Enhancing the Lithium Storage Performance of the Nb2O5 Anode via Synergistic Engineering of Phase and Cu Doping.

Nb2O5 has been viewed as a promising anode material for lithium-ion batteries by virtue of its appropriate redox potential and high theoretical capacity. However, it suffers from poor electric conductivity and low ion diffusivity. Herein, we demonstrate the controllable fabrication of Cu-doped Nb2O5 with orthorhombic (T-Nb2O5) and monoclinic (H-Nb2O5) phases through annealing the solvothermally presynthesized Nb2O5 precursor under different temperatures in air, and the Cu doping amount can be readily controlled by the concentration of the precursor solution, whose effect on the lithium storage behaviors of the Cu-doped Nb2O5 is thoroughly investigated. H-Nb2O5 shows obvious redox peaks (Nb5+/Nb4+ and Nb4+/Nb3+) with much higher capacity and better cycling stability than those for the widely investigated T-Nb2O5. When introducing appropriate Cu doping, the optimized H-Cu0.1-Nb2O5 electrode shows greatly enhanced conductivity and lower diffusion barrier as revealed by the theoretical calculations and electrochemical characterizations, delivering a high reversible capacity of 203.6 mAh g-1 and a high capacity retention of 140.8 mAh g-1 after 5000 cycles at 1 A g-1, with a high initial Coulombic efficiency of 91% and a high rate capacity of 144.2 mAh g-1 at 4 A g-1. As a demonstration for full-cell application, the H-Cu0.1-Nb2O5||LiFePO4 cell displays good cycling performance, exhibiting a reversible capacity of 135 mAh g-1 after 200 cycles at 0.2 A g-1. More importantly, this work offers a new synthesis protocol of the monoclinic Nb2O5 phase with high capacity retention and improved reaction kinetics.

Conformal Conversion of Polyphosphazene@Sb2MoO6 Nanowires to N/S-Doped/Carbon-Coated SbPO4/MoOx for High-performance Lithium Storage.

Alloy-type antimony (Sb) and conversion-type molybdenum (Mo) anodes have attracted extensive attention in the application of lithium-ion batteries (LIBs) owing to their high theoretical capacity. In this study, Sb2MoO6 nanowires are prepared via a hydrothermal method and assessed their thermal behavior upon heat treatment, observing an intriguing transformation from nanowire to Sb2O3/MoOx nanosheets. To enhance structure stability, the Sb2MoO6 nanowires are successfully coated with a polyphosphazene layer (referred to as PZS@Sb2MoO6), which not only preserved the nanowires form but also yielded N/S co-doped carbon-coated SbPO4/MoOx (NS-C@SbPO4/MoOx) nanowires following annealing in an inert environment. This composite benefits from the stable PO4 3- anion that serve as a buffer against volume expansion and form a Li3PO4 matrix during cycling, both of which substantially bolster ion transport and cycle endurance. Doping with heteroatoms introduces numerous oxygen vacancies, augmenting the number of electrochemically active sites, and carbon integration considerably enhances the electronic conductivity of the electrode and alleviates the volume-change-induced electrode pulverization. Employed as anode materials in LIBs, the NS-C@SbPO4/MoOx electrode exhibits remarkable cycling performance (449.8 mA h g-1 at 1000 mA g-1 over 700 cycles) along with superior rate capability (394.2 mA h g-1 at 2000 mA g-1).

Carbon-Coated Tin-Titanate derived SnO2/TiO2 nanowires as High-Performance anode for Lithium-Ion batteries.

Tin dioxide (SnO2) is a promising alternative material to graphite anode, but the large volume change induced electrode pulverization issue has limited its application in lithium-ion batteries (LIBs). In contrast, titanium dioxide (TiO2) anode shows high structure stability upon lithium insertion/extraction, but with low specific capacity. To overcome their inherent disadvantages, combination of SnO2 with TiO2 and highly conductive carbon material is an effective way. Herein, we report a facile fabrication method of carbon-coated SnO2/TiO2 nanowires (SnO2/TiO2@C) using tin titanate nanowires as precursor, which are prepared by reacting SnCl2·2H2O with layered sodium titanate (Na2Ti3O7) nanowires in the aqueous solution though the ion exchange between Sn2+ and Na+. After annealing under argon atmosphere, the hydrothermally carbon-coated tin-titanate nanowires decompose, forming a unique hybrid structure, where ultrafine SnO2 nanoparticles are uniformly embedded within the TiO2 substrate with carbon coating. Consequently, the SnO2/TiO2@C nanowires demonstrate excellent lithium storage capacity with high pseudocapacitance contribution, excellent reversible capacity, and long-term cycling stability (673.7/510.5 mAh/g at 0.5/1.0 A/g after 250/800 cycles), owing to the unique hybrid structure, as the well-dispersion of ultra-small SnO2 within TiO2 nanowire substrate with simultaneous carbon coating efficiently suppresses the volume changes of SnO2, provides abundant reactive sites for lithium storage, and enhances the electrical conductivity with shortened ion transport distance.

