Engineering sulfur defective Bi2S3@C with remarkably enhanced electrochemical kinetics of lithium-ion batteries.

Introducing the appropriate vacancies to augment the active sites and improve the electrochemical kinetics while maintaining high cyclability is a major challenge for its widespread application in electrochemical energy storage. Here, core-shell structured Bi2S3@C with sulfur vacancies was prepared by hydrothermal method and one-step carbonization/sulfuration process, which significantly improves the intrinsic electrical conductivity and ion transport efficiency of Bi2S3. Additionally, the uniform protective carbon layer around surface of composite maintains structural stability and effectively alleviates volume expansion during alloying/dealloying. As a result, the BSC-500 anode exhibits a brilliant reversible capacity of 636 mAh/g at 0.2 A/g and a long-term stable capacity of 524 mAh/g for 500 cycles at a high current density of 3 A/g in lithium-ion batteries. In addition, the assembled Bi2S3@C//LiCoO2 full cell delivered a capacity of 184 mAh/g at 1 A/g and excellent cyclability (125 mAh/g after 1000 cycles). The proposed strategy of combining sulfur vacancies with a core-shell structure to improve the electrochemical kinetics of Bi2S3 in lithium-ion batteries off the prospect for practical applications of transition metal sulfide anodes.

Catalytic Hydroconversion of Model Compounds over Ni/NiO@NC Nanoparticles.

The conversion of lignite into aromatic compounds by highly active catalysts is a key strategy for lignite valorization. In this study, Ni/NiO@NC nanocomposites with a high specific surface area and a vesicular structure were successfully prepared via a facile sol-gel method. The Ni/NiO@NC catalysts exhibited excellent catalytic activity for the catalytic hydroconversion (CHC) of benzyloxybenzene (as lignite-related modeling compounds) under mild conditions (120 °C, 1.5 MPa H2, 60 min). The possible mechanism of the catalytic reaction was investigated by analyzing the type and content of CHC reaction products at different temperatures, pressures, and times. More importantly, the magnetic catalyst could be conveniently separated by a magnet after the reaction, and it maintained high catalytic efficiency after six reuses. This study provides an efficient and recyclable catalyst for the cleavage of >CH-O bonds in lignite, thereby offering another way for improved utilization of lignite.

Promoted kinetics and capacity on the Li2CuTi3O8/C anode by constructing a one dimensional hybrid structure for superior performance lithium ion batteries.

Notably, spinel Li2CuTi3O8 with higher theoretical capacity inherits the characteristics of Li4Ti5O12, which is a promising anode material for lithium ion batteries with high energy density. However, the reversible migration of Cu2+ in Li2CuTi3O8 during the discharge process limits the diffusion of Li+, resulting in poor electrochemical performance. Space confinement is a desirable successful strategy to reduce the size of electroactive materials in return for getting improved kinetics and capacity for secondary ion batteries. Here, we develop a strategy by controlling the precursor of Li2CuTi3O8 in the walls of sulfonated polymer nanotubes, and the highly crosslinked copolymer network in the process of pyrolysis caused strong space confinement for the nanoparticles, which effectively prevented the agglomeration of Li2CuTi3O8 during the calcination process. The hybrid porous nanotubes consisting of Li2CuTi3O8 nanoparticles (5-50 nm) embedded in carbon nanotubes exhibit superior performance (402.8 mA h g-1 at 0.2 A g-1, 101 mA h g-1 at 10 A g-1 after 1000 cycles). This work provides a rapid and durable Li2CuTi3O8 electrochemistry, holding great promise in developing a practically viable Li2CuTi3O8 anode and enlightening material engineering in related energy storage and conversion areas.

Hybrid nanotubes constructed by confining Ti0.95Nb0.95O4 quantum dots in porous bamboo-like CNTs: superior anode materials for boosting lithium storage.

