Layer-by-layered SnS2/graphene hybrid nanosheets via ball-milling as promising anode materials for lithium ion batteries

Controllable Synthesis of Heterogeneous ZnS/SnS2 Encapsulated in Hollow Nitrogen-Doped Carbon Microcubes as Anode for High-Performance Li-ion Capacitors

Li-ion capacitors (LICs) integrate the desirable features of lithium-ion batteries (LIBs) and supercapacitors (SCs), but the kinetic imbalance between the both electrodes leads to inferior electrochemical performance. Thus, constructing an advanced anode with outstanding rate capability and terrific redox kinetics is crucial to LICs. Herein, heterostructured ZnS/SnS2 nanosheets encapsulated into N-doped carbon microcubes (ZnS/SnS2@NC) are successfully fabricated. The sufficient ZnS/SnS2 heterostructure possesses abundant active sites, and the built-in electric field formed at the heterojunction interface can facilitate electron/ion migration. The interconnected hollow carbon layers could reduce the electron transfer resistance effectively and accommodate the volume change of SnS2, thereby maintaining the structural stability. Due to the synergy between multi-components, the ZnS/SnS2@NC anode demonstrates impressive Li storage performance with an excellent cyclic durablity (690 mAh g-1 at 0.5 A g-1 after 600 cycles) and considerable rate capability. Moreover, when matched with active carbon, the ZnS/SnS2@NC based LIC device delivers an admirable energy density of 134.1 Wh kg-1 and a high power output of 11,250 W kg-1, as well as remarkable capacity retention of 73.2 % after 6,000 cycles at 1.0 A g-1. The experimental results demonstrate the significance of optimized heterointerface engineering toward construction of electrode materials with high-performance for Li storage.

The effect of introducing fluorine doping and sulfur vacancies on SnS2 as the anode electrode of LIBs: a density functional theory study

As the anode material of LIBs, the SnS2 electrode boasts a reversible specific capacity as high as 1231 mA h g-1. Additionally, SnS2 possesses a CdI2-type layered structure with a layer spacing of 0.59 nm, which allows it to accommodate numerous lithium ions and facilitate rapid charge transfer. However, as a semiconductor material, SnS2's low electronic conductivity significantly hampers its lithium storage performance. In this paper, we propose enhancing the intrinsic electronic conductance of SnS2 through fluorine doping and the introduction of sulfur vacancies, thereby constructing the F-SnS2-x structure. The stability and superiority of this structure are confirmed by a series of theoretical calculations. The stability and rationality of the structure were characterized using the phonon spectrum. Calculation of the density of states and lithium ion diffusion barriers demonstrates that F-SnS2-x exhibits exceptional electron/lithium ion transport kinetics. Furthermore, the results of lithium ion binding energy and differential charge show that there is a strong interaction between the F-SnS2-x structure and lithium ions, which is advantageous for achieving long-term cycle stability. Importantly, one F-SnS2-x molecule can adsorb up to 4.5 Li atoms, yielding a corresponding theoretical specific capacity of 702 mA h g-1, which surpasses that of SnS2 with 4 atoms (586 mA h g-1). The theoretical calculation results of this work can provide valuable insights for improving the electronic conductivity and lithium storage performance of other metal sulfides.

Arc-Discharge In Situ Synthesis of Dual-Carbonaceous-Layer-Coated SnS Nanoparticles with High Lithium-Ion Storage Capacity

SnS-based carbon composites have garnered considerable concentration as prospective anode materials (AMs) for lithium-ion batteries (LIBs). Nevertheless, most SnS-based carbon composites underwent a two-phase or multistep preparation process and exhibited unsatisfactory LIB performance. In this investigation, we introduce a straightforward and efficient one-step arc-discharge technique for the production of dual-layer carbon-coated tin sulfide nanoparticles (SnS@C). The as-prepared composite is used as an AM for LIBs and delivers a high capacity of 1000.4 mAh g-1 at 1.0 A g-1 after 520 cycles. The SnS@C still maintains a capacity of 476 mAh g-1 after 390 cycles despite a higher current of 5.0 A g-1. The high specific capacity and long life are mainly attributed to a unique dual-carbon layers coating structure. The dual-carbon layers not only could effectively improve electrical conductivity and reduce charge-transfer resistance but also limit the alteration in bulk and self-aggregation of SnS nanoparticles. The SnS@C produced by the arc-discharge technique emerges as a promising applicant for AM in LIBs, and the arc-discharge technique provides an alternative way for synthesizing other transition metal sulfides supported on carbonaceous materials.