Encapsulation of Titanium Disulfide into MOF-Derived N,S-Doped Carbon Nanotablets Toward Suppressed Shuttle Effect and Enhanced Sodium Storage Performance.

Titanium disulfide (TiS2) is a promising anode material for sodium-ion batteries due to its high theoretical capacity, but it suffers from severe volume variation and shuttle effect of the intermediate polysulfides. To overcome the drawbacks, herein the successful fabrication of TiS2@N,S-codoped C (denoted as TiS2@NSC) through a chemical vapor reaction between Ti-based metal-organic framework (NH2-MIL-125) and carbon disulfide (CS2) is demonstrated. The C─N bonds enhance the electronic/ionic conductivity of the TiS2@NSC electrode, while the C─S bonds provide extra sodium storage capacity, and both polar bonds synergistically suppress the shuttle effect of polysulfides. Consequently, the TiS2@NSC electrode demonstrates outstanding cycling stability and rate performance, delivering reversible capacities of 418/392 mAh g-1 after 1000 cycles at 2/5 A g-1. Ex situ X-ray photoelectron spectroscopy and transmission electron microscope analyses reveal that TiS2 undergoes an intercalation-conversion ion storage mechanism with the generation of metallic Ti in a deeper sodiation state, and the pristine hexagonal TiS2 is electrochemically transformed into cubic rock-salt TiS2 as a reversible phase with enhanced reaction kinetics upon sodiation/desodiation cycling. The strategy to encapsulate TiS2 in N,S-codoped porous carbon matrices efficiently realizes superior conductivity and physical/chemical confinement of the soluble polysulfides, which can be generally applied for the rational design of advanced electrodes.

Rational design of hollow Ti2Nb10O29 nanospheres towards High-Performance pseudocapacitive Lithium-Ion storage.

Ti2Nb10O29, as one of the most promising anode materials for lithium-ion batteries (LIBs), possesses excellent structural stability during lithiation/delithiation cycling and higher theoretical capacity. However, Ti2Nb10O29 faces some challenges, such as insufficient ion diffusion coefficient and poor electronic conductivity. To overcome these problems, this study investigates the effect of applying nanostructure engineering on Ti2Nb10O29 and the lithium storage behaviors. We successfully synthesized hollow Ti2Nb10O29 nanospheres (h-TNO NSs) via solvothermal method using phenolic resin nanospheres as the template. The effects of using a template or not and the annealing atmospheres on the microstructures of the as-prepared Ti2Nb10O29 are investigated. Different nanostructures (porous Ti2Nb10O29 nanoaggregates (p-TNO NAs) without a template and core-shelled Ti2Nb10O29@C nanospheres (cs-TNO@C NSs)) were formed through annealing in Ar. When examined as anodes for LIBs, the h-TNO NSs electrode with hollow spherical structure displayed a better lithium storage performance. Compared to its counterparts, p-TNO NAs and cs-TNO@C NSs, h-TNO NSs electrode exhibited a higher reversible capacity of 282.5 mAh g-1 at 1C, capacity retention of 79.5% (i.e., 224.6 mAh g-1) after 200 cycles, and a higher rate capacity of 173.1 mAh g-1 at 10C after 600 cycles. The excellent electrochemical performance of h-TNO NSs is attributed to the novel structure. The hollow nanospheres with cavities and thin shells not only exposed more active sites and improved ion diffusion, but also buffered the volume variation upon cycling and facilitated electrolyte penetration. This consequently enhanced the lithium storage performance of the electrode and its high pseudocapacitive contribution (90% at 1.0 mV s-1).

Introducing Hybrid Defects of Silicon Doping and Oxygen Vacancies into MOF-Derived TiO2-X @Carbon Nanotablets Toward High-Performance Sodium-Ion Storage.