Current commercial lithium ion battery (LIB) anodes comprising graphite and Li4Ti5O12 inevitably suffer from safety risk and low energy density. Hence, a novel anode material of Ti0.95Nb0.95O4/C hybrid nanotubes was developed via a modified sol-gel method combined with subsequent calcination. The hybrids consist of Ti0.95Nb0.95O4 quantum dots that are homogeneously embedded in the walls of porous bamboo-like CNTs. The high capacity feature of multiple redox couples of Ti-Nb-O based anodes is demonstrated by ex situ XPS in the hybrids. With the advantages of stimulative lithium storage, increased conductivity and robust mechanical properties due to the unique hybrid structure, the hybrids exhibit a high capacity (516.8 mA h g-1 at 0.2 A g-1), superior long-term cycling stability (142.7 mA h g-1 at 5 A g-1 after 3000 cycles) and an ultra-high rate capability (234.6 mA h g-1 at 1 A g-1 and 125 mA h g-1 at 8 A g-1). Meanwhile, the hybrids showed superior electrochemical performance compared with the reported Li4Ti5O12 and Ti-Nb-O based anodes. Furthermore, the GITT measurements revealed the fast Li+ transport for the charge-discharge processes of the hybrids. Such prominent merits of the Ti0.95Nb0.95O4/C hybrid nanotubes make them more likely candidates that can replace graphite and Li4Ti5O12 anodes in LIBs.

Insights into the Relationship between the Microstructure and the Catalytic Behavior of Fe2(MoO4)3 during the Ethanolysis of Naomaohu Coal.

Ethanolysis is an effective method to depolymerize weak bonds in lignite under mild conditions, which can result in the production of high-value-added chemicals. However, improving ethanolysis yield and regulating its resulting product distribution is a big challenge. Hence, exploiting highly active catalysts is vital. In this work, Fe2(MoO4)3 catalysts with zero-dimensional nanoparticles, one-dimensional (1D) nanorods, two-dimensional (2D) nanosheets, and three-dimensional (3D) nanoflower structures were successfully prepared and applied in the ethanolysis of Naomaohu coal. The results showed that for all samples, the yield of ethanol-soluble portions (ESP) was significantly improved. The highest yield was obtained for the Fe2(MoO4)3 nanorods, with an increase from 28.84% to 47.68%, and could be attributed to the fact that the Fe2(MoO4)3 nanorods had a higher number of exposed active (100) facets. In addition, the amounts of oxygen-containing compounds, such as ethers, esters, and phenols, increased significantly. The mechanism of ethanolysis catalyzed by the Fe2(MoO4)3 nanorods was also studied using phenylbenzyl ether (BOB) as a model compound. BOB was completely converted at 260 °C after 2 h. It is suggested that Fe2(MoO4)3 nanorods can effectively break the C-O bonds of coal macromolecules, thus promoting the conversion of coal.

A Novel Anode Material Li2 FeGeO4 with Lithium Storage Mechanism Controlled by Both Iron and Germanium Elements.

To obtain anode materials with high capacity/energy density for lithium-ion batteries, a polyanionic compound Li2 FeGeO4 is prepared, which combines the conversion-type Fe-based oxide and the alloy-type Ge-based oxide at the atomic scale. The influence of citric acid in the sol-gel process on the structure and performance of the calcined products (LFG0, LFG1, and LFG2) is investigated. The results demonstrate that citric acid does not affect the phase of Li2 FeGeO4 . However, with the increase of citric acid, the crystallinity and grain size of the final product are reduced and its dispersion becomes better. Among the as-prepared samples, LFG1 exhibits moderate particle size and more uniform dispersion, providing a high discharge capacity of 669.7 mAh g-1 at 0.5 A g-1 after 200 cycles. Based on the ex situ XPS and operando XRD tests, it is found that the electrochemical reaction process of LFG1 is controlled by both the conversion of iron/germanium and the alloying of germanium. In addition, it is verified that the reaction mechanism of LFG1 for aqueous lithium-ion capacitors is also controlled by iron and germanium elements. Importantly, Li2 FeGeO4 is first proved to be a novel anode for lithium-ion batteries and lithium-ion capacitors.