Enhanced charge capacity and stability of Germanium(IV) Sulfide-Based anodes through Triton X100-Assisted synthesis and polysulfide shuttle mitigation

Highly soluble germanium oxide,an amorphous macroreticular form of germanium oxide, was used as a precursor for the deposition of GeS2on reduced graphene oxide (rGO) through a low-temperature, wet-chemistry process. Thermal treatment of the solid provided an ultrathin rGO - supported amorphous GeS2coating. The GeS2@rGO composite was tested as a lithium ion battery (LIB) anode. Leveraging the versatility of wet chemistry processing, we employed strategies initially developed for mitigating polysulfide shuttle effects in lithium-sulfur batteries to enhance anode performance. The anode exhibited exceptional stability, surpassing 1000 cycles, with charge capacities exceeding 1220 and 870 mAh.g-1 at rates of 2 and 5 A.g-1, respectively. Performance improvements were achieved by minimizing GeS2 grain size using the non-ionic surfactant Triton X-100 during synthesis and preventing polysulfide shuttle effects through a negatively charged thick glass fiber separator, fluoroethylene carbonate additive (FEC) in EC:DEC (ethylene carbonate: diethyl carbonate) solvent, and a polyacrylic acid (PAA) binder. These cumulative modifications more than tripled the charge capacity of the germanium sulfide LIB anode. Feasibility was further demonstrated through full cell studies using a LiCoO2 counter electrode.

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.

A facile precursor route towards the synthesis of Fe1-xS@NC-rGO composite anode materials for high-performance lithium-ion batteries

Iron-based sulfides are considered promising anode materials for lithium-ion batteries (LIBs) due to their low cost and high theoretical specific capacities. However, low conductivity and dissolution of lithium polysulfides during the reaction hamper their practical applications. Herein, we firstly synthesized N-doped carbon-coated Fe_1-xS (Fe_1-xS@NC) sheets through vacuum pyrolysis of the precursor Fe_1-xS(en)_0.5 (en = ethylenediamine). Then Fe_1-xS@NC-rGO composites (rGO = reduced graphene oxide) were prepared in which the Fe_1-xS@NC sheets were anchored on the rGO. The performance of the composites as an anode material for LIBs has been investigated. It is found that coating N-doped C on Fe_1-xS surfaces can improve the surface conductivity and electrochemical kinetics of Fe_1-xS, which is beneficial for the conversion between lithium polysulfides and Fe_1-xS. In addition, the coated N-doped C on the Fe_1-xS sheets can serve as a barrier to direct contact between the electrolyte and the material, reducing the dissolution of polysulfides and preventing the loss of active ingredients. More importantly, the double protection of the N-doped C layer and the flexible rGO substrate minimizes the structural damage caused by the cyclic expansion of Fe_1-xS@NC-rGO. As expected, Fe_1-xS@NC-rGO exhibits good rate performance with a reversible capacity of 939.5 mA h g^-1 after 1690 cycles at a current density of 1.0 A g^-1, along with outstanding charge and discharge performance and excellent long-term cycling stability. This work shows that the introduction of NC coating and the rGO matrix into Fe_1-xS would synergistically enhance the performance of Fe_1-xS for LIBs and highlights the effectiveness of the synthetic strategy for double carbon-based materials-protected sulfides in developing superior LIB electrodes.

