Sulfur-Doped Carbon with Enlarged Interlayer Distance as a High-Performance Anode Material for Sodium-Ion Batteries

S-doped carbon is investigated as a high-performance anode material for sodium-ion batteries. Due to the introduction of a high-content of S atoms, the as-obtained S-doped carbon shows an enlarged interlayer distance. As an anode, a high specific capacity of up to 303 mAh g-1 is achieved, even after 700 cycles at 0.5 A g-1.

Surface and interface engineering of electrode materials for lithium-ion batteries

Lithium-ion batteries are regarded as promising energy storage devices for next-generation electric and hybrid electric vehicles. In order to meet the demands of electric vehicles, considerable efforts have been devoted to the development of advanced electrode materials for lithium-ion batteries with high energy and power densities. Although significant progress has been recently made in the development of novel electrode materials, some critical issues comprising low electronic conductivity, low ionic diffusion efficiency, and large structural variation have to be addressed before the practical application of these materials. Surface and interface engineering is essential to improve the electrochemical performance of electrode materials for lithium-ion batteries. This article reviews the recent progress in surface and interface engineering of electrode materials including the increase in contact interface by decreasing the particle size or introducing porous or hierarchical structures and surface modification or functionalization by metal nanoparticles, metal oxides, carbon materials, polymers, and other ionic and electronic conductive species.

A highly ordered meso@microporous carbon-supported sulfur@smaller sulfur core-shell structured cathode for Li-S batteries

For lithium-sulfur batteries, commercial application is hindered by the insulating nature of sulfur and the dissolution of the reaction intermediates of polysulfides. Here, we present an ordered meso-microporous core-shell carbon (MMCS) as a sulfur container, which combines the advantages of both mesoporous and microporous carbon. With large pore volume and highly ordered porous structure, the "core" promises a sufficient sulfur loading and a high utilization of the active material, while the "shell" containing microporous carbon and smaller sulfur acts as a physical barrier and stabilizes the cycle capability of the entire S/C composite. Such a S/MMCS composite exhibits a capacity as high as 837 mAh g(-1) at 0.5 C after 200 cycles with a capacity retention of 80% vs the second cycle (a decay of only 0.1% per cycle), demonstrating that the diffusion of the polysulfides into the bulk electrolyte can be greatly reduced. We believe that the tailored highly ordered meso-microporous core-shell structured carbon can also be applicable for designing some other electrode materials for energy storage.

High-performance asymmetric supercapacitors based on multilayer MnO2 /graphene oxide nanoflakes and hierarchical porous carbon with enhanced cycling stability

In this work, MnO(2)/GO (graphene oxide) composites with novel multilayer nanoflake structure, and a carbon material derived from Artemia cyst shell with genetic 3D hierarchical porous structure (HPC), are prepared. An asymmetric supercapacitor has been fabricated using MnO(2)/GO as positive electrode and HPC as negative electrode material. Because of their unique structures, both MnO(2)/GO composites and HPC exhibit excellent electrochemical performances. The optimized asymmetric supercapacitor could be cycled reversibly in the high voltage range of 0-2 V in aqueous electrolyte, which exhibits maximum energy density of 46.7 Wh kg(-1) at a power density of 100 W kg(-1) and remains 18.9 Wh kg(-1) at 2000 W kg(-1). Additionally, such device also shows superior long cycle life along with ∼100% capacitance retention after 1000 cycles and ∼93% after 4000 cycles.

Enhancing Sodium Ion Battery Performance by Strongly Binding Nanostructured Sb2S3 on Sulfur-Doped Graphene Sheets

Sodium ion batteries (SIBs) have been considered a promising alternative to lithium ion batteries for large-scale energy storage. However, their inferior electrochemical performances, especially cyclability, become the major challenge for further development of SIBs. Large volume change and sluggish diffusion kinetics are generally considered to be responsible for the fast capacity degradation. Here we report the strong chemical bonding of nanostructured Sb₂S₃ on sulfur-doped graphene sheets (Sb₂S₃/SGS) that enables a stable capacity retention of 83% for 900 cycles with high capacities and excellent rate performances. To the best of our knowledge, the cycling performance of the Sb₂S₃/SGS composite is superior to those reported for any other Sb-based materials for SIBs. Computational calculations demonstrate that sulfur-doped graphene (SGS) has a stronger affinity for Sb₂S₃ and the discharge products than pure graphene, resulting in a robust composite architecture for outstanding cycling stability. Our study shows a feasible and effective way to solve the long-term cycling stability issue for SIBs.