Titanium dioxide (TiO2 ) is a promising anode material for sodium-ion batteries (SIBs), which suffer from the intrinsic sluggish ion transferability and poor conductivity. To overcome these drawbacks, a facile strategy is developed to synergistically engineer the lattice defects (i.e., heteroatom doping and oxygen vacancy generation) and the fine microstructure (i.e., carbon hybridization and porous structure) of TiO2 -based anode, which efficiently enhances the sodium storage performance. Herein, it is successfully realized that the Si-doping into the MIL-125 metal-organic framework structure, which can be easily converted to SiO2 /TiO2-x @C nanotablets by annealing under inert atmosphere. After NaOH etching SiO2 /TiO2-x @C which contains unbonded SiO2 and chemically bonded SiOTi, thus the lattice Si-doped TiO2-x @C (Si-TiO2-x @C) nanotablets with rich Ti3+ /oxygen vacancies and abundant inner pores are developed. When examined as an anode for SIB, the Si-TiO2-x @C exhibits a high sodium storage capacity (285 mAh g-1 at 0.2 A g-1 ), excellent long-term cycling, and high-rate performances (190 mAh g-1 at 2 A g-1 after 2500 cycles with 95.1% capacity retention). Theoretical calculations indicate that the rich Ti3+ /oxygen vacancies and Si-doping synergistically contribute to a narrowed bandgap and lower sodiation barrier, which thus lead to fast electron/ion transfer coefficients and the predominant pseudocapacitive sodium storage behavior.

Polyphosphazene-derived P/S/N-doping and carbon-coating of yolk-shelled CoMoO4 nanospheres towards enhanced pseudocapacitive lithium storage.

Transition metal oxides as potentialanodes of lithium-ion batteries (LIBs) possess high theoretical capacity but suffer from large volume expansion and poor conductivity. To overcome these drawbacks, we designed and fabricated polyphosphazene-coated yolk-shelled CoMoO4 nanospheres, in which polyphosphazene with abundant C/P/S/N species was readily converted into carbon shells and provided P/S/N dopants. This resulted in the formation of P/S/N co-doped carbon-coated yolk-shelled CoMoO4 nanospheres (PSN-C@CoMoO4). The PSN-C@CoMoO4 electrode exhibits superior cycle stability of 439.2 mA h g-1at 1000 mA g-1after 500 cycles and rate capability of 470.1 mA h g-1at 2000 mA g-1. The electrochemical and structural analyses reveal that PSN-C@CoMoO4 with yolk-shell structure, coated with carbon and doped with heteroatom not only greatly enhances the charge transfer rate and reaction kinetics, but also efficiently buffers the volume variation upon lithiation/delithiation cycling. Importantly, the use of polyphosphazene as coating/doping agent can be a general strategy for developing advanced electrode materials.

Polyvinylpyrrolidone-regulated synthesis of hollow manganese vanadium oxide microspheres as a high-performance anode for lithium-ion batteries.

We report the fabrication of well-defined phase-pure Mn2V2O7 hollow microspheres (h-MVO), assembled from the porous plate-like building blocks, via a facile solvothermal method followed by annealing, with the assistance of polyvinylpyrrolidone (PVP) as the structure-regulating agent. The microstructure dependent electrochemical properties of h-MVO as anode materials for lithium ion batteries (LIBs) are investigated, and excellent lithium storage performance is obtained with a reversible capacity of 1707 mAh g-1 after 700 cycles at 0.5 A g-1, revealing that the unique hierarchical framework of the h-MVO microspheres with hollow interiors and porous building blocks could not only accelerate the transport of Li+ ions and electrolyte, but also efficiently suppress the electrode pulverization upon cycling. More importantly, we demonstrate that PVP can be an effective agent to tune the microstructures, which would be promising for the development of high-performance energy storage devices.

Polyvinylpyrrolidone regulated synthesis of mesoporous titanium niobium oxide as high-performance anode for lithium-ion batteries.

TiNb2O7 (TNO) as a promising candidate anode for lithium-ion batteries (LIBs) shows obvious advantages in terms of specific capacity and safety, but which undergoes the intrinsic poor electrical and ionic conductivity. Herein, we propose a simple synthesis strategy of mesoporous TNO via a polymeric surfactant-mediated evaporation-induced sol-gel method, using polyvinylpyrrolidone (PVP) with different molecular weights (average Mw: 10000/58000/1300000) as the regulating agent, which greatly affects the lithium storage performance of the as-prepared TNO. The optimized TNO (i.e., PVP of 58000) delivers a high reversible capacity of 303.1 mAh/g at 1 C, with a retention rate of 73.4% (222.5 mAh/g) after 300 cycles. Even at 5 C, a high reversible capacity of 185.6 mAh/g can be achieved, with a retention rate of 72.3% after 1000 cycles. The superior lithium storage behavior is attributed to the fine mesoporous framework consisting of interconnected TNO nanocrystallites with high specific surface area and high mesoporosity, which greatly increases the active sites, improves the Li+ diffusion kinetics and alleviates volume fluctuation induced by the repetitive Li+ insertion-extraction processes.

