A Freestanding Selenium Disulfide Cathode Based on Cobalt Disulfide‐Decorated Multichannel Carbon Fibers with Enhanced Lithium Storage Performance

SeS₂ shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root‐like carbon fiber network decorated with CoS₂ nanoparticles (denoted as CoS₂@LRC) has been designed and prepared as the SeS₂ host for enhancing the lithium storage performance. The integrated electrode is constructed by three‐dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS₂ (70 wt %), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g⁻¹ at 0.2 A g⁻¹. What is more, there are numerous CoS₂ nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g⁻¹.     

Nanohybridization of CoS2/MoS2 Heterostructure with Polyoxometalate on Functionalized Reduced Graphene Oxide for High-Performance LIBs

To address the poor cycling stability and low rate capability of MoS₂ as electrode materials for lithium-ion batteries (LIBs), herein, the CoS₂/MoS₂/PDDA-rGO/PMo₁₂ nanocomposites are constructed via a simple hydrothermal process, combining the advantages of all three, namely, CoS₂/MoS₂ heterojunction and polyoxometalates (POMs) provide abundant catalytically active sites and increase the multi-electron transfer ability, and the positively charged poly(diallyldimethylammonium chloride) modified reduced graphene oxide (PDDA-rGO) improve electronic conductivity and effectively prevent the aggregation of MoS₂, meanwhile stabilize the negatively charged [PMo₁₂O₄₀]³⁻. After the electrochemical testing, the resulting CoS₂/MoS₂/PDDA-rGO/PMo₁₂ nanocomposite achieved 1055 mA h g⁻¹ initial specific capacities and stabilized at 740 mA h g⁻¹ after 150 cycles at 100 mA g⁻¹ current density. And the specific capacities of MoS₂, MoS₂/PDDA-rGO, CoS₂/MoS₂, and CoS₂/MoS₂/PDDA-rGO were 201, 421, 518, and 589 at 100 mA g⁻¹ after 150 cycles, respectively. The fact of the greatly improving capacity of MoS₂-based nanocomposites suggests its potential for high performance electrode materials of LIBs. Moreover, the lithium storage mechanism of CoS₂/MoS₂/PDDA-rGO/PMo₁₂ has been discussed on the basis of cyclic voltammetry with different scan rates.     

Few-Layer MoS2 Nanosheets Encapsulated in N-Doped Carbon Hollow Spheres as Long-Life Anode Materials for Lithium-Ion Batteries

Two-dimensional molybdenum disulfide (MoS₂) has been recognized as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, but its rapid capacity decay owing to poor conductivity, structure pulverization, and polysulfide dissolution presents significant challenges in practical applications. Herein, triple-layered hollow spheres in which MoS₂ nanosheets are fully encapsulated between inner carbon and outer nitrogen-doped carbon (NC) were fabricated. Such an architecture provides high conductivity and efficient lithium-ion transfer. Moreover, the NC shell prevents aggregation and exfoliation of MoS₂ nanosheets and thus maintains the integrity of the nanostructure during the charge/discharge process. As anode materials for LIBs, the C@MoS₂@NC hollow spheres deliver a high reversible capacity (747 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹) and excellent long-cycle performance (650 mA h g⁻¹ after 1000 cycles at 1.0 A g⁻¹), which confirm its potential for high-performance LIBs.     

Synthesis of Porous Ni-Doped CoSe2/C Nanospheres towards High-Rate and Long-Term Sodium-Ion Half/Full Batteries

Carbon-layer-coated porous Ni-doped CoSe₂ (Ni-CoSe₂/C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni-CoSe₂/C is formed by the aggregation of many small particles (20–40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni-CoSe₂/C delivers superior rate performance (314.0 mA h g⁻¹ at 20 A g⁻¹), ultra-long cycle life (316.1 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles), and excellent full-cell performance (208.3 mA h g⁻¹ at 0.5 A g⁻¹ after 70 cycles) when used as an anode material for half/full sodium-ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X-ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na⁺ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni-CoSe₂/C nanospheres have great potential to serve as an electrode material for sodium-ion batteries.     