Tin phosphide as a promising anode material for Na-ion batteries

Sn4 P3 is introduced for the first time as an anode material for Na-ion batteries. Sn4 P3 delivers a high reversible capacity of 718 mA h g(-1), and shows very stable cycle performance with negligible capa-city fading over 100 cycles, which is attributed to the confinement effect of Sn nanocrystallites in the amorphous phosphorus matrix during cycling.

Constructing Highly Oriented Configuration by Few-Layer MoS2: Toward High-Performance Lithium-Ion Batteries and Hydrogen Evolution Reactions

Constructing three-dimensional (3D) architecture with oriented configurations by two-dimensional nanobuilding blocks is highly challenging but desirable for practical applications. The well-oriented open structure can facilitate storage and efficient transport of ion, electron, and mass for high-performance energy technologies. Using MoS2 as an example, we present a facile and effective hydrothermal method to synthesize 3D radially oriented MoS2 nanospheres. The nanosheets in the MoS2 nanospheres are found to have less than five layers with an expanded (002) plane, which facilitates storage and efficient transport of ion, electron, and mass. When evaluated as anode materials for rechargeable Li-ion batteries, the MoS2 nanospheres show an outstanding performance; namely, a specific capacity as large as 1009.2 mA h g(-1) is delivered at 500 mA g(-1) even after 500 deep charge/discharge cycles. Apart from promising the lithium-ion battery anode, this 3D radially oriented MoS2 nanospheres also show high activity and stability for the hydrogen evolution reaction.

Rational Design of Si/SiO2 @Hierarchical Porous Carbon Spheres as Efficient Polysulfide Reservoirs for High-Performance Li-S Battery

Integrated design of Si/SiO2 @hierar-chical porous carbon spheres is made and used as efficient polysulfide reservoir for enhancing lithium-sulfur battery (LSB) in terms of capacity, rate ability, and cycling stability via combined chemical and physical effects.

A facile layer-by-layer approach for high-areal-capacity sulfur cathodes

A layer-by-layer cathode is developed for high-areal-capacity Li-S batteries via a facile approach. Benefitting from the unique structure and favorable adsorption properties of the carbon layers, the fabricated cathodes display high capacity with superior rate and cycling performance. An areal capacity of as high as 11.3 mA h cm(-2) is achieved with a six-sulfur-layer cathode.

Controlling SEI formation on SnSb-porous carbon nanofibers for improved Na ion storage

Porous carbon nanofiber (CNF)-supported tin-antimony (SnSb) alloys are synthesized and applied as a sodium-ion battery anode. The chemistry and morphology of the solid electrolyte interphase (SEI) film and its correlation with the electrode performance are studied. The addition of fluoroethylene carbonate (FEC) in the electrolyte significantly reduces electrolyte decomposition and creates a very thin and uniform SEI layer on the cycled electrode surface, which an promote the kinetics of Na-ion migration/transportation, leading to excellent electrochemical performance.

Biomass-Derived Porous Carbon Materials for Supercapacitor

The fast consumption of fossil energy accompanied by the ever-worsening environment urge the development of a clean and novel energy storage system. As one of the most promising candidates, the supercapacitor owns unique advantages, and numerous electrodes materials have been exploited. Hence, biomass-derived porous carbon materials (BDPCs), at low cost, abundant and sustainable, with adjustable dimension, superb electrical conductivity, satisfactory specific surface area (SSA) and superior electrochemical stability have been attracting intense attention and highly trusted to be a capable candidate for supercapacitors. This review will highlight the recent lab-scale methods for preparing BDPCs, and analyze their effects on BDPCs' microstructure, electrical conductivity, chemical composition and electrochemical properties. Future research trends in this field also will be provided.