Phosphate-Induced Reaction to Prepare Coal-Based P-Doped Hard Carbon with a Hierarchical Porous Structure for Improved Sodium-Ion Storage.

The use of coal as a precursor for producing hard carbon is favored due to its abundance, low cost, and high carbon yield. To further optimize the sodium storage performance of hard carbon, the introduction of heteroatoms has been shown to be an effective approach. However, the inert structure in coal limits the development of heteroatom-doped coal-based hard carbon. Herein, coal-based P-doped hard carbon was synthesized using Ca3(PO4)2 to achieve homogeneous phosphorus doping and inhibit carbon microcrystal development during high-temperature carbonization. This involved a carbon dissolution reaction where Ca3(PO4)2 reacted with SiO2 and carbon in coal to form phosphorus and CO. The resulting hierarchical porous structure allowed for rapid diffusion of Na+ and resulted in a high reversible capacity of 200 mAh g-1 when used as an anode material for Na+ storage. Compared to unpretreated coal-based hard carbon, the P-doped hard carbon displayed a larger initial coulombic efficiency (64%) and proportion of plateau capacity (47%), whereas the unpretreated carbon only exhibited an initial coulombic efficiency of 43.1% and a proportion of plateau capacity of 29.8%. This work provides a green, scalable approach for effective microcrystalline regulation of hard carbon from low-cost and highly aromatic precursors.

Hierarchical BiOCl flowerlike microspheres via a room-temperature solid-state chemical reaction as a new anode for rechargeable magnesium-ion batteries.

Rechargeable magnesium-ion batteries (MIBs) have received much attention in recent years, but their development remains limited due to a lack of anode materials with high capacity and fast diffusion kinetics. Herein, for the first time, hierarchical BiOX (X = Cl, Br, I) flowerlike microspheres composed of interleaved nanosheets are constructed via a simple room-temperature solid-state chemical reaction as the anode for MIBs. Among them, BiOCl flowerlike microspheres deliver good cycling stability (110 mA h g-1 after 100 cycles) and a superior rate capacity (134 mA h g-1 at 500 mA g-1). This is attributed to their unique flowerlike microsphere structure that not only accommodates a volume change to maintain their structural integrity but also shortens the ion-transport path to improve the diffusion rate. Importantly, ex situ tests were carried out to clarify the phase and structure evolution of the BiOCl flowerlike microspheres during cycling. The results show that BiOCl is first transformed to Bi and then alloyed to Mg3Bi2 in the discharging process, and Mg3Bi2 is turned back to Bi in the charging process. Besides, the initial microsphere structure is essentially maintained during the discharging/charging process, indicating the better stability of the structure. The current study demonstrates that the structural design of flowerlike microspheres is an effective strategy to develop promising anode materials for MIBs.

A novel hierarchical book-like structured sodium manganite for high-stable sodium-ion batteries.

As one of the most promising cathodes for rechargeable sodium-ion batteries (SIBs), Layered transition metal oxides with high energy density show poor cycling stability. Judicious design/construction of electrode materials plays a very important role in cycling performance. Herein, a P2-Na0.7MnO2.05 cathode material with hierarchical book-like morphology combining exposed (100) active crystal facets is synthesized by hydrothermal method. Owing to the superiority of the unique hierarchical structure, the electrode delivers a high reversible capacity of 163 mA h g-1 at 0.2C and remarkable high-rate cyclability (88.8% capacity retention after 300 cycles at 10C). Its unique oriented stacking nanosheet constructed hierarchical book-like structure is the origin of the high electrochemical performance, which is able to shorten the diffusion distances of Na+ and electrons, and a certain gap between the nanosheets can also relieve the stress and strain of volume generated during the cycle. In addition, the exposed (100) active crystal facets can provide more channels for the efficient transfer of Na+. Our strategy reported here opens a door to the development of high-stable oxide cathodes for high energy density SIBs.

Hofmann Ni-Pz-Ni Metal-Organic Frameworks Decorated by Graphene Oxide Enabling Lithium Storage with Pseudocapacitance Contribution.