Sulfur-/Nitrogen-Rich Albumen Derived “Self-Doping” Graphene for Sodium-Ion Storage

The development of sodium-ion batteries (SIBs) is hindered by the rapid reduction in reversible capacity of carbon-based anode materials. Outside-in doping of carbon-based anodes has been extensively explored. Nickel and NiS₂ particles embedded in nitrogen and sulfur codoped porous graphene can significantly improve the electrochemical performance. Herein a built-in heteroatom “self-doping” of albumen-derived graphene for sodium storage is reported. The built-in sulfur and nitrogen in albumen act as the doping source during the carbonization of proteins. The sulfur-rich proteins in albumen can also guide the doping and nucleation of nickel sulfide nanoparticles. Additionally, the porous architecture of the carbonized proteins is achieved through removable KCl/NaCl salts (medium) under high-temperature melting conditions. During the carbonization process, nitrogen can also reduce the carbonization temperature of thermally stable carbon materials. In this work, the NS-graphene delivered a specific capacity of 108.3 mAh g⁻¹ after 800 cycles under a constant current density of 500 mA g⁻¹. In contrast, the Ni/NiS₂/NS-graphene maintained a specific capacity of 134.4 mAh g⁻¹; thus the presence of Ni/NiS₂ particles improved the electrochemical performance of the whole composite.     

Dual Dopamine Derived Polydopamine Coated N-Doped Porous Carbon Spheres as a Sulfur Host for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the most promising energy storage systems owing to their high energy density and low cost. However, their wide application is still limited by the rapid capacity fading. Herein, polydopamine (PDA)-coated N-doped hierarchical porous carbon spheres (NPC@PDA) are reported as sulfur hosts for high-performance Li-S batteries. The NPC core with abundant and interconnected pores provides fast electron/ion transport pathways and strong trapping ability towards lithium polysulfide intermediates. The PDA shell could further suppress the loss of lithium polysulfide intermediates through polar–polar interactions. Benefiting from the dual function design, the NPC/S@PDA composite cathode exhibits an initial capacity of 1331 mAh g⁻¹ and remains at 720 mAh g⁻¹ after 200 cycles at 0.5 C. At the pouch cell level with a high sulfur mass loading, the NPC/S@PDA composite cathode still exhibits a high capacity of 1062 mAh g⁻¹ at a current density of 0.4 mA cm⁻².     

Coated/Sandwiched rGO/CoSx Composites Derived from Metal–Organic Frameworks/GO as Advanced Anode Materials for Lithium‐Ion Batteries

Rational composite materials made from transition metal sulfides and reduced graphene oxide (rGO) are highly desirable for designing high‐performance lithium‐ion batteries (LIBs). Here, rGO‐coated or sandwiched CoS_x composites are fabricated through facile thermal sulfurization of metal–organic framework/GO precursors. By scrupulously changing the proportion of Co²⁺ and organic ligands and the solvent of the reaction system, we can tune the forms of GO as either a coating or a supporting layer. Upon testing as anode materials for LIBs, the as‐prepared CoS_x‐rGO‐CoS_x and rGO@CoS_x composites demonstrate brilliant electrochemical performances such as high initial specific capacities of 1248 and 1320 mA h g^?1, respectively, at a current density of 100 mA g^?1, and stable cycling abilities of 670 and 613 mA h g^?1, respectively, after 100 charge/discharge cycles, as well as superior rate capabilities. The excellent electrical conductivity and porous structure of the CoS_x/rGO composites can promote Li⁺ transfer and mitigate internal stress during the charge/discharge process, thus significantly improving the electrochemical performance of electrode materials.     

碳球担载二硫化钴纳米复合电催化剂的制备及其析氢性能研究

采用一步水热法,通过引入载体碳球(CSs)和表面活性剂CTAB,将二硫化钴(CoS_2)纳米颗粒均匀负载在CSs表面.相比于单独的CoS_2,改性后CSs担载的CoS_2(CoS_2/A-CSs)展现出了更好的电催化活性.在电解液为0.5mol/L H_2SO_4溶液中,电流密度为10 mA·cm~(-2)条件下,其析氢反应过电位仅为154 mV.经过12 h的稳定性测试,CoS_2/A-CSs析氢反应过电位为180 mV,这表明其仍具有良好的电化学催化析氢反应活性.这种复合电催化剂的优良性能主要归因于CSs的高导电性和其对CoS_2纳米颗粒的均匀分散;此外,CTAB的引入,促使CSs与CoS_2之间结合的更加紧密,进而加快了活性位点间的电子传导.     

