Bimetallic zeolitic imidazolate framework-derived substrate-free anode with superior cyclability for high-capacity lithium-ion batteries

Freestanding carbon nanofibers loaded with bimetallic hollow nanocage structures were synthesized.The nanocages inherited the rhombic dodecahedral morphology of the zeolitic imidazolate framework(ZIF)precursors,ZIF-8 and ZIF-67.As anode materials for lithium-ion batteries(LIBs),the bimetallic nanocage-loaded freestanding carbon nanofibers effectively buffered volume expansions and alleviated pulverization through their different reduction and oxidation potentials.The higher capacities of the composite anodes arose via the formation of the Li_xZn alloy and Li₂O by Zn and Co ions,respectively,and the enhanced conductivity conferred by the carbon nanofibers.A synergistic effect of the composite components toward the strong electrochemical performance(688 m A h·g^-1at 1200 m A·g^-1)of the bimetallic nanocage-loaded fibers was demonstrated through the superior long-term stability of the anode(1048 m A h·g^-1after 300 cycles at 100 m A·g^-1),suggesting that the fabricated anode can be a promising material for use in portable LIBs.     

Interface-modulated fabrication of hierarchical yolk–shell Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/C dodecahedrons as stable anodes for lithium and sodium storage

Transition-metal oxides (TMOs) have gradually attracted attention from researchers as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of their high theoretical capacity.However,their poor cycling stability and inferior rate capability resulting from the large volume variation during the lithiation/sodiation process and their low intrinsic electronic conductivity limit their applications.To solve the problems of TMOs,carbon-based metal-oxide composites with complex structures derived from metal-organic frameworks (MOFs) have emerged as promising electrode materials for LIBs and SIBs.In this study,we adopted a facile interface-modulated method to synthesize yolk-shell carbon-based Co3O4 dodecahedrons derived from ZIF-67 zeolitic imidazolate frameworks.This strategy is based on the interface separation between the ZIF-67 core and the carbon-based shell during the pyrolysis process.The unique yolk-shell structure effectively accommodates the volume expansion during lithiation or sodiation,and the carbon matrix improves the electrical conductivity of the electrode.As an anode for LIBs,the yolk-shell Co3O4/C dodecahedrons exhibit a high specific capacity and excellent cycling stability (1,100 mAh·g-1 after 120 cycles at 200 mA·g-1).As an anode for SIBs,the composites exhibit an outstanding rate capability (307 mAh·g-1 at 1,000 mA·g-1 and 269 mAh·g-1 at 2,000 mA·g-1).Detailed electrochemical kinetic analysis indicates that the energy storage for Li+ and Na+ in yolk-shell Co3O4/C dodecahedrons shows a dominant capacitive behavior.This work introduces an effective approach for fabricating carbonbased metal-oxide composites by using MOFs as ideal precursors and as electrode materials to enhance the electrochemical performance of LIBs and SIBs.     

高性能自支撑不锈钢网@MoS2锂离子电池负极材料

为了提高MoS₂作为Li离子电池负极材料整体的导电性和稳定性,将纳米化的MoS₂与其它导电性好的材料进行复合,通过水热法在导电基底不锈钢网(Stainless steel net, SS)上原位合成了一层MoS₂纳米花,制备了无粘结剂的自支撑结构的SS@MoS₂负极材料。纳米花状的MoS₂和导电性优异的SS提高了电子和Li离子的扩散速率,同时改善了电极的反应动力学。当作为Li离子电池负极材料时,SS@MoS₂电极表现出优异的储Li性能,特别是具有显著的大倍率充放电性能,即在1 000 mA/g的大电流密度下循环600次,比容量仍保持在862.1 mA·h/g。      

Freestanding nanosheets of 1T-2H hybrid MoS2 as electrodes for efficient sodium storage

Molybdenum disulfide(MoS₂) is a promising electrode material for sodium-ion batteries as it offers a large capacity through a distinct conversion reaction.However,the electrochemical potential of MoS₂ is often restrained by the poor conductivity as the dominant 2 H phase is a semiconductor while the metallic1 T phase is thermodynamically unstable.In this work,we report a hybrid design and material preparation of freestanding nanosheets of MoS₂ composed of both 1 T and 2 H phases based on mild hydrothermal reaction.The introduction of the metallic 1 T-MoS₂ phase into 2 H-MoS₂ and their intimate hybridization enable a significant improvement in electronic conductivity,while the freestanding architecture avoids possible electrochemical aggregation.When used as electrodes for sodium storage,such a hybrid MoS₂ affords a high capacity of~500 mA h g^-1 at 0.5 A g^-1 after 300 cycles,and retains capacity of~200 mA h g^-1 at a high current rate of 4 A g^-1,thus demonstrating their potential in high-performance battery applications.     