Hofmann metal-organic frameworks (MOFs) are a variety of hybrid inorganic-organic polymers with a stable framework, plentiful adjustable pore size, and redox active sites, which display great application potential in energy storage. Unfortunately, the rapid and uncontrollable rate of coordination reaction results in a large size and an anomalous morphology, and the low electrical conductivity also severely limited further development, so there are few literature studies on Hofmann MOFs as anode materials for rechargeable batteries. Introducing graphene oxide can not only greatly facilitate the formation of a continuous conductive network but also effectively anchor and disperse MOF particles by utilizing the two-dimensional planar structure, thus reducing the sizes and agglomeration of particles. In this work, various mass ratios of graphene oxide with 3D Hofmann Ni-Pz-Ni MOFs were prepared via a simple one-pot solvothermal method. Benefiting from the gradually increasing capacitance characteristic during the continuous charge/discharge process, the Ni-Pz-Ni/GO-20% electrode exhibits a great reversible capacity of 896.1 mAh g-1 after 100 cycles and excellent rate capability, which will lay a theoretical foundation for exploring the high-performance Hofmann MOFs in the future.

Mapping Chinese annual gross primary productivity with eddy covariance measurements and machine learning.

Annual gross primary productivity (AGPP) is the basis for grain production and terrestrial carbon sequestration. Mapping regional AGPP from site measurements provides methodological support for analysing AGPP spatiotemporal variations thereby ensures regional food security and mitigates climate change. Based on 641 site-year eddy covariance measuring AGPP from China, we built an AGPP mapping scheme based on its formation and selected the optimal mapping way, which was conducted through analysing the predicting performances of divergent mapping tools, variable combinations, and mapping approaches in predicting observed AGPP variations. The reasonability of the selected optimal scheme was confirmed by assessing the consistency between its generating AGPP and previous products in spatiotemporal variations and total amount. Random forest regression tree explained 85 % of observed AGPP variations, outperforming other machine learning algorithms and classical statistical methods. Variable combinations containing climate, soil, and biological factors showed superior performance to other variable combinations. Mapping AGPP through predicting AGPP per leaf area (PAGPP) explained 86 % of AGPP variations, which was superior to other approaches. The optimal scheme was thus using a random forest regression tree, combining climate, soil, and biological variables, and predicting PAGPP. The optimal scheme generating AGPP of Chinese terrestrial ecosystems decreased from southeast to northwest, which was highly consistent with previous products. The interannual trend and interannual variation of our generating AGPP showed a decreasing trend from east to west and from southeast to northwest, respectively, which was consistent with data-oriented products. The mean total amount of generated AGPP was 7.03 ± 0.45 PgC yr-1 falling into the range of previous works. Considering the consistency between the generated AGPP and previous products, our optimal mapping way was suitable for mapping AGPP from site measurements. Our results provided a methodological support for mapping regional AGPP and other fluxes.

Optimizing the rate performance and cycle life of Li2 MTi3O8 (M = Mn, Co, Zn)/CNTs for lithium-ion battery anodes by constructing a one-dimensional carbon-based hybrid structure.

One-dimensional nanohybrids Li2MTi3O8/CNTs (M = Mn, Co, Zn), i.e., Li2MTi3O8 nanoparticles embedded in carbon nanotubes, were synthesized by following a combination of methods involving sol-gels, solid phase grinding and calcination. As anodes for lithium-ion batteries, Li2MTi3O8/CNTs (especially Li2CoTi3O8/CNTs) exhibited superior electrochemical performance.

Amylopectin-Assisted Fabrication of In Situ Carbon-Coated Na3V2(PO4)2F3 Nanosheets for Ultra-Fast Sodium Storage.