CoS2 Nanoparticles Embedded in Covalent Organic Polymers as Efficient Electrocatalyst for Oxygen Evolution Reaction with Ultralow Overpotential

Cobalt disulfide (CoS₂) has been explored as attractive electrocatalyst for oxygen evolution reaction (OER). However, bulk CoS₂ sheets have limited catalytic activity due to low exposure of active sites. Herein, through an in-situ vulcanization approach, CoS₂ nanoparticles are embedded into bipyridine-containing covalent organic polymer (BP-COP). The as-prepared nanocomposite CoS₂@BP-COP exhibits high catalytic activity toward OER with an ultra-low overpotential of 270 mV (vs. RHE) at a current density of 10 mA cm⁻², a small Tafel slope of 36 mV dec⁻¹, and an excellent durability for 24 h without decay. The surface of CoS₂ is partially converted into CoOOH to form CoS₂/CoOOH as active sites under OER conditions. CoS₂@BP-COP displays superior OER catalytic activity to CoS₂ nanosheets and commercially available RuO₂ under the same conditions. The outstanding OER performance activity of CoS₂@BP-COP could be attributed to the uniform and small particle sizes of CoS₂/CoOOH distributed in BP-COP.     

Catalytically Active CoSe2 Supported on Nitrogen-Doped Three Dimensional Porous Carbon as a Cathode for Highly Stable Lithium-Sulfur Battery

Lithium-sulfur batteries are promising secondary energy storage devices that are mainly limited by its unsatisfactory cyclability owing to inefficient reversible conversion of sulfur and lithium sulfide on the cathode during the discharge/charging process. In this study, nitrogen-doped three-dimensional porous carbon material loaded with CoSe₂ nanoparticles (CoSe₂-PNC) is developed as a cathode for lithium-sulfur battery. A combination of CoSe₂ and nitrogen-doped porous carbon can efficiently improve the cathode activity and its conductivity, resulting in enhanced redox kinetics of the charge/discharge process. The obtained electrode exhibits a high discharge specific capacity of 1139.6 mAh g⁻¹ at a current density of 0.2 C. After 100 cycles, its capacity remained at 865.7 mAh g⁻¹ thus corresponding to a capacity retention of 75.97 %. In a long-term cycling test, discharge specific capacity of 546.7 mAh g⁻¹ was observed after 300 cycles performed at a current density of 1 C.     

Dramatically Enhanced Li-Ion Storage of ZnO@C Anodes through TiO2 Homogeneous Hybridization

Amorphous nanoparticles of ZnO and TiO₂ embedded in carbon nanocages (AZT⊂CNCs) were successfully synthesized through a simple annealing process of TiO₂-coated zeolitic imidazolate framework-8 (ZIF-8). In the current anode of AZT⊂CNCs, tiny ZnO and TiO₂ nanoparticles were uniformly distributed in the carbon matrix (carbon nanocages), which could effectively buffer the volume expansion of electroactive ZnO and provide excellent electric conductivity. After fully investigating the electrochemical performance of the AZT⊂CNCs samples obtained with different additive amounts of tetrabutyl orthotitanate (TBOT) for TiO₂ coating, it has been found that AZT-30 (0.1 g ZIF-8 with 30 mL TBOT) shows the best cycle stability (510 mA h g⁻¹ after 350 cycles at 200 mA g⁻¹) and a superior rate capability (610 mA h g⁻¹ after 3500 cycles at 2 A g⁻¹). The greatly enhanced Li-ion storage performance could be ascribed to the fact that the introduction of amorphous TiO₂ could activate the reversible lithiation/delithiation reaction of ZnO during the charge/discharge process.     

Hierarchical Carbon Nanowire/Ni@MnO2 Nanocomposites for High-Performance Asymmetric Supercapacitors

A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO₂ (CC/N-CNWs/Ni@MnO₂) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO₂ is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO₂ electrode exhibits a higher specific capacitance of 571.4 F g⁻¹ compared with those of CC/N-CNWs@MnO₂ (311 F g⁻¹), CC/Ni@MnO₂ (196.6 F g⁻¹), and CC@MnO₂ (186.1 F g⁻¹) at 1 A g⁻¹ and remarkable rate capability (367.5 F g⁻¹ at 10 A g⁻¹). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO₂ as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg⁻¹ at a power density of 900 W kg⁻¹ and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.     

