ is significantly reduced at the SnSe (400) rather than the usual (111) facet, which is conducive to the uniformity of ion insertion into SnSe, thus effectively enhancing the reaction kinetics and reversibility of lithium/sodium storage. Therefore, SnSe/NC hollow nanospheres with rich SnSe (400) and good dispersion formed at 550 °C delivered the best reversible specific capacity and rate performance. After a long period of 900 cycles, the capacity retention of lithium/sodium ion batteries is close to 84.88% and 77.05%, respectively. Our findings provide valuable insights into the design of metal selenides for advanced LIBs/SIBs.

Recent Advancements in Selenium-Based Cathode Materials for Lithium Batteries: A Mini-Review

Selenium (Se)-based cathode materials have garnered considerable interest for lithium-ion batteries due to their numerous advantages, including low cost, high volumetric capacity (3268 mAh cm−3), high density (4.82 g cm−3), ability to be cycled to high voltage (4.2 V) without failure, and environmental friendliness. However, they have low electrical conductivity, low coulombic efficiency, and polyselenide solubility in electrolytes (shuttle effect). These factors have an adverse effect on the electrochemical performance of Li-Se batteries, rendering them unsuitable for real-world use. In this study, we briefly examined numerous approaches to overcoming these obstacles, including selecting an adequate electrolyte, the composition of Se with carbonaceous materials, and the usage of metal selenide base electrodes. Furthermore, we examined the effect of introducing interlayers between the cathode and the separator. Finally, the remaining hurdles and potential study prospects in this expanding field are proposed to inspire further insightful work.

Fabrication of MnSe/SnSe@C heterostructures for high-performance Li/Na storage

Novel heterostructured MnSe/SnSe@C nanoboxes display excellent electrochemical performance.

Dimethyltin(IV)-4,6-dimethyl-2-pyridylselenolate: an efficient single source precursor for the preparation of SnSe nanosheets as anode material for lithium ion batteries

The air stable tin(IV) complex [Me₂Sn{2-SeC₅H₂(Me-4,6)₂N}₂] has been synthesized, characterized by NMR, elemental analysis, and single crystal XRD, and employed as a single source molecular precursor (SSP) for the facile synthesis of orthorhombic SnSe nanosheets. The crystal structure, phase purity, morphology and band gap of the nanosheets were investigated by pXRD, EDS, electron microscopy and diffuse reflectance spectroscopy techniques, respectively. It was found that the preferential orientation of planes and the morphology of the nanosheets rely upon the reaction conditions. The band gaps of the nanosheets were blue shifted with respect to the bulk band gap of the material. The synthesized SnSe nanosheets have been employed as an anode material in lithium ion batteries (LIBs). The material exhibits an initial specific capacity of 1134 mA h g^-1 at a current density of 50 mA g^-1 and was found to retain a capacity of 380 mA h g^-1 even after 70 cycles with 100% efficiency.

Solution-Synthesized SnSe1-xSx: Dual-Functional Materials with Enhanced Electrochemical Storage and Thermoelectric Performance

The exploration of materials with multifunctional properties, such as energy harvesting and storage, is crucial in integrated energy devices and technologies. Herein, through an organic-free "soft chemical" solution method, a series of dual-functional SnSe_1-xS_x (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanoparticles have been developed toward high-performance electrochemical energy storage and thermoelectric conversion. Among the synthesized S-substituted SnSe, SnSe_0.5S_0.5 exhibits the highest rate capacity (546.1 mA h g^-1 at 2 A g^-1) and the best reversible capacity (556.2 mA h g^-1 at 0.1 A g^-1 after 100 cycles), which are much enhanced compared to those of SnSe. Density functional theory calculation confirms that the composition regulation by S substitution can lower the diffusion barrier of Li⁺, boost the diffusion rate of Li⁺, and in turn enhance the electrochemical kinetics, thus increasing the Li⁺ storage performance. Meanwhile, partially replacing Se by S decreases the lattice thermal conductivity, leading to an improved peak zT of 0.64 at 773 K in SnSe_0.9S_0.1, which is enhanced compared to the value for SnSe obtained at the same temperature. This study develops a combined composition tuning-nanostructuring approach for optimizing the electrochemical and thermoelectric performance of dual-functional SnSe.

One-Pot Synthesis of High-Performance Tin Chalcogenides/C Anodes for Li-Ion Batteries

Tin chalcogenides are considered as promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical lithium-storage capacity. Herein, we have successfully synthesized the composites of tin chalcogenides and graphite, that is, SnS/C, SnSe/C, and SnS_0.5Se_0.5/C, via a simple one-pot solid-state method. During the electrochemical test, they exhibit excellent lithium-storage ability and cyclic performance as the anode electrodes of LIBs due to the introduction of carbon. In particular, (i) SnS/C displayed a high specific capacity of 875 mAh g^-1 at 0.2 A g^-1 over 200 cycles; (ii) SnSe/C presents 734 mAh g^-1 at 0.2 A g^-1 after 100 cycles, and it delivers 690 mAh g^-1 at 1.0 A g^-1 over 300 cycles; and (iii) the SnS_0.5Se_0.5/C composite electrode delivers a specific capacity of 643 mAh g^-1 at 0.5 A g^-1 over 150 cycles. Furthermore, another series of tin-based composites have also been successfully fabricated (i.e., Sn/C, SnS₂/C, SnSe₂/C, and SnTe/C), showing the general applicability of the synthetic route applied here. Our synthetic approach demonstrates a promising route for the large-scale production of high-performance tin chalcogenides/C anode materials for LIBs and other battery systems (e.g., Na-ion and K-ion batteries).