Si/C particles on graphene sheet as stable anode for lithium-ion batteries

Silicon is considered as one of the most promising anodes for Li-ion batteries (LIBs),but it is limited for commercial applications by the critical issue of large volume expansion during the lithiation.In this work,the structure of silicon/carbon (Si/C) particles on graphene sheets (Si/C-G) was obtained to solve the issue by using the void space of Si/C particles and graphene.Si/C-G material was from Si/PDA-GO that silicon particles was coated by polydopamine (PDA) and reacted with oxide graphene (GO).The Si/C-G material have good cycling performance as the stability of the structure during the lithiation/dislithiation.The Si/C-G anode materials exhibited high reversible capacity of 1910.5 mA h g-1 and 1196.1 mA h g-1 after 700 cycles at 357.9 mA g-1,and have good rate property of 507.2 mA h g-1 at high current density,showing significantly improved commercial viability of silicon electrodes in high-energy-density LIBs.     

Glucose‐Induced Synthesis of 1T‐MoS2/C Hybrid for High‐Rate Lithium‐Ion Batteries

1T phase MoS₂ possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T‐MoS₂/C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer‐layer 1T‐MoS₂ nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change during cycling. The high intrinsic conductivity of 1T‐MoS₂ also contributes to a faster transfer of lithium ions and electrons. Moreover, much smaller and fewer‐layer nanosheets can shorten the diffusion path of lithium ions and accelerate reaction kinetics, leading to an improved electrochemical performance. It delivers a high initial capacity of 920.6 mAh g^?1 at 1 A g^?1 and the capacity can maintain 870 mAh g^?1 even after 300 cycles, showing a superior cycling stability. The electrode presents a high rate performance as well with a reversible capacity of 600 mAh g^?1 at 10 A g^?1. These results show that the 1T‐MoS₂/C hybrid shows potential for use in high‐performance lithium‐ion batteries.     

Understanding of the capacity contribution of carbon in phosphorus-carbon composites for high-performance anodes in lithium ion batteries

Phosphorus has recently received extensive attention as a promising anode for lithium ion batteries (LIBs) due to its high theoretical capacity of 2,596 mAh·g-1.To develop high-performance phosphorus anodes for LIBs,carbon materials have been hybridized with phosphorus (P-C) to improve dispersion and conductivity.However,the specific capacity,rate capability,and cycling stability of P-C anodes are still less than satisfactory for practical applications.Furthermore,the exact effects of the carbon support on the electrochemical performance of the P-C anodes are not fully understood.Herein,a series of xP-yC anode materials for LIBs were prepared by a simple and efficient ball-milling method.6P-4C and 3P-7C were found to be optimum mass ratios of x/y,and delivered initial discharge capacities of 1,803.5 and 1,585.3.mAh.g-1,respectively,at 0.1 C in the voltage range 0.02-2 V,with an initial capacity retention of 68.3％ over 200 cycles (more than 4 months cycling life) and 40.8％ over 450 cycles.The excellent electrochemical performance of the 6P-4C and 3P-7C samples was attributed to a synergistic effect from both the adsorbed P and carbon.     

Interface-modulated approach toward multilevel metal oxide nanotubes for lithium-ion batteries and oxygen reduction reaction

Metal oxide hollow structures with multilevel interiors are of great interest for potential applications such as catalysis,chemical sensing,drug delivery,and energy storage.However,the controlled synthesis of multilevel nanotubes remains a great challenge.Here we develop a facile interface-modulated approach toward the synthesis of complex metal oxide multilevel nanotubes with tunable interior structures through electrospinning followed by controlled heat treatment.This versatile strategy can be effectively applied to fabricate wire-in-tube and tubein-tube nanotubes of various metal oxides.These multilevel nanotubes possess a large specific surface area,fast mass transport,good strain accommodation,and high packing density,which are advantageous for lithium-ion batteries (LIBs)and the oxygen reduction reaction (ORR).Specifically,shrinkable CoMn2O4 tube-in-tube nanotubes as a lithium-ion battery anode deliver a high discharge capacity of ～565 mAh.g-1 at a high rate of 2 A.g-1,maintaining 89％ of the latter after 500 cycles.Further,as an oxygen reduction reaction catalyst,these nanotubes also exhibit excellent stability with about 92％ current retention after 30,000 s,which is higher than that of commercial Pt/C (81％).Therefore,this feasible method may push the rapid development of one-dimensional (1D) nanomaterials.These multifunctional nanotubes have great potential in many frontier fields.     

