In Situ-Formed Hollow Cobalt Sulfide Wrapped by Reduced Graphene Oxide as an Anode for High-Performance Lithium-Ion Batteries

Enhancing Rapid Li+/Na+ Storage Performance via Interface Engineering of Reduced Graphene Oxide-Wrapped Bimetallic Sulfide Nanocages

Transition-metal sulfide is considered to be an admirable transformational electrode material due to low cost, large specific capacity, and good reversibility in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, the reduced graphene oxide-wrapped open bimetallic sulfide (NiS2-Co3S4@rGO) nanocage, derived from nickel-cobalt Prussian blue, was obtained by two-step calcination. There are luxuriant pore structures in the nanocage composite with a specific surface area of 85.28 m2 g-1, which provides plentiful paths for rapid transmission of Li+/Na+ and alleviates the volume stress caused by insertion and extraction of alkali metal ions. The excellent interface combination of bimetallic sulfide wrapped in reduced graphene oxide improves the conductivity and overall performance of the battery. Thanks to the special interface engineering, the open NiS2-Co3S4@rGO nanocage composite displays rapid lithium storage properties with an average diffusion coefficient of 8.5 × 10-13 cm2 s-1. Moreover, after 300 cycles, the reversible capacity of the composite is 1113.2 mAh g-1 at 1 A g-1. In SIBs, the capacity of the open NiS2-Co3S4@rGO composite is 487.9 mAh g-1 when the current density is 5 A g-1. These preeminent performances demonstrate the enormous development prospects of bimetallic sulfide nanocage as anode material in LIBs and SIBs.

Pristine cobalt humic acid xerogels embedded with ultrafine cobalt sulfide for enhanced and stable lithium-ion storage

The electrochemical performance of pristine metal-organic xerogels as anodes in lithium-ion batteries is reported for the first time. We propose a novel synthesis approach for the in situ generation of highly dispersed, ultrafine cobalt sulfide nanoparticles on humic acid gels (CoSHA). The CoS nanoparticles in CoSHA have an average diameter of approximately 3 nm. CoSHA electrodes demonstrate enhanced lithium storage capacity, delivering a capacity of 662 mAh g-1 at 0.1 A g-1. They also show stable long-term cycling performance, with no capacity decay after 900 cycles at 1.0 A g-1. Furthermore, our experiments indicate that the improved lithium-ion adsorption results from the oxygen-containing functional groups in humic acid and the ultrafine CoS active sites. This study offers a practical methodology for synthesizing ultrafine metal sulfides and new insights into using pristine gel-based electrodes for energy storage and conversion.

Recent Advancements of Graphene-Based Materials for Zinc-Based Batteries: Beyond Lithium-Ion Batteries

Graphene-based materials (GBMs) possess a unique set of properties including tunable interlayer channels, high specific surface area, and good electrical conductivity characteristics, making it a promising material of choice for making electrode in rechargeable batteries. Lithium-ion batteries (LIBs) currently dominate the commercial rechargeable battery market, but their further development has been hampered by limited lithium resources, high lithium costs, and organic electrolyte safety concerns. From the performance, safety, and cost aspects, zinc-based rechargeable batteries have become a promising alternative of rechargeable batteries. This review highlights recent advancements and development of a variety of graphene derivative-based materials and its composites, with a focus on their potential applications in rechargeable batteries such as LIBs, zinc-air batteries (ZABs), zinc-ion batteries (ZIBs), and zinc-iodine batteries (Zn-I2 Bs). Finally, there is an outlook on the challenges and future directions of this great potential research field.

Silver boosts ultra-long cycle life for metal sulfide lithium-ion battery anodes: Taking AgSbS2 nanowires as an example