Wearable Fabrics with Self-Branched Bimetallic Layered Double Hydroxide Coaxial Nanostructures for Hybrid Supercapacitors

We report a flexible battery-type electrode based on binder-free nickel cobalt layered double hydroxide nanosheets adhered to nickel cobalt layered double hydroxide nanoflake arrays on nickel fabric (NC LDH NFAs@NSs/Ni fabric) using facile and eco-friendly synthesis methods. Herein, we utilized discarded polyester fabric as a cost-effective substrate for in situ electroless deposition of Ni, which exhibited good flexibility, light weight, and high conductivity. Subsequently, the vertically aligned NC LDH NFAs were grown on Ni fabric by means of a hot-air oven-based method, and fluffy-like NC LDH NS branches are further decorated on NC LDH NFAs by a simple electrochemical deposition method. The as-prepared core-shell-like nanoarchitectures improve the specific surface area and electrochemical activity, which provides the ideal pathways for electrolyte diffusion and charge transportation. When the electrochemical performance was tested in 1 M KOH aqueous solution, the core-shell-like NC LDH NFAs@NSs/Ni fabric electrode liberated a maximum areal capacity of 536.96 μAh/cm² at a current density of 2 mA/cm² and excellent rate capability of 78.3% at 30 mA/cm² (420.5 μAh/cm²) with a good cycling stability. Moreover, a fabric-based hybrid supercapacitor (SC) was assembled, which achieves a stable operational potential window of 1.6 V, a large areal capacitance of 1147.23 mF/cm² at 3 mA/cm², and a high energy density of 0.392 mWh/cm² at a power density of 2.353 mW/cm². Utilizing such high energy storage abilities and flexible properties, the fabricated hybrid SC operated the wearable digital watch and electric motor fan for real-time applications.

High-Performance Anode Material Sr2FeMo0.65Ni0.35O6-δ with In Situ Exsolved Nanoparticle Catalyst

A metallic nanoparticle-decorated ceramic anode was prepared by in situ reduction of the perovskite Sr2FeMo0.65Ni0.35O6-δ (SFMNi) in H2 at 850 °C. The reduction converts the pure perovksite phase into mixed phases containing the Ruddlesden-Popper structure Sr3FeMoO7-δ, perovskite Sr(FeMo)O3-δ, and the FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the SFMNi ceramic anode is greatly enhanced by the in situ exsolved Fe-Ni alloy nanoparticle catalysts that are homogeneously distributed on the ceramic backbone surface. The maximum power densities of the La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte supported a single cell with SFMNi as the anode reached 590, 793, and 960 mW cm(-2) in wet H2 at 750, 800, and 850 °C, respectively. The Sr2FeMo0.65Ni0.35O6-δ anode also shows excellent structural stability and good coking resistance in wet CH4. The prepared SFMNi material is a promising high-performance anode for solid oxide fuel cells.

Strain Engineering of a MXene/CNT Hierarchical Porous Hollow Microsphere Electrocatalyst for a High-Efficiency Lithium Polysulfide Conversion Process

Tensile-strained Mxene/carbon nanotube (CNT) porous microspheres were developed as an electrocatalyst for the lithium polysulfide (LiPS) redox reaction. The internal stress on the surface results in lattice distortion with expanding Ti-Ti bonds, endowing the Mxene nanosheet with abundant active sites and regulating the d-band center of Ti atoms upshifted closer to the Fermi level, leading to strengthened LiPS adsorbability and accelerated catalytic conversion. The macroporous framework offers uniformed sulfur distribution, potent sulfur immobilization, and large surface area. The composite interwoven by CNT tentacle enhances conductivity and prevents the restacking of Mxene sheets. This combination of tensile strain effect and hierarchical architecture design results in smooth and favorable trapping-diffusion-conversion of LiPS on the interface. The Li-S battery exhibits an initial capacity of 1451 mAh g^-1 at 0.2 C, rate capability up to 8 C, and prolonged cycle life.