Tungsten diselenide nanoplates as advanced lithium/sodium ion electrode materials with different storage mechanisms

Transition-metal dichalcogenides (TMDs) exhibit immense potential as lithium/sodium-ion electrode materials owing to their sandwich-like layered structures.To optimize their lithium/sodium-storage performance,two issues should be addressed:fundamentally understanding the chemical reaction occurring in TMD electrodes and developing novel TMDs.In this study,WSe2 hexagonal nanoplates were synthesized as lithium/sodium-ion battery (LIB/SIB) electrode materials.For LIBs,the WSe2-nanoplate electrodes achieved a stable reversible capacity and a high rate capability,as well as an ultralong cycle life of up to 1,500 cycles at 1,000 mA·g-1.Most importantly,in situ Raman spectroscopy,ex situ X-ray diffraction (XRD),transmission electron microscopy,and electrochemical impedance spectroscopy measurements performed during the discharge-charge process clearly verified the reversible conversion mechanism,which can be summarized as follows:WSe2 + 4Li+ + 4e-←→ W + 2Li2Se.The WSe2 nanoplates also exhibited excellent cycling performance and a high rate capability as SIB electrodes.Ex situ XRD and Raman spectroscopy results demonstrate that WSe2 reacted with Na+ more easily and thoroughly than with Li+ and converted to Na2Se and tungsten in the 1st sodiated state.The subsequent charging reaction can be expressed as Na2Se → Se + 2Na+ + 2e-,which differs from the traditional conversion mechanism for LIBs.To our knowledge,this is the first systematic exploration of the lithium/sodium-storage performance of WSe2 and the mechanism involved.     

Facile one-pot synthesis of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> hollow spheres with controllable number of shells for high-performance supercapacitors

In this work,single-and double-shelled NiCo2O4 hollow spheres have been synthesized in situ by a one-pot solvothermal method assisted by xylose,followed by heat treatment.Employed as supercapacitor electrode materials,the double-shelled NiCo2O4 hollow spheres exhibit a remarkable specific capacitance (1,204.4 F·g-1 at a current density of 2.0 A·g-1) and excellent cycling stability (103.6％ retention after 10,000 cycles at a current density of 10 A·g-1).Such outstanding electrochemical performance can be attributed to their unique internal morphology,which provides a higher surface area with a larger number of active sites available to interact with the electrolyte.The versatility of this method was demonstrated by applying it to other binary metal oxide materials,such as ZnCo2O4,ZnMn2O4,and CoMn2O4.The present study thus illustrates a simple and general strategy for the preparation of binary transition metal oxide hollow spheres with a controllable number of shells.This approach shows great promise for the development of next-generation high-performance electrochemical materials.     

Interconnected silicon hollow nanospheres for lithium-ion battery anodes with long cycle life

Silicon is a promising candidate for the anode material in lithium-ion batteries due to its high theoretical specific capacity. However, volume changes during cycling cause pulverization and capacity fade, and improving cycle life is a major research challenge. Here, we report a novel interconnected Si hollow nanosphere electrode that is capable of accommodating large volume changes without pulverization during cycling. We achieved the high initial discharge capacity of 2725 mAh g(-1) with less than 8% capacity degradation every hundred cycles for 700 total cycles. Si hollow sphere electrodes also show a Coulombic efficiency of 99.5% in later cycles. Superior rate capability is demonstrated and attributed to fast lithium diffusion in the interconnected Si hollow structure.     

石墨烯负载花球状二氧化锰复合材料制备及其电容性能研究

利用高锰酸钾与乙醇之间的氧化还原反应,在多孔石墨烯表面沉积纳米二氧化锰花球,获得了一种新型的复合电极材料。通过XRD,TG,SEM,TEM等分析手段确定了材料的晶体结构、化学成分、微观形貌特征。电化学性能测试表明:纳米二氧化锰花球具有优异的比电容,但是倍率性能和循环性能不足。通过在石墨烯表面负载纳米二氧化锰花球,能够显著增加石墨烯的比电容,同时改善纳米二氧化锰花球的倍率性能和循环性能。采用0.5mol/L K_2SO_4电解液,进行三电极循环伏安测试,复合电极材料在2mV·s^-1扫速下的比电容高达295F·g^-1,在1000mV·s^-1扫速下,比电容仍然可达102F·g^-1,同时100mV·s^-1,1000次循环后,电容循环保持率可达96.3%。这表明石墨烯负载花球状二氧化锰材料是一种极具潜力的超级电容器电极材料。     