Metal sulfide, being a high-capacity anode material, is a promising anode material for rechargeable lithium-ion batteries (LIBs). However, most research efforts have focused on improving their low cycling performance due to multiple combined factors, including low conductivity, huge volume changes, multi-step conversion/alloying reactions, and redox shuttling effect, during the cycling process. Here, we report that by using AgSbS₂ nanowires as LIB anode materials, a record-breaking long cycle life metal sulfide anode has been achieved through the silver synergistic electrochemical performance effect. We found that while the AgSbS₂ nanowire anode is cycled, Ag precipitated out to form a nanocrystal tightly connected with Sb and S and plays a key role in highly-reversible electrochemical performance. Ag can effectively enhance the electrode conductivity, increase ion diffusion rate, serve a diluent huge volume changes during conversion-alloying reactions, improve the absorbability and catalytic ability towards LiPSs to reduce shutting effect of sulfur, and enhanced Li⁺ adsorption. As a result, AgSbS₂ nanowire anodes maintain 90% capacity retention over 5000 and 7000 cycles at the current densities of 500 mA g^-1 and 2000 mA g^-1, respectively, whereas the capacities of Sb₂S₃ nanowire and Sb₂S₃/C nanowire anodes drop rapidly within 10 cycles. The ultra-stable cycle life is superior to the state-of-the-art metal sulfide anodes. Finally, using AgSbS₂ nanowires as the anode combined with the cathode LiNi₅Co₃Mn₂, a full battery after 480 cycles was assembled to verify that its stability (high retention rate of 99.5%) can be used in the current commercial battery architecture. This work solves multiple problems related to shuttling effects and complex reactions of metal sulfide anodes, and provides important progress for the future development of metal sulfide anodes for LIBs.

Composite Nanoarchitectonics with CoS2 Nanoparticles Embedded in Graphene Sheets for an Anode for Lithium-Ion Batteries

Cobalt sulfides are attractive as intriguing candidates for anodes in Lithium-ion batteries (LIBs) due to their unique chemical and physical properties. In this work, CoS2@rGO (CSG) was synthesized by a hydrothermal method. TEM showed that CoS2 nanoparticles have an average particle size of 40 nm and were uniformly embedded in the surface of rGO. The battery electrode was prepared with this nanocomposite material and the charge and discharge performance was tested. The specific capacity, rate, and cycle stability of the battery were systematically analyzed. In situ XRD was used to study the electrochemical transformation mechanism of the material. The test results shows that the first discharge specific capacity of this nanocomposite reaches 1176.1 mAhg-1, and the specific capacity retention rate is 61.5% after 100 cycles, which was 47.5% higher than that of the pure CoS2 nanomaterial. When the rate changes from 5.0 C to 0.2 C, the charge-discharge specific capacity of the nanocomposite material can almost be restored to the initial capacity. The above results show that the CSG nanocomposites as a lithium-ion battery anode electrode has a high reversible specific capacity, better rate performance, and excellent cycle performance.

High-Capacity Anode Material for Lithium-Ion Batteries with a Core-Shell NiFe2O4/Reduced Graphene Oxide Heterostructure

A novel composite consisting of transition-metal oxide and reduced graphene oxide (rGO) has been designed as a highly promising anode material for lithium-ion batteries (LIBs). The anode material for LIBs exhibits high-rate capability, outstanding stability, and nontoxicity. The structural characterization techniques, such as X-ray diffraction, Raman spectra, and transmission electron microscopy, indicate that the material adopts a unique core-shell structure with NiFe₂O₄ nanoparticles situated in the center and an rGO layer coated on the surface of NiFe₂O₄ particles (denoted as NiFe₂O₄/rGO). The NiFe₂O₄/rGO material with a core-shell structure exhibits an excellent electrochemical performance, which shows a capacity of 1183 mA h g^-1 in the first cycle and maintains an average capacity of ∼1150 mA h g^-1 after 900 cycles at a current density of 500 mA g^-1. This work provides a broad field of vision for the application of transition-metal-oxide materials in electrodes of lithium-ion batteries, which is of great significance for further development of lithium-ion batteries with excellent performance.

Cobalt Selenide Hollow Polyhedron Encapsulated in Graphene for High-Performance Lithium/Sodium Storage