Na3V2(PO4)2F3 is one of the most studied polyanion type cathode materials for sodium-ion batteries (SIBs) and offers great promises. However, the inferior rate capability induced by its sluggish diffusion of electrons and ions greatly limits the practical application of electrode materials in SIBs. Herein, we develop an efficient method to fabricate in situ carbon-coated Na3V2(PO4)2F3 nanosheets by using cost-effective amylopectin. The amylopectin not only could induce the nucleation of Na3V2(PO4)2F3 along its backbone to form a 2D nanostructure, but also act as a source of amorphous carbon for in situ coating on the active material surface. The composite exhibits extraordinary rate capability (104 mA h g-1 at 40 C, 51 mA h g-1 at 150 C) and desirable cycling stability. Such satisfactory achievements, especially the superior rate performance, should be ascribed to its unique 2D nanostructure which shortens the Na+ diffusion length, and the in situ carbon coating endows the composites with effective electron transport. Even applied to full cells, the obtained devices still display an exceptionally high energy density (94.8 W h kg-1), high power density (7295 W kg-1), and excellent cyclic stability.

Ti3C2 MXene with pillared structure for hybrid magnesium-lithium batteries cathode material with long cycle life and high rate capability.

Cationic surfactants (CS) pillared Ti3C2 composites (Ti3C2/CS) were prepared by a facile electrostatic assembly method, which have large interlayer spacing and slight N-doping. In hybrid magnesium-lithium batteries (HMLBs), the Ti3C2/CS composites exhibit excellent performance by utilizing both Li+ and Mg2+ as charge carriers. Among these composites, the Ti3C2/CTAB (CTC) electrode displays a reversible capacity of 115.9 and 60 mAh g-1 in APC/LiCl (APCL) and APC electrolytes at 0.1 A g-1, and it also exhibits excellent high rate performance and ultralong cycle performance. It is verified that CS is vital to significantly improve the diffusion kinetics of Mg2+ on the electrode surface. The CS can act as the conductive "bridge" which connects different Ti3C2 layers and the interlayer pillar which expands the interlayer distance. In addition, the N element in CS is effective in neutralizing electronegativity and enhancing electrical conductivity for the CTC electrode. The electrode design strategy can adapt to the synthesis of cathode materials with high rate capability in HMLBs.

Energetics of lipid transport by the ABC transporter MsbA is lipid dependent.

The ABC multidrug exporter MsbA mediates the translocation of lipopolysaccharides and phospholipids across the plasma membrane in Gram-negative bacteria. Although MsbA is structurally well characterised, the energetic requirements of lipid transport remain unknown. Here, we report that, similar to the transport of small-molecule antibiotics and cytotoxic agents, the flopping of physiologically relevant long-acyl-chain 1,2-dioleoyl (C18)-phosphatidylethanolamine in proteoliposomes requires the simultaneous input of ATP binding and hydrolysis and the chemical proton gradient as sources of metabolic energy. In contrast, the flopping of the large hexa-acylated (C12-C14) Lipid-A anchor of lipopolysaccharides is only ATP dependent. This study demonstrates that the energetics of lipid transport by MsbA is lipid dependent. As our mutational analyses indicate lipid and drug transport via the central binding chamber in MsbA, the lipid availability in the membrane can affect the drug transport activity and vice versa.

T-Nb2O5 nanoparticles confined in carbon nanotubes with fast ion diffusion rates for lithium storage.

A T-Nb2O5/CNT nanohybrid with short transmission paths, many active sites, and favorable mechanical flexibility can achieve the fast transportation of ions/electrons. The obtained nanohybrid with continuous conductive networks exhibited better lithium storage performance than sodium storage performance, due to lower resistance to the diffusion of Li+ ions crossing the carbon matrix.

Sulfur-doped carbon nanotubes with hierarchical micro/mesopores for high performance pseudocapacitive supercapacitors.