硫与Mn2O3空心球的复合结构及其在锂硫电池中的应用

在水热条件下,以碳球为模板合成了Mn₂O₃空心球,并用作锂硫电池的载硫基底材料。测试结果表明载硫量为51%的Mn₂O₃-S复合材料显示了较高的比容量,良好的循环稳定性和倍率性能。循环100圈后,最终可逆容量仍保持657 mA·g^-1,证明该Mn₂O₃空心球是一种有潜力的载硫基底材料。     

硫与Mn2O3空心球的复合结构及其在锂硫电池中的应用

在水热条件下,以碳球为模板合成了Mn₂O₃空心球,并用作锂硫电池的载硫基底材料。测试结果表明载硫量为51%的Mn₂O₃-S复合材料显示了较高的比容量,良好的循环稳定性和倍率性能。循环100圈后,最终可逆容量仍保持657 mA·g^-1,证明该Mn₂O₃空心球是一种有潜力的载硫基底材料。     

Rational Construction of 2D Fe3O4@Carbon Core–Shell Nanosheets as Advanced Anode Materials for High-Performance Lithium-Ion Half/Full Cells

Transition metal oxides have vastly limited practical application as electrode materials for lithium-ion batteries (LIBs) due to their rapid capacity decay. Here, a versatile strategy to mitigate the volume expansion and low conductivity of Fe₃O₄ by coating a thin carbon layer on the surface of Fe₃O₄ nanosheets (NSs) was employed. Owing to the 2D core–shell structure, the Fe₃O₄@C NSs exhibit significantly improved rate performance and cycle capability compared with bare Fe₃O₄ NSs. After 200 cycles, the discharge capacity at 0.5 A g⁻¹ was 963 mA h g⁻¹ (93 % retained). Moreover, the reaction mechanism of lithium storage was studied in detail by ex situ XRD and HRTEM. When coupled with a commercial LiFePO₄ cathode, the resulting full cell retains a capacity of 133 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, which demonstrates its superior energy storage performance. This work provides guidance for constructing 2D metal oxide/carbon composites with high performance and low cost for the field of energy storage.     

An Aligned and Laminated Nanostructured Carbon Hybrid Cathode for High‐Performance Lithium–Sulfur Batteries

An aligned and laminated sulfur‐absorbed mesoporous carbon/carbon nanotube (CNT) hybrid cathode has been developed for lithium–sulfur batteries with high performance. The mesoporous carbon acts as sulfur host and suppresses the diffusion of polysulfide, while the CNT network anchors the sulfur‐absorbed mesoporous carbon particles, providing pathways for rapid electron transport, alleviating polysulfide migration and enabling a high flexibility. The resulting lithium–sulfur battery delivers a high capacity of 1226 mAh g⁻¹ and achieves a capacity retention of 75 % after 100 cycles at 0.1 C. Moreover, a high capacity of nearly 900 mAh g⁻¹ is obtained for 20 mg cm⁻², which is the highest sulfur load to the best of our knowledge. More importantly, the aligned and laminated hybrid cathode endows the battery with high flexibility and its electrochemical performances are well maintained under bending and after being folded for 500 times.     

PEO-b-PS Block Copolymer Templated Mesoporous Carbons: A Comparative Study of Nitrogen and Sulfur Doping in the Oxygen Reduction Reaction to Hydrogen Peroxide