In-situ encapsulation of α-Fe2O3 nanoparticles into ZnFe2O4 micro-sized capsules as high-performance lithium-ion battery anodes

Transition metal oxides as anode materials for high-performance lithium-ion batteries suffer from severe capacity decay,originating primarily from particle pulverization upon volume expansion/shrinkage and the intrinsically sluggish electron/ion transport.Herein,in-situ encapsulation of α-Fe2O3 nanoparticles into micro-sized ZnFe2O4 capsules is facilely fulfilled through a co-precipitation process and followed by heat-treatment at optimal calcination temperature.The porous ZnFe2C4 scaffold affords a synergistic confinement effect to suppress the grain growth of α-Fe2O3 nanocrystals during the calcination process and to accommodate the stress generated by volume expansion during the charge/discharge process,leading to an enhanced interfacial conductivity and inhibit electrode pulverization and mechanical failure in the active material.With these merits,the prepared α-Fe2O3/ZnFe2O4 composite delivers prolonged cycling stability and improved rate capability with a higher specific capacity than sole α-Fe2O3 and ZnFe2O4.The discharge capacity is retained at 700 mAh g-1 after 500 cycles at 200 mA g-1 and 940 mAh g-1 after 50 cycles at 100 mA g-1.This work provides a new perspective in designing transition metal oxides for advanced lithium-ion batteries with superior electrochemical properties.     

Nitrogen and Phosphorus Codoped Vertical Graphene/Carbon Cloth as a Binder‐Free Anode for Flexible Advanced Potassium Ion Full Batteries

With the fast development in flexible electronic technology, power supply devices with high performance, low‐cost, and flexibility are becoming more and more important. Potassium ion batteries (KIBs) have a brilliant prospect for applications benefiting from high voltage, lost cost, as well as similar electrochemistry to lithium ion batteries (LIBs). Although carbon materials have been studied as KIBs anodes, their rate capability and cycling stability are still unsatisfactory due to the large‐size potassium ions. Herein, a nitrogen (N) and phosphorus (P) dual‐doped vertical graphene (N, P‐VG) uniformly grown on carbon cloth (N, P‐VG@CC) is reported as a binder‐free anode for flexible KIBs. With the combined advantages of rich active sites, highly accessible surface, highly conductive network, larger interlayer spacing as well as robust structural stability, this binder‐free N, P‐VG@CC anode exhibits high capacity (344.3 mAh g^?1), excellent rate capability (2000 mA g^?1; 46.5% capacity retention), and prominent long‐term cycling stability (1000 cycles; 82% capacity retention), outperforming most of the recently reported carbonaceous anodes. Moreover, a potassium ion full cell is successfully assembled on the basis of potassium Prussian blue (KPB)//N, P‐VG@CC, exhibiting a large energy density of 232.5 Wh kg^?1 and outstanding cycle stability.     

Advanced Matrixes for Binder-Free Nanostructured Electrodes in Lithium-Ion Batteries

Commercial lithium-ion batteries (LIBs), limited by their insufficient reversible capacity, short cyclability, and high cost, are facing ever-growing requirements for further increases in power capability, energy density, lifespan, and flexibility. The presence of insulating and electrochemically inactive binders in commercial LIB electrodes causes uneven active material distribution and poor contact of these materials with substrates, reducing battery performance. Thus, nanostructured electrodes with binder-free designs are developed and have numerous advantages including large surface area, robust adhesion to substrates, high areal/specific capacity, fast electron/ion transfer, and free space for alleviating volume expansion, leading to superior battery performance. Herein, recent progress on different kinds of supporting matrixes including metals, carbonaceous materials, and polymers as well as other substrates for binder-free nanostructured electrodes in LIBs are summarized systematically. Furthermore, the potential applications of these binder-free nanostructured electrodes in practical full-cell-configuration LIBs, in particular fully flexible/stretchable LIBs, are outlined in detail. Finally, the future opportunities and challenges for such full-cell LIBs based on binder-free nanostructured electrodes are discussed.     

ZnS-PANI nanocomposite with enhanced electrochemical performances for lithium-ion batteries

A simple two-step method of coprecipitation followed by polymerization successfully yielded ZnS-PANI nanocomposite. This composite was characterized using XRD, FTIR, SEM, BET, and XPS. The results indicate that the morphology of the ZnS-PANI nanocomposite possesses a uniform spherical shape. The ZnS-PANI electrode shows an excellent initial discharge capacity of 1182.1 mAh/g, a high discharge capacity of 693.5 mAh/g at a current rate of 0.1 °C after 500 cycles, good cycling stability, and an excellent rate capability of 673 mAh/g at 2.0 °C, when used as anode materials for lithium-ion batteries (LIBs). The excellent electrochemical performances make the nanosized ZnS-PANI nanocomposite a promising candidate for the LIBs.