Owing to the high specific capacities, high electrochemical activity, and various electronic properties, transition metal selenides are considered as promising anodes for lithium- and sodium-ion storage. However, poor electronic conductivity and huge volume expansion during cycling are still responsible for their restricted electrochemical performance. Herein, CoSe hollow polyhedron anchoring onto graphene (CoSe/G) is synthesized by self-assembly and subsequent selenization. In CoSe/G composites, the CoSe nanoparticles, obtained by in situ selenization of metal-organic frameworks (MOFs) in high temperature, are distributed among graphene sheets, realizing N element doping, developing robust heterostructures with a chemical bond. The unique architecture ensures the cohesion of the structure and endorses the reaction kinetics for metal ions, identified by in situ and ex situ testing techniques, and kinetics analysis. Thus, the CoSe/G anodes achieve excellent cycling performance (1259 mAh g^-1 at 0.1 A g^-1 after 300 cycles for lithium storage; 214 mAh g^-1 at 2 A g^-1 after 600 cycles for sodium storage) and rate capability (732 mAh g^-1 at 5 A g^-1 for lithium storage; 290 mAh g^-1 at 5 A g^-1 for sodium storage). The improved electrochemical performance for alkali-ion storage provides new insights for the construction of MOFs derivatives toward high-performance storage devices.

Synthesis and Applications of Nanostructured Hollow Transition Metal Chalcogenides

Nanostructures with well-defined structures and rich active sites occupy an important position for efficient energy storage and conversion. Recent studies have shown that a transition metal chalcogenide (TMC) has a unique structure, such as diverse structural morphology, excellent stability, high efficiency, etc., and is used in the fields of electrochemistry and catalysis. The nanohollow structure metal chalcogenide has broad application prospects due to the existence of a large number of active sites and a wide internal space, allowing a large number of ions and electrons to be transported. Summarizing synthetic strategies of nanostructured hollow transition metal sulfides (HTMC) and their applications in the field of energy storage and conversion is discussed here. Through some representative examples, the fabrication and properties of various hollow structures are analyzed, which prompt some emerging nanoengineering designs to be applied to transition metal chalcogenides. It is hoped that the construction of the HTMC will lead to a deeper understanding for the further exploration of energy storage and conversion.

Core-Shell FeSe2 /C Nanostructures Embedded in a Carbon Framework as a Free Standing Anode for a Sodium Ion Battery

Embedding the functional nanostructures into a lightweight nanocarbon framework is very promising for developing high performance advanced electrodes for rechargeable batteries. Here, to realize workable capacity, core-shell (FeSe₂ /C) nanostructures are embedded into carbon nanotube (CNT) framework via a facile wet-chemistry approach accompanied by thermally induced selenization. The CNT framework offers 3D continuous routes for electronic/ionic transfer, while macropores provide adequate space for high mass loading of FeSe₂ /C. However, the carbon shell not only creates a solid electronic link among CNTs and FeSe₂ but also improves the diffusivity of sodium ions into FeSe₂ , as well as acts as a buffer cushion to accommodate the volume variations. These unique structural features of CNT/FeSe₂ /C make it an excellent host for sodium storage with a capacity retention of 546 mAh g^-1 even after 100 cycles at 100 mA g^-1 . Moreover, areal and volumetric capacities of 5.06 mAh cm^-2 and 158 mAh cm^-3 are also achieved at high mass loading 16.9 mg cm^-2 , respectively. The high performance of multi-benefited engineered structure makes it a potential candidate for secondary ion batteries, while its easy synthesis makes it extendable to further complex structures with other morphologies (such as nanorods, nanowires, etc.) to meet the high energy demands.

Preparation of cobalt sulfide@reduced graphene oxide nanocomposites with outstanding electrochemical behavior for lithium-ion batteries

Cobalt sulfide@reduced graphene oxide composites were prepared through a simple solvothermal method. The cobalt sulfide@reduced graphene oxide composites are composed of cobalt sulfide nanoparticles uniformly attached on both sides of reduced graphene oxide. Some favorable electrochemical performances in specific capacity, cycling performance, and rate capability are achieved using the porous nanocomposites as an anode for lithium-ion batteries. In a half-cell, it exhibits a high specific capacity of 1253.9 mA h g-1 at 500 mA g-1 after 100 cycles. A full cell consists of the cobalt sulfide@reduced graphene oxide nanocomposite anode and a commercial LiCoO2 cathode, and is able to hold a high capacity of 574.7 mA h g-1 at 200 mA g-1 after 200 cycles. The reduced graphene oxide plays a key role in enhancing the electrical conductivity of the electrode materials; and it effectively prevents the cobalt sulfide nanoparticles from dropping off the electrode and buffers the volume variation during the discharge-charge process. The cobalt sulfide@reduced graphene oxide nanocomposites present great potential to be a promising anode material for lithium-ion batteries.