Rational Construction of C@Sn/NSGr Composites as Enhanced Performance Anodes for Lithium Ion Batteries

As a potential anode material for lithium-ion batteries (LIBs), metal tin shows a high specific capacity. However, its inherent "volume effect" may easily turn tin-based electrode materials into powder and make them fall off in the cycle process, eventually leading to the reduction of the specific capacity, rate and cycle performance of the batteries. Considering the "volume effect" of tin, this study proposes to construct a carbon coating and three-dimensional graphene network to obtain a "double confinement" of metal tin, so as to improve the cycle and rate performance of the composite. This excellent construction can stabilize the tin and prevent its agglomeration during heat treatment and its pulverization during cycling, improving the electrochemical properties of tin-based composites. When the optimized composite material of C@Sn/NSGr-7.5 was used as an anode material in LIB, it maintained a specific capacity of about 667 mAh g^-1 after 150 cycles at the current density of 0.1 A g^-1 and exhibited a good cycle performance. It also displayed a good rate performance with a capability of 663 mAh g^-1, 516 mAh g^-1, 389 mAh g^-1, 290 mAh g^-1, 209 mAh g^-1 and 141 mAh g^-1 at 0.1 A g^-1, 0.2 A g^-1, 0.5 A g^-1, 1 A g^-1, 2 A g^-1 and 5 A g^-1, respectively. Furthermore, it delivered certain capacitance characteristics, which could improve the specific capacity of the battery. The above results showed that this is an effective method to obtain high-performance tin-based anode materials, which is of great significance for the development of new anode materials for LIBs.

Enabling Reversible Reaction by Uniform Distribution of Heterogeneous Intermediates on Defect-Rich SnSSe/C Layered Heterostructure for Ultralong-Cycling Sodium Storage

2D layered Sn-based materials have attracted enormous attention due to their remarkable performance in sodium-ion batteries. Nevertheless, this promising candidate involves a complex Na⁺ -storage process with multistep conversion-alloying reactions, which induces the uneven dispersion of heterogeneous intermediate accompanied by severe agglomeration of metallic Sn⁰ , inescapably resulting in poor reaction reversibility with sluggish rate capability and inferior cyclic lifespan. Herein, a delicately layered heterostructure SnSSe/C consisting of defect-rich SnSSe and graphene is designed and successfully achieved via a facile hydrothermal process. The equal anionic substitution of Se in SnSSe crystal can trigger numerous defects, which can not only facilitate Na⁺ diffusion but also accelerate the nucleation process by inducing quantum-dot-level uniform distribution of heterogeneous intermediates, Na₂ Se/Na₂ S and Sn⁰ . Concurrently, in situ formed uniform Na₂ Se/Na₂ S grain boundaries confined by this unique layered heterostructure may effectively suppress the agglomeration of metallic Sn⁰ nanograins and boost the reversibility of conversion-alloying reaction. As a result, the SnSSe/C displays significant improvement in Na-storage performance, in terms of remarkable rate capability and ultralong cycling lifespan. This work, focusing on controlling intermediate distribution, provides an effective strategy to boost reaction reversibility, which can be wildly employed in conversion-based electrodes for energy storage regions.

Recent Developments of Tin (II) Sulfide/Carbon Composites for Achieving High-Performance Lithium Ion Batteries: A Critical Review

The ever-increasing worldwide energy demand and the limited resources of fossil have forced the urgent adoption of renewable energy sources. Additionally, concerns over CO₂ emissions and potential increases in fuel prices have boosted technical efforts to make hybrid and electric vehicles more accessible to the public. Rechargeable batteries are undoubtedly a key player in this regard, especially lithium ion batteries (LIBs), which have high power capacity, a fast charge/discharge rate, and good cycle stability, while their further energy density improvement has been severely limited, because of the relatively low theoretical capacity of the graphite anode material which is mostly used. Among various high-capacity anode candidates, tin (II) sulfide (SnS₂) has been attracted remarkable attention for high-energy LIBs due to its enormous resource and simplicity of synthesis, in addition to its high theoretical capacity. However, SnS₂ has poor intrinsic conductivity, a big volume transition, and a low initial Coulombic efficiency, resulting in a short lifespan. SnS₂/carbon composites have been considered to be a most promising approach to addressing the abovementioned issues. Therefore, this review summarizes the current progress in the synthesis of SnS₂/carbon anode materials and their Li-ion storage properties, with special attention to the developments in Li-based technology, attributed to its immense current importance and promising prospects. Finally, the existing challenges within this field are presented, and potential opportunities are discussed.