Phase structure engineering of MnCo2Ox within electrospun carbon nanofibers towards high-performance lithium-ion batteries.

Metal oxides are prospective alternative anode materials to the commercial graphite for lithium ion batteries (LIBs), while their practical application is seriously hampered by their poor conductivities and large volume changes. Herein, we report the controllable synthesis of amorphous/crystalline MnCo2Ox nanoparticles within porous carbon nanofibers (marked as MCO@CNFs) through a facile electrospinning strategy and subsequent annealing reactions. The phase structures from Co/MnOX to amorphous MnCo2Ox and crystalline MnCo2O4.5 can be readily tuned by thermal reduction/oxidation under controlled atmosphere and temperature. When examined as anode for LIBs, the optimized MCO@CNFs delivers a high stable capacity of 780.3 mA h g-1 at 200 mA g-1 after 250 cycles, which is attributed to the synergistic effect of the distinctive amorphous structure and defective carbon nanofiber matrices. Specifically, the amorphous structure with rich defects offers more reactive sites and multiple pathways for the Li+ diffusion, while carbon hybridization sufficiently improves the electrode conductivities as well as buffers the volume changes. More importantly, we demonstrate a convenient synthesis strategy to control the metal-to-oxide structure evolution within carbon matrices, which is of great importance in exploring high-performance electrodes for next generation LIBs.

Metal-organic framework derived vanadium-doped TiO2@carbon nanotablets for high-performance sodium storage.

Titanium dioxide (TiO2) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO2via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal-organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO2 with simultaneous carbon hybridization and controlled V-doping amount (denote as VxTiO2@C, where × represents the V/Ti molar ratio (RV/Ti)). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the VxTiO2@C. When used as an anode for SIBs, the V0.1TiO2@C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO2@C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V0.1TiO2@C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti3+ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V0.1TiO2@C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways.

Classification of Rice Yield Using UAV-Based Hyperspectral Imagery and Lodging Feature.

High-yield rice cultivation is an effective way to address the increasing food demand worldwide. Correct classification of high-yield rice is a key step of breeding. However, manual measurements within breeding programs are time consuming and have high cost and low throughput, which limit the application in large-scale field phenotyping. In this study, we developed an accurate large-scale approach and presented the potential usage of hyperspectral data for rice yield measurement using the XGBoost algorithm to speed up the rice breeding process for many breeders. In total, 13 japonica rice lines in regional trials in northern China were divided into different categories according to the manual measurement of yield. Using an Unmanned Aerial Vehicle (UAV) platform equipped with a hyperspectral camera to capture images over multiple time series, a rice yield classification model based on the XGBoost algorithm was proposed. Four comparison experiments were carried out through the intraline test and the interline test considering lodging characteristics at the midmature stage or not. The result revealed that the degree of lodging in the midmature stage was an important feature affecting the classification accuracy of rice. Thus, we developed a low-cost, high-throughput phenotyping and nondestructive method by combining UAV-based hyperspectral measurements and machine learning for estimation of rice yield to improve rice breeding efficiency.

MOF-Derived CoS2/N-Doped Carbon Composite to Induce Short-Chain Sulfur Molecule Generation for Enhanced Sodium-Sulfur Battery Performance.