Level the Conversion/Alloying Voltage Gap by Grafting the Endogenetic Sb2Te3 Building Block into Layered GeTe to Build Ge2Sb2Te5 for Li-Ion Batteries

Many research efforts for advanced Li-ion batteries have been made to design new material with large capacity and long cycle life, but little attention has been paid to regulate the voltage platform until now. Although quite attractive for the binary Ge-based chalcogenides, challenge is that a large potential gap as well as incongruous reaction kinetics is typically found between their conversion step (>1.6 V) and alloying region (<0.4 V). Herein, we propose an endogenetic structural design by grafting Sb₂Te₃ building block into layered GeTe to establish a ternary Ge₂Sb₂Te₅ compound, which can effectively level such a big potential gap. Turning from semiconductive GeTe into metallic conductive Ge₂Sb₂Te₅, the reaction kinetics can be enhanced. The Li_xTe formation step in Ge₂Sb₂Te₅ is found declined to 1.30 V, and the enlistment of Sb (∼0.78 V) bridges the conversion and alloying plateau; thus, the incongruous reaction kinetics and large potential gap between the conversion-alloying step can be alleviated. Furthermore, there is a spatially confined and synergistic effect among Te, Sb, and Ge components, conducting the Li_xTe and Li_xGe processes in a more harmonious and gentle way. Therefore, Ge₂Sb₂Te₅ exhibites much enhanced cyclability and rate performance, with 546 mAh/g remained at 2000 mA/g. This unique design strategy can be leveraged to manipulate the voltage profile of other compounds.

Sn-C and Se-C Co-Bonding SnSe/Few-Layered Graphene Micro-Nano Structure: Route to a Densely Compacted and Durable Anode for Lithium/Sodium-Ion Batteries

Developing anodes with a high and stable energy density for both gravimetric and volumetric storage is vital for high-performance lithium/sodium-ion batteries. Herein, an SnSe/few-layered graphene (FLG) composite with a high tap density (2.3 g cm^-3) is synthesized via the plasma-milling method, in which SnSe nanoparticles are strongly bound with the FLG matrix, owing to both Sn-C and Se-C bonds, to form nanosized primary particles and then assemble to microsized secondary granules. The FLG can effectively alleviate the large stress generated from the volume expansion of SnSe during cycling based on its superstrength. Furthermore, as demonstrated by the density-functional theory calculations, the Sn-C and Se-C co-bonding benefitting from the formation of substantial vacancy defects on the P-milling-synthesized FLG enables strong affinity between SnSe nanoparticles and the FLG matrix, preventing SnSe from aggregating and detaching even after long-term cycling. As an anode for lithium-ion batteries, it exhibits high gravimetric and volumetric capacities (864.8 mAh g^-1 and 1990 mAh cm^-3 at 0.2 A g^-1), a high rate (612.6 mAh g^-1 even at 5.0 A g^-1), and the longest life among the reported SnSe-based anodes (capacity retention of 92.8% after 2000 cycles at 1.0 A g^-1). Subsequently, an impressive cyclic life (capacity retention of 91.6% after 1000 cycles at 1.0 A g^-1) is also achieved for sodium-ion batteries. Therefore, the SnSe/FLG composite is a promising anode for high-performance lithium/sodium-ion batteries.

Synthesis and Electrochemical Performance of ZnSe Electrospinning Nanofibers as an Anode Material for Lithium Ion and Sodium Ion Batteries

ZnSe nitrogen-doped carbon composite nanofibers (ZnSe@N-CNFs) were derived as anode materials from selenization of electrospinning nanofibers. Electron microscopy shows that ZnSe nanoparticles are distributed in electrospinning nanofibers after selenization. Electrochemistry tests were carried out and the results show the one-dimensional carbon composite nanofibers reveal a great structural stability and electrochemistry performance by the enhanced synergistic effect with ZnSe. Even at a current density of 2 A g-1, the as-prepared electrodes can still reach up to 701.7 mA h g-1 after 600 cycles in lithium-ion batteries and 368.9 mA h g-1 after 200 cycles in sodium-ion batteries, respectively. ZnSe@N-CNFs with long cycle life and high capacity at high current density implies its promising future for the next generation application of energy storage.

Yolk–shell structured SnSe as a high-performance anode for Na-ion batteries

Yolk–shell structured SnSe nanoparticles have been investigated as anode materials in Na-ion batteries for the first time, and exhibit excellent Na⁺ storage performance.