The electrochemical storage mechanism of an In2S3/C nanofiber anode for high-performance Li-ion and Na-ion batteries

There are only a handful of reports on indium sulfide (In2S3) in the electrochemical energy storage field without a clear electrochemical reaction mechanism. In this work, a simple electrospinning method has been used to synthesize In2S3/C nanofibers for the first time. In lithium-ion batteries (LIBs), the In2S3/C nanofiber electrode can not only deliver a high initial reversible specific capacity of 696.4 mA h g-1 at 50 mA g-1, but also shows ultra-long cycle life with a capacity retention of 80.5% after 600 cycles at 1000 mA g-1. In sodium-ion batteries (SIBs), the In2S3/C nanofibers electrode can exhibit a high initial reversible specific capacity (393.7 mA h g-1 at 50 mA g-1) and excellent cycling performance with a high capacity retention of 97.3% after 300 cycles at 1000 mA g-1. The excellent electrochemical properties mainly benefited from In2S3 being encapsulated by a carbon matrix, which buffers the volume expansion and significantly improves the conductivity of the composite. Furthermore, the structural evolution of In2S3 during the first lithiation/delithiation and sodiation/desodiation processes has been illustrated by ex situ XRD. The results confirm that the reaction mechanism of In2S3 in both LIBs and SIBs can be summarized as conversion reactions and alloying reactions, which provide theoretical support for the development of In2S3 in the field of electrochemistry.

Ultrastable Li-ion battery anodes by encapsulating SnS nanoparticles in sulfur-doped graphene bubble films

As an anode electrode material for lithium-ion batteries, SnS has high specific capacity and has received widespread attention, but its practical application is still hindered by the low reversibility of the conversion reaction and the large irreversible capacity caused by the solid electrolyte interphase (SEI). In this paper, SnS nanoparticles are encapsulated into a sulfur-doped graphene bubble film (SnS@G) by a scalable electrostatic self-assembly of SnS₂/graphene oxide and hexadecyl trimethyl ammonium bromide, followed by the thermal decomposition of SnS₂ and sulfur doping in graphene. Due to electrostatic attraction, the SnS nanoparticles are tightly wrapped in multilayer graphene sheets to form a flake-graphite-like structure. Compared with the disordered stacked SnS/graphene sheet composite, the closely packed SnS@G shows a much lower specific surface area and smaller irreversible Li⁺ consumption and surface film resistance after lithiation. The SnS@G composite anode exhibits great initial coulombic efficiency (83.2%), which is the highest value among the chemically synthesized SnS anodes. It also presents unprecedented cycling stability (1462 mA h g^-1 after 200 cycles at 0.1 A g^-1 and 1020 mA h g^-1 after 500 cycles at 1 A g^-1) and superior rate capabilities (750 mA h g^-1 at 5 A g^-1) upon Li storage, which demonstrates its excellent electrochemical performance and great potential as a negative electrode material for lithium-ion batteries.

Few-layer WS2 nanosheets with oxygen-incorporated defect-sulphur entrapped by a hierarchical N, S co-doped graphene network towards advanced long-term lithium storage performances

Tungsten sulfide (WS₂) with two-dimensional layered graphene-like structure as an anode for lithium-ion batteries (LIBs) has attracted large attention owing to its high theoretical capacity and unique S–W–S layer structure. However, it also always suffers from poor electrical conductivity and volume expansion during lithiation/delithiation process in the practical application. Herein, we demonstrate the successful synergistic regulation of both structural and electronic modulation by simultaneous oxygen incorporation in defect-sulphur WS₂ nanosheets embedded into a conductive nitrogen and sulfur co-doped graphene framework (denoted as O-DS-WS₂/NSG), leading to dramatically enhanced lithium storage. Such a unique structure not only increases the accessible active sites for Li⁺ and enhances the kinetics of ion/electron transport, but also relieves the volume effect of WS₂. Furthermore, the surface defects and heteroatom incorporation can effectively regulate the electronic structure, improve the intrinsic conductivity and offer more active sites. Consequently, electrochemical performance results demonstrate that the obtained O-DS-WS₂/NSG nanocomposites possess great application prospects in LIBs with high specific capacity, superior rate performance as well as excellent cycle stability.