Highly porous NiCo2O4 Nanoflakes and nanobelts as anode materials for lithium-ion batteries with excellent rate capability

Highly porous NiCo2O4 nanoflakes and nanobelts were synthesized by using a hydrothermal technique, followed by calcination of the NiCo2O4 precursors. The as-synthesized materials were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller methods. The NiCo2O4 nanoflakes and nanobelts were applied as anode materials for lithium-ion batteries. Owing to the unique porous structural features, the NiCo2O4 nanoflakes and nanobelts exhibited high specific capacities of 1033 and 1056 mA h g(-1), respectively, and good cycling stability and rate capability. These exceptional electrochemical performances could be ascribed to the remarkable structural feature with a high surface area and void spaces within the surface of nanoflakes and nanobelts, which provide large contact areas between electrolyte and active materials for electrolyte diffusion and cushion the volume variation during the lithium-ion insertion/extraction process.

Free-standing hierarchically sandwich-type tungsten disulfide nanotubes/graphene anode for lithium-ion batteries

Transition metal dichalcogenides (TMD), analogue of graphene, could form various dimensionalities. Similar to carbon, one-dimensional (1D) nanotube of TMD materials has wide application in hydrogen storage, Li-ion batteries, and supercapacitors due to their unique structure and properties. Here we demonstrate the feasibility of tungsten disulfide nanotubes (WS2-NTs)/graphene (GS) sandwich-type architecture as anode for lithium-ion batteries for the first time. The graphene-based hierarchical architecture plays vital roles in achieving fast electron/ion transfer, thus leading to good electrochemical performance. When evaluated as anode, WS2-NTs/GS hybrid could maintain a capacity of 318.6 mA/g over 500 cycles at a current density of 1A/g. Besides, the hybrid anode does not require any additional polymetric binder, conductive additives, or a separate metal current-collector. The relatively high density of this hybrid is beneficial for high capacity per unit volume. Those characteristics make it a potential anode material for light and high-performance lithium-ion batteries.

Rational Screening of Artificial Solid Electrolyte Interphases on Zn for Ultrahigh-Rate and Long-Life Aqueous Batteries

Solid electrolyte interphase (SEI) on Zn anodes plays a pivotal role for high-rate and long-life aqueous batteries, because it effectively inhibits side reactions and dendritic growth. Many materials are explored as SEIs by a trial-and-error approach. Herein, an exercisable way is proposed to screen the potential SEIs on Zn anodes in view of dendrite-suppressing ability and charge-transfer property theoretically. As an output of this screening, Zn₃ (BO₃ )₂ (ZBO) is checked experimentally. In symmetrical cells, Zn@ZBO runs over 250 h at an ultrahigh current density of 50 mA cm^-2 for a large areal capacity 10 mAh cm^-2 . In full cells, Zn@ZBO||MnO₂ shows an impressive cumulative capacity (≈406 mAh cm^-2 ) under harsh conditions, i.e., a lean electrolyte condition (10 µL mAh^-1 ), limited Zn supply (negative/positive electrode capacity ratio, N/P ratio = 2.3), and high areal capacity (5.0 mAh cm^-2 ). The significance of this work lies in not only the first report of ZBO on Zn showing excellent electrochemical performance, but also a feasible way to screen the promising SEI materials for other metal anodes.

Walnut-like Porous Core/Shell TiO2 with Hybridized Phases Enabling Fast and Stable Lithium Storage

TiO₂ is a promising and safe anode material for lithium ion batteries (LIBs). However, its practical application has been plagued by its poor rate capability and cycling properties. Herein, we successfully demonstrate a novel structured TiO₂ anode with excellent rate capability and ultralong cycle life. The TiO₂ material reported here shows a walnut-like porous core/shell structure with hybridized anatase/amorphous phases. The effective synergy of the unique walnut-like porous core/shell structure, the phase hybridization with nanoscale coherent heterointerfaces, and the presence of minor carbon species endows the TiO₂ material with superior lithium storage properties in terms of high capacity (∼177 mA h g^-1 at 1 C, 1 C = 170 mA g^-1), good rate capability (62 mA h g^-1 at 100 C), and excellent cycling stability (∼83 mA h g^-1 was retained over 10 000 cycles at 10 C with a capacity decay of 0.002% per cycle).

Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium-Sulfur Battery

A porous interconnected 3D boron-doped graphene aerogel (BGA) was prepared via a one-pot hydrothermal treatment. The BGA material was first loaded with sulfur to serve as cathode in lithium-sulfur batteries. Boron was positively polarized on the graphene framework, allowing for chemical adsorption of negative polysufide species. Compared with nitrogen-doped and undoped graphene aerogel, the BGA-S cathode could deliver a higher capacity of 994 mA h g(-1) at 0.2 C after 100 cycles, as well as an outstanding rate capability, which indicated the BGA was an ideal cathode material for lithium-sulfur batteries.

High-Performance Flexible Quasi-Solid-State Supercapacitors Realized by Molybdenum Dioxide@Nitrogen-Doped Carbon and Copper Cobalt Sulfide Tubular Nanostructures

Flexible quasi-/all-solid-state supercapacitors have elicited scientific attention to fulfill the explosive demand for portable and wearable electronic devices. However, the use of electrode materials faces several challenges, such as intrinsically slow kinetics and volume change upon cycling, which impede the energy output and electrochemical stability. This study presents well-aligned molybdenum dioxide@nitrogen-doped carbon (MoO2@NC) and copper cobalt sulfide (CuCo2S4) tubular nanostructures grown on flexible carbon fiber for use as electrode materials in supercapacitors. Benefiting from the chemically stable interfaces, affluent active sites, and efficient 1D electron transport, the MoO2@NC and CuCo2S4 nanostructures integrated on conductive substrates deliver excellent electrochemical performance. A flexible quasi-solid-state asymmetric supercapacitor composed of MoO2@NC as the negative electrode and CuCo2S4 as the positive electrode achieves an ultrahigh energy density of 65.1 W h kg-1 at a power density of 800 W kg-1 and retains a favorable energy density of 27.6 W h kg-1 at an ultrahigh power density of 12.8 kW kg-1. Moreover, it demonstrates good cycling performance with 90.6% capacitance retention after 5000 cycles and excellent mechanical flexibility by enabling 92.2% capacitance retention after 2000 bending cycles. This study provides an effective strategy to develop electrode materials with superior electrochemical performance for flexible supercapacitors.

A Low-Strain Potassium-Rich Prussian Blue Analogue Cathode for High Power Potassium-Ion Batteries

Most of the cathode materials for potassium ion batteries (PIBs) suffer from poor structural stability due to the large ionic radius of K⁺ , resulting in poor cycling stability. Here we report a low-strain potassium-rich K_1.84 Ni[Fe(CN)₆ ]_0.88 ⋅0.49 H₂ O (KNiHCF) as a cathode material for PIBs. The as-prepared KNiHCF cathode can deliver reversible discharge capacity of 62.8 mAh g^-1 at 100 mA g^-1 , with a high discharge voltage of 3.82 V. It can also achieve a superior rate performance of 45.8 mAh g^-1 at 5000 mA g^-1 , with a capacity retention of 88.6 % after 100 cycles. The superior performance of KNiHCF cathode results from low-strain de-/intercalation mechanism, intrinsic semiconductor property and low potassium diffusion energy barrier. The high power density and long-term stability of KNiHCF//graphite full cell confirmed the feasibility of K-rich KNiHCF cathode in PIBs. This work provides guidance to develop Prussian blue analogues as cathode materials for PIBs.