Carbon materials slightly doped with heteroatoms such as nitrogen (N-RFC) or sulfur (S-RFC) are investigated as active catalysts for the electrochemical bielectronic oxygen reduction reaction (ORR) to H₂O₂. Mesoporous carbons with wide, accessible pores were prepared by pyrolysis of a resorcinol-formaldehyde resin using a PEO-b-PS block copolymer as a sacrificial templating agent and the nitrogen and sulfur doping were accomplished in a second thermal treatment employing 1,10-phenanthroline and dibenzothiophene as nitrogen and sulfur precursors, respectively. The synthetic strategy allowed to obtain carbon materials with very high surface area and mesopore volume without any further physicochemical post treatment. Voltammetric rotating ring-disk measurements in combination with potentiostatic and galvanostatic bulk electrolysis measurements in 0.5 m H₂SO₄ demonstrated a pronounced effect of heteroatom doping and mesopores volume on the catalytic activity and selectivity for H₂O₂. N-RFC electrode was employed as electrode material in a 45 h electrolysis showing a constant H₂O₂ production of 298 mmol g⁻¹ h⁻¹ (millimoles of H₂O₂ divided by mass of catalyst and electrolysis time), with a faradic efficiency (FE) up to 61 % and without any clear evidence of degradation. The undoped carbon RFC showed a lower production rate (218 mmol g⁻¹ h⁻¹) but a higher FE of 76 %, while the performances drastically dropped when S-RFC (production rate 11 mmol g⁻¹ h⁻¹ and FE=39 %) was used.     

Enhanced electrochemical performance of carbon-coated TiO2 nanobarbed fibers as anode material for lithium-ion batteries

We report the electrochemical performance of carbon-coated TiO₂ nanobarbed fibers (TiO₂@C NBFs) as anode material for lithium-ion batteries. The TiO₂@C NBFs are composed of TiO₂ nanorods grown on TiO₂ nanofibers as a core, coated with a carbon shell. These nanostructures form a conductive network showing high capacity and C-rate performance due to fast lithium-ion diffusion and effective electron transfer. The TiO₂@C NBFs show a specific reversible capacity of approximately 170 mAh g^− 1 after 200 cycles at a 0.5 A g^− 1 current density, and exhibit a discharge rate capability of 4 A g^− 1 while retaining a capacity of about 70 mAh g^− 1. The uniformly coated amorphous carbon layer plays an important role to improve the electrical conductivity during the lithiation–delithiation process.     

In-situ Grown SnO2 Nanospheres on Reduced GO Nanosheets as Advanced Anodes for Lithium-ion Batteries

Nanostructured tin dioxide (SnO₂) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (1494 mA h g⁻¹) and excellent stability. Unfortunately, the rapid capacity fading and poor electrical conductivity of bulk SnO₂ material restrict its practical application. Here, SnO₂ nanospheres/reduced graphene oxide nanosheets (SRG) are fabricated through in-situ growth of carbon-coated SnO₂ using template-based approach. The nanosheet structure with the external layer of about several nanometers thickness can not only accommodate the volume change of Sn lattice during cycling but also enhance the electrical conductivity effectively. Benefited from such design, the SRG composites could deliver an initial discharge capacity of 1212.3 mA h g⁻¹ at 0.1 A g⁻¹, outstanding cycling performance of 1335.6 mA h g⁻¹ after 500 cycles at 1 A g⁻¹, and superior rate capability of 502.1 mA h g⁻¹ at 5 A g⁻¹ after 10 cycles. Finally, it is believed that this method could provide a versatile and effective process to prepare other metal-oxide/reduced graphene oxide (rGO) 2D nanocomposites.     

The Efficient K Ion Storage of M2P2O7/C (M=Fe,Co, Ni) Anode Derived from Organic-Inorganic Phosphate Precursors

Metal phosphates have been widely explored in lithium ion batteries and sodium ion batteries owing to high theoretical capacities, mild toxicity and low cost. However, their potassium ion battery applications are less reported due to the limited conductivity and the slow diffusion kinetics. Considering these drawbacks, novel structured M₂P₂O₇/C (M=Fe, Co, Ni) nanoflake composites are prepared through an organic-phosphors precursor-assisted solvothermal method and a subsequent high temperature annealing process. The designed Co₂P₂O₇/C composite exhibits the highest rate capacity with 502 mAh g⁻¹ at 0.1 A g⁻¹ and good cyclability for 900 cycles at 1 A g⁻¹ and 2 A g⁻¹ when compared with Ni and Fe based composites. The superior electrochemical performance can be attributed to their unique nanoparticle-assembled nanoflake structure, which can afford enough active sites for K⁺ intercalation. In addition, the robust pyrophosphate crystal structure and the in situ formed carbon composition also have positive effects on enhancing the long-term cycling performance and the electrode's conductivity. Finally, this organic-phosphors precursor induced simple approach can be applied for easy fabrication of other pyrophosphate/carbon hybrids as advanced electrodes.