Dissolution of intermediate sodium polysulfides (Na2Sx; 4≤x≤8) is a crucial obstacle for the development of room-temperature sodium-sulfur (Na-S) batteries. One promising strategy to avoid this issue is to load short-chain sulfur (S2-4), which could prohibit the generation of soluble polysulfides during the sodiation process. Herein, unlike in the previous reported cases where short-chain sulfur was stored by confinement within a small-pore-size (≤0.5 nm) carbon host, we report a new strategy to generate short-chain sulfur in larger pores (>0.5 nm) by the synergistic catalytic effect of CoS2 and appropriate pore size. Based on density functional theory calculations, we predict that CoS2 can serve as a catalyst to weaken the S-S bond in the S8 ring structure, facilitating the formation of short-chain sulfur molecules. By experimentally tuning the pore size of the CoS2-based hosts and comparing their performances as cathodes in Na-S and Li-S batteries, we conclude that such a catalytic effect depends on the proximity of sulfur to CoS2. This avoids the generation of soluble polysulfides and results in superior electrochemical properties of the composite materials introduced here for Na-S batteries. As a result, the optimized CoS2/N-doped carbon/S electrode showed excellent electrochemical performance with high reversible specific capacities of 488 mA h g-1 (962 mA h g(s)-1) after 100 cycles (0.1 A g-1) and 403 mA h g-1 after 1000 cycles (1 A g-1) with a superior rate performance (262 mA h g-1 at 5.0 A g-1).

Selenizing CoMoO4 nanoparticles within electrospun carbon nanofibers towards enhanced sodium storage performance.

Transition metal oxides/selenides as anodes for sodium-ion batteries (SIBs) suffer from the insufficient conductivity and large volumetric expansion, which leads to the poor electrochemical performance. To address these issues, we herein demonstrate a facile selenization method to enhance the sodium storage capability of CoMoO4 nanoparticles which are encapsulated into the electrospun carbon nanofibers (CMO@carbon for short). The partially and fully selenized CoMoO4 within carbon nanofibers (denote as CMOS@carbon and CMS@carbon, respectively) can be readily obtained by controlling the annealing temperature (at 400 and 600 °C, correspondingly). When examined as anode materials for SIBs, the CMOS@carbon nanofibers display an outstanding electrochemical performance with a higher reversible capacity of 396 mA h g-1 after 200 cycles at 0.2 A g-1 and a high-rate capacity of 365 mA h g-1 at 2 A g-1, as compared with the CMO@carbon and CMS@carbon counterparts. The enhanced sodium storage performance of the CMOS@carbon can be owing to the partial selenization of the CoMoO4 nanoparticles which are rooted into the porous electrospun carbon nanofibers, thus endowing them with superior ionic/electronic charge transfer efficiencies and a cushion against the electrode pulverization during cycling. Moreover, this work proposed a useful strategy to enhance the sodium storage performance of metal oxides via controlled selenization, which is promising for exploiting the advanced anode materials for SIBs.

Synergizing Phase and Cavity in CoMoOx Sy Yolk-Shell Anodes to Co-Enhance Capacity and Rate Capability in Sodium Storage.

Sodium-ion batteries (SIBs) have been recognized as the promising alternatives to lithium-ion batteries for large-scale applications owing to their abundant sodium resource. Currently, one significant challenge for SIBs is to explore feasible anodes with high specific capacity and reversible pulverization-free Na+ insertion/extraction. Herein, a facile co-engineering on polymorph phases and cavity structures is developed based on CoMo-glycerate by scalable solvothermal sulfidation. The optimized strategy enables the construction of CoMoOx Sy with synergized partially sulfidized amorphous phase and yolk-shell confined cavity. When developed as anodes for SIBs, such CoMoOx Sy electrodes deliver a high reversible capacity of 479.4 mA h g-1 at 200 mA g-1 after 100 cycles and a high rate capacity of 435.2 mA h g-1 even at 2000 mA g-1 , demonstrating superior capacity and rate capability. These are attributed to the unique dual merits of the anodes, that is, the elastic bountiful reaction pathways favored by the sulfidation-induced amorphous phase and the sodiation/desodiation accommodatable space benefits from the yolk-shell cavity. Such yolk-shell nano-battery materials are merited with co-tunable phases and structures, facile scalable fabrication, and excellent capacity and rate capability in sodium storage. This provides an opportunity to develop advanced practical electrochemical sodium storage in the future.

Embedding amorphous lithium vanadate into carbon nanofibers by electrospinning as a high-performance anode material for lithium-ion batteries.

We design and fabricate a novel hybrid with amorphous lithium vanadate (LiV3Ox, LVO for short) uniformly encapsulated into carbon nanofibers (denoted as LVO@CNFs) via an easy electrospinning strategy followed by proper postannealing. When examined for use as anode materials for lithium-ion batteries (LIBs), the optimized LVO@CNFs present a high discharge capacity of 603 mAh g-1 with a capacity retention as high as 90% after 200 cycles at 0.5 A g-1 and a high rate capacity of 326 mAh g-1 after 400 cycles even at a high rate of 5 A g-1. The superior electrochemical performance with excellent cycling stability and rate capability is attributed to the full encapsulation of the amorphous LVO into the conductive carbon nanofibers, which hold enlarged electrochemically active sites for lithium storage, facilitate the charge transfer, and efficiently alleviate the volume changes upon lithium insertion/extraction. More importantly, the current synthesis can be a general strategy to fabricate various alkaline earth metal vanadates, which is promising for developing advanced electrochemical energy storage devices.