Tuning the Bifunctional Oxygen Electrocatalytic Properties of Core-Shell Co3O4@NiFe LDH Catalysts for Zn-Air Batteries: Effects of Interfacial Cation Valences

The rational design of excellent electrocatalysts is significant for triggering the slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable metal-air batteries. Hereby, we report a bifunctional catalytic material with core-shell structure constructed by Co₃O₄ nanowire arrays as cores and ultrathin NiFe-layered double hydroxides (NiFe LDHs) as shells (Co₃O₄@NiFe LDHs). The introduction of Co₃O₄ nanowires could provide abundant active sites for NiFe LDH nanosheets. Most importantly, the deposition of NiFe LDHs on the surface of Co₃O₄ can modulate the surface chemical valences of Co, Ni, and Fe species via changing the electron donor and/or electron absorption effects, finally achieving the balance and optimization of ORR and OER properties. By this core-shell design, the maximum ORR current densities of Co₃O₄@NiFe LDHs increase to 3-7 mA cm^-2, almost an order of magnitude increases compared to pure NiFe LDH (0.45 mA cm^-2). Significantly, an OER overpotential as low as 226 mV (35 mA cm^-2) is achieved in the designed core-shell catalyst, which is comparable to and/or even better than those of commercial Ir/C. Hence, the primary zinc-air battery employing Co₃O₄@NiFe LDH as an air electrode achieves a high specific capacity (667.5 mA h g^-1) and first-class energy density (797.6 W h kg^-1); the rechargeable battery can show superior reversibility, excellent stability, and voltage gaps of ∼0.8 V (∼60% of round-trip efficiency) in >1200 continuous cycles. Furthermore, the flexible quasi-solid-state zinc-air battery with bendable ability holds practical potential in portable and wearable electronic devices.

Long-Life Lithium-Sulfur Batteries with a Bifunctional Cathode Substrate Configured with Boron Carbide Nanowires

Developing high-energy-density lithium-sulfur (Li-S) batteries relies on the design of electrode substrates that can host a high sulfur loading and still attain high electrochemical utilization. Herein, a new bifunctional cathode substrate configured with boron-carbide nanowires in situ grown on carbon nanofibers (B₄ C@CNF) is established through a facile catalyst-assisted process. The B₄ C nanowires acting as chemical-anchoring centers provide strong polysulfide adsorptivity, as validated by experimental data and first-principle calculations. Meanwhile, the catalytic effect of B₄ C also accelerates the redox kinetics of polysulfide conversion, contributing to enhanced rate capability. As a result, a remarkable capacity retention of 80% after 500 cycles as well as stable cyclability at 4C rate is accomplished with the cells employing B₄ C@CNF as a cathode substrate for sulfur. Moreover, the B₄ C@CNF substrate enables the cathode to achieve both high sulfur content (70 wt%) and sulfur loading (10.3 mg cm^-2 ), delivering a superb areal capacity of 9 mAh cm^-2 . Additionally, Li-S pouch cells fabricated with the B₄ C@CNF substrate are able to host a high sulfur mass of 200 mg per cathode and deliver a high discharge capacity of 125 mAh after 50 cycles.

Recent Progress in Some Amorphous Materials for Supercapacitors

A breakthrough in technologies having "green" and sustainable energy storage conversion is urgent, and supercapacitors play a crucial role in this area of research. Owing to their unique porous structure, amorphous materials are considered one of the best active materials for high-performance supercapacitors due to their high specific capacity, excellent cycling stability, and fast charging rate. This Review summarizes the synthesis of amorphous materials (transition metal oxides, carbon-based materials, transition metal sulfides, phosphates, hydroxides, and their complexes) to highlight their electrochemical performance in supercapacitors.

Spinel manganese-nickel-cobalt ternary oxide nanowire array for high-performance electrochemical capacitor applications

Aligned spinel Mn-Ni-Co ternary oxide (MNCO) nanowires are synthesized by a facile hydrothermal method. As an electrode of supercapacitors, the MNCO nanowire array on nickel foam shows an outstanding specific capacitance of 638 F g(-1) at 1 A g(-1) and excellent cycling stability. This exceptional performance benefits from its nanowire architecture, which can provide large reaction surface area, fast ion and electron transfer, and good structural stability. Furthermore, an asymmetric supercapacitor (ASC) with high energy density is assembled successfully by employing the MNCO nanowire array as positive electrode and carbon black as negative electrode. The excellent electrochemical performances indicate the promising potential application of the ASC device in the energy storage field.