     

Hierarchical MoS<Subscript>2</Subscript> intercalated clay hybrid nanosheets with enhanced catalytic activity

Emerging hierarchical MoSR/pillared-montmorillonite (MoS2/PMMT) hybrid nanosheets were successfully prepared through facile in-situ hydrothermal synthesis of MoS2 within the interlayer of cetyltrimethylammonium bromide PMMT,and their catalytic performance was evaluated by the reduction reaction of 4-nitrophenol (4-NP) using NaBH4 as a reductant.Microstructure and morphology characterization indicated that MoS2/PMMT exhibited hybrid-stacked layered structures with an interlayer spacing of 1.29 nm,and the MoS2 nanosheets were intercalated within the montmorillonite (MMT) layers,with most of the edges exposed to the outside.The catalytic activity and stability of MoS2/PMMT were both enhanced by the MMT.With the MoS2/PMMT as the catalyst,the apparent reaction rate constant of the 4-NP reduction was 0.723 min-1 and was maintained at ～0.679 min-1 after five reaction cycles.The structural evolution of MoS2/PMMT and the possible catalysis mechanism for the reduction reaction of 4-NP were investigated.The as-prepared MoS2/PMMT hybrid nanosheets are promising candidates for catalytic application in the water-treatment and biomedical fields.The strategy developed in this study can provide insights for designing hybrid nanosheets with diverse heterogeneous two-dimensional (2D) nanomaterials.     

Synergistically Designed Dual Interfaces to Enhance the Electrochemical Performance of MoO2/MoS2 in Na- and Li-Ion Batteries

It is indispensable to develop and design high capacity, high rate performance, long cycling life, and low-cost electrodes materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, MoO₂/MoS₂/C, with dual heterogeneous interfaces, is designed to induce a built-in electric field, which has been proved by experiments and theoretical calculation can accelerate electrochemical reaction kinetics and generate interfacial interactions to strengthen structural stability. The carbon foam serves as a conductive frame to assist the movement of electrons/ions, as well as forms heterogeneous interfaces with MoO₂/MoS₂ through C S and C O bonds, maintaining structural integrity and enhancing electronic transport. Thanks to these unique characteristics, the MoO₂/MoS₂/C renders a significantly enhanced electrochemical performance (324 mAh g⁻¹ at 1 A g⁻¹ after 1000 cycles for SIB and 500 mAh g⁻¹ at 1 A g⁻¹ after 500 cycles for LIBs). The current work presents a simple, useful and cost-effective route to design high-quality electrodes via interfacial engineering.     

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.     

Fe~(3+) -stabilized Ti_3C_2T_x MXene enables ultrastable Li-ion storage at low temperature

It is highly important to develop ultrastable electrode materials for Li-ion batteries(LIBs),especially in the low temperature.Herein,we report Fe³⁺-stabilized Ti₃C₂T_x MXene(donated as T/F-4:1)as the anode material,which exhibits an ultrastable low-temperature Li-ion storage property(135.2 m A h g^-1after300 cycles under the current density of 200 m A g^-1at-10℃),compared with the negligible capacity for the pure Ti₃C₂T_x MXene(26 m A h g^-1at 200 m A g^-1).We characterized as-made T/F samples via the Xray photoelectron spectroscopy(XPS),Fourier transformed infrared(FT-IR)and Raman spectroscopy,and found that the terminated functional groups(-O and-OH)in T/F are Li⁺ storage sites.Fe³⁺-stabilization makes-O/-OH groups in MXene interlayers become active towards Li⁺,leading to much more active sites and thus an enhanced capacity and well cyclic stability.In contrast,only-O/-OH groups on the top and bottom surfaces of pure Ti₃C₂T_x MXene can be used to adsorb Li⁺,resulting in a low capacity.Transmission electron microscopy(TEM)and XPS data confirm that T/F-4:1 holds the highly stable solid electrolyte interphase(SEI)layer during the cycling at-10℃.Density functional theory(DFT)calculations further uncover that T/F has fast diffusion of Li⁺ and consequent better electrochemical performances than pure Ti₃C₂T_x MXene.It is believed that the new strategy used here will help to fabricate advanced MXene-based electrode materials in the energy storage application.