Increasing the specific surface area and the amount of doping heteroatoms is an effective means to improve the electrochemical properties of carbon nanotubes (CNTs). The usual activation method makes it difficult for the retention of the heteroatoms while enlarging the specific surface area, and it can be found from literatures that specific surface area and S-content of carbon-based electrode materials are mutually exclusive. Here, CNTs with high specific surface area and sulfur content are constructed by simple activation of sulfonated polymer nanotubes with KHCO3, and the excellent electrochemical performance can be explained by the following points: first, KHCO3can be decomposed into K2CO3, CO2and H2O during the activation process. The synergistic action of physical activation (CO2and H2O) and chemical activation (K2CO3) equips the electrode material with high specific surface area of 1840 m2g-1and hierarchical micro/mesopores, which is beneficial to its double-layer capacitance. Second, compared with reported porous CNTs prepared by chemical activation (KOH) or physical activation (CO2or H2O), the mild activator KHCO3makes the sulfur content at a high level of 4.6 at%, which is very advantageous for high pseudocapacitance performance.

Restraining polysulfide shuttling by designing a dual adsorption structure of bismuth encapsulated into carbon nanotube cavity.

The shuttle effect derived from the dissolution of lithium polysulfides (LIPs) seriously hinders commercialization of lithium-sulfur (Li-S) batteries. Hence, we skillfully designed 1D cowpea-like CNTs@Bi composites with a double adsorption structure, where the bismuth nanoparticles/nanorods are encapsulated in the cavities of CNTs, avoiding the aggregation of bismuth nanoparticles during cycling and improving the conductivity of the electrode. Meanwhile, the sulfur was evenly distributed on the surface of bismuth nanoparticles/nanorods, ensuring effective catalytic activity and displaying high sulfur loading. Under the synergetic effects of the physical detention of abundant pores and chemical adsorption of bismuth, LIPs can be minimised, effectively curbing the shuttle effect. Benefiting from the above advantages, the CNTs@Bi/S cathodes exhibit a high capacity of 1352 mA h g-1, long cycling lifespan (708 mA h g-1 after 200 cycles at 1 C) and excellent coulombic efficiency. As the anodes of lithium-ion batteries (LIBs), the CNTs@Bi composites also show excellent performance due to the encapsulated structure to accommodate the serious volume change. This work offers an innovative strategy for improving the performances of the Li-S batteries and LIBs.

A high-performance rechargeable Mg2+/Li+ hybrid battery using CNT@TiO2 nanocables as the cathode.

Porous CNT@TiO2 nanocables are prepared via an impregnation method combined with calcination, which not only display the illusive capacity of 233.5 mAh g-1 but also possess outstanding rate performance (144.9 mAh g-1 at 500 mA g-1). Compared with TiO2 nanoparticles and nanotubes, CNT@TiO2 exhibits the excellent electrochemical performance on account of the unique coaxial nanocable feature (short ion diffusion path, large contact surface area, supernal conductivity, and favorable structure stability), which simultaneously overcomes the aggregation of TiO2 particles and the collapse of TiO2 nanotubes. Importantly, there are no significant changes in the morphology and phase after long cycling, meaning that CNT@TiO2 has a highly structural stability and reversibility. Therefore, CNT@TiO2 can be applied as a promising cathode material for Mg2+/Li+ hybrid batteries.

Rational design of FeTiO3/C hybrid nanotubes: promising lithium ion anode with enhanced capacity and cycling performance.

Ilmenite FeTiO3 has the advantage of high theoretical capacity and abundant sources as an anode material for lithium-ion batteries (LIBs). However, it suffers inferior rate capability caused by the aggregation of particles. To solve this problem, FeTiO3 nanoparticles embedded in porous CNTs were developed by the sol-gel route and subsequent calcination. The unique hybrids have a uniform distribution of FeTiO3 nanoparticles (5-20 nm) in the carbon matrix. Electrochemical tests prove that the porous FeTiO3/C hybrid nanotubes deliver a high capacity of 612.5 mA h g-1 at 0.2 A g-1 after 300 cycles. Moreover, they present remarkable rate capability and exceptional cycling stability, possessing 163.8 mA h g-1 at 5 A g-1 for 1000 cycles. The enhanced electrochemical performance of the FeTiO3/C hybrid is derived from the shortened Li+ transport length, good structure stability and conductive carbon matrix, which simultaneously solves the major problems of pulverization and agglomeration of FeTiO3 nanoparticles during cycling.