One-step preparation of few-layer oxygen incorporation in defect-sulphur WS₂ nanosheets embedded into the NSG framework exhibits excellent Li-ion storage properties.

Production of SnS2 Nanostructure as Improved Light-Assisted Electrochemical Water Splitting

Tin disulfide (SnS₂) has gained a lot of interest in the field of converting solar energy into chemical fuels in light-assisted electrochemical water splitting due to its visible-light band gap and high electronic mobility. However, further decreasing the recombination rate of electron-hole pairs and increasing the density of active states at the valence band edge of the photoelectrodes were a critical problem. Here, we were successful in fabricating the super-thin SnS₂ nanostructure by a hydrothermal and solution etching method. The super-thin SnS₂ nanostructure as a photo-electrocatalytic material exhibited low overpotential of 0.25 V at the current density of −10 mA·cm⁻² and the potential remained basically unchanged after 1000 cycles in an H₂SO₄ electrolyte solution, which was better than that of the SnS₂ nanosheet and SnS/SnS₂ heterojunction nanosheet. These results show the potential application of super-thin SnS₂ nanostructure in electrochemical/photo-electrocatalytic field.

Sandwich-like SnS2/Graphene/SnS2 with Expanded Interlayer Distance as High-Rate Lithium/Sodium-Ion Battery Anode Materials

SnS₂ materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS₂/graphene/SnS₂ (SnS₂/rGO/SnS₂) composite with ultrathin SnS₂ nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C-S bonds. Owing to the graphene sandwiched between two SnS₂ sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Å for SnS₂, which could facilitate the insertion/extraction of Li⁺/Na⁺ ions with rapid transport kinetics as well as inhibit the restacking of SnS₂ nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS₂ nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g^-1 for Li/Na-ion batteries even at 10 A g^-1. No distinct morphology changes occur after 200 cycles, and the SnS₂ nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.

Two-phase interface hydrothermal synthesis of binder-free SnS2/graphene flexible paper electrodes for high-performance Li-ion batteries

Binder-free SnS₂/graphene flexible paper produced from a two-phase interface hydrothermal reaction with excellent electrochemical performance for lithium-ion batteries.

Hierarchical porous MnCo2O4 yolk-shell microspheres from MOFs as secondary nanomaterials for high power lithium ion batteries

Hierarchical porous MnCo2O4 yolk-shell microspheres have been synthesized via a facile chemical precipitation method with subsequent calcination treatment. The hierarchical porous MnCo2O4 yolk-shell microspheres as secondary nanomaterials can improve the effective contact area between the MnCo2O4 electrode and electrolyte, accommodate the volume variations during cycling, and shorten the Li+ diffusion path in the nanoparticles. Benefiting from their particular structure and interconnected pores, as anodes for lithium ion batteries, the hierarchical porous MnCo2O4 yolk-shell microspheres show high reversible lithium storage capacity, excellent cycling performance and enhanced rate capability. More importantly, they also exhibit long-life and high-rate lithium storage as high as 691.3 mA h g-1 after 500 cycles even at 1 C.

Nitrogen-Doped TiO2-C Composite Nanofibers with High-Capacity and Long-Cycle Life as Anode Materials for Sodium-Ion Batteries

Nitrogen-doped TiO₂-C composite nanofibers (TiO₂/N-C NFs) were manufactured by a convenient and green electrospinning technique in which urea acted as both the nitrogen source and a pore-forming agent. The TiO₂/N-C NFs exhibit a large specific surface area (213.04 m² g^-1) and a suitable nitrogen content (5.37 wt%). The large specific surface area can increase the contribution of the extrinsic pseudocapacitance, which greatly enhances the rate capability. Further, the diffusion coefficient of sodium ions (D _Na+) could be greatly improved by the incorporation of nitrogen atoms. Thus, the TiO₂/N-C NFs display excellent electrochemical properties in Na-ion batteries. A TiO₂/N-C NF anode delivers a high reversible discharge capacity of 265.8 mAh g^-1 at 0.05 A g^-1 and an outstanding long cycling performance even at a high current density (118.1 mAh g^-1) with almost no capacity decay at 5 A g^-1 over 2000 cycles. Therefore, this work sheds light on the application of TiO₂-based materials in sodium-ion batteries.