Selective immunoglobulin A deficiency (SIgAD) primarily leads to recurrent infections and autoimmune diseases: A retrospective study of Chinese patients in the past 40 years.

Selective immunoglobulin A deficiency (SIgAD) is considered to be the most common human primary immune-deficiency disease in the world. However, the incidence in China is obviously lower than Caucasian races. The definition of SIgAD has changed over time with the progress of people's understanding. The scientific community did not reach a consensus on the definition until 1999. As a result, many previously reported cases need to be excluded under the current definition. SIgAD can lead to several spectra of diseases including infections and autoimmune diseases. We retrospectively summarized the SIgAD patients in Peking Union Medical College Hospital (PUMCH), and summarized the Chinese SIgAD reported in China and abroad in past 40 years. Fourty three SIgAD patients were confirmed in the study, in which 9 were healthy without clinical symptoms. Of the 34 patients with clinical symptoms, recurrent infections were found in 29 (85.3%) patients; 13 (38.2%) patients were with autoimmune diseases; 6 (17.6%)cases had allergic symptoms; 3 patients (8.8%) were with tumors, only one case (2.9%) had a family history. Compared with other countries, sIgAD patients in China showed similar symptoms, but the rate of recurrent infections and autoimmune diseases were higher than some other countries; most of the allergic symptoms are drug allergy, different with the allergic sequelae reported in other countries, such as asthma, rhinitis, food allergy and atopic dermatitis; and it is rare to have family history in Chinese patients. We also figured out that more female SIgAD patients tend to have more autoimmune diseases than men (P = 0.039).

Porous N-doped carbon nanoflakes supported hybridized SnO2/Co3O4 nanocomposites as high-performance anode for lithium-ion batteries.

Alloy-/conversion-type metal oxides usually exhibit high theoretical lithium storage capacities but suffer from the large volume change induced electrode pulverization and the poor electric conductivity, which limit their practical applications. Hybrid/mixed metal oxides with different working mechanisms/potentials can display advantageous synergistic enhancement effect if delicate structure engineering is performed. Herein, atomically hybridized SnO2/Co3O4 nanocomposites with amorphous nature are successfully cast onto the porous N-doped carbon (denoted as NC) nanoflakes through facile pyrolysis of the tin (II) 2-ethylhexanoate (C16H30O4Sn) and cobalt (II) 2-ethylhexanoate (C16H30O4Co) mixture within NC nanoflakes in air at 300 °C for 1 h. The Sn/Co atomic ratio and the loading amount of SnO2/Co3O4 can be readily controlled, whose effect on lithium storage are investigated as anodes for lithium ion batteries (LIBs). Notably, SnO2/Co3O4@NC (RSn/Co = 1.25) nanoflakes exhibit the most excellent lithium storage properties, delivering a reversible capacity of 1450.3 mA h g-1 after 300 cycles at 200 mA g-1, which is much higher than that of the single metal oxide SnO2@NC and Co3O4@NC electrodes.

Embedding CoMoO4 nanoparticles into porous electrospun carbon nanofibers towards superior lithium storage performance.

CoMoO4 nanoparticles have been successfully in-situ formed and simultaneously embedded within the porous carbon nanofibers (CoMoO4/CNFs) via a facile electrospinning-annealing strategy. The porous CoMoO4/CNFs exhibit a specific surface area of 255.3 m2/g and a pore volume of 0.52 cc/g with average pore diameter of 43.5 nm. The carbon content in the CoMoO4/CNFs can be readily controlled by adjusting the annealing temperature. When examined as anode materials for lithium ion batteries (LIBs), the CoMoO4/CNFs demonstrate superior electrochemical performance, delivering a high reversible capacity of 802 mA h/g after 200 cycles at 200 mA/g and a high-rate capacity of 574 mA h/g at 2000 mA/g. The excellent lithium storage behavior can be attributed to the incorporation of CoMoO4 nanoparticles into the porous N-doped graphitic carbon nanofibers, which efficiently buffer the volume changes of CoMoO4 upon lithiation/delithiation and maintain the overall electrode conductivity/integrity.