Morphology Processing by Encapsulating GeP5 Nanoparticles into Nanofibers toward Enhanced Thermo/Electrochemical Stability

Compared with elemental phosphorus, GeP₅, with much better thermostability and super higher conductivity, can exhibit a comparable capacity (>2000 mA h g^-1) with a much higher first Coulombic efficiency (95%) for lithium-ion batteries. However, such high capacity is accompanied by large volume expansions, leading to fast capacity fading. To improve the cycle stability, fabricating a special nanostructure to reduce the volume stress and compositing with a carbon matrix to buffer the volume change are highly required. However, nanostructured metal phosphides were rarely reported up to now because they are difficult to be synthesized via a normal wet chemistry method or gas phosphorization because of lack of proper reactants and poor thermostability of phosphides. Herein, we successfully achieve uniform carbon-encapsulated GeP₅ nanofibers (GeP₅@C-NF) by processing GeP₅ nanoparticles into carbon nanofibers via electrospinning. After carbon encapsulation, the thermostability of GeP₅ can be greatly improved to over 600 °C for higher battery safety. Such a nanofiber structure in which nanosized GeP₅ is embedded in a carbon matrix can greatly accommodate the large volume changes during lithiation and provide fast electron transportation, thus contributing to a long cycle life (>1000 mA h g^-1 after 200 cycles) and high rate performance (803 mA h g^-1 at 2000 mA g^-1). This morphology processing technique can be easily extended to other metal phosphide anodes which are limited by a lack of appropriate synthesis methods and poor thermostability.

Lithium-ion storage performances of sunflower-like and nano-sized hollow SnO2 spheres by spray pyrolysis and the nanoscale Kirkendall effect

Nanostructured metal selenides with a variety of morphologies are crucial for fabricating porous, hollow metal-oxide nanomaterials by nanoscale Kirkendall diffusion. Herein, SnSe-SnO2 composite powders and SnSe nanospheres were synthesized via one-pot spray pyrolysis by optimizing the concentration of the Se precursor in the spray solution; these were then used to fabricate sunflower-like SnO2 and hollow SnO2 nanospheres, respectively, via nanoscale Kirkendall diffusion. Post-treatment of the SnSe-decorated SnO2 under air produced sunflower-like SnO2, in which ray and disk florets consisting of hollow nanoplates and dense nanospheres, respectively, were present. The mean diameter of the homogeneous hollow SnO2 nanospheres was 150 nm. The hollow morphology shortens the diffusion length, increasing the contact area between the electrolyte and voids and buffering large volume changes during repeated cycling. As anode materials for lithium-ion batteries, the hollow SnO2 nanospheres showed excellent cycling and rate performances. The discharge capacity of the hollow SnO2 nanospheres, after 500 cycles from 0.001 V to 3.0 V, was 1043 mA h g-1, at a current density of 3.0 A g-1. The hollow SnO2 nanospheres showed a high reversible capacity of 638 mA h g-1, even at current density as high as 10 A g-1.

Tin Selenide (SnSe): Growth, Properties, and Applications

The indirect bandgap semiconductor tin selenide (SnSe) has been a research hotspot in the thermoelectric fields since a ZT (figure of merit) value of 2.6 at 923 K in SnSe single crystals along the b-axis is reported. SnSe has also been extensively studied in the photovoltaic (PV) application for its extraordinary advantages including excellent optoelectronic properties, absence of toxicity, cheap raw materials, and relative abundance. Moreover, the thermoelectric and optoelectronic properties of SnSe can be regulated by the structural transformation and appropriate doping. Here, the studies in SnSe research, from its evolution to till now, are reviewed. The growth, characterization, and recent developments in SnSe research are discussed. The most popular growth techniques that have been used to prepare SnSe materials are discussed in detail with their recent progress. Important phenomena in the growth of SnSe as well as the problems remaining for future study are discussed. The applications of SnSe in the PV fields, Li-ion batteries, and other emerging fields are also discussed.

Tin Selenides with Layered Crystal Structures for Li-Ion Batteries: Interesting Phase Change Mechanisms and Outstanding Electrochemical Behaviors

Tin selenides with layered crystal structures, SnSe and SnSe₂, were synthesized by a solid-state method and electrochemically tested for use as Li-ion battery anodes. The phase change mechanisms of these compounds were thoroughly evaluated by ex situ X-ray diffraction and Se K-edge extended X-ray absorption fine structure techniques. SnSe showed better electrochemical reversibility of Li insertion/extraction than SnSe₂, which was attributed to remarkable conversion/recombination reactions of the former compound during lithiation/delithiation. Additionally, the electrochemical performance of SnSe was further enhanced by preparing carbon-modified nanocomposites using two different methods, that is, heat treatment (HT) for producing a carbon coating using polyvinyl chloride as a precursor and high-energy ball milling (BM) using carbon black powder. The SnSe/C electrode produced by BM showed a highly reversible initial capacity of 726 mA h g^-1 with a good initial Coulombic efficiency of ∼82%, excellent cycling behavior (626 mA h g^-1 after 200 cycles), and a fast C-rate performance (580 mA h g^-1 at 2C rate).